2 2017 15 jaes by JAES

IMPRESSUM J O U R N A L O F A P P L I E D E N G I N E E R I N G S C I E N C E (J A E S) The journal publishes original and review articles covering the concept of technical science, energy and environment, industrial engineering, quality management and other related sciences. JAES is Open-Access Journal that follows new trends and progress proven practice in listed fields, thus creating a unique forum for interdisciplinary or multidisciplinary dialogue. Electronic journal editing and transparent editorial and review policy are provided, with: • • • • •

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All published articles are indexed by international abstract base Elsevier Bibliographic Databases through service SCOPUS since 2006 and through service SCImago Journal Rank since 2011. Serbian Ministry of Education, Science and Technological Development admitted the Journal of Applied Engineering Science in a list of reference journals as Leading national journal M51. International Editorial Advisory Board Prof. dr Branko Vasić, Faculty of Mechanical Engineering, Belgrade; Prof. dr Dragan Aleksendrić, Faculty of Mechanical Engineering, Belgrade; Prof. dr Dragan Milutinović, Faculty of Mechanical Engineering, Belgrade; Doc. dr Goran Vorotović, Faculty of Mechanical Engineering, Belgrade; Prof. dr Ivan Blagojević, Faculty of Mechanical Engineering, Belgrade; Prof. dr Jezdimir Knežević, MIRCE Akademy, United Kingdom; Prof. dr Jozef Aronov, Russian Research Institute for Certification, Russia; Prof. dr Miloš Knežević, Faculty of Civil Engineering, Podgorica, Montenegro; Prof. dr Miodrag Zec, Faculty of Philosophy, Belgrade; Prof. dr Mirjana Misita, Faculty of Mechanical Engineering, Belgrade; Prof. dr Mirko Vujošević, Faculty of Organizational Science, Belgrade; Prof. dr Nebojša Bojović, Faculty of Traffic and Transportation, Belgrade; Dr Nebojša Kovačević, Geotechnical Consulting Group, United Kingdom; Prof. dr Nenad Đajić, Faculty of Mining and Geology, Belgrade; Prof. dr Nenad Zrnić, Faculty of Mechanical Engineering, Belgrade; Prof. dr Radivoje Mitrović, Faculty of Mechanical Engineering, Belgrade; Prof. dr Robert Bjeković, Hochschule Ravensburg-Weingarten, Germany; MSc Sonny Siniša Vidović, Energy Testing and Balance, USA Prof. dr Vesna Spasojević Brkić, Faculty of Mechanical Engineering, Belgrade; Prof. dr Vladimir Popović, Faculty of Mechanical Engineering, Belgrade; Prof. dr Vukan Vučić, University of Pennsylvania, USA; Prof. dr Zdravko Milovanović, Faculty of Mechanical Engineering, Banja Luka; Prof. dr Željko Kamberović, Faculty of Technology and Metallurgy, Belgrade;

Publisher Institute for Research and Design in Commerce and Industry - IIPP; www.iipp.rs Copublisher Faculty of Mechanical Engineering – Belgrade University; www.mas.bg.ac.rs For copublisher: Prof. dr Radivoje Mitrović Faculty of Transport and Traffic Engineering – Belgrade University; www.sf.bg.ac.rs For copublisher: Prof. dr Nebojša Bojović Editor in Chief Prof. dr Gradimir Danon, Faculty of Forestry, Belgrade; Executive editor Mr Nada Stanojević, Faculty of Mechanical Engineering, Belgrade; Technical editor Darko Stanojević, Faculty of Mechanical Engineering, Belgrade; Publishing Council Dragan Đorđević, Belgrade Waterworks and Sewerage, Belgrade; Dušan Đurašević, Euro Sumar, Belgrade; Nenad Jankov, Power Plant Kostolac B, Kostolac; Miroslav Vuković, CBRE Serbia, Belgrade; Milutin Ignjatović, Institute for Transport and Traffic CIP, Belgrade; Editorial Office Miloš Vasić, Miloš Dimitrijević, Ivana Ćuk, Milica Mikić, Ljubica Knežević; Printed by: Sigra star, Belgrade; Papers are indexed by SCOPUS UDC 33 ISSN 1451-4117 Online ISSN 1821-3197 www.engineeringscience.rs

Journal of Applied Engineering Science 15(2017)2

CONTENTS

Martin Hrabala, Michaela Opletalováb, David Tučekc TEACHING BUSINESS PROCESS MANAGEMENT: 113 - 121 IMPROVING THE PROCESS OF PROCESS MODELLING COURSE Said Berdoudi, H.Hebhoub, R. Djebien VALORIZATION AND RECYCLING OF QUARRIES WASTE 122 - 127 AS AN ADDITION IN CEMENT Boukarta Soufiane, Berezowska-Azzag Ewa “URBAN ISLAND” AS AN ENERGY ASSESSMENT TOOL. THE CASE 128 - 139 OF MOUZAIA, AL ALGERIA Vladimir Ilyich Fedyukov, Ekaterina Yurevna Saldaeva, Maria Sergeyevna Chernova, Vasilii Yurevich Chernov 140 - 148 TRUNK ASYMMETRY AND SPRUCE WOOD RESONANT PROPERTIES VARIABILITY WITH RESPECT TO THE CARDINAL POINTS AND THE TREE HEIGHT A.Meena Kowshalya, M.L. Valarmathi THINK SMART, THINK SOCIAL! THE ROAD MAP FROM SMARTER OBJECTS TO 149 - 154 SOCIAL OBJECTS IN SOCIAL INTERNET OF THINGS - A SURVEY Katerina Georgieva Gabrovska-Evstatieva, Boris Ivanov Evstatiev COST-BENEFIT ANALYSIS OF PV GENERATORS AT RESIDENTIAL BUILDINGS IN 155 - 165 THE REGION OF RUSE, BULGARIA Oleg Vladimirovich Emelianov, Alexander Nikolaevich Shuvalov, Milan Prokić ON THE QUESTION OF PREDICTING THE SERVICE LIFE OF LATTICE STEEL 166 - 172 STRUCTURAL ELEMENTS

Monika Bučkova, Martin Krajčović, Boris Jerman 173 - 180 IMPACT OF DIGITAL FACTORY TOOLS ON DESIGNING OF WAREHOUSES

Ivan Milorad Rakonjac, Ivana Milorad Rakonjac, Miloš Petar Gašić COMPARATIVE REVIEW OF THE RISK ASSESSMENT QUANTITATIVE MODELS 181 - 186 FOR PUBLIC OPEN SPACES LIGHTING DESIGN OPTIMISATION Olga Tarasova, Mariia Chernova 187 - 191 INVESTIGATION OF FEEDING ROLLERS ALIGNMENT IN A HORIZONTAL PLANE

Goran Radoičić, Miomir Jovanović TRANSIENT SIMULATION OF IMPULSE WIND EFFECT ON A TALL SHIPYARD 192 - 202 FRAME STRUCTURE

Journal of Applied Engineering Science 15(2017)2

EDITORIAL

Respected readers, As a new member of the Editorial board, I am honored to address you on this occasion. Our magazine enters its 15th year of existence, which is a proof of its longevity and improvement. Knowing that, in our digital age, the information is the „essence“ which in Serbian language equals to the notion of a „bit“ which, itself, represents the basis of every information revolution, it’s important to notice that the magazine stands as an important part of the information system of Serbian and world science. It is evident that the era of autonomous vehicles, autonomous aircrafts-drones, 3D printing and different „thinking machines“ has begun. Consequently comes race against time which must and can Doc. dr Goran Vorotović produce people capable of coping with new trends. From the aspect of integration in the information age, evident postindustrial revolution, which I would refer to as evolution, presented two trends of thinking: the first one refers to nurturing of traditional values incarnated in complex systems design and maintenance, while the other one leans on the integration of information systems in the above mentioned. That provided the necessary conditions for the apparition of mechatronics. On the other hand, ecological demands initiated particular level of problem analysis for, I am sure You will agree, the protection of environment stands as a top priority and goal for all of us who practice mechanical systems design, exploitation and maintenance. If we look back on all said above, the apparition of numerically guided electric vehicles, for example, presents no ”miracle“, but a natural evolutional development which we must address from the aspect of „supervision“, without „fearing“ the smart machines and consequences that might develop if they become „conscious “ someday. History has shown – progress can’t be stopped. In this regard, the above mentioned ongoing evolution is incarnated through the phenomenon of the Internet of Things (IoT), which has consolidated partial elements of different systems by raising the level of informational consciousness on a global network. Thanks to the endless possibilities of internet, we have constant flow of scientific ideas and results of research work. By virtue of IoT, the results are even tested in real time. On the other hand, the general public is able to participate in scientific research through quick result analysis and publishing it in relevant scientific magazines. In the end, the communication in our magazine is also raised to the internet level. The fact that the IoT studies are more and more present in schools and colleges and that they are included in the national development strategy in most countries is a reason for optimism. Needless to say that the most successful companies today are the ones in the field of informatics, and that fact encourages those strategies. A large number of those companies is connected to IoT by following the results of scientific research and by enabling unimagined development of scientific thought in the field of informatics through different actions, sponsorships and direct investments. Accordingly, by its constant improvement, informatics, the science’s child, grows and becomes science’s younger brother. Few days ago, I read in the news outlets: „Humanity has only 100 years left“. That thesis came from the famous Stephen Hawking. It is clear that, using his reputation and critique of pure reason assumptions, professor Hawking pointed out the paths of development of humanity, which, without science and technology, has no future in the endless universe only by using the survival on Earth parable. In that sense, and considering the professor Hawking’s words, and the stands of all our predecessors and contemporaries, our mission, including critical view, remains to become an integral part of the modern internet era and to „embrace it“. With respect, Doc. dr Goran Vorotović University of Belgrade, Faculty of Mechanical Engineering

Journal of Applied Engineering Science 15(2017)2

Original Scientific Paper

Paper number: 15(2017)2, 419, 113 - 121

doi:10.5937/jaes15-12172

TEACHING BUSINESS PROCESS MANAGEMENT: IMPROVING THE PROCESS OF PROCESS MODELLING COURSE Martin Hrabala* Tomas Bata University in Zlín, Zlín, Czech Republic Michaela Opletalováb Tomas Bata University in Zlín, Zlín, Czech Republic David Tučekc Tomas Bata University in Zlín, Zlín, Czech Republic

Process approach is a part of many organizations´ management systems. Process oriented organizations focus on value added processes, their management, performance measurement, improvement and automation. However, in many higher education institutions is not process management implemented and its teaching does not always correspond with business needs and practice. This paper deals with the latter side of process management in higher education - course of process management held at Faculty of management and economics of Tomas Bata University in Zlín. The main purpose of the paper is to present the results of the research among Czech universities and their approach to BPM education and a case study of process management course and its improvement at Faculty of Management and Economics at Tomas Bata University in Zlín. To improve the course, the very aspects of process management such as customer focus or performance measurement were applied. The performed action research is then described in form of the case study. Key words: Active learning, Business process management, Higher education, Process improvement, Process modelling INTRODUCTION Business Process Management (BPM), whether as a managerial discipline or technology competence, stays one of the priorities of companies. According to APQC (2016), process management is the priority for 86,1% of companies before performance management, change management or big data. Therefore, BPM can belong among key competencies for future managers, process owners, business analysts, industrial engineers or IT specialists. Knowledge and training of other workers facilitates and accelerates BPM implementation. BPM can be understood as a holistic managerial discipline which emphasizes processes as key organizational assets. To distinguish between BPM and its technology support in the form of software applications we will address to managerial discipline as BPM and to its technical means as Business Process Management Systems or Suits (BPMS). As indicated, BPM is the managerial discipline which evolved from Total Quality

Management (TQM), Business Process Reengineering, Lean, and today includes variety of methods and techniques (Jeston and Nelis, 2008). Organizational process is a set of interrelated activities which together aim to achieve certain goal. Every process should therefore have its customer who demands certain value. In the late 1980s and especially 90s organizations started their reengineering programs which should radically improve performance and break organizational silos within processes. This era is connected with Hammer together with Davenport who described the practice of reengineering and developed its methodology (Hammer, 1990; Davenport and Short, 1990). However, improvements were often disputable and projects´ failure rate was high. According to Smith and Fingar (2007), instead of reengineering organizations needed continuous improvement of their processes. Thus, third wave of process management started - after waves of TQM and BPR. Today, we can see variety of BPM projects in industries, services or non-profit sector. Whether they are using Lean, Six Sigma or BPR,

*Tomas Bata University in Zlín, Department of Industrial Engineering and Information Systems, Zlín, Czech Republic, hrabal@fame.utb.cz

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they are always process and customer focused. All these aspects are indicators of the importance of BPM specialists in modern organizations. Thus, their effective education and training is needed through their studies in a university. PROCESS MANAGEMENT IN HIGHER EDUCATION Little different situation is in the higher education. It is obvious that many universities and business schools are structured according to functions such as finance, marketing, management, logistics etc. Similarly are structured also study programs and students cannot appropriately interconnect ideas and knowledge. Also these programs and their graduates do not correspond with requirements of business, information technology development and the idea of flat organizations (Walker and Black, 2000). Although universities, especially these with economic and management study programs, partly recognize and teach BPM but they remain in functional silos themselves (Hars, 2002). The functional structure results in the lack of cross-functionality and process awareness of students (Seethamraju, 2012). In literature can be found suggestions how to apply BPR to higher education. According to Davis and Mehta (1997) there are following steps of BPR: • creating adequate culture, • set up BPR team and steering committee, • complete feasibility study, • developing vision, • training the team, • informing everyone in the organization about BPR efforts, • analysing work to be reengineered, • selecting and training staff in the reengineered process, • training leaders in new roles. Processes suitable for BPR can be, according to these authors, e.g. accreditation, curriculum design, faculty development and evaluation, student grading and evaluation, research etc. Abdous (2011) proposes the practice of BPR in the following steps: • Initiation • Analysis • Reengineering • Implementation • Evaluation. But it is rather simple application of Hammer´s and Champy´s methodology. 114

Critical success factors of BPR in higher education are: understanding a context, shared vision, and involvement of management and leveraging of information technologies (Ibid.). According to Ahmad, Francis and Zairi (2007) is stressed teamwork and quality oriented culture, quality management system, rewards, change management, less bureaucratic and participative style, role of information technologies, project management and adequate financial results the main critical success factors of BPR. Process description can be valuable for multiple reasons. According to [12], process definition, design and description are relevant for accreditation, or in case of merges of several schools. Process management also becomes one of the key components of management system of tertiary institutions in the Czech Republic. According to Individual National Project EFIN, process management should be part of institutions´ maturity model and can be roadmap for next improvement of performance. (Tuček and Basl, 2011) According to Walker and Black (2000) is defined process oriented undergraduate curricula derived from generic high-level processes which can be found in most of organizations: acquisition of resources and payment, conversion or service provision, and acquisition of customers and revenue collection. Subjects are then structured into courses of acquisition of capital resources, human resources acquisition, conversion and service, sales / collection / customer service, and organizational performance measurement and management. Processes are therefore integrative theme for functional knowledge (e.g. finance) and skills (e.g. communication). TEACHING PROCESS MODELLING AND MANAGEMENT Although business schools are mostly organized according to functions, they often provide process management courses to some extent. Bandara et al. (2010) provided case studies of five universities - Bentley University, Georgia State University, Queensland University of Technology, University of Pretoria and University of Vienna. In most cases they provide courses or programs of BPM and related disciplines such as Industrial Engineering, Six Sigma, Business analysis etc. Courses mostly respect both managerial and technology aspects of BPM. Students are introduced to BPM, BPR, Lean, automation and workflow techniques and can Journal of Applied Engineering Science 15(2017)2, 419

Martin Hrabala - Teaching business process management: Improving the process of process modelling course

analyse and model processes. Graduates then know BPMS such as ARIS, Bizagi, or Inno8 and can utilize it together with knowledge of Enterprise Resource Planning systems (ERP). But even BPM courses with long tradition lack pedagogical resources - both materials in form of textbooks and case studies, and instructors who are trained and experienced. One of the developed programmes provides Queensland University of Technology. Lectures are complemented by practical workshops in PC labs where students can train process modelling in ARIS and YAWL. Students also conduct assignments in form of projects and go through required readings per week. After a course is gathered students´ feedback. (Recker and Rosemann, 2009) Another example is Tomas Bata University in Zlín which started with process modelling in 2010. The optional subject Computer Support of Business Processes was parallel with mandatory subject Reengineering. The former provided training in process modelling with ARIS Business Designer, the latter general theory of BPR and BPM. (Tučková and Tuček, 2010) METHODOLOGY Prevalent method used in this paper is the case study and the action research. Case study is a method designed to particular in-depth study of a specific case in certain context. Action research is then intervention method to improve specific process and analyse the results of the action. (Pickard, 2013). In this paper, we describe the case study of BPM education at the Faculty of Management and Economics at Tomas Bata University in Zlín together with its improvement. The case study focuses on the innovation of Business Process Management course at the faculty. This course was at first concerned only with theoretical concepts of Business Process Reengineering (BPR), later it was merged with optional course Computer Support of Enterprise Processes. This connection lead to a new concept of teaching - lectures are still prevalently concerned with theoretical aspects of BPM and BPR but seminars are focused on practical training of process modelling in specialized software application ARIS. The course is mandatory for students in these study programmes: Enterprise economics, Marketing and management, and Industrial Engineering. This is especially challenging because Journal of Applied Engineering Science 15(2017)2, 419

students have different background and demands. The action research was conducted as an application of process improvement on the education process itself. After process analysis of BPM course we performed survey among students which can be viewed as process customers and collected data about their expectations before and feedback after absolving the course. Analysis of this feedback provided insight into the students´- customers´ value and suggestions for improvement were developed. The course takes place in winter semester. The improvement project started in the academic year 2014/2015 and continued in 2015/2016. The procedure was as follows: • Introducing the subject and gathering expectations from students (voice of customer) • Running the course • Gathering and analysis of students´ feedback on the course • Suggesting improvements and their implementation with the subject´s guarantee • Running the improved course • Gathering and analysis of students´ feedback on the course to evaluate the improvement The course was innovated with regard to students´ expectations which are considered as customers of educational process and which could be slightly different from expectations of labour market and employers, but also with regard to current trends in BPM and its education. Requirements of employers on graduates’ competencies were also taken into consideration. Currently, the labour market places great emphasis on the practical skills of graduates, no longer so much on their knowledge. In connection with this trend, it was decided to innovate BPM course as a course, which is the cornerstone of effective management skills, analytical skills and skills of continuous improvement in organization of any type. To support innovative teaching of BPM course, research was conducted whose aim was to determine the current state of BPM teaching level at universities in the Czech Republic. As part of this research were interviewed 33 respondents public, private and state tertiary institutions. The questionnaire was aimed to determine whether and how these schools are preparing students in the field of Business Process Management. Respondents were selected according to the focus of taught subjects: economics, business economics, management and business management. So fields where is the premise of teaching BPM 115

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with respect to future employability of graduates in the labour market. The questionnaire was completed by 17 respondents (51% of interviewed respondents). The results showed that 10 respondents have BPM course directly incorporated into study program and 5 respondents teach BPM topic in some main courses. Only 2 respondents answered that they do not teach BPM topic at all. These 2 respondents stated that they do not include the teaching of any element of BPM as well as their school has not mapped own processes and does not practice BPM at the level of their management.Other respondents classified to the teaching BPM theory, process analysis and improvement, process controlling and economic evaluation of processes. Conversely, the teaching of process modelling and/or process simulation in special software is very infrequent.Some respondents also try to approach the BPM teaching comprehensively and systematically pick on it for another subject as logistics, information systems, business economics or production management. Research has found no relationship between the type of university (public, state, and private), size of school or school focus (economic, technic) and level of standard of BPM education. The research also showed that the overall level of BPM teaching at Czech universities is low to moderate. Business Process Management as part of job of middle and senior manager, project manager, process engineer or leader should be seen as one of the basic field with a maximum practical benefit to students of economic and technical fields. RESULTS Based on the above facts it was decided to innovate the course towards practical skills. Original course of BPM was merely theoretical and students lacked practical skills. After its merge with optional course Computer Support of Enterprise Processes it gained the practical seminars with training in computer lab but the studentsâ&#x20AC;&#x2122; feedback indicated discontinuities between content of lectures, seminars and assigned seminar works. Moreover, seminar work was above the skills of students who have not yet developed proper competencies in process redesign and also didnÂ´t manage to convince entrepreneurs to provide them an opportunity to lead a redesign effort. At the end of winter semester of 2014 the feedback on original course was gathered and analysed, suggestions for im116

provement were developed and implemented for next academic year. Final evaluation from students of original course was 3.4 points out of five and standard deviation 0.9. Only 30% of students stated that they plan to utilize process modelling in their master thesis but 55% of them want to use it during their career. There were no significant distinctions between students from different fields. New course design comprised of changed seminars curriculum and seminar work requirements. The goals of the course innovation were to promote the process thinking across several fields of study, their cross-functional cooperation, and competence in teamwork, process design and modelling. These goals were determined new form of the course and its process.At first, requirements on seminar works were changed. Because process orientation promotes teamwork and cross-functionality, instead of individual work on process redesign in specific organization, students form own teams and design their own processes in virtual companies. Among themes for the assignment were e.g. supply chain management, sales of goods, technological preparation of production, organizing marketing campaigns, management of hotel etc. On the seminars, students become acquainted with tools such as SIPOC and process flowchart, later they adopted methodology of ARIS and created models according to case studies. Finally, each team developed SIPOC and process models in ARIS for their assigned projects and presented it. Seminars were conducted in modern interactive way, especially in the teamwork part of the course. This interactive learning should promote cross-functional collaboration in the design phase of BPM. The aim of this teaching method was to prepare the students for interdisciplinary teamwork, communication, other views on one issue creating processes and procedures and independent thinking and decision making.The direction in which the course was upgraded is considered the most modern method of learning today. Students are taught interactively acquainted with the field and at the context of their own experience through playing games and independent work they have the greatest chance to memorize everything and practically use it in the future.

Journal of Applied Engineering Science 15(2017)2, 419

Martin Hrabala - Teaching business process management: Improving the process of process modelling course

Figure 1: Process of the BPM course (own processing)

The redesign course description After the studentsÂ´ registration to the course and the start of semester, the course begin with introduction of BPM as a managerial discipline, requirements to complete the course and software application ARIS. After the introduction, students form teams and choose project topic which they conduct through the run of the course. Students had the task to develop business model of a virtual organization. They should identify the voice of a customer, define a product, vision and mission. On the basis of their strategy students designed value chain, and its main, management and support processes. Finally, students modelled these processes.Before students start with modelling in ARIS, they became acquainted with SIPOC and simple flowchart diagrams which they apply within their team projects on flipcharts. Later start lessons in ARIS: orientation in the application and structure of the database, meaning of the individual models and symbols, creating value-added chain diagrams (VAC), function allocation diagrams (FAD), event-driven process chain (EPC) and key performance indicators diagram (KPI). Each type of model is explained in the context

of business. VAC diagrams are used to model value chains and processes with subprocesses. FAD and KPI diagrams are connected to the theme of process context, management and performance measurement. EPC express the detailed process description. Students learn how to systematically build a complex model which is composed of interlinked diagrams which describe different perspectives on a business and its processes. Figure 2 shows the structure of a process model and its decomposition. The course continues with teamwork on the assigned projects where student teams work on their own process models which they finally present to the whole class. The project should contain the simple description of the organization and its context, process model composed of SIPOC, VAC, FAD, KPI and EPC diagrams together with an organization charts. In the end of the semester, studentsÂ´ knowledge is verified via a test in ARIS. After passing the test, students may proceed to the final evaluation of the course. After seminars, a feedback on the course is gathered and analysed. The conception and structure of the BPM course is shown in the table 1.

Figure 2: Process model structure and its hierarchy (own processing) Journal of Applied Engineering Science 15(2017)2, 419

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Table 1: BPM course outline (own processing) Goal of the course

Student understands and can apply concepts of BPM and BPR Student can create various process models in ARIS

Methodology and tools

DMAIC methodology ARIS method (ARIS Designer and Express)

Materials

Presentations Case studies ARIS guidebook

Tasks

Process modelling in ARIS Team project

Content of seminars

1. Introduction - the course and BPM, assigning team projects 2. Development of strategy and overview process map 3. SIPOC and flowcharts – teamwork, setting up repositories 4. Value chains – theory, and modelling VAC 5. Performance measurement – theory, modelling FAD and KPIs 6. Process analysis – modelling EPC 7. Organization structures – theory, modelling organization charts 8. Summary of modelling – modelling complex case study 9. Teamwork – conducting team projects 10.Presentation of team projects 11.Test – verification of knowledge

Students´ feedback on the redesign course After the end of the semester we analysed students´ feedback on the new course. The rate of questionnaires return was much lower only 18 students responded out of 110. Again, we tracked students´ satisfaction was 4.1 out of 5 points with standard deviation 1.1. There were higher disproportions between the satisfaction rates of different fields of study. However, only one student declared that he is willing to use process modelling in master thesis, three do not plan to use it and fourteen do not know yet. But five of them plan to utilize the BPM knowledge in their practice after graduation. The reason why not to use BPM are mainly different fields of interest or the fact, that student does not have exact idea what topic of thesis to choose or which profession does he aspire on. Among the highest ranked knowledge and skills which students gained during the course were stated process management and teamwork, followed by project management, computer literacy, and analytical and systemic thinking. On the contrary, the less rated was economic knowledge. The very software tool ARIS Designer was accepted positively. But it would be beneficial to try another BPMS, compare them and try to trans118

fer skills among various software applications. In the most cases, students positively assess the teamwork projects as they helped them to understand the concept of BPM, and perspectives of other functions (such as industrial engineering, marketing, finance, management etc.). DISCUSSION Business Process Management course is set up to reflect 6 fundamental pillars of process orientation: customer focus, teamwork, crossfunctional processes, analytic and systemic thinking, and especially computer literacy especially in ARIS software application. The course is prevalently focused on the design phase of the process lifecycle. It is stressed that the design is determined by the strategy and designed models must be implemented and their performance measured and continuously improved. To clarify the relations between process and project management, DMAIC (define, measure, analyse, improve, control) methodology is used as a means of process lifecycle description and management.Students focus on the design phase within the course and can relate phases of measure while methods used in other phases are presented in different courses according to Journal of Applied Engineering Science 15(2017)2, 419

Martin Hrabala - Teaching business process management: Improving the process of process modelling course

the field of study. Among them we can mention Lean, Activity Based Costing, simulations, linear programming etc. Through such mental model, student can orient themselves in various management and economic disciplines in relation to a business process.The only obstacle in maximizing the positive impact of innovation the teaching of the course were students from different fields of study. Students come from different focus areas and for some of them, this topic is more tangible than for others. Some students consider the topic of BPM as very abstract and generally not engaged by their field of study. All students are taught together in one block of seminars. Effective innovation that would allow teaching more focused on students and adapt on their pace and knowledge could be separate students to the various seminars based on their field of study. Lectures could stay for all students together and seminars will be separated. This amendment would allow teacher better work with students even more and adapt to their future work and practice.

CONCLUSIONS After the first innovation of the BPM course towards the interactive learning and discussion it was shown that students accepted this innovation very positively. Especially personal response and a change in studentsÂ´ understanding of the issues showed that the changes were step in the right way. Teachers can compare between different academic years and changes were considerable. Students easily understand the issues, they associate the issue with practical problems better and they learn how to think over the discussed topics. Based on experience, the course will leave in this form for the next academic year. There will be only few little changes in schedule of seminars to better match the pace and knowledge of students who come from different disciplines. Since we consider this course to be extremely beneficial for students and their future practice, it would be appropriate to think about extending this philosophy of education at other colleges, where is BPM fully or marginally engaged.

Figure 3: Process lifecycle (own processing)

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This course is crucial for understanding the organization management and function and students should be prepared on these issues.Every day in practice we encounter a lack of understanding of concepts such as strategy, vision, mission, business management or process. These concepts should be known by each manager and owner of the organization. They should be able practice methodologies associated with these concepts. Students of economic and technical field should be those who will be hold management positions in organizations. People at these functions have to create plans, make right choices and decisions and lead organization to success and profit. They should be able to establish long-term plans for achieving key goals and fulfil the vision and mission of the organization. They should also be able to communicate strategy and corporate culture, analyse processes and implement changes. In all of these basic daily activities could be process management very helpful and it can become an effective tool and a means to control. Interactive teaching approach basic skills such as communication, teamwork, negotiation and presentation of student work and results of his team. These practical skills are invaluable to a student in any job in any position and also in everyday life.Changes in attitude of students, their enthusiasm and understanding of the issue and the overall concept of teaching BPM could convince more universities and colleges to apply the same or similar approach. ACKNOWLEDGMENT The authors are thankful to the Internal Grant Agency of FaME TBU No. IGA/FaME/2015/043 (Management and software support of internal processes in hospitals in Czech Republic) for financial support to carry out this research.

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REFERENCES 1) APQC, 2016. Process and Performance Management, https://www.apqc.org/knowledge-base/download/363319/K06479_ 2016_PPM_Priorities_Survey_Summary.pdf (viewed at 9 Apr. 2016) 2) Abdous M., 2011. Towards a framework for business process reengineering in higher education, Journal of Higher Education Policy and Management, (33)4, pp. 427-433. 3) Ahmad H., Francis A. and Zairi M., 2007. Business process reengineering: Critical success factors in higher education, Business Process Management Journal, (13)3, pp. 451-469. 4) Bandara, W. vom et al., 2010. Business Process Management Education in Academia: Status, Challenges, and Recommendations, Communication of the Association for the Information Systems, (21), pp. 744-776. 5) Brennan L. and Austin W., 2003. Addressing the Need for Management Processes for Higher Education Accreditation, Innovative Higher Education, (28)1, pp. 49-62. 6) Davenport T. H. and Short J. E., 1990. The New Industrial Engineering: Information Technology and Business Process Redesign, Sloan Management Review, (31)4, pp. 11-27. 7) Davis J. and Mehta K., 1997. Reengineering a School of Business of the Future: A Mission/Vision Model for Higher Education in Transformational Times, SAM Advanced Management Journal, (62)2, pp. 8-15. 8) Hammer M., 1990. Reengineering Work: DonÂ´t Automate, Obliterate, Harvard Business Review, July-August, pp. 104-112. 9) Hars A., 2002. Using BPR Tools in Business Process Education. In A. W. Scheer, F. Abolhassan, W. Jost and M. Kirchmer (Eds.), Business Process Excellence: ARIS in Practice, Berlin: Springer, pp. 175-186. 10) Jeston J. and Nelis J., 2008. Business process management: Practical guidelines to successful implementations, Amsterdam: Elsevier/Butterworth-Heinemann. 11) Recker J. and Rosemann M., 2009. Teaching Business Process Modelling: Experiences and Recommendations, Communication of the Association for the Information Systems, (25), pp. 1-16. Journal of Applied Engineering Science 15(2017)2, 419

Martin Hrabala - Teaching business process management: Improving the process of process modelling course

12) Seethamraju R., 2012. Business process management: a missing link in business education, Business Process Management Journal, (18)3,pp. 532-547. 13) Smith H. and Fingar P., 2007. Business process management: the third wave. [4th Anniversary ed.]. Tampa, Fla: Meghan-Kiffer Press. 14) Tuček D. and Basl J., 2011. Using BPM Principles to Increase the Efficiency of Processes in Higher Education in the CR. In: Proceedings of the 2th International Conference on Education and Educational Technologies. Greece, Corfu: World Scientific and Engineering Academy and Society (WSEAS/ NAUN), pp. 47-51.

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15) Tučková Z. and Tuček D., 2010. Increasing knowledge by teaching of modern BPM systems. In: Latest Trends on Engineering Education. Greece, Corfu: World Scientific and Engineering Academy and Society (WSEAS), pp. 487-492. 16) Walker K. B. and Black E. L., 2000. Reengineering the undergraduate business core curriculum: aligning business schools with business for improved performance, Business Process Management Journal, (6)3, pp. 194-213. Paper sent to revision: 24.10.2016 Paper ready for publication: 29.11.2016.

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Original Scientific Paper

doi:10.5937/jaes15-12743

Paper number: 15(2017)2, 420, 122 - 127

VALORIZATION AND RECYCLING OF QUARRIES WASTE AS AN ADDITION IN CEMENT Said Berdoudi* National Polytechnic School of Algiers, Hacen Badi Elharrach, Algeria H.Hebhoub University of Skikda, Skikda, Algeria R.Djebien University of Skikda, Skikda, Algeria The management of mining waste is one of the major environmental problems which are facing the mining professionals, during their activity and even after the closure of the mine. Indeed, excavated materials from mines belong to a category of waste, and especially when dealing with an open pit, are generally left on the surface.In this experimental study, the utilization of sand waste marble dust as an additive in cement production has been investigated. The aggregate used in this study is a sand of marble wastes (excess loads of sand exposed to bad weather conditions) of the derived marble quarry from Fil-fila (Skikda, east of Algeria). The study focuses the effect of marble waste sand fillers substitution in the cement paste and mortar (5, 10, 15 and 20â&#x201E;&#x2026;) with a finesse greater than that of cement, to compare the results obtained through control samples (0%) of cement paste properties in the fresh condition and the mechanical performances of mortar in the hardened condition.The obtained results show that the sand marble wastes fillers can be technically used as additive in cement. Therefore, it can be possible to prevent the environmental pollution especially in this region with excessive marble production and to well manage natural resources. Key words: Wastes, Sand; Mining; Marble; Fillers; Cementation; Additives INTRODUCTION Waste management is currently one of the major encountered problems especially in developing countries. Our study is registered in a politic of recycling and valorizing of wastes that can be used in the cement formulation. According to Amritpal and Rajwinder , (2015) [01] the consumption of cement and cost are more and more increasing, blended cement based on the partial replacement of Portland cement clinker by wastes has been recently the object of many investigations (Gurumoorthy, 2014) [07]. Corinaldesi and al, (2010) [6] reported that marble waste, consisting of very fine particles, was one of the environmental problems around the world . However this marble dust can be used either to produce new products or as an admixture so that the natural sources are used more efficiently and the environment will be saved properly (Hameed and Sekar, 2009) [08]. Many studies have shown the importance of using these wastes, Hebhoub et al (2013) [10] have recently used this type of waste as sand

introduced in mortars. Using marble waste in hydraulic concrete and mortars were also studied by evaluating their fresh and hardened state properties (Hebhoub and al (2011), Aruntas and al (2010), Belaidi and al, (2012)) [9, 2, 3]. The world preoccupation aims firstly at reducing the cost of cement and secondly the environmentâ&#x20AC;&#x2122;s impact, Therefore, construction industry is seeking to other alternatives in order to meet the needs of cement manufacturing as it was demonstrated by Niyazi ugri, (2013) [13] . We are so interested in making a cement CEM II from a cement CEM I by adding fillers of marble waste sand (marble powder exposed to bad weather conditions).In this study we recover and introduce this type of marble (marble waste sand) from the quarry of Fil-fila as substitute filler in cement, the deposit is located in 25 km in the eastern side of Skikda city, Algeria.

* Mining engineering laboratory, National Polytechnic School of Algiers, Hacen Badi Elharrach, Algiers, Algeria berdoudisaid@yahoo.fr

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Figure1: Marble powder exposed to bad weather conditions of Fil-fila quarry (Algeria)

CHARACTERIZATIONS OF THE USED MATERIALS The materials used, in this study, are: • Cement CEM I class 42.5 coming from the cement works of Hdjar Soud Company (Algeria). • Fillers of marble waste sand are obtained from the local quarry by grinding in a standard normalized ball. • The mortars are prepared with standard sand CEN according to the norm EN 196-1, this

natural siliceous sand with an apparent density of 1.63 g/Cm3 and an absolute density of 2.5g/Cm3, this sand is inert from a chemical point of view with fineness module of 2.33. The results characterizations tests are shown in the Table 1. According to the results listed in Table 1 and chemical analysis, the marble waste sand is limestone fillers (98.67 CaCO3). The addition of marble waste sand fillers in cement leads to increase the CaO quantity. This increase gives a lot of C3S and reduces the quantity of C2S, C3A and C4AF.

Table 1: Results of characterizations tests Characteristics

CEM I 42.5

Marble wastes sand fillers

Characteristics

CEM I 42.5

Marble wastes sand fillers

Absolute density (g/cm3)

3.33

2.79

Insoluble residue

0.85

0.035

Specific surface (Blaine)(cm2/ g)

3200

6500

CaO (free)

0.4

CaO

61.31

55.29

2.52

Al2O3

5.45

0.14

MAF

1.54

Fe2O3

3.54

0.09

LSF

0.88

SiO2

22.73

0.53

1.93

MgO

0.48

0.2

C 3S

28.14

Na2O

0.19

0.00

C 2S

38.71

K2O

0.63

0.01

C 3A

8.45

Cl-

0.035

0.025

C4AF

10.76

SO3

2.44

0.04

CaCO3

98.67

Loss on ignition

2.45

43.40

Journal of Applied Engineering Science 15(2017)2, 420

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EXPERIMENTAL PROGRAM In the experimental program, we study the substitution of a cement part by the marble wastes sand additions, by varying the substitutions rate (0℅, 5℅, 10℅, 15℅, 20℅). The work is divided into two series. Step 1: Manufacture starting from cement CEM I and marble wastes sand fillers a cement pastes with substitutions rates (0℅, 5℅, 10℅, 15℅, 20℅). The constants and variables parameters are water/cement ratio which is equal to 0.27 and the

substitution rate respectively. Tests made in this company are consistency, setting and steadiness. Step 2: Manufacture starting from cement CEM I and marble wastes sand fillers mortars with substitutions rates (0℅, 5℅, 10℅, 15℅, 20℅).The constants and variables parameters are water/cement ratio which is equal to 0.5 and sand, substitution rate respectively. Tests on hardened mortar samples are compressive , tensile strength in flexion at 2, 7, 28 and 90 days and shrinkage test at 2,7, 28 days.

Figure 2: Variation of consistency according to the substitution rate.

EFFECT OF MARBLE WASTE SAND FILLERS ON THE CEMENT PASTE CHARACTERISTICS Consistency Generally, the consistency variation is weak for all mixtures. The bad consistency is obtained for the witness concrete of 0% substitution rate (cement rich in C3A) in accordance with Messan, (2006) [11], for a specific sur-

face Blaine of the marble wastes higher than that of CEMI, the variation is a decreasing substitution function till 5% where the effect reverses to stabilize between 10% and 20%. As a consequent, the fillers effect is insignificant. From this perspective, Neto and Campiteli, (1990) [12] found out that the consistency of cements, containing up to 15% of limestone rich in CaCO3, decreased, especially for the finer cements.

Figure 3: Variation of the start and end of setting time versus the substitution rate

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Said Bedoudi - Valorization and recycling of quarries waste as an addition cement

Start and end of setting time The figure 3 gives the variation of setting time’s start and end concerning the substitution rate. Vuk and al, (2001) [16] point out that the effects of clinker composition were less significant when the cement fineness was higher. In this study; the results show that the importance of the specific surface of Blaine is in a reversal relation with time. For W/C constant, the start and the end of setting time vary according to the substitution rate, the minimum values are obtained for the witness concrete (the pres-

ence of a large quantity of C3A giving a fast setting) as it was proved by Messan, (2006) [11]. The maximal values are obtained for a substitution rate of 15% of the marble wastes fillers. Steadiness The hydration reaction is accelerated by a thermal treatment of the cement paste so that they can note the possible expansion of the cement in a very short time. We check the stability to ensure that the cements do not contain substances causing, over time, a dangerous expansion.

Figure 4: Variation of the steadiness versus the substitution rate

For a specific surface Blaine of marble wastes sand fillers higher than that of cement CEMI, the maximal value is obtained for a substitution rate of 5%, beyond this value, the expansion is a decreasing function and the pointer opening remains always inferior to 10 mm. EFFECT OF MARBLE WASTE SAND FILLERS ON THE MORTAR CHARACTERISTICS Compressive strength In the Figure 5, the effect of the substitution rate on the compressive strength for a specific surface Blaine of marble wastes sand fillers higher than that of cement, is indicated. The best compression performances are given by

the mortar of 5% of substitution rate; the variation in short-term (2, 7 days) is less important than the one in medium and long terms (28, 90days). The substitution rate increase leads to improve the resistance of the witness mortar till a substitution rate of 5% for all terms. Pawar and al, (2014), Caré and al, (2002) [14, 5]; found that this percentage was estimated at 10%, the effect is reversed beyond 5%. Between 0% and 5% of substitution rate, the CaO increases; that gives a high compressive strength, the CaCO3 presence favors the hydration of the C3S from the first moments all the more since the particles are fine (Caré and al, (2002)) [05].

Figure 5: Variation of the compressive strength versus the substitution rate Journal of Applied Engineering Science 15(2017)2, 420

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Said Bedoudi - Valorization and recycling of quarries waste as an addition cement

Benia, (2011) [04] explains that the specific surface of Blaine is proportional to the speed of the hydraulic reaction and the resistance increase in a short term. The C2S reacts slowly, it confers to cement a resistances lower than the C3S, but it develops them in a long-term, that explains the resistances between 28 and 90 days. Flexural strength The best performances are obtained for the formulation of 5% of substitution rate. The order of mixtures classification is the same for all formulations. For a stronger specific surface of Blaine, the different formulations behavior is the same in medium and long terms, the maximal value is obtained for a substitution rate of 5% while the minimal value,

in accordance with the study executed by Rai and al, (2011) [15] is obtained for a rate of 20%. Shrinkage The Figure 7 shows the shrinkage variation according to the substitution rate. The shrinkage variation of 2 days according to the substitution rate is insignificant, the addition effect is more remarkable in the seven day, we can also note a shrinkage increase between 0% and 10% according to the substitution rate, and the speed is the same in 28 days. The shrinkage increase is proportional to the one of age. The grind fineness is proportional to the speed of hydration reactions and the shrinkage, as approved by Care and al, (2002) [05].

Figure 6: Variation of the tensile strength in flexion versus the substitution rate

Figure 7: Variation of the shrinkage versus the substitution rate

CONCLUSION This work is about the study of the salvage of marble wastes sand as an additive in cement. We conclude, from this study, that: • The addition of marble wastes sand fillers leads to ameliorate the cement consistency; 126

they decrease the quantity of C3A. • The stability maximal value is obtained for a substitution rate of 5%. • Adding marble wastes fillers accelerates, in a short term, the mechanical resistance of mortars, for a higher specific surface of Journal of Applied Engineering Science 15(2017)2, 420

Said Bedoudi - Valorization and recycling of quarries waste as an addition cement

•

• •

•

Blaine, which implies that the addition of sand marble wastes sand fillers, with high grinding fineness in cement, allows immediate formwork. The substitution of clinker by sand marble waste sand fillers gives a good mechanical resistance when finesse is really increased. The increase of substitution rate improves the resistance of witness mortar till a substitution rate of 5% for all terms. The best performances, in compressive and tensile strength in flexion, are given by a mortar of 5% of the substitution rate. Introducing sand marble wastes sand fillers leads to increase the cohesion. The grind fineness is proportional to the speed of hydration reactions and the shrinkage. The addition of 5% of marble wastes sand fillers permits to move from CEMI cement of the 42.5 class to CEM II of the 52.5 class for a specific surface of Blaine superior to a specific surface Blaine of cement CEMI.

ACKNOWLEDGMENT The authors would thank the staff of the Civil Engineering Laboratories in Skikda University, the National school of Algiers for their assistance and support during this study’s course and GICA Company (Hdjar EL Soud), for their generous financial support. REFERENCES 1) Amritpal Kaur, Er., Rajwinder Singh, Er. (2015). Strength and duriabilty properties of concrete with partial replacement of cement with metakaolin and marble dust, Int. J. Eng. Res. Tech, 04, 1032-1035. 2) Aruntas, H.Y., Guru, M., Dayi, M., Tekin, I. (2010). Utilization of waste marble dust as an additive in cement production, Mater. Des, 31, 4039–4042. 3) Belaidi, A.S.E., Azzouz, L., Kadri, E., Kenai. S. (2012). Effect of natural pozzolana and marble powder on the properties of self-compacting concrete, Const. Build. Mat, 31, 251–257. 4) Benia, M. )2011.( Influence de la surface spécifique des ciments aux ajouts minéraux sur le comportement mécanique du mortier et du béton à base de matériaux locaux, méJournal of Applied Engineering Science 15(2017)2, 420

moire de magister, Université de Msila. 5) Caré, S., linder, R., Baroghel Bouny, V., De Larrard, F., Charonnat, Y. (2002). Effet des additions minérales sur les propriétés d’usage du béton-plan d’expérience et analyse statique, LCPC. OA33. 6) Corinaldesi, V., Moriconi, G., Naik, T.R. (2010). Characterization of marble powder for its use in mortar and concrete, Constr. Build. Mater, 24, 113-117. 7) Gurumoorthy, N. (2014). Influence of marble dust as partial replacement of cement in concrete, Int. j. Eng. Res. Tech, 3, 734-740. 8) Hameed, M.S., Sekar, A.S.S. (2009). Properties of green concrete containing quarry rock dust and marble sludge powder as fine aggregate, ARPN. J. of Eng and Appl. Scies, 4, 83-89. 9) Hebhoub, H. (2011(. Recycled aggregate substitution for hydraulic concrete « marble waste», Ph.D. Diss, Skikda University. 10) Hebhoub, H., Belachia, M., Djebien, R. (2013). Introduction of sand marble wastes in the composition of mortar, Struc. Eng. Mec, 49, 491-498. 11) Messan, A. )2006). Contribution à l’étude du comportement au très jeune âge des structures mince en mortier, Ph.D .Diss, Montpellier. 12) Neto, C.S., Campiteli, V.C. (1990). The influence of limestone additions on the rheological properties and water retention value of Portland cement slurries, Car-bonate Additions to Cement, ASTM, STP, 1064, 24-72. 13) Niyazi ugri, K. (2013). Role of construction industry wastes on the properties of mortars, J. Sie. Tech, 3, 109-113. 14) Pawar, M., Dewangan, A. (2014). The significance of partial replacement of cement with waste marble powder, Period. Res, 3, 1-6 15) Rai, B., Naushad, H.K., Abhishek, Kr., Rushad, S.T., Duggal, S.K. (2011). Influence of marble powder/granules in concrete mix, Int .j. civil .Stru. Eng, 1, 827-834. 16) Vuk, T., Tinta, V., Gabrovsek, R., Kaucic, V. (2001). The effects of limestone addition, clinker type and fineness on properties of Portland cement, Cem. Concr. Res, 31, 135- 139. Paper sent to revision: 18.12.2016 Paper ready for publication: 03.11.2017. 127

Original Scientific Paper

doi:10.5937/jaes15-12951

Paper number: 15(2017)2, 421, 128 - 139

“URBAN ISLAND” AS AN ENERGY ASSESSMENT TOOL. THE CASE OF MOUZAIA, ALGERIA Boukarta Soufiane* Institute of architecture, University of Blida I, Route de Soumaa, Blida, Algeria Berezowska-Azzag Ewa Ecole Polytechnique d’Architecture et d’Urbanisme, Laboratoire VUDD

Residential buildings in Algeria are responsible for 41% of total country’s energy consumption. In this study, a holistic approach has been adopted to analyze the building stock of a middle-sized city (Mouzaia) in Algeria according to their energy consumption. The purpose of this paper is to test the pertinence of the urban island scale as an energy assessment tool. This study is based on a statistical approach of the islands’ typologies to single out a model able to estimate the energy load of a simple dwelling or for an island according to a set of indicators. Thus, Urban islands were clustered according to their geometrical and physical attributes that considers a large panel of indicators such as island’s area, built-up area, compactness, porosity, land use, areal density, built density, solar admittance and the passive volume. The conclusion of this analysis shows the classification profiles of the building stock of Mouzaia according to their energy consumption with an accuracy level of 86%. Also, this model developed can be implemented to a GIS tool in order to identify within a large scale the different scenarios which could be adopted to reduce the energy load of dwellings. Key words: Algeria, Sensitivity analysis, Existing buildings, Urban islands, Typology, Energy use INTRODUCTION The recent data from APRUE [01] confirms that the residential sector is responsible of about 41% of the energy end use in Algeria. Concretely, this consumption is higher for the electricity (121mtoe) than for the gas 12 mtoe.. Algeria like other countries in the world, has adopted a policy to reduce and control its energy consumption and to mitigate the GHG emissions. This policy can be presented mainly within four adopted strategies: (i) A motivating strategy which encourages the use of more renewable energy by inhabitant to attain the objective of 40% and a decreasing of 27% the carbon emissions by 2030 [01, 04]. To reach this goal, the Algerian government funds 50 % of the total cost of installation of solar water heaters and 45% of the cost to convert cars to natural gas [01, 04]. However, the experience is not well supported by the medias; (ii) pilot project strategy: where a set of prototype buildings have been already tested.However, even if the built pilot projects have got an important insulation rate, the experience showed that there is a gap between research studies and the construction results.

This conclusion highlights the importance of the monitoring in this kind of projects; (iii) Training strategy: Many architects and engineer currently trained in the area of building energy efficiency. Unfortunately, this strategy remains without real impact because of the lack of constraining legislative frame that imposes a particular constructive mode. The existing regulation (DTR) [20], which is considered as a statistic calculator, does not take into account the design parameters, it calculates only the energy budget based on the U-values of the different materials used in the studied building;. (iv) Marketing and management strategy, for which Algeria has performed a labeling system for household appliances [19]. This strategy will also be extended to the building field. The energy policy mastering in Algeria is recent and remains conducted within a top-down approach. At the local level, the energy is not a particular subject of attention, essentially due to the cheaper cost of energy, 5 DZD/Kwh (0.05 €). Also, to satisfy the Algerians’ energy demand, the Algerian government subsidies in energy are about 1.5

* Institute of architecture and urban planning, university Blida 1, route de Soumaa BP 270 Blida (09000), Algerie sofiansasse@gmail.com

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Boukarta Soufiane - “Urban Island” as an energy assessment tool. The case of Mouzaia, Algeria

to 2 billion dollars yearly [18]. Besides, considering the rapid increasing rate of urbanization in the recent years, a more constraining legislative frame could increase the cost and the duration of the operational studies, and causes eventually a delay of the presidential program which aims to build 3 million of dwellings in 15 years [04]. The prospective study of the fossil energy reserves shows a probable limitation in the oil production for the 2030’s horizon of about 700 000 barrel a day, which could quietly cover the national needs [07]. However, the understanding reasons of the important energy consumption in building stock in the Algerian context have not yet been sufficiently highlighted by research in urban studies. Therefore, in this paper, we will focus our attention on the energy consumption of buildings to single out the most relevant parameters affecting the energy consumption and the impact carbon footprint in the context of Algeria. The conclusions of this work will help architects, engineers and decision makers to determine the priorities for energy conservation measures (ECMs) [08] in residential buildings, in order to reduce the environmental impact of CO2 emissions, through the implementation of a realistic and effective action plan. List Of Abbreviations Kwh/m²/y U EPI Mtoe GHG G IS DZD ECMs DEM PCA

Kilowatt hour/m²/year heat transfer coefficient Energy performance index Million Tonnes of Oil Equivalent Greenhouse gas emission Geographical Information System Algerian Dinar Energy conservation measures Digital Elevation Models Principal Component Analysis

STATE OF THE ART Energy assessment methods The research of most relevant parameters influencing the energy demand in residential building has been widely treated in the scientific literature [09]: (i) the occupant behavior: which constitutes the most important uncertainty factor when predicting the energy demand using a simulation model. The occupant behavior varies widely and can increase the energy consumption up to 100% [16]. Several researches [03], [29], [16], [32], [25] and [22] showed that occupant behavior and profile can modify the energy demand Journal of Applied Engineering Science 15(2017)2, 421

from simple to double of the predicted values [10], which is than very difficult to estimate. Generally, according to these studies, we can classify the behavior of occupants in three lifestyles: thrifty one, standard or normal and wasteful lifestyle which consumes energy willingly [12]. Also, it is pointed that predicting an occupant behavior is so complex that some researchers prefer studying spaces with only one person occupancy [idem]. (ii) The design factor: considered as the most studied field. There is mainly two approaches to identify the design impact on the energy demand: (a) Engineering approach [23], [05], [28] and [17], based on determinist algorithm used as a simulation model. This approach is considered by the scientific community as the most accurate one. It allows the isolation of the occupant’s impact and highlights subsequently the importance of other parameters of the building design. But the simulation models’ cost and their technical complexity make them difficult to generalize. Besides, this approach enables us to study the importance of new nonexisting parameters especially the technological ones. (b) Statistical approach, called also historicist approach [10]. It tends to develop models of prediction based on the correlation of the energy end-use with a set of indicators obtained from the existing building stock. It is used at the macro (top-down) scale as well as at the micro scale (bottom-up) [14]. In other hand, the statistical approach is particularly used at the macro scale to appreciate the energy load of a city or country for a long-term period and it is frequently presented within a GIS-based analysis [02]. The main-used descriptors are the socio-economic data, the energy cost and the climatic conditions [16]. On the other hand, at the micro scale, the design parameters commonly used of the existing building stock used are the glazing rate, materials, age of building and household size. The statistical approach is widely used by the European community and it constitutes a legislative framing tool in various countries, such as Italy [06] and Greece [11]. It is nevertheless limited by the strict and limited use of extracted data from the existing building stock, which does not allow introducing new parameters, specifically the technological ones. (iii) Urban context: its importance has been demonstrated by a lot of researchers [23], [28], [24] and [27]. It’s interpreted by the impact of climatic and microclimatic urban conditions which impact the energy demand by about 10% [23] 129

Boukarta Soufiane - “Urban Island” as an energy assessment tool. The case of Mouzaia, Algeria

and estimating an increase up to 50% [24], if we add the transportation field. The urban context influences the solar admittance, lighting, ventilation quality and the urban transportation which is not the objective of this study, but other researchers had already validated this correlation [21]. Thus, a set of parameters, like density and urban heat island, describing the urban context according to its impact on the energy demand of buildings, climatic and microclimatic conditions, has been highlighted by the scientific community. (iv) Building energy systems: used for cooling, heating or lighting. This factor is incontestable and it is possible to predict its impact using the engineering method, but its introduction in a statistical approach requires a ponderous survey in terms of time and costs. Some researchers showed its impact on buildings’ energy load as it has been done for example in the European project TABULA [15] and in Belgium [26]. Sampling methods The state of the art examination lets us to classify the sampling methods into three registers: (i) the Archetype Approach: this approach is based on a DOE, a Design Of Experiments which is a generic building characterized by a set of the design parameters representing correctly the building stock. Parekh (reported by Lukas.G et al) [16] classifies the criteria of structuring a validate archetype in: (a) Geometrical criteria, (b) thermal and (c) operating systems. J.Bouyer [05], in his thesis, has performed a campaign of 2000 simulations by diversifying randomly a set of seven geometrical and physical indicators. (ii) Sampling approach: this method is based on a typology of building which are clustered according to a panel of indicators and every sample building

is assigned by its energy performance index (EPI) (Kwh/m²). To estimate the energy demand of a building, the author of this research checked the rate of similarity between the considered buildings and the identified sample. Once, the similarity is strong enough, the energy demand will be estimated by multiplying the area of the considered building by the performance energy index of the sample. The project Energy and Environment Prediction (EEP) proposes a typology based on an existing building stock which has been characterized by the heated area, façade area, age of the building and the glazing rate [13]. A typology of 100 building has been performed. The land use is not analyzed per se as a factor but introduced via the building function. The scale of analysis is the building one which is generalized [17] to the entire city by interpreting the similarities between the 100 buildings considered as reference and the building stock. Also, and based on the urban bloc as sampling, Maizia.M et al [17] have considered the typology performed by the IAURIF (Institut d’Aménagement et d’Urbanisme de l’Ile de France). 25 urban blocks have been identified based on the geometrical criteria such as the areal density, built density, area, facades perimeter and the mean height of urban blocks. In the same track S.Salat [24] and Manoj Kumar [26] have leaned on the dwelling type as sampling approach. Then, every dwelling typology is characterized by its geometrical and physical criteria. Kumar Singh identifies 5 typologies for the case of Belgium and S.Salat for the French case identifies 6 typologies which are (see Figure.1 below): individual and identical individual dwelling, village type, the collective habitat continuous low, collective habitat continuous high and the collective habitat discontinuous.

Figure 1: Built density (COS) and Housing typology [24]

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Boukarta Soufiane - “Urban Island” as an energy assessment tool. The case of Mouzaia, Algeria

This typology represents correctly all the French cities and also the countries of the Maghreb as Algeria which is our case of study. These similarities are explained by the fact that the major part of the Algerian middle-sized cities has been established at the period of the French colonization. Thus, the tranposability of the sampling method is possible and it allows besides comparing the two sides of the Mediterranean. (iii) Finally, the third method tends to identify the typologies based on equal urban fragment as it has been done by S.Salat [24] who selected different fragments of 200*200m, 400*400m, 800*800m, or Steemers [28] and Ratti.C et al [23] who used Digital Elevation Models (DEM) for a fragment of 400*400m. We must note here that, by selecting this method, S.Salat [24] showed that the urban fragments characterization change with the dimension of the fragment selected which means that we cannot generalize the findings. However, this approach is a very useful to assess and compare side to side different urban fragments as density, compactness and mobility parameters correlated to the energy consumption for each urban fragment. Methodological choice and justification

to evaluate the energy demand in our case is the statistical approach because it represents the real energy consumed and it takes into consideration all the factors impacting the energy demand cited above. (ii) Secondly, the choice regarding the scale for our study is argued by the fact that the scale of a building considered individually risks to eliminate the impact of the urban context, on the other hand, the neighborhood scale doesn’t allow to consider the design parameters of buildings, a neighborhood could shelter in the same time collective habitat, individual dwellings or even mixed one. So, we have selected the “urban island” scale as an intermediate one between the building scale and the neighborhood one. The island scale considered as the principal unit of the urban composition allows considering both, the spatial and functional specificities of buildings. The objective of this research takes into account the pertinence of the scale of the urban island. And (iii) For our paper’s purpose, we have selected the sampling approach. The scale of the sample is here considered at the island scale, and based on its land use and housing typology. The hierarchical identification and characterization of urban islands is conducted within the logic presented in the Table 1 below:

Our methodological choice is organized according to: (i) First, the most advantageous method Table 1: Structure of the sampling method Dwelling type

Chosen criteria

Individual discontinuous

Density built

Areal density

Individual identical

compactness

Solar admittance

Collective continuous

Passive volume

Urban heating island

Collective discontinuous

Housing mean area

Housing per island

Village type

porosity

End use energy

Island area

End use Energy/housing

Based on this table of characterization, we have, firstly, identified every single island according to its housing type by a Google Map scan within the scale of 400*400m, followed by an in situ validation to confirm the urban islands identified. Secondly, every type has been characterized by a Journal of Applied Engineering Science 15(2017)2, 421

set of indicators as presented on Table 1. Thirdly, a sensitivity analysis is performed between the identified indicators and the energy end-use per housing. Then, based on the most important factors, an estimative model is carried out based on a multiple linear regression. Finally, and based 131

Boukarta Soufiane - “Urban Island” as an energy assessment tool. The case of Mouzaia, Algeria

on the Principal Component Analysis (PCA), we have clustered our urban islands into three clusters according to their energy consumption and the most important factors. The section below presents the findings of our approach. RESULTS AND DISCUSSION We have selected the middle-sized city of Mouzaia as case study. Mouzaia was established during the French colonization period, located at 13km from the Mediterranean Sea (36° 28′ 00″ Nord

2° 41′ 00″ East) and it has an altitude of 113m. Its urban density is estimated to 623 inhab/km² [31]. The Climate of Mouzaia city is considered as a temperate one, hot and humid in summer, cold and rainy in winter. The average yearly temperature is 18.1°C. The mean precipitation is about 684 mm. August is the hottest month of the year with an average temperature of 26.4°C and January is the coldest month with 11.1°C as average temperature [30].

Figure 2: location of Mouzaia city [31]

Identification of Island typologies The sampling has been done at the island scale within Google Map. 121 islands have been identified and characterized within the criteria presented in the Table 1 and the identified typology in Table 2. And, a site visit was necessary to confirm the identification of urban islands.

Table 2 below shows that the individual housing constitutes the dominant typology which is a common tendency of all the middle-sized cities in Algeria. It can also be noted that the actual tendency of urbanization is dominated by the spreading of the collective habitat which is mainly located on the city outskirt.

Table 2: Island’s typology and frequency

132

Island typology

Island N

frequency %

Mixed

15.71

Individual discontinue housing

40.50

Individual continue housing

11.57

Collective discontinue dwelling

20.66

Collective continue dwelling

2.47

Equipment

7.43

Village type

1.66

Total

121

100

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Boukarta Soufiane - “Urban Island” as an energy assessment tool. The case of Mouzaia, Algeria

Sampling: By applying the quota sampling method we have reduced the number of island to be studied from 121 to 31 respecting a good representation of the entire islands according to their frequency in the city. Data collection and Islands Characterization After the examination of the current state of the art, we have selected a set of indicators to characterize the urban islands selected for the study: (i) Areal density (Ad) represents the ratio of built area to the island area. (ii) Built Density (Bd) is calculated by the ratio between the sum of all the floors’ built area and the island area. (iii) The compactness (S/V) determines heat loss and gain of buildings. It is estimated by the ratio be-

tween the envelope areas of the building and its volume. (iv) Passive volume corresponds to the volume part of a building which is naturally heated, ventilated and lighted. Its depth is commonly estimated by twice the height of each floor [24]. (v) The solar admittance (As) allows estimating the solar potential of an urban island or an individual building. It’s estimated by the ratio between the sum of all the facades areas according to their orientation coefficients and the sum of all the areas façade. (vi) Porosity (Po) considers the urban ventilation potential. It’s estimated by the difference between the volume built and the volume of the void between buildings. (vii) The Energy end use of the selected islands has been acquired from “Sonelgaz”, the firm in charge to invoice the energy consumption in Algeria.

Figure. 3: Island typology map

We note that the energy consumption obtained represents the gas and the electricity. But, we choose to aggregate the data on the table 3 below for synthesis reasons. Also, we couldn’t acquire all the islands’ energy consumption. The islands’ missing data are 17, 18, 22, 23, 24, 25 and 65 and are presented on the table by NI (Not identified). This missing data can reduce the ac-

Journal of Applied Engineering Science 15(2017)2, 421

curacy of the estimative model and reduce by the way the number of the islands studied to 21. In addition, for every single island we have identified its area, number of housing per island and its built area. The calculated and collected data is presented on the Table below.

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Boukarta Soufiane - â&#x20AC;&#x153;Urban Islandâ&#x20AC;? as an energy assessment tool. The case of Mouzaia, Algeria

Table 3: Island characterization Isl

Type

E (kwh)

Ind-C

0.46

1.38

0.40

0.80

108166

Ind-C

0.46

0.92

0.39

0.80

86051

Ind-C

0.53

1.06

0.38

0.60

135441

Mixed

0.62

1.24

0.48

0.59

130316

Mixed

0.43

1.29

0.33

0.81

80709

Ind-C

0.42

1.26

0.48

0.82

98211

Mixed

0.62

1.24

0.33

0.79

86127

Mixed

0.62

1.24

0.34

0.79

132767

Ind-C

0.54

1.08

0.26

0.80

81062

Mixed

0.52

1.04

0.37

0.78

76559

Mixed

0.63

1.89

0.35

0.80

107166

Ind-C

0.68

2.04

0.30

0.79

125808

Mixed

0.40

0.80

0.34

0.80

92322

Mixed

0.51

1.02

0.51

0.81

66981

Mixed

0.45

0.57

0.80

123127

Mixed

0.56

0.52

0.80

61470

Mixed

0.36

0.72

89.51

0,42

0.79

N-I

Mixed

0.37

0.74

92.92

0,41

0.81

N-I

Mixed

0.35

0.70

91.79

0,41

0.80

N-I

Ind-D

0.32

0.64

98.98

0,43

0.81

N-I

Ind-D

0.41

0.82

88.3

0,42

0.79

N-I

Mixed

0.33

0.66

98.56

0,43

0.80

N-I

Col-D

0.2

1.00

100

0,40

0.81

N-I

C-Ind

0.92

1.84

71,77

0,29

0.80

N-I

C-Ind

0.55

2.2

91,44

0,29

0.81

N-I

Col-D

0.55

2.75

100

0.19

0.80

155382

111

Col-D

0.28

1.4

100

0.29

0.79

162147

112

Col-D

0.23

1.15

100

0.31

0.80

82330

113

Col-D

0.26

1.3

100

0.30

0.80

153020

114

Col-D

0.25

1.25

100

0.28

0.78

46489

Where: Ind-C: Individual continuous housing/ /Mixed: Individual+facilities /Ind-D : Individual discontinuous housing /Col-D : collective discontinuous dwelling / Col-C : collective continuous dwelling. Predicting model

portance of each selected indicator. All the indicators show a significance rate (P value) below 0.05 except the solar admittance which affect the energy end-use by -24.9% and the built density with a negative correlation of -37.2%, as shown on the Table below.

By performing a bivariate correlation (2-tailed) between the energy end-use per housing and a set of indicators we have estimated the im-

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Journal of Applied Engineering Science 15(2017)2, 421

Boukarta Soufiane - “Urban Island” as an energy assessment tool. The case of Mouzaia, Algeria

Table 4: Bivariate correlation

Parameters built area housing per island solar admittance compactness passive volume Built density Areal density porosity

EEU/housing (R) 78.2 -78.4 -24.9 -50.2 -58.9 -37.2 -68.6 -68.6

sig .000** .000** .276* .02** .005** .097* .001** .001**

**Correlation is significant at the 0.05 level (2-tailed). *Correlation is not significant at the 0.05 level (2-tailed)

But, once we perform a multiple linear regression, the most relevant model considers only three main indicators which are the housing mean area, areal and the built density (see table. 6). The model

has a coefficient of correlation (R) of 0.927 and R² 0.86 which means that the model has a good potential of estimation. We have selected the third model according to its higher value of the R².

Table 5: Accuracy of the estimative models model

R²

R² adjusted

Standard error

,816

,665

,647

114,55581

,887

,787

,763

93,91634

,927

,860

,835

78,30257

Table 6: The selected (3) estimative model

Model (Constante) Housing mean area Areal density Built density

Coefficient 355,024 ,558 830,684 -132,655

Using this model we can estimate the energy end-use per housing based on the model described on the table above. Then, all the city of Mouzaia could be represented and we can also use this model to implement a Geographical Information System (GIS) to assess and compare the different scenarios by changing the input values which are the areal density, the built density and the mean area per housing in the model equation presented below. EEUh=355.024+0.558HMA+830.68Ad–132.65 Db With: EEUh - is the energy end use per housing HMA - is the housing mean area Ad - is the areal density of the island Db - is the built density

Journal of Applied Engineering Science 15(2017)2, 421

Standard error 74,829 ,170 172,090 44,480

Sig. ,000 ,004 ,000 ,008

Energy profiles To carry out the islands energy profile we have performed Principal Component Analysis based on the most relevant indicators obtained by the estimative model which are: the housing’s mean area, areal density and the built density. We have added to the PCA, the compactness and the density of housing per island. This PCA would help architects and urban designers to improve their architectural housing design at the earlier stage. The PCA’s representation quality is 82.96% which means that the typology of urban islands is correctly presented.

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Boukarta Soufiane - â&#x20AC;&#x153;Urban Islandâ&#x20AC;? as an energy assessment tool. The case of Mouzaia, Algeria

Figure 4: Islands selected by the quota method

Based on this PCA representation, we have performed a scatter diagram of the 21 island and we have marked them according to their correspondent clusters. We can distinguish three classes: (a) Cluster 1 represented by the red color and it has a frequency of 52.4% on our sample. It is characterized by the most important Energy end use per housing, areal density and mean area per housing. In the other side, this class has the weakest rate of housing per island and built density. Its compactness is average to intermediate between the two classes 2 and 3.

(b) Cluster 2 represented by the orange color and its sample frequency is 19%. It is mainly composed by individual continuous housing and mixed islands. The energy end use of this class is average between the classes 1 and 3. Itâ&#x20AC;&#x2122;s characterized by an average areal density, built density and mean area per housing. Its compactness is also average but we note that the most compact island is present in this class and the same island has the weakest value of built density and housing per island.

Figure 5: The PCA map

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Journal of Applied Engineering Science 15(2017)2, 421

Boukarta Soufiane - “Urban Island” as an energy assessment tool. The case of Mouzaia, Algeria

(c) Cluster 3 represented by the green color and it represents 28.6% of our sample. It represents the best cluster in term of energy consumption per housing compared to cluster 1 and 2 and it’s only composed by the collective discontinuous dwellings. This cluster has the most important value of built density and housing by island. It has the weakest rate of areal density, mean area per housing, and compactness. The compactness is calculated at the island scale and if we consider the compactness per dwelling, the

value has to be lesser. This could be explained by the calculation method which considers the entire collective dwelling per island. If we take an island of collective dwelling we can get two rate of compactness, the first one at the island scale, which we have considered in the PCA performed. And the second one could be calculated at the scale of the dwelling where the compactness has to be lesser and explain more better the situation of the compactness in this cluste.

Figure 6: Islands classification

CONCLUSION In this paper we choose the urban island as an energy assessment tool and selected Mouzaia, a middle-sized city in Algeria, to test the pertinence of the urban island scale. We selected the statistical-based approach instead of the engineering method because the purpose is to study the real impact of the urban island’s parameters on the energy consumption which is very difficult to estimate using the engineering one. The sample method was based on housing typology and land use. Every urban island is characterized by a set of indicators to correlate them with the energy consumption per housing. We have carried Journal of Applied Engineering Science 15(2017)2, 421

out an estimative model based on the built density, areal density and the housing’s mean area. Also, we have performed an island energy profile basing on a PCA, and by considering in addition to the indicators cited above, the density of housing per island and the compactness. Three energy profiles were identified and the most efficient island, in our case study, is the collective discontinuous one. Our findings match the results of S.Salat [24] and Giuliano [10] who has performed for the region of Lombardy in Italy a model to predict energy end use based on the compactness factor and his model was above 70% of accuracy. In our case, the compactness has a determination coefficient of 50.2% which is 137

Boukarta Soufiane - “Urban Island” as an energy assessment tool. The case of Mouzaia, Algeria

closer from the Giuliano [10] model. This difference could be explained by impact of the occupant behavior which varies from country to country and city to city. The developed model could be also implemented to a GIS tool which allows a large scale study to compare the scenarios of the potential saving energy according to the variation in terms of the built density, areal density and the housing’s mean area. Also and finally, the island scale could also be considered to study in addition the housing parameters, other phenomenon such as microclimatic phenomenon in particularly the impact of urban heat island. REFERENCES 1) Aprue, M. . Final report, “Consommation Energétique Finale de l’Algérie, Chiffres clés Année 2012”. Retrieved from http://www.aprue.org.dz/ 2) Alessio Mastruccia Olivier, (. (2014). Estimating energy savings for the residential building stock of an entire city: A GIS-based statistical downscaling approach applied to Rotterdam. Energy and Buildings, 75, 358-367. 3) Bartiaux, F. (2003). A socio-anthropological approach to energy-related behaviours and innovations at the household level. In Summer study: Time to turn down energy demand. dynamics of consumption. (pp. 12391250). 4) Bouamama Wahiba, (2013). Au Sujet De La Politique D’efficacité Energétique En Algérie : Approche Systémique Pour Un Développement Durable.Cas De : Programme Eco-Bat Cnerib. magister thesis, university of tlemcen. 5) Bouyer, J. (2009). Modélisation et simulation des microclimats urbains - Etude de l’impact de l’aménagement urbain sur les consommations énergétiques des bâtiments. PHD thesis, université de Nantes. 6) Caputo, P., Costa, G., & Ferrari, S. (2013). A supporting method for defining energy strategies in the building sector at urban scale. Energy Policy, 55, 261-270. 7) Cherfi souhila, (2010). L’avenir energetique de l’algerie : quelles seraient les perspectives de consommation, de production et d’exportation du petrole et du gaz, en algerie, à l’horizon 2020-2030 ?. recherches economiques et manageriales, 7, 27-49. 8) Constantinos A. Balarasa, G.(. (2007). Euro138

pean residential buildings and empirical assessment of the Hellenic building stock, energy consumption, emissions and potential energy savings. Building and Environment, 42, 1298-1314. 9) Corgnati SP, F. (2013). Reference buildings for cost optimal analysis: method of definition and application.. Applied Energy, 983-993. 10) Dall’o’, G., Galante, A., & Torri, M. (2012). A methodology for the energy performance classification of residential building stock on an urban scale. Energy and Buildings, 48, 211-219. 11) Dascalaki, E.G., Droutsa, K., Gaglia, A.G., Kontoyiannidis, S., & Balaras, C.A. (2010). Data collection and analysis of the building stock and its energy performance: An example for Hellenic buildings. Energy and building, 42, 1231-1237. 12) Hong, T., & Wen Lin, H. (2012). Occupant Behavior: Impact on Energy Use of Private Offices. In: 1st Asia conference of International Building Performance Simulation Association. 13) Jones, P.J., Lannion, S., & Williams, J. (2001). Modelling building energy use at urban scale. In: Seventh International IBPSA Conference, Rio de Janeiro. Brazil.13-15. August. 14) Kavgic, M., Mavrogianni, A., Mumovic, D., Summerfield, A., Stevanovic, Z., & DjurovicPetrovic, M. (2010). A review of bottom-up building stock models for energy consumption in the residential sector. Building and Environment, 45, 1683-1697. 15) Loga, T., Diefenbach, N., & eds., (2010). Use of building typologies for energy performance assessment of national building stocks, existent experiences in European countries and common approach. In First TABULA Synthesis Report. June. Retrieved from www.buildingtypology.eu/downloads/ public/docs/report/TABULA SR1.pdf 16) Lukas, G., Swan, V., & Ugursal, I. (2009). Modeling of end-use energy consumption in the residential sector: A review of modeling techniques. Renewable and Sustainable Energy Reviews, 13, 1819-1835. 17) Maïzia, M., Sèze, C., Berge, S., Teller, J., Reiter, S., & Ménard, R. (2009). Energy Requirements Of Characteristic Urban Blocks. Journal of Applied Engineering Science 15(2017)2, 421

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18) In: Proc. Of CISBAT: Renewables in a changing climate: From Nano to urban scale. 19) Mebtoul Abderahmane, (2013). Quelles perspectives énergétiques pour l’Algérie. CDER, Preuzeto sa http://portail.cder.dz/ spip.php?article2958 20) Ministère de l’énergie Aprue, (2010). receuil de textes legislatifs et réglementaire sur la maitrise de l’énergie. U . Algeria. 21) Ministère de l’habitat et de l’urbanisme, C. (2004). DTR C3.2, Règlement Thermique des Bâtiments d’Habitation et Règles de Calcul des Déperditions Calorifiques, 22) Newman, P., & Kenworthy, J.R. (1995). Sustainability and Cities: Overcoming automobile dependence. Washington DC: Island Press. 23) Ouyang, J., & Hokao, K. (2009). Energy-saving potential by improving occupants’ behavior in urban residential sector in Hangzhou City. China, Energy and Buildings, 41(7), 711-720. 24) Ratti, C., Baker, N., & Steemers, K. (2005). Energy consumption and urban texture. Energy and Buildings, 37, 762-776. 25) Salat, S. (2011). Les villes et les formes urbaines: sur l’urbanisme durable. In Hermann (Ed.), . France. 26) Shakouri Hassanabadi, M., Banihashemi, S., & Rasouli Javaheri, A. (2012). Analysis and Comparison of Impacts of Design Optimization Approaches with Occupant Behavior on Energy Consumption Reduction in

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Residential Buildings. IACSIT International Journal of Engineering and Technology, 4(6), December. 27) Singh, K.M., Mahapatra, S., & Teller, J. (2013). An analysis on energy efficiency initiatives in the building stock of Liege, Belgium. J. Energy Policy, 62(7), 29-741. 28) Steadman, P. (1979). Energy and patterns of land use. U Energy conservation through building design, Watson, D. McGraw-Hill. (str. 246-260). New York. 29) Steemers, K. (2003). Energy and the city: Density, buildings and transport. Energy and Buildings, 35, 3-14. 30) Subrémon, H. (2009). Pour une anthropologie sensible de la consommation d’énergie. Université de Paris X - Nanterre. Thèse PHD en sciences sociales pour l’obtention du doctorat de sociologie Habiter avec l’énergie. 31) Weather Data Retrieved from http://meteo.dz 32) Yearbook of Algerian cities Retrieved from http://m.annuaire-mairie.fr 33) Yu, Z., Fung, C.M., Haghighat, F., Morofsky, E., & Yoshino, H. (2011). A systematic procedure to study the influence of occupant behavior on building energy consumption. J. Energy and Buildings, 43, 1409-1417. Paper sent to revision: 16.01.2017. Paper ready for publication: 24.04.2017.

139

Original Scientific Paper

doi:10.5937/jaes15-13159

Paper number: 15(2017)2, 422, 140 - 148

TRUNK ASYMMETRY AND SPRUCE WOOD RESONANT PROPERTIES VARIABILITY WITH RESPECT TO THE CARDINAL POINTS AND THE TREE HEIGHT Vladimir Ilyich Fedyukov* Volga State University of Technology, Russian Federation Ekaterina Yurevna Saldaeva Volga State University of Technology, Russian Federation Maria Sergeyevna Chernova Volga State University of Technology, Russian Federation Vasilii Yurevich Chernov Volga State University of Technology, Russian Federation Decks of musical instruments are developed from sawn wood products of strictly radial cutting and, as a rule, for this purpose the wood is selected according to the radius of a trunk from a certain forest site. An important factor for manufacturing high-quality (custom-made) musical instruments is the account of position of the best zone of a tree trunk with respect to the cardinal points. Observance of this condition becomes complicated by the fact that frequently trunks have the form of an abnormal cylinder with a displaced and curved axis (asymmetry). Physical and mechanical properties of wood vary greatly along trunk height; it is sometimes difficult to define the part of trunk wood with the best acoustic parameters. The paper presents the following research results: external and internal asymmetry of spruce trunks; macrostructures and acoustic constants of wood on northern and southern sides of a trunk; changes of cross-section sound velocity in wood along tree height and depending on the trunk diameter; dependence of sound velocity in wood on biometric data of a trunk. Based on the results of the experiment done, the estimation of cardinal points and position of wood at trunk height influencing the parameters of its ‘musicality’ is made. The data obtained and conclusions of the research are of scientific interest and bear practical recommendations for correct selection of wood with unique acoustic properties from a spruce-tree trunk. Key words: Ascoustic constant, Internal and external tree trunk asymmetry, Resonant properties, Spruce growing, Wood macrostructure, Wood density

INTRODUCTION No practical value is usually given to and change of wood properties depending on its facing the cardinal points is not taken into account with forest products of general and special purpose, including timber blanks and parts for manufacturing musical instruments for wide use. It is considered, e.g., that the cardinal points do not considerably influence the contents of late wood, and eccentric growth of a trunk is caused mainly by the impact of other factors: non-uniform development of a tree crown, exposure to wind, etc. [19]. Meanwhile, in ancient times, violins and other musical instruments master craftsmen paid special attention to selection of material from a

tree-trunk for making custom-made instruments. Many of them preferred wood from the northern side of a tree trunk, and they saw ‘the best firewood’in the southern part of a tree trunk [10]. There are practically no special scientific research works concerning dendro-acoustical differences of wood depending on the cardinal points. However there are data on macrostructure and anatomical structure peculiarities of different sectors of a tree trunk. It is also necessary to note, that from time immemorial there is a standard opinion on tree annual rings orientation with respect to the cardinal points: the part of a tree facing the south has wider annual rings than the parts facing other cardinal

* Volga State University of Technology, 424000, The Republic of Mari El, Yoshkar-Ola, Lenin Sq., b. 3., Russia fedzyukovvi@volgatech.net

140

Vladimir Ilyich Fedyukov - Trunk asymmetry and spruce wood resonant properties variability with respect to the cardinal points and the tree height

points. This opinion is considered so constant that it is assigned a value of a natural surveyor’s compass for defining the meridian fora given locality. Some authors attempted to check up the position of poles in the geological past and courses of carboniferous zones to find out conditions of their formation by studying standing fossil stubs in order to define the directions of mineral coals search [14]. From the view point of wood science, the work of N.L. Kossovich is of great interest presenting the following results through the example of research of the pine and the spruce [13]: • during the first 30 years of growth the contents of late wood prevails on the southern side of a pine tree trunk at height of 6.5 m when, in the opinion of the author, the influence of the cardinal points on formation of macrostructure is shown more strongly, whereas at height of 13.1 m it is not observed, while at the age of more than 30 years the difference is observed towards both increase and decrease at these heights; • on the southern side of a trunk false annual rings occur more often, namely, 7 times in 8 cases; • at an early age, approximately up to 10 years, wider annual rings appear on the southern part of a trunk, and at the age over 10 years they are found on the northern one; in the latter case this difference makes 3-4 %; • it is important to note, that in comparison of a shade-tolerant spruce and a light-demanding pine the difference of the average contents of late wood on the northern and southern sides of a trunk was not found out; • there is an essential difference between the northern and the southern parts of a pine trunk in anatomical structure. For example, wider tracheids occur more often on the southern side and narrow ones, on the contrary, occur relatively less often; the maximum southern tracheids lay in the group of 30-40 microns, and the northern ones lay within the limits of 20-30 microns. The author describes intrinsic peculiarities of the pine and the spruce in view of the contents of vertical resin ducts. So, if the pine does not have sharp difference between the northern and the southern sides in this respect, spruce wood has much more vertical resin ducts on the northern side of a trunk; in the bottom part of a tree this difference increases more than threefold.

Journal of Applied Engineering Science 15(2017)2, 422

In recent years there were scientific results, confirming distinction of a gain of annual growth rings of wood on the example of a white acacia; on the southern and east parties of a trunk annual growth rings are much wider, than on the northern and western parties; the author assumes the reason of such distinction in day length and temperature of a cambial layer on parts of the world [12]. The scientific results submitted above confirm the necessity of purposeful studying of spruce wood within the framework of the research under consideration. The choice of the material given is caused by its wide application in the manufacture of many kinds of musical instruments. This is connected with the fact that macrostructure parameters (width of annual rings and late wood contents) are included in national standards of many countries as the basic criterion for selecting resonant forest products. The role of microstructure in formation of acoustic properties of wood is studied and confirmed in early research works which results are published last century [02, 11, 18] and a current one [05, 06, 07]. The data on fluctuation of wood density values inside a tree trunk are of great practical interest under selection of material for manufacturing resonant assortments; material porosity which substantially influences acoustic parameters, e.g., velocity of sound and its frequencyamplitude response is connected to density. Therefore, in the work under consideration, density was studied in interrelation with the dynamic modulus of elasticity and the sound velocity included in the formula for defining acoustic constant as the basic criterion of wood ‘musicality’ according to formulas for sound velocity and Young’s dynamic modulus in wood. MATERIALS AND METHODS The research was carried out on the territory of Kirov and Perm regions belonging to the zone of taiga woods of Russia in respect of forest growth conditions. Research plots are presented by stands of mature spruce trees at the age of 120-150 years and of II-III bonitet classes in view of productivity. The asymmetry was studied on trunk collars of circular saw cuts 50 mm thick from 9 average spruce trees (characteristic average ones for the forest research plots) at trunk height of 1.3 m and at its different relative heights: 0.2 Н; 0.5 Н; 0.7 Н (Figure 1), where Н is the height of a tree.

141

Vladimir Ilyich Fedyukov - Trunk asymmetry and spruce wood resonant properties variability with respect to the cardinal points and the tree height

and the same diameter strictly; basically, Аint characterizes the bias of medullary sheath from the trunk center (Figure 2, b).To perform these measurements the diameter was selected where there was a maximal difference in size of radii R and r. Diameters and radii were measured in four directions: north-south (NS); eastwest (EW); south-east – north-west (SENW); south-west – north-east (SW-NE). Research into revealing the difference between the southern and northern sides of a trunk in respect of macrostructure, wood density and acoustic constant were carried out by means of cores selected with increment borers. The method revealing standing resonant wood by means of cores has been researched rather recently [3, 4, 9]. For this purpose cross-section radial cores 4.0 mm in diameter were taken from the northern and southern sides of sample trees with an increment borer before cutting (Figure 3).

Figure1: Sample selection chart

Before average trees cutting the marks were made on their trunks approximately at breast height with respect to four cardinal points which were then transferred onto the wood samples studied for revealing external and internal asymmetry (Figure 2).

Figure 3: Wood (core) sampling from a standing tree with an increment borer: a - on a tree; b - main axes of core anisotropy Figure 2:Trunk asymmetry factors(boon bias): а - external asymmetry, Аext = D/d ; b - internal asymmetry, Аint=R/r

External asymmetry,Аext,was defined as the ratio of D maximum diameter (with indication of a direction in respect of the cardinal points) to d minimum one (Figure 2, а). Internal asymmetry,Аint,(boon bias according to GOST 2140 ‘Flaws in wood’)was studied through the ratio of R larger radius to r smaller one at one

142

As a rule, wood structure along the length of a radial core is non-uniform and, accordingly, physical and mechanical parameters of heartwood and sapwood differ from each other. This difference is well appreciable even with the naked eye, first of all, because of the wood macrostructure: narrow annual growth layers in a peripheral zone of a trunk and wide ones close to juvenile zone(Figure 4, а).

Journal of Applied Engineering Science 15(2017)2, 422

Vladimir Ilyich Fedyukov - Trunk asymmetry and spruce wood resonant properties variability with respect to the cardinal points and the tree height

Figure 4:General view of wood macrostructure according to the trunk zone: a - elements of wood macrostructure (EW - early wood; LW - late wood; AL - annual layer); b - scheme of core division according to zones (N – near-core zone; W– working zone; U–undercork zone)

Generally, rather homogeneous wood between under cork and core zones is taken for deck manufacturing. Taking this fact into consideration, we studied this part of a trunk conditionally marked by letter W, Working zone, on cores (Figure 4, b).

Basic physical and dendroacoustical properties of wood, namely, humidity, density, macrostructure, velocity of ultrasound, were defined in laboratory environment. The general order of complex research is presented in Figure 5.

Figure 5: Principle diagram of experimental measurements

Wood macrostructure was studied with electronic dendrometer (Figure 5, 2. Macrostructure) which action principle is based on defining the width of early (b1) and late (b2) zones in annual rings according to their micro hardness [16]. Sound velocity in wood (С) was defined using pulse ultrasonic method through fixation of elastic longitudinal wave propagation time (τ) along the sample (l):

It is necessary to note, that a piezoelectric transducer with 60 kHz frequency was used in the device, which is optimal for wood studies. The sound velocity in the material and the material density, ρ,given, it is possible to define Young’s dynamic modulus,Е, from the following known ratio:

(2)

(1) Journal of Applied Engineering Science 15(2017)2, 422

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Vladimir Ilyich Fedyukov - Trunk asymmetry and spruce wood resonant properties variability with respect to the cardinal points and the tree height

It is known, that today acoustic constant of sound radiation (К) suggested by academician N.N. Andreyev [01] is accepted as basic criterion of ‘musicality’ of the given material in many countries: (3) Note. Threshold value is K ≥ 12.0 m4/kg•s for resonant wood in a longitudinal direction along fibers, and under cross-section radial measurements K ≥ 3.5 m2/kg•s [08, 19]. Small transformations and joint solution of equations 2 and 3 allow to define the size of acoustic constant К through С and ρ:

(4)

Thus, the physical essence of resonant wood represents combination of incongruous properties, i.e., high indices of rigidity, sound velocity and low density. Variability of sound velocity in wood along the height of a trunk was studied on 16 newly felled spruce trees. For this purpose the velocity of ultrasonic signal across a trunk was measured at standard height of 1.3 m and at rela-

tive levels of 0.2Н, 0.5Н and 0.7Н with the help of УК-14П device; for best contact of piezoelectric transducers with wood the places of measurements were carefully cleared of bark and cambium. The diameter of spruce trees varied within the limits of 30-40 cm at breast height, and their height was 23-28 m(Figure 1). At the moment of measurements wood moisture content humidity obviously exceeded the limit of saturation of its cellular walls, which allowed to make velocity calculations without correction for influence of humidity; physical and mechanical properties of wood depend almost not at all on its moisture content humidity above the given limit (W ≈ 30 %). Sound velocity at relative heights of trees gives rather precise representation on the dynamics of resonant properties of wood along a trunk even without acoustic constants representation. This is due to the fact that according to formula 4 sound velocity at the given density of material predetermines its resonant properties; besides, the density of spruce wood in a longitudinal direction of a trunk varies insignificantly [17]. Since the diameter of a tree changes with its height, the nature of trunk diameter influence on cross-section sound velocity was studied simultaneously on the same 16 sample trees.

Table 1: Spruce tree trunks asymmetry indices on separate cuts External asymmetry tree (cut) index number

144

Asymmetry direction

Д, mm

d, mm

*1-III

E-W

417

2-II

SE-NW

*3-II

Internal asymmetry Аext

Asymmetry direction

R, mm

408

1.02

W-E

355

332

1.07

SE-NW

328

299

*4-I

SE-NW

359

*5-I

N-S

6-IV

r, mm

Аint

218

199

1.10

N-S

176

156

1.13

1.10

SE-NW

184

144

1.28

350

1.03

SE-NW

202

157

1.29

359

355

1.01

N-S

189

170

1.11

SE-NW

336

328

1.02

W-E

180

149

1.21

*6-V

N-S

319

317

1.01

S-N

169

150

1.13

7- VII

N-S

299

290

1.03

NW-SE

162

135

1.20

8-I

SE-NW

332

326

1.02

NE-SW

174

152

1.14

8-III

E-W

298

294

1.01

NW-SE

155

139

1.12

*9- II

SE-NW

330

313

1.05

NW-SE

183

147

1.24

Journal of Applied Engineering Science 15(2017)2, 422

Vladimir Ilyich Fedyukov - Trunk asymmetry and spruce wood resonant properties variability with respect to the cardinal points and the tree height

Notes. Index number of a cut coincides with relative height of its measurements on a trunk, e.g., I and II mean 0.1Н and 0.2Н, accordingly. *Cuts where the contingency of external and internal asymmetry of a trunk in one direction is found out. Despite of some divergences, estimation of the data obtained by Student’s test has not confirmed reliability of difference of average values of radii in all the directions measured. Thus, the following conclusions can be drawn based on the results of spruce trunks asymmetry studies: • there is no precise longitude-latitude regularities in formation of both external and internal asymmetry of spruce trunks; obviously, other factors come out here, e.g., light and wind modes, macro-and microexposition of the locality, tree inclination, etc. which in aggregate negate the influence of the cardinal points on asymmetry and corresponding physical and mechanical properties of wood formation • internal asymmetry has a greater absolute value than external one, and they do not always coincide in direction: quite externally round trunks have explicit asymmetry in the position of medullary sheath;

• internal asymmetry along one and the same trunk can vary both in direction and in value. Quite probably, this is connected with the fact that during different periods of growth a tree is exposed to unequal impact of certain factors of the environment, and, as a consequence, convolute trunks are quite frequently formed which are rather well appreciable even by sight based upon the inclination of wood fibers; it is also possible to assume, that medullary sheath does not always remain strictly vertical, has small bias against the trunk axis during certain periods of tree growth for some reasons, but all this is necessary to be proved. Macrostructure and acoustic constant of wood on the northern and southern sides of a trunk. Initial comparison of trees has shown that there are some differences in macrostructure and dendroacoustics on the northern and southern sides of a trunk. However these differences come out individually both on separate trunks and plots. For example, it is found out that on a plot with rather bad growth conditions (bilberry spruce forest) the contents of late wood on the northern side is less than on the southern one.

Table 2: Average indices of spruce tree trunks wood macrostructure and acoustic constant Index name

Northern side

Southern side

Х±т

Units of meas.

Tree ring width or Anual ring width

1.63+0.02

1.58+0.02

Late wood content

30.59±1.86

30.83±2.02

Acoustical constant

m4/ kg•s

3.52+0.07

3.41±0.09

Average data on the objects and trees are given in Table 2. Note.The indices of acoustic constant are given for standard moisture content of wood, W = 12%. Based on the research results, it is possible to note that macrostructure and acoustic constants of wood at a certain height inside trunks have, on the average, identical indices irrespective of the cardinal points. The check of uniformity of the data obtained by Student’s test at 0.05 level of significance have confirmed the absence of authentic difference in these indices on the northern and southern sides of spruce trees. Journal of Applied Engineering Science 15(2017)2, 422

Change of sound cross-section velocity in wood along the tree height and depending on its diameter. The research results show that the velocity of sound in wood across the trunk depends on individual peculiarities of trees and can vary within the limits of 1000-1800 m/s; the factor of variation amounts to about 35 %. There is a certain regularity of increase in sound velocity moving from the stem base to the top, which is expressed through first order equation y = 143.0x + 66.3; this regularity is illustrated in Figure 6.

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Vladimir Ilyich Fedyukov - Trunk asymmetry and spruce wood resonant properties variability with respect to the cardinal points and the tree height

Figure 6: Changing of sound cross-section velocity in wood along the trunk height

Unfortunately, the opportunity of longitudinal selection of the given material is essentially limited in comparison with cross-section selection, especially last years in connection with reduction of resonant spruce trunk thickness. Nevertheless, carrying out acoustical diagnostics and maximal use of resonant wood on the length of forest products gains special practical value now. Relationship of sound velocity in wood and biometric data of a trunk. To study this question, diameters of a trunk at height of 1.3 m (D1.3) and at relative heights 0.2 Н, 0.5 Н and 0.7 Н (D02, D05, D07, accordingly) are taken as analyzed indices. Due to significant dispersion of the results of measuring ultrasound velocity in wood across trunks (by diameter), we consider only one-factorial quadratic equations of regression, as artificial increase of equations accuracy at the expense of their complication will reflect casual fluctuations of control points. The nature of trunk diameter impact on sound velocity at different levels of its height is expressed through the following parabolic equations (their graphic representation is given in Figure 7): at the height of 1.3 m:

(6) (7) (8)

Note: The diameter ismeasured strictly in NS direction. Check of the results obtained against Fisher’s ratio test has shown that all equations of regression are n ot significant. Hence, it is possible to speak about the absence of total regularity of trunk diameter impact on sound velocity. C-curves have little difference in nature depending on diameters of a trunk at different levels, i.e. the degree of relationship is practically identical here; obviously, except for an absolute diameter value there are other factors which give rather significant dispersion of velocity of ultrasonic signal passing across the tree trunk.

(5)

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Vladimir Ilyich Fedyukov - Trunk asymmetry and spruce wood resonant properties variability with respect to the cardinal points and the tree height

Figure 7: Dependence of sound velocity on trunk diameter at its different levels: a - at the height of 1.3 m; b – 0.2 Н; c – 0.5 Н; d – 0.7 Н

CONCLUSION On this stage of research the basic conclusion consists in the fact that obligatory use of wood from the northern side of a tree trunk cannot be considered a common rule and criterion for manufacturing decks of musical instruments; however, in certain growing conditions, trees can have the best resonant wood on the northern side in comparison with other sides of a tree trunk. Hence, despite the lack of regularity in formation of dendroacoustic properties in respect of the cardinal points, one should not ignore the technique of wood selection for manufacturing musical instruments accepted by ancient masters (using separate sectors of a trunk). Even in case of absence of difference in acoustic parameters, the instrument made of wood from one trunk sector gives somewhat greater effect than the one made of wood from other parts of a trunk; it is known that selection of monogamous material is of especially great value for manufacturing so-called custom-made instruments with unique acoustic properties required [20].The top part of a trunk differs from the bottom one in better acoustic properties. The results obtained mainly Journal of Applied Engineering Science 15(2017)2, 422

confirm the existing opinions of scientists and experts that long ago, when there were opportunities to select rather thick spruce trees, masters, as a rule, used to collect wood at 4-6 m apart the spruce stem base for manufacturing decks of musical instruments [15]. In case of necessity to take strictly radial cores as test samples for carrying out scientific research, it is not enough to be guided by the generatrix forming a trunk, and repetitive coring along mutually perpendicular radii is required. If it is required to be limited to one drilling, it is necessary to use indicating transducers for defining the boon position. The main thing, in both cases it is necessary to specify the direction of drilling on a core with respect to the cardinal points, and in order to obtain reliable results it is expedient to analyze identical samples, e.g., taken only from the northern side of a trunk.

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REFERENCES 1) Andreyev, N.N. (1938). On the tree for musical instruments. Moscow: CMSRL. 2) Aturina, N.V. (1937). Study of the microscopic structure of the resonant spruce (Picea excels Link) with regard to its technical features. St. Petersburg. 3) Bucur, V. (1983). An ultrasonic method for measuring the elastic constants of wood increment cores bored from living trees. Ultrasonic, 116-126. 4) Bucur, V. (2006). Acoustics of Wood. Berlin: SpringerVerlag. 5) Blskоva, G., & Brdarоv, N. (2003). Sounding wood acoustic characteristics studies. U: Collection of scientific reports at 50th anniversary of the Forest Engineering Institute, Woodworking and furniture production section, Sofia. 49-53. 6) Fabisiak, E. (2005). Variability of the basic anatomic elements and wood density in selected wood species. Rozprawy Naukowe. 7) Fedyukov, V.I., Saldaeva, E.Y., Tsvetkova, E.M., & ChavchavadzeЕ.S., (2016). Resonance wood microstructure peculiarities. Wood Research, 61(3), 413-422. 8) Fedyukov, V.I., Shurgin, A.I., Saldaeva, E.Y., & Tsvetkova, E.M. (2015). Theoretical studies and measurements of elastic-acoustic performance of wood with different methods for selection of resonant growing crop. Wood Research, 60(3), 417-428. 9) Fedyukov, V.I., & Makaryeva, T.A. (1992). The diametrical rod as object for nondestructive method resilient-viscous characteristics definition of standing and sawn resonant wood. U: Proceedings actes working session de travaill, Nancy, France. 344-345.

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10) Fuhr, K. (1926). Die akustischen Intsel der Geige. Verlag von Carl Markg. 11) Ille, R. (1979). Rezonaromidiavosmrku pro mistrovskflhousle. Dinvo, 34, 303-304. 12) Klisz, M., Ukalska, J., & Wojda, T. (2014). Radial growth of selected stands of back locust in Poland. Ann. Warsaw Univ. Life Sci. Forest. And Wood Technol, 85, 123-130. 13) Kossovich, N.L. (1935). Research into the differences of wood anatomy structure on northern and southern sides of a coniferous tree trunk. Botanical journal, 20(5), 455-472. 14) Krishtofovich, А.N. (1932). Fossil forests as indicators of cardinal points position in the geological past and displacement theory of Wegener. Proc. Of the Academy of Sciences of the USSR, 3, 415-433. 15) Kuznetsov, I.I. (1930). Resonant wood and deck. Forestry and forestry, 42-44. 16) Fedyukov, V.I., & Veselov L.N., (1999). Pat. 2130611 RU Method for resonant wood properties diagnostics and a device for its application. Bul. of invent., 4, 17) Polouboyarinov, О.I. (1976). Wood density. Moscow: Forestry. 18) Rajcan, E. (1990). Die Physikalisch – akustischencharakteristiken von holzals material fur die production von streichinstrumenten. U: Latest achievements in research of wood structure and physics, Zvolen. 19) Ugolev, B.N. (2001). Wood-forest with the basics of merchandising. Moscow. 20) Vitachek, E.F. (1964). Essays on the History of manufacture of stringed instruments.Moscow: Music. Paper sent to revision: 10.02.2017. Paper ready for publication: 21.03.2017.

Journal of Applied Engineering Science 15(2017)2, 422

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Review Paper

doi:10.5937/jaes15-12161

Paper number: 15(2017)2, 423, 149 - 154

THINK SMART, THINK SOCIAL! THE ROAD MAP FROM SMARTER OBJECTS TO SOCIAL OBJECTS IN SOCIAL INTERNET OF THINGS - A SURVEY A.Meena Kowshalya* Government College of Technology, India M.L.Valarmathi ACCET, India Internet of Things, the one paradigm many vision idea is ruling the world. By 2025 over trillions and trillions of objects will be connected to the internet. Social networking concepts are revolutions beyond IoT. One of the many visions of IoT is to make objects not only smarter but also socially conscious. A new paradigm named Social Internet of Things evolved which integrated two technologies namely Internet of Things and Social Networking. A SIoT comprises of socially aware smart objects that can autonomously establish and enable collaboration with other smart objects that are friends. In this paper we study the role, characteristics of social objects and their relationships. Five kinds of relationships are identified. These relationship and characteristics helps in revealing the level of trust between objects. Experiments were conducted for 85 social objects in an office environment and the types of objects, their relationships, interest, activities etc were discovered. Key words: Internet of Things, Smart objects, Social Internet of Things, Object relationships, Social awareness INTRODUCTION Internet of things is a novel paradigm that is based on pervasive presence of numerous things or objects. These things or objects include sensors, actuators, RFIDs, mobile phones etc., which collaborate among each other through addressing mechanisms with their friends and friend of friends to achieve a desired tasks. The future internet will embody millions of objects. IoT will provide the opportunities for users, manufacturers and service providers and make all real virtual. Bringing IoT into real world can be possible through integration of several technologies. Few technologies include identification; sensing and communication technologies and SOA based architecture for middleware. IoT finds its application almost in all fields including transportation and logistics domain, healthcare domain, smart environment domain, personal and social domain. Much research in standardization activity, addressing and networking issues, security and privacy has made comfortable use of IoT services across the globe. The above mentioned aspects has diverted to a different thinking of IoT ie., making IoT sociable. One can think of a new vision of IoT, making objects smarter and social.

Social Networking concepts can be used to provide social capabilities to objects in IoT. This kind of thinking has led to a new paradigm known as Social Internet of Things (SIoT) where objects are able to collaborate with each other autonomously via owners. These objects can crawl the billions of IoT objects for discovering services. Social objects can also autonomously advertise themselves to the rest of the internet community. This new vision of IoT called SIoT is a 10 year old research area that has opened many research application areas. Primarily three kinds of objects can be identified. i) Objects that have higher interoperability with external systems and collaborate with human social networks. ii) Objects that interact with surrounding and exhibit partial pseudo social behavior with neighbors. iii) Objects that are able to build their own social network and collaborate with other social objects. This paper is organized as follows. Section 2 describes the key enabling technologies of IoT, Section 3 introduces the concept of Social Internet of Things, and Section 4 presents the experimental setup followed by Conclusion.

* Government College of Technology, Thadagam Main Road, PN Pudur, Coimbatore, Tamil Nadu 641013, India; meenakowshalya.gct@gmail.com

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A.Meena Kowshalya - Think smart, think social! The road map from smarter objects to social objects in social internet of things - a survey

IOT- ONE PARADIGM AND MANY VISIONS IoT had made anytime, anywhere, any how access of things. The facet includes many visions. These differences in the vision depend on interests of the stakeholders and their background. Today the numbers of objects connected to the internet are higher compared to the magnitude of the internet. We are in need of different technologies to interact with each other. The need for pervasive computing is more since computing and communication technologies will be embedded in our environments. Enabling technologies of IoT The key enabling technologies of IoT described by: i) Tagging Things ii) Sensing Things iii) Thinking things iv) Shrinking Thinks RFID and related technologies enable real time identification and tagging. Sensor technologies enable detection of environmental status and sensory information. Smart technologies build intelligence at the networks border. Nanotechnologies enable the networking of smaller and smaller things. The complete IoT vision can be achieved only if objects are able to collaborate with each other in an open way and autonomously. Current implementations allow objects to collaborate only with small closed groups. Even small group collaborations need IPC gateways. Thus the number of embedded computing devices will increase in the environment leading to scalability problems. One solution to this issue is trusted social communities among objects. This can be achieved by Social Internet of Things. The social networking concept integrated along with IoT has led to a new type of network which can be modeled with social behavior and social relationships between objects. Objects that are smarter and socially conscious build a SIoT community [01]. Smart objects Modern technologies have made smart objects available. [02] derives and analyzes the transformation of smart objects into socially conscious smart objects. Smart objects are considered as the building blocks of Internet of Things [03]and are classified according to their awareness, representation and interaction. Three main catego150

ries were identified: i) Activity aware smart objects: maintain logs of information about work activities of its own and others ii) Policy aware smart objects: understand events and activities with respect to predefined policies. iii) Process aware smart objects: understand inbuilt processes and provides context aware guidelines. Recent smart objects also exhibit pseudo social behavior. The distinction between a “Thing” that is simply connected to an internet and a “Thing” that takes part in active role in the network has to be clearly defined. An acting object is an object that is able to translate the awareness of casual relationships into actions. An active object has the ability to stimulate action and participate in social web, having a self-confident role within the social web. [04 - 07] lists smart objects namely Smart-Its, Blog-jects, Embodied Micro blogging, spontaneous and their activities. Many unanswered problems exists in the IoT arena. A few includes what really objects talk about, does these conversations are useful and do they promote developments for human society, should objects need a separate social network that of humans. The concept of social networks of IoT objects separated from that of a human but submissive to their need is supported by recent studies [08 – 11]. SOCIAL INTERNET OF THINGS A novel paradigm of “social network of intelligence objects” based on the notion of social relationships among objects [12]. Objects establish social relationships with each other autonomously. These gave IoT a structure that can be navigable, scalable and can perform efficient service discovery [13]. [14, 15] have studied SIoT environment and has proved that the network is navigable and efficient service search can be performed. This enables to generate trust among objects to influence the level of interaction between Things that are friends. A social network allows people to increase popularity, find old friends, get filtered information and find new friends. Things in turn publish and find information and services, update services and get environmental characteristics. [16] has studied social virtual objects in the cloud.This is the right time to define kind of social relationship and Journal of Applied Engineering Science 15(2017)2, 423

A.Meena Kowshalya - Think smart, think social! The road map from smarter objects to social objects in social internet of things - a survey

behavior among objects. [18] proposed a community detection algorithm for the Social Internet of Things based on movement, preference and social similarity. Object relationships Five kinds of object relationships are identified [12]: i) Parental object relationship ii) Co location object relationship iii) Co work object relationship iv) Social object relationship v) Owner object relationship Parental object relationships are defined among similar objects build by the same manufacturer. Co location object relationship is determined whenever objects reside constantly at same place. Co work object relationship is defined as the relationship between objects when they come into contact at their ownerâ&#x20AC;&#x2122;s work place. Social object relationship is established when objects come into contact periodically or continuously for purely reasons related to relations among owners. Ownership object relationship is established when objects owned by the same user come into contact. Relation structures for social relations A widely accepted classification of social relations is proposed by [17] through his relation model theory. Four basic relational frames or structures are sources for generating social actions. These are derived from four elementary models of [17]. The relational frames are: i) Community sharing ii) Equality matching iii) Authority ranking iv) Market pricing

Communal sharing relationships can be associated with behaviors of objects which are not relevant individually but have a collective relevance. Communal sharing objects are associated to whole group. Equality matching relationship may represent all forms of information exchange between objects that operate as equals and that request and provide information amongst them in view of providing IoT services to users while maintaining individuality. These objects associate to a service that it advertises. Authority ranking relationship is asymmetrical based on precedence, hierarchy, status, command and difference. They are established between objects of different kinds of complexity and hierarchal levels. The service advertised is associated to the whole group of objects or to the object of highest rank. Market pricing relationships are based on proportionality with interactions organized with reference to a common scale of ratio values. These can be associated with interactions that objects have whenever they find themselves having to work together in the view of achieving mutual benefit. Cooperation among smart objects iscrucial in many IoT applications. EXPERIMENTAL RESULTS - CASE STUDY OF AN OFFICE ENVIRONMENT A total of 85 objects were used to study the social relationships and behavior of objects in an office. The office consisted of 50 PCs, 8 smart phones, 22 laptops and 5 tablets. All 50 PCs belong to the same manufacturer. Table 1 lists the type of devices that were available in the office. A total of 65 users were asked to make use of the objects. All objects were connected across social networking sites. The interests and activities of all objects were audited. Each device was initialized with social profiles of participants.

Figure 1: Layout of the Social graph Journal of Applied Engineering Science 15(2017)2, 423

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A.Meena Kowshalya - Think smart, think social! The road map from smarter objects to social objects in social internet of things - a survey

Also the participants were asked to log on to Facebook in order to keep track of their friends and interests. The devices were kept powered

on all the time. Figure 1 shows the social graph of the 85 users. The graph was generated by SocNetV1.9

Table 1: Total number of objects S.No

Objects/ Things

Manufacturer – number of devices

Total Objects

PCs

Dell - 50

Smart phones

Samsung -5; Apple -3

Laptops

Dell -15; Hp -7

Tablets

Samsung – 5

Each device performs a periodic Bluetooth device discovery every 100+/-10.11 seconds for duration of 10.11s to find out about nearby devices. The experimental hardware is an HTC s620 Windows Mobile Smartphone. HTC s620 has a 200MHz TI processor, 64MB of RAM, 128MB of ROM and a MicroSD slot. The radio interfaces include a quad-band GSM/EDGE cellular radio, Bluetooth v1.2 and 802.11b/g. The Bluetooth radio is a class 2 device with a radio range of around 10-20 meters. Each device records the results of the periodic device discovery and all data communications. In addition, the devices record details of the user’s social profile and its

evolution, and application level messaging. All traces are recorded constantly in text files on the device’s SD memory card.All traces are time stamped based on the device clock and reported as a relative time in seconds since the start of the experiment.The device clocks are set manually to the same reference time at the beginning of the experiment.The types of object relationships were analyzed as shown in table 2. Figure 2 shows the different types of device relationships. Table 3 shows the interest of 85 objects and their activities. Figure 3 gives the estimate of percentage of objects according to 7 interest groups.

Table 2: Types of object relationships Type of relationship

Number of objects

Percentage

Parental Object Relationship

76.47%

Co work Object Relationship

41.17%

Co location Object Relationship

58.82%

Ownership Object Relationship

Social Object Relationship

100%

Figure 2: Percentage of various kinds of object types

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A.Meena Kowshalya - Think smart, think social! The road map from smarter objects to social objects in social internet of things - a survey

Table 3: Interests and activities identified among 85 objects Types of interest

# of users

Percentage

Music

8.23

Sports

4.7

News

49.41

Facebook

75.29

Online shopping

68.23

Education

Others

4.7

Figure 3: Objects classified according to interests CONCLUSION

REFERENCES

Social Internet of Things has integrated two new technologies namely Internet of Things and Social Networks. The SIoT community is comprised of socially connected intelligent objects capable of collaborating with each other autonomously. This paper has introduced the notion of smart objects in IoT becoming socially aware in the SIoT world. The key enabling technologies of IoT were discussed. The role, characteristics and relationship between social objects were identified and analyzed. A real time SIoT environment was build comprising of 85 devices/objects. The relationship between objects and their activities were discovered. As a future work, we would like to focus on security and privacy issues in building a real time reliable SIoT community.

1) AtzoriLuigi, Antonio Iera, and Giacomo Morabito 2011, SIoT: Giving a social structure to the internet of things,Communications Letters, IEEE15.11 : 1193-1195. 2) Atzori Luigi, Antonio Iera, and Giacomo Morabito 2014, From smart objects to social objects: The next evolutionary step of the internet of things.,Communications Magazine, IEEE 52.1, 97-105. 3) Kortuem, Gerd, et al 2010, Smart objects as building blocks for the internet of things,Internet Computing, IEEE 14.1 , 44-51. 4) Holmquist, Lars Erik, et al 2001, Smart-its friends: A technique for users to easily establish connections between smart artefacts, Ubicomp 2001: Ubiquitous Computing. Springer Berlin Heidelberg 5) Bleecker, Julian 2006, A manifesto for networked objectsâ&#x20AC;&#x201D;cohabiting with pigeons, arphids and aibos in the internet of things. 153

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A.Meena Kowshalya - Think smart, think social! The road map from smarter objects to social objects in social internet of things - a survey

1) Mendes, Paulo2011, Social-driven internet of connected objects,Proc. of the Interconn. Smart Objects with the Internet Workshop. 2) Nazzi, Elena, and Tomas Sokoler 2011,Walky for embodied microblogging: sharing mundane activities through augmented everyday objects,Proceedings of the 13th International Conference on Human Computer Interaction with Mobile Devices and Services. ACM. 3) Kranz, Matthias, Luis Roalter, and Florian Michahelles 2010, Things that twitter: social networks and the internet of things, What can the Internet of Things do for the Citizen (CIoT) Workshop at The Eighth International Conference on Pervasive Computing (Pervasive 2010) 4) Ning, Huansheng, and Ziou Wang 2011, Future internet of things architecture: like mankind neural system or social organization framework, Communications Letters, IEEE 15.4 ,461-463. 5) Evangelos A, Kosmatos, Tselikas Nikolaos D, and Boucouvalas Anthony C 2011, Integrating RFIDs and smart objects into a UnifiedInternet of Things architecture,Advances in Internet of Things. 6) Jian, An, et al 2011, Nodes social relations cognition for mobility-aware in the internet of things,Internet of Things (iThings/CPSCom), 2011 International Conference on and 4th International Conference on Cyber, Physical and Social Computing. IEEE.

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7) Atzori Luigi, et al 2012, The social internet of things (siot)â&#x20AC;&#x201C;when social networks meet the internet of things: Concept, architecture and network characterization,Computer Networks 56.16, 3594-3608. 8) Kleinberg, Jon 2000,The small-world phenomenon:An algorithmic perspective,Proceedings of the thirty-second annual ACM symposium on Theory of computing. ACM. 9) MeenaKowshalya.A, M.L.Valarmathi 2015, Improved Network Navigability and Service Search in Social Internet of Things (SIoT), International Journal of Research and Scientific Innovation, 2(11),77-75 10) Nitti Michele, Luigi Atzori, and Irena PletikosaCvijikj 2014, Network navigability in the social internet of things,Internet of Things (WFIoT), 2014 IEEE World Forum on. IEEE. 11) Farris Ivan et al 2015, Social Virtual Objects in the Edge Cloud,IEEE Cloud Computing 2.6, 20-28. 12) Fiske, Alan P 1992,The four elementary forms of sociality: framework for a unified theory of social relations,Psychological review 99.4 , 689. 13) A. Meena KOWSHALYA , M. L. VALARMATHI (2016), Community Detection in the Social Internet of Things Based on Movement, Preference and Social Similarity, Studies in Informatics and Control, 25(4), 499-506. Paper sent to revision: 22.10.2016. Paper ready for publication: 24.02.2017.

Journal of Applied Engineering Science 15(2017)2, 423

Original Scientific Paper

doi:10.5937/jaes15-12875

Paper number: 15(2017)2, 424, 155 - 165

COST-BENEFIT ANALYSIS OF PV GENERATORS AT RESIDENTIAL BUILDINGS IN THE REGION OF RUSE, BULGARIA Katerina Georgieva Gabrovska-Evstatieva* Ruse university “Angel Kanchev”, Bulgaria Boris Ivanov Evstatiev Ruse university “Angel Kanchev”, Bulgaria

In this study a method for cost-benefit analysis of investments in PV generators at residential buildings has been presented. The benefits are evaluated in two categories: financial benefits in terms of net present value of the money and the return on the investment; the ecological benefits presented in saved CO2 emissions in tons and in percentages. A cost-benefit analysis of a PV investment at an apartment in the city of Ruse is presented with different scenarios in terms of installed power. Two risk factors are also evaluated – the buying price of PV energy and the selling price of conventional energy. The obtained results showed that the investment could payback for 6 to 9 years, if the installation is properly sized. The ecological benefits have been evaluated to be approximately 1t CO2 annually or a reduction of 35% to 42%. Key words: Cost-benefit analysis, PV generators, Residential buildings INTRODUCTION The constantly increasing prices of energy resources imply the search for reduction of the energy demand and increasing of the energy production. This has led to the creation of a number of stimuli in Bulgaria for using of renewable energy sources (RES), mainly in the form of preferential buying prices of the produced energy. This has led to the creation of an enormous amount of PV plants above 30 kWp but showed as an ineffective approach. Until the last year there were almost no small power plants (under 30 kWp) connected to the grid, because such procedure was requiring multiple permits and technical projects. In 2016 the Commission for Energy and Water Regulation simplified significantly the procedure which opens new possibilities for application of RES in residential buildings in Bulgaria. On the other hand during the last years the price of energy from PV sources has been constantly dropping down which is another reason to investigate their payback at resident buildings. According to [09] the advance in the solar technology is expected to reduce the price of the generated PV energy to 4-5 ct/kWh by 2025 and to 2-4 ct/ kWh by 2050, which would make it competitive even to atomic energy.

Numerous studies have investigated the possibilities to use PV energy sources in residential and public buildings. Nafeh A. E. (2009) explored the electrification of remote households in Egypt using en-tirely PV sources [02]. Kolhe et al. (2002) analysed different combinations of PV and diesel generators of a school located in India for one life cycle of the PV modules. The study showed that using only PV gen-erators is an acceptable solution if the energy consumption is low [05]. In another study for residential buildings in Malaysia, Elhassan et all. (2012) showed that consid-ering the reduction in the amount of the purchased energy, the payoff time of the investment is 14 years [03]. Ziuku et all. (2012) investigated the period for return on the investment of an integrated PV system in a residential building in South Africa. The results showed that the investment will pay off in 8 years [10]. Manohar et all. (2015) performed a cost-benefit analysis of a solar PV system in Trinidad and Toba-go and the results were unsatisfactory with 32.9 years payback period [06]. The available studies show the investment results from application of PV energy sources vary widely, depending on many factors such as geographical location, application, price of electrical

* Ruse university “Angel Kanchev”, 8 Studentska str., POB 7017, Ruse, Bulgaria; kgg@ami.uni-ruse.bg

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Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

energy, buying price of energy from RES, local regulations, etc. The goal of this study is to perform a cost-benefit analysis of an investment in a low power PV plant at a residential building or a small house for the region of Ruse, Bulgaria. The analysis will assess the economic as well as ecological benefits from such invest-ment and will allow to verify its feasibility for the geographical and economic conditions of Bulgaria. MATERIALS AND METHODS Energy production and consumption The energy balance of a residential building is: Econs = Econv + Epv (used)

(1)

where: ECONS - is the consumed electrical energy in kWh; ECONV - is the bought energy from conventional sources in kWh;

EPV(USED) - the part of PV energy which is used in kWh; The total produced PV energy is: EPV = EPV(USED) + Epv (EXC)

(2)

where EPV(EXC) is the excess energy. In this study it is assumed that two streams of information are available: â&#x20AC;˘ The mean hourly energy consumption of the apartment/house for each month of the year ECONS(t); â&#x20AC;˘ The mean hourly energy production from the PV modules for each month of the year EPV(t). The block diagram of the algorithm, used to distinguish between used and excess energy from the PV generator is presented in Figure 1.

Figure 1: Algorithm of the method for estimation of the used amounts of energy

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Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

In block 2 are initialized the input/output variables and in block 3 – the time variable. If for a cer-tain hour of the day the energy production from the PV generator is lower than the energy consumption, in blocks 5 and 6 the amount of used PV energy and bought conventional energy are updated. Otherwise in blocks 7 and 8 the

used PV energy and the excess PV energy are updated. When the last sample (hour of the day) is reached, the algorithm returns the used PV energy EPV(USED), the excess PV energy EPV(EXC) and the bought conventional energy ECONV. The algorithm is also presented in a more generalized form in Figure 2.

Figure 2: Simplified energy production-consumption model

Investment expenses Two types of expenses, related to the investment in PV energy sources, can be distinguished: • The initial investment; • The monthly maintenance expenses. The initial expenses CINV are:

CINV = CPV .PRP +CEQ , €

(3)

where CPV - is the price for 1 kW rated power in €/kWp; PRP - the installed rated power in kWp; CEQ - the additional expenses, related to the investment in €. In this study the monthly maintenance expense CMN, related to the PV generator, are estimated with:

CMN = PRP .CMN €, 0

(4)

where CMN0 is the monthly expenses for maintenance of 1 kW installed PV power in €/kWp. Financial benefits from the investment In the present study the financial benefits have two components: benefits from not buying conJournal of Applied Engineering Science 15(2017)2, 424

ven-tional energy and benefits from selling excess energy. The daily financial benefits CFIN. BEN could be ex-pressed with:

CFIN . BEN = CCONV .EPV(USED) +CPV .EPV ( EXC ) ,€ (5) where CCONV - is the selling price of energy from conventional sources in €/kWh; CPV - the buying price of energy from PV sources in €/kWh. Then the daily money flow Ci(t) for the ith day becomes:

i i ,€ Ci (t)= CFIN . BEN − CMN and the net money flow for the kth month is: 30/31

Bk =

∑ C (t) ,€

(6)

i=0

The net present value (NPV) of the invested money is estimated with: n

NPV(t)= ∑ k=1

Bk (t) n

(1+ r )

− CINV ,€

(7)

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Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

The cost of capital, r can be obtained with:

nr − inf 1+ inf

The potential CO2 emissions if the PV source was not installed can be estimated with: (8)

where nr is the monthly nominal rate of return and inf is the monthly inflation. Another indicator for the investment is the return on investment (ROI): ROI =

∑ C (t) .100 , %

(9)

CINV

CO 2 POT = ECONS .CO 2CONV , g CO2

Then the daily energy savings from the PV investment are:

CO 2 SAV = CO 2 POT − CO 2 PV, g CO2

CO 2CONV + PV = ECONV .CO 20 , g CO2,

(10)

where CO20 is the relative emission factor which can be obtained with: EPV(USED) E .CO 2CONV + PV + CONV .CO 2CONV (11) CO 20 = ECONS ECONS

(13)

The following coefficient is defined in order to assess the emission savings:

Other benefits from the investment Considering the energy produced by conventional sources leads to significantly higher CO2 emis-sions than from renewable sources, other benefits related to the investment are CO2 emission savings. The daily emissions of the apartment with a PVhybrid energy supply is:

(12)

kCO 2

∑ CO2 ∑ CO2

SAV

.100 , %

(14)

POT

where kCO2EC shows the percentile emissions savings as a consequence from the investment. RESULTS AND DISCUSSION Parameters of the study The object of the investigation is a four room apartment with PVC windows, insulation and central heating. Its energy consumption for each month of the year is presented in Table 1.

g CO2/kWh Table 1: Electrical energy consumption of the investigated apartment Month

Monthly energy consumption, kWh

Mean daily energy consumption, kWh

January

265,21

8,56

February

296,11

9,87

March

355,25

12,69

April

312,00

10,06

May

329,75

10,99

June

266,61

8,89

July

288,93

9,32

August

197,82

6,38

September

325,04

10,83

October

317,64

10,25

November

526,96

17,57

December

324,36

10,46

Different studies [04,08] have reported similar distributions of the daily household energy consumption, characterized with a minimum during the night and a maximum in the evenings. Ghaemi and Brauner (2009) also reported peaks in

158

the morning during the weekdays and a peak at around 13:00 h dur-ing the weekends [04]. They also created an average normalized load profile to be used for comparison, with three peaks (Figure 3), which is used in the present study.

Journal of Applied Engineering Science 15(2017)2, 424

Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

Figure 3: Normalized average household consumption pattern reported in [04]

The hourly energy production from 1 kWp installed PV power in the city of Ruse (Bulgaria) has been used for each month of the year. The data has been acquired from the Zita Ruse PV power plant, the information for which is available in [11]. According to the National Renewable Energy Laboratory the maintenance fee for PV installations bellow 10 kW varies between 0 and 40 $/kWp [12]. Considering in the present study we investigate low power household installations (1 kWp and 2 kWp), we assume the maintenance fee would be 0 €/kWp. According to the Covenant of Mayors (2010) the emission factor for Bulgaria with and without lifecycle analysis (LCA) is 819 g CO2/kWh and 906 g CO2/kWh respectively [01]. The LCA emission factor for PV power plants varies between 20 and 50 g CO2/kWh. More recent data from the Bulgarian Ministry of the Environment and Water (2014) [07] claims the average emission factor for Bulgaria in 2013 was 616 g CO2/kWh, however there is no up-to date information on the LCE emission factor. That’s why in this study we will increase the standard emission factor with

the same ratio as the Covenant of Mayors increase, in order to obtain the LCE emission factor for Bulgaria: CO2CONV=616×906/819=681 g CO2/kWh. Another important parameter is the buying price of PV energy. There was a rapid drop of that price in the recent years from 0.2 €/kWh a couple of years ago to 0.13 €/kWh in 2017. Considering cur-rently in Bulgaria the installed rated PV power is more than the consumption of the country, this price is expected to further drop down. On the other hand the energy consumption worldwide continuously in-creases, it is quite likely the price of conventional energy will increase. For the above reasons two risk factors will be investigated in this study: • The buying price of the excess energy decreases by 50% from 0.13 to 0.065 €/kWh; • The conventional energy price increases from 0.14 to 0.20 €/kWh. The other parameters of the performed analysis are presented in Table 2.

Table 2: Other parameters of the cost-benefit analysis. Parameter

Value

Price for 1 kW installed PV power, €/kWp [13,14]

1500

Life expectancy, years

Price of conventional energy, €/kWh [15]

0.14

LCA emission factor of conventional energy, g CO2/kWh

681

LCA emission factor of PV generators, g CO2/kWh [01]

Annual nominal rate of return, %

Annual inflation, %

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Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

Table 3: Scenarios for the cost-benefit analysis

Parameters of the scenario Scenario 1 Installed power: 1 kW, no batteries Scenario 2 Installed power: 2 kW, no batteries Electrical production and consumption The mean values of the electrical production, consumption and the required additional con-

160

ven-tional energy for each month of the year if Scenario 1 and 2 are used are presented in Figure 4 and Figure 5 respectively.

Journal of Applied Engineering Science 15(2017)2, 424

Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

Figure 4: Mean electrical consumption, production and bought conventional energy with Scenario 1 for each month of the year

Journal of Applied Engineering Science 15(2017)2, 424

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Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

Figure 5: Mean electrical consumption, production and bought conventional energy with Scenario 2 for each month of the year

The ratio between consumed and excess PV energy for the two scenarios is presented in Figure 6.

Figure 6: Mean daily consumed PV energy, excess PV energy and percentile energy savings for each month of the year according to: a) Scenario 1; b) Scenario 2

162

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Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

For Scenario 1 the generated PV energy will generally be lower than the consumption of the apartment during the months January, February, March, October, November and December. In August a lot of excess energy is expected which could be explained with the lower energy consumption due to the holiday season as well as lower cloudiness during this month. For the rest of the months there will be av-erage excess energy. For Scenario 2 the peak of the produced energy (on average) will be higher than the consumption for every month of the year except November and December, which is expected to lead to significant amounts of excess energy, especially during the summer months.

Benefits from the investment The initial investment for Scenarios 1 is 1500 € and the performed analysis showed that the ROI with the current prices, with increased conventional energy price (0.20 €/kWh) and with reduced buying price of PV energy (0.065 €/kWh) is 256 %, 361% and 242% respectively. In the first case the NPV reaches 0 € during the 8th year, in the second case during the 6th year and in the third case during the 9th year. The NPV values at the end of the 25 years period are respectively 3481 €, 5563 € and 3217 € (Figure 7).

Figure 7: NPV for Scenario 1 with the current prices (a), with price of conventional energy 0.20 €/kWh (b) and with buying price of PV energy 0.065 €/kWh (c)

The results show that the buying price of PV energy has no significant effect on the investment according to Scenario 1, which is explained by the low amounts of excess (sold) energy. According to the expectations the increase in the price of the conventional energy could significantly reduce the payback times of the investment. The initial investment for Scenarios 2 is 3000 € and the ROI with the current prices, with increased conventional energy price (0.20 €/kWh) and with reduced buying price of PV energy (0.065 €/kWh) is 250%, 322% and 199% respectively. For the three cases the NPV reaches 0 € during the 9th year, 7th and 11th year respecJournal of Applied Engineering Science 15(2017)2, 424

tively, and the price at the end of the 25 year period reaches 6738 €, 9515 € and 4723 € respectively (Figure 8). In this situation the increased amount of excess energy makes the buying price of PV energy an important risk factor, which could significantly influence the payback of the investment. The ecological effect from the investment according to Scenario 1 and 2 have been estimated re-spectively as 0.93 t CO2 and 1.13 t CO2 annually. If corresponding legislation is implemented in Bulgar-ia, these savings could be an additional form of income, however at the time being there are no such op-tions. 163

Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

Figure 8: NPV for Scenario 2 with the current prices (a), with price of conventional energy 0.20 €/kWh (b) and with buying price of PV energy 0.065 €/kWh (c)

The percentile CO2 reductions for the two scenarios according to Equation (14) are 35.3% and 42.3% respectively, which is a significant reduction, considering only the consumed PV energy is ac-counted in the equation. CONCLUSION In the present study a cost-benefit analysis has been performed on a PV system investment in a common apartment or a small house. The analysis was performed using experimental data for one year period, including the mean daily energy consumption for each month of the year and the mean hourly en-ergy production from 1 kW installed power in the city of Ruse (Bulgaria) for the different months of the year. Next the benefits of two types of investment were estimated for 1 kWp and 2 kWp PV power-plant. In the first scenario some amounts of excess energy were available during the summer months, while in the second there is a significant excess energy. If the current prices of energy in Bulgaria are used, in both cases the investment will pay back on the 8th to 9th year and the ROI will be around 250%. Two risk factors were analysed. The increase in the price of conventional energy has slightly higher impact on the first scenario. The decrease in 164

the buying price of PV energy on the other hand significantly increases the payback period for the second scenario and has little impact on the first scenario. Considering the enormous amount of installed PV power in Bulgaria, the buying price of PV energy is expected to further drop in the near future. That is why the risk for the investment financial benefits could be lowered if the PV plant is well sized so that it doesn’t generate a lot of excess energy. Another benefit from the investment are the saved CO2 emissions, which are approximately 1 t CO2 annually for both scenarios. This could be an additional form of income if appropriate legislation is introduced. The obtained results show that promoting PV sources for own needs in residential houses could be a viable solution for reducing the conventional energy consumption in Bulgaria and decrease the energy dependency. REFERENCES 1) Covenant of Mayors, (2010). Technical annex to the SEAP template instructions document: The emis-sion factors. 2) El-Shafy, N. (2009). An Optimum Control Strategy for Energy Management in a Remote Area Stand-Alone PV System. The Open Renewable Energy Journal, 2, 91-98. Journal of Applied Engineering Science 15(2017)2, 424

Katerina Georgieva Gabrovska-Evstatieva - Cost-benefit analysis of PV generators at residential buildings in the region of Ruse Bulgaria

3) Elhassan, Z. A. M., Zain, М. F. M., Sopian, К., Abass, A. A. (2012). Design and performance of pho-tovoltaic power system as a renewable energy source for residential in Khartoum. International Journal of the Physical Sciences, 7 (25), 4036-4042. 4) Ghaemi, S., Brauner, G. (2009). User behavior and patterns of electricity use for energy saving. Internationale Energiewirtschaftstagung an der TU Wien, IEWT (2009). 5) Kolhe, M., Kolhe, S., Joshi, J. C. (2002). Economic Viability of Stand-alone Solar Photovoltaic System in Comparison with Dieselpowered System for India. J. Energy Economics, 24 (2):155-165. 6) Manohar, K., Ramkissoon, R., Adeyanju, A. (2015). Cost Benefit Analysis of Implementing a Solar Photovoltaic System. International Journal of Innovative Research in Science, Engineering and Technol-ogy, 4 (12), 1-8. 7) Ministry of the Environment and Water. (2014). Estimation and forecast of the emission factor of greenhouse gases for the national electrical network of Bulgaria for the period 2014-2020 (In Bulgarian), Sofia, Bulgaria.http://www5.moew.government. bg/wp-content/uploads/file/Climate/Climate_ Change_Policy_Directorate/IECCP/AKTUALNO/Bulgaria_EGEF_2014.pdf 8) Paateron, J., Lund, P. (2005). A model for generating household electricity load profiles. Int. J. Energy Res, 30, 273–290.

Journal of Applied Engineering Science 15(2017)2, 424

9) Ranabhat, K, Patrikeev, L., Revina, A.A., Adrianov, K., Sofronova, E. (2016). An introduction to solar cell technology. Journal of Applied Engineering Science, 14 (4), 405, 481-491. 10) Ziuku S., Meyer, E. (2012). Economic viability of a residential building integrated photovoltaic gen-erator in South Africa. International Journal of Energy And Environment, 3 (6), 905-914. 11) https://www.sunnyportal.com, retrieved on February 1st, 2017. 12) http://www.nrel.gov/analysis/tech_cost_om_ dg.html, retrieved on February 1st, 2017. 13) http://www.motto-engineering.com/bg/produkti/solarni-sistemi/mrezhovi-solarni-sistemi/mrejova-fotovoltaichna-sistema-3kwp-153-detail, retrieved on February 1st, 2017. 14) h t t p : / / e c o s o l a r - b g . c o m / м р е ж о в и фотоволтаични-централи, retrieved on February 1st, 2017. 15) https://www.energo-pro.bg/bg/Dejstvashticeni-na-elektroenergiyata-Bitovi-klienti, retrieved on Feb-ruary 1st, 2017. Paper sent to revision: 02.04.2016. Paper ready for publication: 05.02.2017.

165

Original Scientific Paper

doi:10.5937/jaes15-13599

Paper number: 15(2017)2, 425, 166 - 172

ON THE QUESTION OF PREDICTING THE SERVICE LIFE OF LATTICE STEEL STRUCTURAL ELEMENTS Oleg Vladimirovich Emelianov* Magnitogorsk State Technical University, Magnitogorsk, Russian Federation Alexander Nikolaevich Shuvalov Moscow State University of Civil Engineering, Moscow, Russian Federation Milan Prokic LLC Velesstroy, Moscow, Russian Federation Present paper deals with the evaluation of fatigue strength at crack initiation stage in the double angle elements of lattice steel structures.The current construction norms for steel structures do not include check for fatigue strength at crack initiation stage, and the calculation of elements endurance limit does not account actual stress-strain state in stress concentration zones, material deformation characteristics in these areas, and strength properties of steel. Experimental study of the stress-strain state kinetics in the areas of gusset plate breakage of double angle welded joints was carried out by strain gauge method. Results were obtained regarding the stress state stabilization under cyclic loading and stress intensity factor. During cyclic tests, maximum load level varied depending on the yield stress.The formation of fatigue cracks was detected in the zone of gusset plate breakage.The curve at fatigue cracks initiation stage, by deformational fracture criteria at “stiff” loading, was described by the equations presented in the “Standards of strength calculation of equipment and pipelines of nuclear power plants”.Calculation analysis of results for number of cycles before fatigue crack initiation has been made and good agreement with test results has been obtained. Key words: Steel lattice structures, Fatigue crack, Fatigue strength, Elastoplastic deformation of the material, Deformation fracture criterion, Cyclic loading, Stress intensity factor INTRODUCTION Welded steel structures and constructions (reservoirs, gas tanks, pipelines, pressure vessels, masts, towers, crane beams, load-bearing structures of industrial buildings, etc.) have found wide application in various branches of industry. Failures in operation of structures usually occur as a result of the bearing capacity loss or failure of the individual construction elements [01]. Accidents are often accompanied by, considerable material and environmental damage, and sometimes, even human losses. For steel lattice structures, which operate under cyclic loads (truss structures of industrial buildings with underslung cranes, bunker structures and unloading racks, towers, masts, power lines supports, etc.), the presence of structural stress concentration, residual welding stresses and initial technological welding defects is characteristic. For design of struc-

tural elements considering the operating conditions of such structures, additional analysis of fatigue strength must be performed [06,07]. In current construction norms (SP 16.13330.2011) calculation of the fatigue is provided only when the number of loading cycles ≥105 and it is performed by comparing the maximum normal stresses with calculated fatigue strength, which is given for several types of welded joints. In construction norms, influence of defects on the strength and lifetime of the structure is ignored. It is assumed that during the lifetime of structure, calculated sections must be free from cracks, including fatigue cracks. However, operating experience of building structures under cyclic load shows that the elastoplastic material deformation is accompanied with a damage accumulation and leads to the fatigue crack initiation in stress concentration zones [10, 11].

*Nosov Magnitogorsk State Technical University, Magnitogorsk, 455000, Russia; oleg_emelianov58@mail.ru

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Oleg Vladimirovich Emilianov - On the question of predicting the service life of lattice steel structural elements

Figure 1: Welded double angle connection fatigue failure

MATERIAL AND METHODS OF TESTING

To describe the process of fatigue cracks initiation, a number of models have been proposed, based on the presence of local plastic deformations. Present paper studies the effect of cyclic influences in which the stress magnitude in structure sections is constantly changing with time.

Welded elements for the tests (Figure 2) were made form low alloy steel 10G2S1 (┘└70×6) and steel S390 (┘└ 80×8) obtained by heat treatment of VSt3sp (RSt37-2) steel during the rolling process. Mechanical properties of steels determined by the test results of standard samples are shown in Table 1.

Figure 2: Welded T-section connection out of double angles Table 1: Mechanical properties of steels Steel properties Steel grade

y, MPa

в, MPa

10G2S1

350

530

S390

390

542

Journal of Applied Engineering Science 15(2017)2, 425

Sk, MPa

E, MPa

57,4

956

2×105

1020

2×105

167

Oleg Vladimirovich Emilianov - On the question of predicting the service life of lattice steel structural elements

The study of fatigue cracks initiation conditions in welded joints with double angles was carried out by cyclic tension loading in the zone of gusset plate breakage with preset load level (“soft” loading”). Cyclic loading of the connection was carried out at various load levels up to the joint failure. In the process of loading the moment of fatigue cracks initiation was recorded. Tests were carried out on a hydraulic pulsator system GRM-1 with loading frequency 7.25 Hz and cycle asymmetry coefficient R = 0,2. Maximum rated load levels were σ ̅_n=σ_n/σ_ т = 0,175; 0,231; 0,351; 0,526 for elements of 10G2S1 steel and σ ̅_n=σ_n/σ_т = 0,208; 0,229; 0,261; 0,313; 0,417 for elements of S390 steel. Since the conditions of fatigue cracks initiation were investigated in joints which do not contain defects form processing, testing was preceded by an external inspection of welded joints. After the completion of tests, fractures and internal technological defects were inspected.

TEST RESULTS AND THEIR DISCUSSION Main cracks with 2 4 mm length, were detected on the angle heel edge in the gusset plate breakage area. At this length, the number of sample loading cycles was determined, corresponding to that crack. The share of the relative service life at crack initiation stage was 0,127÷0,7 (average 30%) of total fatigue service life of double angle welded joints (Table 2). It should be noted that the share of relative service life of welded joints from S390 steel is lower than in joints from 10G2S1 steel. This takes place at the crack initiation stage with the same level of nominal cyclic stresses. Figure 3 shows a comparison of the fatigue strength results obtained by calculation according to the existing construction norms, with the results of experimental fatigue tests of welded standard elements out of double angles.

S390

10G2S1

Steel grade

Table 2: Number of cycles before fatigue crack initiation and joint failure

168

Maximum level of nominal stresses,

Number of cycles

,MPa Before crack initiation l = 2 ÷ 4 mm length

before joint failure

0,526

18300

26100

70,11

0,351

117900

467600

25,21

0,351

105700

459000

23,03

0,231

335000

722100

46,39

0,231

308900

624200

49,49

0,175

722970

2033625

35,55

0,417

56100

202300

27,73

0,417

18300

180100

10,16

0,313

74800

590700

12,66

0,313

86400

549000

15,74

0,261

217100

705000

30,79

0,23

312000

1200100

26,00

0,23

332900

1281100

25,99

0,208

459600

2098900

21,90

Journal of Applied Engineering Science 15(2017)2, 425

Oleg Vladimirovich Emilianov - On the question of predicting the service life of lattice steel structural elements

Figure 3: Calculated fatigue strength curve and results of fatigue tests for structural elements form 10G2S1 и S390 steel

It can be seen that the calculation with the use of current construction norms (SP 16.13330.2011) overestimates values of fatigue strength for 10G2S1 steel, and underestimates fatigue strength for the S390 steel [08]. This is caused by fact that in these construction norms (for the elements of groups 3-8) calculated fatigue resistance is independent of strength and cyclic properties of the steel, the design parameters of welded joint (width of the angles, length and throat of welded joints) [02]. It is quite difficult to detect a fatigue crack on time. Therefore, to ensure the safety and calculated service life of welded steel structures during the design calculations must be performed not only on the assumption of cracks absence, but also their emergence and development, predicting the limit state of crosssections, in which the cracks are developed. Since fatigue cracks are formed in areas with high stress concentration, the actual strain and stress distribution in these areas is important for predicting the number of cycles to crack initiation. Features of such calculations are the mechanical characteristics of metal in various areas of Journal of Applied Engineering Science 15(2017)2, 425

joint and presence of residual welding stresses. Study of welded joints strain state, as well as cyclic deformation diagrams for joints with different classes of construction steels was conducted by Larionov V.V. [04]. Currently, construction norms for structures calculation are developed, in which fatigue crack initiation is considered to be a limit state of structure. These norms are based on deformation failure criterions, which are taking into account the kinetics of local elastoplastic deformations at unitary and cyclic loading. For calculating the maximum local strains and stresses, most widely used are formula of Makhutov N.A. [5], allowing to determine stress intensity factors Kσi and deformation factors Kεi in elastoplastic area by the values of stress intensity factor in elastic deformation area ασ. The dependence of elastic stress intensity factors on the design parameters of typical welded elements of double angles are given in paper [02]. However, these expressions do not take into account specific material resistance to elastoplastic deformation. N.A. Makhutov proposed dependences for account 169

Oleg Vladimirovich Emilianov - On the question of predicting the service life of lattice steel structural elements

ing material properties, which allow estimating the material resistance in elastoplastic deformation area under static and cyclic loading [05]. In present paper, an experimental study of the stress-strain state kinetics under elastoplastic material deformation in areas of gusset plate breakage of double angle welded joints (Figure 2) using foil strain gauges with 1.0 mm base.

It was found that the stabilization of stressstrain state occurs after 5-10 loading cycles and ασ = Kεi(k) in the investigated relative range of cyclic loads application σn=σn/σy=0,16÷0,62 (Figure 4). Material in the stress concentration zones was working in “stiff” loading conditions, with constant amplitude of deformations Ea.

Figure 4: Dependence of strain concentration factors in stabilized range Kεi(k) on the cyclic loading level in the gusset plate breakage area

A suggested fatigue curve equations at crack initiation stage for steels with ratio σТ/σв≤0,7 and the number of loading cycles ≤106 by failure criterion at “stiff” loading are: By “Standards of strength calculation of equipment and pipelines of nuclear power plants” [09]: (1)

where nσ – safety factor for stresses; [σaF ] – the amplitude of conventional elastic stresses taking into account stress intensity factor, which can be determined from [σaF]=(σнmax-σнmin ) ασ/2; φs -a coefficient that depends on the welding type, welded materials and post weld heat treatment (φs≤1); Rcт, Eт, ψт, σmт, R-1т – material properties at a temperature ТºС; ecт – plasticity characteristic: ecт=0,005ψт-((σF )max-σmт)/(2Eт ) at (σF )max>σmт and ecт=0,005ψт at (σF )max<σmт; m – exponent: m = 0,5; RcT – strength characteristic: RcT=RmT (1+1,4ψT); (σF)max – maximum conditional elastic 170

stress cycle with account for conditional elastic stress intensity factor; R-1T=0,4RmT; r – asymmetry coefficient of stress cycle r=(σmт-2[σaF])/(σmт ); In case when local deformations in stress concentration zones from service loads in strained state are determined experimentally and by solving the elastoplastic problem. Then, the number of cycles before crack initiation is calculated by equation [2]: (2) where εa=(σнmax-σнmin)Kεi(k))/2E; r*=σmin⁄σmax; r=1(2σa*/(σmax*)(m^(0)) ; Et, ψt, σвt, σ(-1)t – material characteristics at a temperature ТºС. As applied to welded joints, heat treated or without heat treatment, which contain residual stresses in the absence of experimental data in equation (2) instead of the fatigue limit σ(-1)t fatigue limit for welded joints σ(-1с)=σ(-1) (1-σ0⁄(σв)) [03] is introduced.

Journal of Applied Engineering Science 15(2017)2, 425

Oleg Vladimirovich Emilianov - On the question of predicting the service life of lattice steel structural elements

For welded joints without heat treatment in a first approximation residual stresses σ_0 are assumed equal to the yield stress of material or weld metal. In calculations, the value of relative narrowing is recommended to be taken according to the guides “Steel structures” volume 1-ψrn=0,8ψt; “Welding in mechanical engineering” volume 3-ψrn=(0,15÷0,6)ψt. Figure 5 a, b shows a comparison of curves calculated according to the equation (1) and (2) with the experimental data, within the investigat-

ed range of fatigue failures. In the calculations were accepted: equation (1) − nσ=2, φs= 0,75 for 10G2S1 steel, φs= 0,65 for S390 steel; equation (2) − relative narrowing in the transition area ψrn=0,6ψt. The graphs show that within the investigated range of fatigue failures, a good agreement between curves calculated by equation (2) and experimental data is obtained. Calculation by the equation (1) gives lower values of cycles before fatigue crack initiation for 10G2S1 steel.

(a)

(b)

Figure 5: Comparison of calculated curves for cycles before fatigue crack initiation with the results of endurance tests of structural elements from 10G2S1 steel and S390 steel: a) by the equation (1); b) by the equation (2)

Journal of Applied Engineering Science 15(2017)2, 425

171

Oleg Vladimirovich Emilianov - On the question of predicting the service life of lattice steel structural elements

CONCLUSION 1) According to current construction norms (SP 16.13330.2011), the calculation of lattice steel structural elements out of double angles overestimates fatigue strength for 10G2S1 steel, and underestimates fatigue strength for the S390 steel. This is because in these construction norms, fatigue resistance calculation does not consider strength and cyclic properties of the steel and design parameters of welded joint (width of the angles, length and throat of welded joints). 2) The share of the relative service life at crack initiation stage was on average 30% of total fatigue service life for all tested joints out of double angles. 3) The safety and calculated service life of welded steel structures depends on the presence of stress concentrations, residual welding stresses and initial technological welding defects. Therefore, design calculations of steel structures must be performed not only with the assumption of cracks absence, but also their emergence and development, predicting the limit state of cross-sections, in which the cracks are developed. 4) Comparison of experimental data with calculated number of cycles before fatigue crack initiation by the expressions (1) and (2) showed that good agreement is obtained with size of relative narrowing in the transition area ψ_rn=0,6ψ^t. Calculations by equation (1) with a voltage safety factor equal n_σ=2 give underestimated values for number of cycles before fatigue crack initiation for 10G2S1 steel. REFERENCES

structures for strength and durability: handbook, Moscow: Mashinostroenie, 223 p. 4) Larionov V.V., Bogdyl’ P.T. (1973): Study of the state of strain in welded joints using photoelastic coatings, in connection with strength at loading cycles, Low-Cycle Fatigue in Welded Structures, Seminar Materials [in Russian], Leningrad pp. 63-67 5) Makhutov N.A. (1981): Strain fracture criteria and strength design of structural members, Moscow: Mashinostroenie, 272 p. 6) Maksimović S., Blažić M., Maksimović M. (2010): Design of constructions with respects to fatigue and fracture mechanics, Journal of Applied Engineering Science, Vol. 8, No. 4, pp. 181-188 7) Perović Z.D. (2014): Accuracy of numerical methods for assessment of fatigue crack growth in welded joints, Zavarivanje i zavarene konstrukcije, vol. 59, no. 4, pp. 151157 8) PNAE G-7-002-86. Standards of strength calculation of equipment and pipelines of nuclear power plants (1989): Moscow: Metallurgiya, 524 p. 9) SP 16.13330.2011. Steel structures. The updated edition SNiP II-23-81* (2011): Moscow: OAO «TsPP» Publ., 173 p. 10) Tetelman A.S., McEvily A.J. (1967) Fracture of structural materials, New York: John Wiley, p. 186 11) Wood W.A. (1958): Recent observations on fatigue fracture in metals. ASTM STP 237, pp. 110-121 Paper sent to revision: 04.02.2016. Paper ready for publication: 05.03.2017.

1) Emelianov O.V., Bultykov A.V., Shuvalov A.N. (2012): Influence of Design Parameters of Elements Welded of Double Angles on the Level of Stress Concentration of Connection in the Zone of a Gusset Breakage, Industrial and Civil Engineering, 12, pp. 10-12 2) Eremin K.I., Makhutov N.A., Pavlova G.A., Shishkina N.A. (2011): The register of accidents of buildings and constructions of 20012010, Magnitogorsk: Magnitogorsk publishing, 318 p. 3) Kogaev V.P., Makhutov N.A., Gusenkov A.P. (1985): Calculation of machine parts and 172

Journal of Applied Engineering Science 15(2017)2, 425

Original Scientific Paper

doi:10.5937/jaes15-13245

Paper number: 15(2017)2, 426, 173 - 180

IMPACT OF DIGITAL FACTORY TOOLS ON DESIGNING OF WAREHOUSES Monika Bučková* University of Zilina, Faculty of Mechanical Engineering, Slovakia Martin Krajčovič University of Zilina, Faculty of Mechanical Engineering, Slovakia Boris Jerman, University of Ljubljana, Faculty of Mechanical Engineering, Slovenia In this article the basic information for cost reduction in warehouse facilities by use of new technologies is presented. The core of article constitutes of the description of new technologies and their impact on design warehouses. The article discusses the influence of new technology on the way the data is collected, on the storage of goods, their processing and on the sequences of delivery of goods to customers in the requested format and quality. Key words: Warehouses, Logistics, 3D designing, Static analysis, Simulation INTRODUCTION One of the most important parts of company logistics system is storage which somehow intersects space and time. It’s an activity where the physical and other parameters of the stored material should not change. From an economic point of view the stored material do not gain greater utility value; on the contrary, the storing gives rise of costs, which further affect the profitability of products. Therefore, the logical action of companies is to minimize their stocks and thus minimize the storage costs. Storage and its proper functioning has a significant impact on ensuring a higher level of customer service and on protection of utility value of goods [05]. The possibility of usage of software for 3D warehouse designing, for fast static capacity calculations and for computer simulations of warehouse operations during early stages of the designing process (development of technologies, design of warehouses and their logistics) present an obvious advantage. It allows systematic control of the design process, by which the balance between goals and resources of the company can be achieved. Through the numerical calculations of factors which affect storage process, the so called “bottle necks” and other problematic areas of the warehousing process can be identify. Because of the increasing demands for the reduction of the time between the issuance of individual parts or semi-products from the storage, the emphasis on quality stor-

age design and preparation of storage processes is increasing. Such a preparation can detect and eliminate problems in storage processes in the planning phase before putting the semiproduct into the real-world production or before the shipment of goods to customers. Between main questions that for warehouse planning and designing can be included for example [01]: • Specify way how to evaluate the effectiveness of storage management. • Specify the methods of picking or of modifications of goods according to the order. • Capacity planning in the warehouse. • Editing and evaluation of material flow in the warehouse. • Analysis of the influence of automated systems on warehouse management. • Labor needs, etc.

Methods of digital factory as 3D modeling, automated static capacity calculations, computer simulation and automated data collection can provide us answers to these questions. These methods belong to main current trends in designing of warehouses. Between other trends we can for example include [01]: • Globalization (integrated logistics, creating global markets, global competition and production, worldwide sales and purchase). • Pressure to reduce costs to remain competitive in global markets. *University of Zilina, Faculty of Mechanical Engineering, 010 26, Univerzitná 8215/1, 010 08 Zilina, Slovakia; 173 monika.buckova@fstroj.uniza.sk

Monika Buckova - Impact of digital factory tools on designing of warehouses

• Requirements of customers for personalized products and services. • New information and communication systems and technologies. • Legislative requirements (for example Waste act, Green logistic concept). • Increasing demand for specialty workers. DESIGNING OF WAREHOUSE Designing of warehouse is complicated, multilevel system, which is continually influenced by various factors. Project of warehouse designing requires implementation of several basic steps:

We can divide all basic steps into three main phases: 1) Phase - Technical solutions of warehouse 2) Phase - Layout of warehouse 3) Phase - Organizational solutions of warehouse This complicated, creative activity requires highly qualified specialists. Members of designing team are selected according to phase of designing. Therefore designed model of storage must be simple, information must be clear and communication between team members must be prompt. WAREHOUSE DESIGNING USING DIGITAL FACTORY Modern warehouses are working in dynamic environment of global supply chains.Companies must be able to compete in dynamic markets. Therefore quick design of warehouse and logistics processes is essential. As it is important in companies to plan deployment of assembly or production workplaces, it is important to plan storage and logistic processes. In recent years companies begin to use digital factory concept to accelerate designing process and to eliminate risk of wrong design. Digital factory represents the most progressive approach to complex, integrated design of products, manufacturing processes and manufacturing systems. Concept of digital factory is based on three elements [09]: • Digital product with its static a dynamic aspects. • Digital design of manufacturing process. • Digital manufacturing with usage of planning data for increasing company processes.

Figure 1: Steps of warehouse designing

174

Digital factory modules designed for warehousing and logistics offer all necessary features for design and verification of all aspects of warehousing process. Processes of storage and warehouse logistics can be visualized with 2D and 3D animation and improved by connecting individual software solutions for 3D design, static parameters calculation and computer simulation. Digitizing, modeling, simulation and emulation are used to understanding of comprehensive manufacturing processes and creation of new knowledge, which is used for optimization of real production systems [06].

Journal of Applied Engineering Science 15(2017)2, 426

Monika Buckova - Impact of digital factory tools on designing of warehouses

Modern computer equipment complemented with warehouse designing software allows transition from standard technology design (for example mechanical drawings in 2D view) to complete 3D view on storage model and to dynamic verification of processes using computer simulation.

panies, direct production to international markets, working with electronic documentation etc. We can include between main requirements for realization of virtual development environment: • Optimized business processes. • The availability of electronic data about products and processes for all team members. • Electronic documentation. • Communication interface to outside world. • Easy to use of all tools at workplace, for example: through tablet, phone, etc. The impact of new trends and continued development of technologies causes, that tools and methods of digital factory can be currently included into all steps of warehouse designing. Digital factory tools is used as sectional element and we can use it as communication tool to exchange data in various design phases.

Figure 2: Software connection between Factory CAD / Flow and Tecnomatix Plant Simulation 12.1

Processes of 3D storage designing are currently changing. They are characterized by aspects such as rising complexity, shortening intermediate times, larger development teams, same development goals, globally operating comJournal of Applied Engineering Science 15(2017)2, 426

Figure 3: Using digital factory tools for designing warehouse scheme

Development of above mentioned requirements causes that 3D designing, static calculations, computer simulation and system for automated data collection are gradually included in initial steps of warehouse and logistics designing. 175

Monika Buckova - Impact of digital factory tools on designing of warehouses

Implementation of these tools moves towards to collection constantly greater number of data. Therefore connectivity between systems should be the first condition of successful usage of systems.

mation points, visualize them and hiding them. It is possible to place object in warehouse layout with accuracy of millimetres, and to rotate objects by using these added animation points.

INPUT INFORMATION FOR WAREHOUSE MODELS CREATION Necessary data to establish program of warehousing are based on production plan, yearly quantity of production and norms of material consumption per product. From these data, will be determined yearly need for different types of materials. All collected data that software can get are important for creation of individual logistics elements statistics. Calculated statistics are basis for optimization or improvement. Therefore, at the beginning of designing and improving, it is important to select goals such as reducing costs, improving inventory levels, service levels, improve ROI values etc. The most important step is enabling software to collect data, to sort data, to process them and then to send them to team members online. Members can make better decision while designing processes with collected information. 3D MODELLING During the first phase of designing of warehouse and its logistics is appropriate to start with 3D digitizing because it facilitates and accelerates another analyses of input data. Digitalization opens the door to great opportunities. The digital future will combine the products with the software solution, which is already happening [10]. For creating 3D models of warehouse and logistics elements can be used manual collection of information, created 3D libraries or 3D laser scanners. Created 3D models are basis for creating mechanical drawings, for design of most suitable warehouse area arrangement, for optimization of material flows and for final visualization of the designed solution. The combination of software applications with hardware resources like 3D projectors, 3D cameras, 3D scanners, allows interpretation of future warehouse real picture in virtual reality [03]. Information obtained in the first step of warehouse designing is used to create models of warehouse hall, manipulated objects and logistics. Created objects and their individual elements can be flexibly animate in software. New possibilities of software allow adding and removing these ani176

Figure 4: Object created in Inventor Professional, stored in the form .JT then uploaded to Tecnomatix Plant Simulation

Enrolment of graphical inheritance depends on created graphics. It is always necessary to duplicate entire graphic object. This duplication of facilities is particularly challenging for the graphics card of computer. Long processing graphic data can cause problems with model rendering. Therefore it was developed option to create our own 3D libraries. It is possible to create own special folder where own specific models can be saved and thereby reduce duplication time of model itâ&#x20AC;&#x2122;s processing. In this step the process of define 3D models and interconnectivity between various software is important, because it facilitates the work of team members. 3D LAYOUT DESIGN AND STATIC CALCULATION DURING WAREHOUSES DESIGNING 3D designing is applicable in design of warehouse building and in verification conflict situations between static and dynamic elements Journal of Applied Engineering Science 15(2017)2, 426

Monika Buckova - Impact of digital factory tools on designing of warehouses

is to use single database of 3D models for all software tools and ability to use 3D models that are constantly updated. Perfect example is connection between software for 3D designing, static capacity calculation and computer simulation, where same database can remove duplication of data collection and data evaluation.

Software for analysing material flow offer possibility of creating analyses, reports, graphs that are basis for improving warehouse logistic solutions. They are primarily used in process of detailed store design. The disadvantage of software designed for 3D design and static calculation can be small range of analyses implemented into software, impossibility or small possibility to create own specific analyses for individual companies. Software for static analyses and 3D viewing of warehouses also do not involve sequence of processes in analysis. Therefore warehouse design should continue with computer simulation after 3D design and static analysis. COMPUTER SIMULATION IN WAREHOUSE DESIGNING

Figure 5: Viewing material flow in the software for 3D designing and static analyses Factory CAD / Flow

Connected software modules for 3D designing, for static capacity calculation and optimization of material flow objects makes it possible to improve layout of warehouse and calculate logistic capacity in one step. You can analyses using such as connection for example: • Transport distances. • Frequency of transport included with transport costs. • Total length of material flow. • Total number of rides. • Total time of transport and handling. • Quantity of transport material. • Unavailable time of transport equipment. • Total capacity of transport equipment. • Needed warehouse space, etc. Journal of Applied Engineering Science 15(2017)2, 426

Computer simulation allows effectively emulate and predict behaviour of selected dynamic process considering to their abilities and has many benefits. It helps managers at all levels of company to make responsible decision. It is based on capturing of real state or expected state of production system, its essential processes inside system and connections to external systems which may affect the entire production system and transformation them as computer model to virtual world, where we can make experimentations with virtual system. Simulation is one of the best tools for experimenting with proposals to improve material input processes, deployment of goods in warehouse, goods despatch or delivery processing etc. Every change is made in virtual enterprise and therefore we can decide which alternative is suitable for us before we implement this change in real system [02]. Pre-designed layout and concept of processes serves as basis for creation of conceptual simulation models. After conceptual simulation models are approved they will accelerate creation of detailed simulation models. We can described several steps to use simulation model in detailed warehouse design: 1) Creating of conceptual model - Conceptual design simulations should be easy to use and facilitate effective communications. During this design phase, many options remain open including site and warehouse layout, delivery schedules and operating hours. Unfortunately, historical data often is not avail177

Monika Buckova - Impact of digital factory tools on designing of warehouses

able, let alone detailed equipment specifications. However, the extensive capabilities of simulation software support conceptual simulations that facilitate quick ware house design, process flow animation and the visualization of key performance indicators. [11] b) Detailed warehouse design – This step determinates many warehouse specification: capacity of warehouse and handling units, turnover of product range, size of production and transport batch, capacity of operators. c) Creation of detailed simulation model - Creation of a model created on the basis of approved and verified data from detailed design. d) Evaluation of simulation results – set, selection and evaluation indicators, which the company wants to monitor. This phase also shows influence of random events on warehouse and helps to select so called “bottle necks”. e) Planning and optimization of operations – We can use found “bottle necks” to optimize layout and processes in warehouse. Optimization answers the question: What can ensure optimal outputs of a given model when changing values of inputs? As objective and universal criterion of optimality in warehouses, the total costs of warehouse are most often used [04]. f) Creation of final version of warehouse layout and final version of designed processes. g) Selection of data collection method – estimate connection between simulation model and designed warehouse by clarifying question of how the simulation model will be used for daily/weekly planning, how data will be collected and how to process these data. h) Redesign of existing processes - editing model and other proposals to experiment with it - At various intervals, every warehouse operation requires redesign. For example, redesign usually becomes necessary when new customers have to be served or technological innovations are introduced. Simulation is extremely valuable in these instances. Accurate data is readily available for existing operations. Simulation is perfect tool to address even the most challenging redesign efforts. You can quickly and accurately build simulation models, as well as communicate alternative designs and results in clear reports and 3D animations [11].

178

Figure 6: Visualization of material flow in software Plant Simulation

The most important connecting element between each step from 3D modelling to computer simulation is feedback. All software components effect on how the warehouse and logistics will be designed. Changes made in detailed simulation models should be able to transfer back to layout and to designing of processes. Therefore common database is needed. AUTOMATED DATA COLLECTION Feedbacks manage behaviour of complex systems. Therefore feedbacks are very important for modelling and simulation. One of the biggest mistakes in use of computer simulation in designing of warehouses is not to transfer simulation model from designing phase to phase of planning and management in daily functioning of store. Model must be prepared for using during designing phase and also for working in daily planning. If model has right construction we can implement into model data from forecasts as well as data from real “world” during daily work of warehouse. Therefore it is necessary to have regard on technology of automated data collection and data acquisition while designing store and building simulation model. Recent software for automatJournal of Applied Engineering Science 15(2017)2, 426

Monika Buckova - Impact of digital factory tools on designing of warehouses

ed data collection and processing data allow: • Securing wireless communications networks. • Monitoring and supervision of logistic vehicles. • Automatically control of logistic elements in system. • Remote elements monitoring of logistic system. • To gather data and information on operations for further processing. • Process collected data and create reports and analyses like special OEE software for transport equipment. • Planning logistic resources based on collected data. • Generate and share analysis results to other software – for example: software for computer simulation. This data can be used in simulation software to make periodic simulations of requirements for warehouse and to estimate capacity utilization in logistics. For example introduction of automated logistics brings out significant time savings when transferring material even guarantee delivery of material to the production line at the right time and quantity without potential human errors [08]. Enterprises need to have an integrated telecommunications network and information technology through which they can transmit the necessary information and dates within the organization too [07]. Using and automatization of data collection process, transmission for computer simulation, automatic periodic runs of simulation model and automatic generation of results can be used to create warehouse control mechanism. This mechanism is capable for early detection of massive requirements on storage capacities and to alert managers for intervention. Using such a simulation model managers can test multiple variations of corrective actions and select the most suitable solution in terms of capacity and economic indicators. Therefore the use of digital factory tools is advantageous. Usage of these tools do not end in warehouse designing. These tools can be used in planning of daily activities in warehouse with right setup of processes and appropriate combination of software solutions. Remote and real-time assessment of machine’s performance requires an integration of many difJournal of Applied Engineering Science 15(2017)2, 426

ferent technologies including sensory devices, reasoning agents, wireless communication, virtual integration and interface platforms [05]. CONCLUSION Submitted processing of new trends using and their impact on warehouse designing indicates greater need for digital factory tools using in designing and optimizing storage. Through right chosen indicators, it is necessary to create model that will be able to exchange data between the designers, warehouse and managers. Correctly selected sequence of steps and use of 3D design in early stages of warehouse designing should be also used to support management decisions. Managers should have software that can analyse several potential solutions and allows to select the only one with the best output parameters. Further research and development in area of designing stores with using digital factory tools speeds up process of company logistics planning and improves warehouse management. Digital factory will increase quality and accuracy of management decisions and decrease time to adopt to new situations with greater potential for costs savings. ACKNOWLEDGEMENT This paper is the part of research supported by project KEGA 004ŽU-4-2016. REFERENCES 1) Dilský, S. (2014). Návrh systému interaktívneho logistického plánovania. Žilinská univerzita v Žiline - Strojnícka fakulta - Katedra priemyselného inžinierstva. Dizertačná práca 1 CD ROM. 2) Dilský, S. (2013). Simulation using digital factory software tool: Plant simulation. In AIE - Advanced industrial engineering: Monograph. (pp. 67-80). Bielsko-Biała. ISBN 97883-927531-6-2. 3) Furmann, R. (2011). 3D laser scanning: Support the implementation the digital factory. In Digital factory management methods and techniques in engineering production. (pp. 25-28). Bielsko-Biała: Wydawnictwo Akademii techniczno-humanistycznej. 4) Furtáková, S., Gregor, M., & Hnát, J. (2014). Simulation Metamodelling of Chosen Production System. In: FAIM: Proceedings of the 24th International Conference on Flex179

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ible Automation & Intelligent Manufacturing - Capturing Competitive Advantage via Advanced Manufacturing and Enterprise Transformation. Lancaster, USA: DEStech, Pennsylvania 17602.917-926. 5) Gregor, M., Haluška, M., Fusko, M., & Grznár, P. (2015). Model of Intelligent Maintenance systems. In: 6th DAAAM International Symposium on Intelligent Manufacturing and Automation. 1097-1101. doi:10.2507/26th. daaam.proceedings.154 6) Gregor, M., Herčko, J., & Grznár, P. (2015). The Factory of the Future Production System Research. In: ICAC: Proceedings of the 21st International conference on automation and computing, Glasgow, UK. Glasgow, UK.101105. doi:10.1109/IConAC.2015.7313998 7) Mičieta, B., Biňasová, V., & Haluška, M. (2014). The approaches of advanced industrial engineering in next generation manufacturing systems. Communications: Scientific letters of the University of Žilina, 16(3A),

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8) Mičieta, B., Herčko, J., Botka, M., & Zrnić, N. (2016). Concept of intelligent logistic for automotive industry. Journal of Applied Engineering Science, 14(2), 233-238. doi:10.5937/ jaes14-10907 9) Palajová, S. (2012). Simulačné metamodelovanie výrobných systémov. (p. 149). Žilinská univerzita v Žiline - Strojnícka fakulta - Katedra priemyselného inžinierstva. Dizertačná práca. 10) Rakyta, M., Fusko, M., Herčko, J., Závodská, Ľ., & Zrnić, N. (2016). Proactive approach to smart maintenance and logistics as a auxiliary and service processes in a company. Journal of applied engineering science, 14(4), 433-442. doi:10.5937/jaes14-11664 11) Retrieved from http://www.cardsplmsolutions. nl /en/plm-software/tecnomatix/plant-simulation-warehousing -logistics-7 2016 Jun 20. Paper sent to revision: 21.02.2017. Paper ready for publication: 27.04.2017.

Journal of Applied Engineering Science 15(2017)2, 426

Original Scientific Paper

doi:10.5937/jaes15-13926

Paper number: 15(2017)2, 427, 181 - 186

COMPARATIVE REVIEW OF THE RISK ASSESSMENT QUANTITATIVE MODELS FOR PUBLIC OPEN SPACES LIGHTING DESIGN OPTIMISATION Ivan Milorad Rakonjac* Unicons University, Faculty of Project and Innovation Management, Belgrade, Serbia Ivana Milorad Rakonjac University of Belgrade, Faculty of Architecture, Belgrade, Serbia Miloš Petar Gašić University of Belgrade, Faculty of Architecture, Belgrade, Serbia The key focus in the paper is on the presentation of the risk assessment model in the optimisation design process by establishing the link between the various phases that result in the successful project implementation. Through the comparative analysis of the quantitative risk assessment models a number of impacts on the design process are shown which occur in different project phases. This approach has proved the RAKA model (Risk Analysis by Key-factors Assessment) to be the most adequate mathematical model for the assessment of the risks on the project goals in the optimisation process of the development of the products for the accomplishing lighting of the open public spaces. The particularities of the model are best described by the predetermined criteria which contribute to the optimisation of the design process through the quantitative analysis of the project risks, according to the predetermined project goals sets. The influence of the risks on the project goals are shown by mathematical formulas in which the criteria of the design team are taken into account, leading to the efficiency improvement and enhancement in the implementation phases of the project. Key words: Risk management, New product development, User needs, Ambiance value INTRODUCTION Primary aim of the lighting in a public open space is to enable perception of the elements in space and provide a safe environment for the users in the night hours. The importance of the lighting lies in achieving the primary aim through yielding a pleasant ambiance and providing a desirable visual experience by accentuation of the architectural values in space. A favourable lighting should provide not only minimal ambiance lighting which reveals the points of risk and enables orientation, but also the emphasis on the architectural values (Rakonjac et al. 2016). The optimisation of the lighting design process of the public spaces is possible through appropriate activity in the development phase of the industrial products for public space lighting. The production process of the urban lighting equipment is determined by the requirements which derive from the lighting design process which is influenced by the user needs, as well as the conditions of the spe-

cific space. Therefore, it is of vital significance to determine the requirements and to systematically follow the process of their fulfilment from the very beginning of the development process, by documentation and information flow (Ninkovic et al. 2012). Every deviation from the requirements can be tracked in the later phases of the design process in multiple ways. Risk management is a very important aspect within this concept. RISK MANAGEMENT Risk management in the design process of the projects has been recognised in previous research (Cooper, 2003; Kayis, Arndt, & Zhou, 2007, Stamenkovic et al. 2011), but it was not sufficiently considered in literature, especially when a new industrial product development is aimed (Keizer, Vos, & Halman, 2005; Gidel et al. 2005). Empirical research in this field is rarely applied (Oehmen et al. 2014). The importance of the quantitative risk analysis in the design process of the public space light

*Unicons University, Faculty of Project and Inovation Management, Bože Jankovića 14, Belgrade, Serbia; ivan.rakonjac@gmail.com

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Ivan Milorad Rakonjac - Comparative review of the risk assessment quantitative models for public open spaces lighting design optimisation

ing was presented in the paper (Rakonjac et al. 2011) along with the mathematical model for the assessment of the level of influence of the risks to the project goals, by the acronym RAKA (Risk Analysis by Key-factors Assessment). Risk management is the process which is treated by the model in the industrial product development process aimed for the lighting of the public spaces. This process is the integral part of the project management and it is depicted as a system on the Figure 1. The concept of the system is based on the impact of the managerial structure within the system of the project, devoted to the achievement of certain project goals.

Having in mind the unstable nature of risk, one disturbance can lead to the error occurrence simultaneously at multiple pairs of input-output variables. Also, a set of disturbances can provoke an error for one pair of input-output variables. Since a risk can have positive or negative effect on the project goals (PMI 2008, Ward 2010) equivalently the nature of disturbance will result with the error occurrence in the system which would be characterised as favourable if it has a positive influence on the project goals, or unfavourable if it has negative influence on the project goals. The nature of the error is stochastic in most of the cases (Gidel et al. 2005, Stanisavljev et al. 2015). Figure 2 depicts the characteristic of the error.

Figure 1: Block diagram of the project management process

PM stands for the project management structure, while RM stands for project risks management. The input variables to the system are presented by the predetermined project goals, while the output variables show the accomplished values. These variables can be shown as input vectors X= (x1, x2, x3,..., xn) and output vectors Y=(y1, y2, y3, ..., yn) respectively, with the elements (x1, x2, x3,..., xn) displaying the wanted outcomes followed by the realised goals (y1, y2, y3, ..., yn). The risk represents a disturbance in the system, namely an unpredicted change of variables which influences the outputs of the system. These disturbances can be generated within system (internal risks) or outside of the system (external risks). The disturbance occurrence in the system causes deviations of the realised project goals in comparison to desired (predetermined) project goals. This deviation is called an error. Hence, the very notion of disturbance, or risk, is directly attached to the notion of error. The equation 3.1 shows the error for the i pair of the input-output variables. Zi=Xi - Yi

182

(1)

Figure 2: Characteristic of the error

The managerial structure of the system inclines towards direct, proactive and/or corrective compensation for the disturbance, by means of feedback. If the error is favourable, it has to be taken advantage of, so that the project goals would be met or even surpassed. If the error is unfavourable, compensation is needed. To make this process feasible, it is necessary to apply some of the appropriate models for quantitative assessment of the system disturbance level, i.e. risk. Based on the previous considerations, as well as the known nature and mechanisms for project risks quantification, the following systems features can be identified: â&#x20AC;˘ Input system variables represent the desired project goals; â&#x20AC;˘ Output system variables represent the achieved project goals; â&#x20AC;˘ An error occurs by deviation of the achieved from the desired project goal; Journal of Applied Engineering Science 15(2017)2, 427

Ivan Milorad Rakonjac - Comparative review of the risk assessment quantitative models for public open spaces lighting design optimisation

• System disturbances are project risks. • One disturbance can provoke the occurrence of multiple errors in the system; • Multiple disturbances can provoke the occurrence of one error in the system; • Probability of the error occurrence in the system is directly linked to the probability of the risk occurrence; • Probability of (non)detection of the error occurrence is directly linked to the (non)detection of the risk occurrence, • Probability of the error appearance in the system is determined by the probability of the occurrence and the probability of (non)detection of the system error; • The error magnitude signifies a relative measure of deviation of the output to the input variable, and it is directly influenced by the magnitude of the risk consequences; • The favourable error occurs under the effects of risks which are identified as opportunities. • The unfavourable error occurs under the effects of risks which are identified as threats. • The total disturbance level of the system is called the risks sum and represented as the function of the error occurrence and the error magnitude. Since the set of the systems features is defined, one can approach to identifying the available mathematical models for the risk assessment.

The assessment of the error magnitude, which represents the impact or the consequence of the risk event on the project goals in terms of the plan and the budget, should be displayed by a simple function. On the other hand, modelling of the technical product features is left to the user, given the particularities of the process of the industrial product development which is subject to the project risks quantification. In this case, the product is the equipment for the lighting of the open public spaces. There is often confusion when it comes to terminology in the project risks management, and the mix up of the notions (Carbone and Tipett, 2004). It is therefore necessary to uniformly define the variables. A comparative view of several available models for the risks quantification is provided in the Table 3.1. The models can be applied on the project of industrial product development for the lighting of the open public spaces. After reviewing the Table 1 it can be noted that the models proposed by Carbone and Tippett (2004) and by Kerzner (2009) are different from the RAKA model since the risks recognised as the opportunities are not taken into account. In addition, the quantification result has different purpose. Kerzner (2009) uses the mathematical function which determines the risk factor as the multiplication of the failure probability factor and the failure consequence, as follows:

MODELS FOR THE QUANTITATIVE PROJECT RISKS ANALYSIS

F=Pf + Cf - PfCf

After all the available approaches were analysed, their deficiencies were ascertained as well as their advantages, the principles for selecting the model can be established. The framework of the model should have the quality to enable a wide array of application, and the relevant approach towards complexity. The model has to be complex to the extent in which the project of the public space is complex. The probability of the risk occurrence is additionally determined by the feature of manifestation, namely how the system disturbance is revealed, by multiplying the occurrence probability with the (non)detection probability of the actual disturbance.

Journal of Applied Engineering Science 15(2017)2, 427

(2)

where Pf stands for the probability of failure and Cf for the consequence of failure. The RFMEA (Carbone i Tippett 2004) introduces a tool that is relatively simple and intuitive. By modification of the standard FMEA format, in the RFMEA the concept of risk presentation is expanded by adding the attribute of risk detection. In this way, a new value is added to the model which allows for more precise calculation of the risk level and the priority number of risks. However, the major drawbacks of this model are incapability of generalisation of the variables, and the necessity to have internal scales and the risk legend. In the standard FMEA process, modalities of failure are appraised by occurrence, severity and detection of collapse. 183

Ivan Milorad Rakonjac - Comparative review of the risk assessment quantitative models for public open spaces lighting design optimisation

Table 1: Comparative view of the project risks quantification models

RAKA model Rakonjac et al. (2011)

RFMEA Carbone and Tippett (2004)

Risk Value Method Browning et al. (2002), Browning and Hillson (2003)

Risk assessment model Kerzner (2009)

Probability of error appearance

Probability, Uncertainty

Probability of failure

Probability of error occurrence

Likelihood

Probability of (non) detection

Detection

Error magnitude

Impact

Consequence, Impact

Consequence of failure

Risk (Disturbance)

Risk Event

Risk

opportunities

Combined effect

Threats

Combined effect

Threats

Quantification Result

Risks sum (the level of risk on the project goals)

Risk value (the level of risk on the project goals)

Risk factor (total effect to all the project goals)

Result representation

[0,1]

Terminology

Threats/

Risk score Risk priority number Internal scale, risk legend

By multiplying these three values, the risk priority number (RPN) is obtained: RPN=OSD

(3)

where O stands for t he occurrence of failure, S for the severity of failure, and D for the detection of failure. Besides the risk priority number RFMEA model incorporates the risk score as multiplication of the likelihood and the impact (Carbone and Tippett 2004). The risk value method proposed by Browning et al. (2002), which is described in more detail in the paper from Browning and Hillson (2003) represents the model that describes the product attributes by the utility functions. The model is described by the following equation: (4) in which stands for the product attributes, J for the vector of the m attribute of the product, and U for the utility function, which assigns one number to each option of the given attribute J. 184

Even though the risk detection cannot be taken in consideration by this model, it is essentially very similar to the RAKA model. If the terminology distinctions are set aside, as well as the fact that RAKA model includes the concept of detection probability, or probability of not detecting the error, depending on the error deriving from either opportunity or threat, there are differences in the functions which connect these variables. The â&#x20AC;&#x153;Risk Value Methodâ&#x20AC;? (Browning et al. 2002, Browning and Hillson, 2003) has focus on the quantitative analysis of highly complex systems, presenting the risk value as the integral of the multiplication of the probability and the impact for all the risk outcomes. On the other hand, through the RAKA model the impacts of all the risks (both opportunities and threats) which influence all the project goals are integrated. In this way, the approach to the quantification of risks sum is simplified, since it is often not possible to ascertain the influence of every single risk to the deviations of the achieved project goal in comparison to the predetermined goal, especially when the effects of all the risks are combined. Journal of Applied Engineering Science 15(2017)2, 427

Ivan Milorad Rakonjac - Comparative review of the risk assessment quantitative models for public open spaces lighting design optimisation

The above considerations can be explained by the formula: (5) where the abbreviations stand for: - total number of the elements of the project goal set , total number of the elements of the set identified as the threats, (ni-mi) - number of the elements of the set identified as the opportunities, - consequence of the error, where l stands for the predefined project goal, Pe’- probability of the occurrence of the unfavourable error, Pd’- probability of not detecting the error due to the risk classified as the threat, Pe’’ - probability of the occurrence of the favourable error, Pd’’- probability of detecting the error due to the risk classified as the opportunity. The RAKA model allows for the quantitative assessment of the risks sum for combined effects of the identified set of risks on the project goal. The universal nature of the RAKA model can be seen from the fact that all the variables are determined on the interval, so that there is no need for an additional legend or a key to understand the quantitative risk levels. Also, this model equally encompasses the threats and the opportunities, making the quantification of the combined influence of all the risk events on project goals possible. This also implies the risk level estimation for all the determined project goals, which may prove as valuable information in the process of risk action planning. The application of the model in industrial product development for the lighting of the public open spaces particularly contributes to the advancements in the lighting design process. These advancements can foremost be identified as the savings of time in the design process, and also in the implementation phase of the projects of the lighting of the public open spaces.

Journal of Applied Engineering Science 15(2017)2, 427

CONCLUSION It can be concluded that all of the reviewed models can be applied in practice. However, in cases when the focus is on the risk management in the optimisation process for the lighting design of the public open spaces, it is of critical importance to incorporate the combined risks influence on the project goals, taking the threats as well as the opportunities into account. Of all the presented models only the RAKA model makes this approach possible. As previously explained, to achieve a successful lighting design project of the open public space it is important to address the requests that determine needs for undisturbed activities flow, as well as obtaining the aesthetic values. This can be accomplished through the design of the urban lighting equipment, including previously mentioned technical and aesthetic features. Considering that the ergonomic and aesthetic criteria are included in the RAKA model, its contribution is apparent in the advancement of the lighting design process by optimisation of the lighting equipment in the development and production phases. Since the end users and their needs are envisioned by the model, the requirements for more efficient functional lighting are better met and the security and safety issues more adequately addressed. These improvements can be noted in both the design and implementation phase of the project. On the other hand, by emphasizing the aesthetic criteria of the product in the risk management model it is possible to achieve a step forward in harmonising the urban lighting equipment appearance with the architectural value system. Determination of these ergonomic and aesthetic criteria would enable more successful light effects achievements in the process of design, which contributes to an adequate ambience and the space aura. Considering that the open space lighting can be regarded as an obligatory element within any urban space structure, the RAKA model can also be implemented in the field of the trade export promotion (Spasojević-Brkić el al. 2015). The RAKA model proves as an universal risk assessment model for the urban city spaces design process, because it answers the need to achieve both functional lighting and to accentuate architectural and ambience space values in the process of industrial product development for the open public space lighting. 185

Ivan Milorad Rakonjac - Comparative review of the risk assessment quantitative models for public open spaces lighting design optimisation

REFERENCES 1) Browning, T. & Hillson, D. (2003). „A quantitative framework for multi-dimensional risk and opportunity management“, Working Paper, Texas Christian University, Neely School of Business, pp. 1-28. 2) Browning, T.R., Fricke, E. & Negele, H. (2006) „Key concepts in modeling product development processes“, Systems Engineering 9(2), pp.104–128. 3) Carbone, T.A. & Tippett, D.D. (2004) “Project Risk Management Using the Project Risk FMEA”, Engineering Management Journal, 16(4), pp.28–35. 4) Cooper, L.P. (2003). “A research agenda to reduce risk in new product development through knowledge management: a practitioner perspective.” Journal of Engineering and Technology Management, 20(1), pp. 117140. 5) Gidel, T., Gautier, R. & Duchamp, R. (2005). “Decision-making framework methodology: An original approach to project risk management in new product design”. Journal of Engineering Design, 16(1), pp. 1–23. 6) Kayis, B., Arndt, G., & Zhou, M. (2007). “A risk mitigation methodology for new product and process design in concurrent engineering projects”. CIRP ANNALS Manufacturing Technology, 56(1), pp. 167–170. 7) Keizer, J.A., Vos, J. & Halman, J.I.M. (2005). “Risks in new product development: Devising a reference tool”. R&D Management, 35(3), pp. 297–309. 8) Ninković, D., Sedmak, A., Rakonjac, I., Misita, M. (2012) „Information-communication and Documentation Flow within R&D Function Model“. Technics Technology Education Management, 7(1), pp. 137-146. 9) Oehmen, J., Olechowski, A., Kenley, C.R. & Ben-Daya, M. (2014). “Analysis of the effect

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of risk management practices on the performance of new product development programs”. Technovation, 34(8), pp. 441-453. 10) Rakonjac, I., Rakonjac, I., Kirin, S., Spasojević-Brkić, V., Sedmak, A. (2011). “Risk Analysis by Key-coefficient Assessment - Public Lighting Project Example”. Technics Technology Education Management, 6(4), pp. 1016-1023. ISSN 1840-1503. 11) Rakonjac, I., Rakonjac, I., Fotirić, N., Rajković, I., Gašić, M (2016). “Аnaliza svetlosnih karakteristika u eksploatacionom veku instalacije osvetljenja / Lighting Features Life Cycle Analysis for a Lighting System”. Structural Integrity and Life, 16(2), pp. 81-86. ЕISSN:1820-7863, ISSN:1451-3749. 12) Spasojević-Brkić, V., Veljković, Z. & Golubović, T. (2015). “Fulfilling the requirements for export of metal industry products from Serbia and Bosnia and Herzegovina cross-border area to EU market”. Journal of Applied Engineering Science - JAES, 13(3), pp. 25-36. DOI: 10.5937/jaes13-7785. ISSN: 1451-4117. 13) Stanisavljev, S., Ćoćkalo, D., Klarin, M., Spasojević, B.V. & Đorđević, D. (2015). „Stohastic Model to Determine the Elements of the Production Cycle Time: Case of Serbian Textile Industry”. Fibres & Textiles in Eastern Europe, 23(5), pp. 23-29. 14) Stamenković, D., Popović. V., Spasojević Brkić, V. & Radivojević, J. (2011). “Combination free replacement and pro-rata warranty policy optimization model”. Journal of Applied Engineering Science, 9(4), 456-464. DOI: 10.5937/JAES9 - 1202. ISSN: pp. 14514117. Paper sent to revision: 02.08.2016. Paper ready for publication: 07.05.2017.

Journal of Applied Engineering Science 15(2017)2, 427

Original Scientific Paper

doi:10.5937/jaes15-12449

Paper number: 15(2017)2, 428, 187 - 191

INVESTIGATION OF FEEDING ROLLERS ALIGNMENT IN A HORIZONTAL PLANE Ol’ga Tarasova* Volga State University of Technology, Yoshkar-Ola, Russia Mariia Chernova Volga State University of Technology, Yoshkar-Ola, Russia This research represents the ways of estimation of woodworking machines’ feed roll-ers arrangement in a horizontal plane as exemplified by control of the position of the feed rollers axes on a frame saw. Some significant considerations have been stated in relation to standard methods of control GOST 10294, which contain accuracy value and monitoring techniques. Some methods are recommended in the following research, which allow monitor-ing value of possible deviations of mutual arrangement of feed rollers in a horizontal plane. This is done with due consideration of inaccuracy of their setting, as well as radial beats that results from exploitation, by means of conducting measurements in two mutually perpendicu-lar planes. Key words: Arrangement accuracy, Axes alignment, Feeding rollers, Setting inaccuracy INTRODUCTION Produce of solid timber has been in favour in all countries, in comparison with composite and polymeric materials. It has certain advantages in ecological and esthetic rates. It features high solidity, but as all materials it possesses some drawbacks, namely: anisotropic properties, flammability, non waterproof, a bit difficult in processing etc. Industrial timber stocks decrease gradually. Legal and illegal cutting, forest fires and other factors contribute much to this process. For this reason, manufactures have to solve the problem of efficient use of round timber involving added-value wood conversion, introduction of new technologies of processing and application of immediate diagnosing of woodworking machinery status. Analyzing the situation in fitting enterprises of woodworking complex, specifically in Mari El Republic, Russia, it should be noted that manufacture of doors, windows, parquet blocks and other types of products often use machinery fitted in the 80-th of the previous century. Some minor exceptions are enterprises equipped in the early 2000. Physical deterioration and obsolescence of machine-tool holding arises. Only up-to-date diagnosing and scheduled preventive repair with adjustment on manufacturing and geometrical accuracy together with replacing of cutting tool provide an opportunity to accomplish production

of quality products, which meet all consumers’ requirements [10, 1, 12]. Methods of diagnosing produce, tools, log-processing equipment (log frame) and other appliances are regulated in GOST 2140 – 81, GOST 5524 – 75, GOST 10294 – 90 [02, 03, 04], RPI [09, 11] and other reference documents. In order to adhere accuracy parameters of adjustment, equipment design should provide access of diagnostic devices to control points and cross-sections without disassembly of units and mechanisms. This should eliminate possibility of damaging the objects while connected to diagnostic (control) devices. Aim of the research: creation of the elements of immediate diagnosing system of the position of interworking parts of log-processing equipment in a horizontal plane. It should be based on the investigation and improvement of standard control methods with elaboration and standardization of new techniques. Objectives under solution: 1) to analyze reference documents and technical publications about control methods of geometrical and technological adjustment of log frame; 2) to substantiate type and construction for evaluation of deviation rectilinear surfaces (flat and cylindrical) from horizontal position of basing and guiding devices of woodwork-

*Volga State University of Technology, 424000, The Republic of Mari El, Yoshkar-Ola, Lenin Sq., b. 3., Russia; smirnovaev@volgatech.net

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Olga Tarasova - Investigation of feeding rollers alignment in a horizontal plane

ing machines and log frames. 3) to develop new techniques (instead of obsolete standards) on the basis of patented device and evaluate horizontal misalignment. The analysis of publications and reference documents [4, 5, 6, 7] has allowed to reveal about 40 control rates of log-processing equipment. Only 30% of them have standard techniques, most of which are out of date and considered to be improper. Relating to the process of timber manufacturing special attention should be given to the principal goals of technical diagnostics: • evaluation of equipment technical condition; • establishing quantitative connections between inaccuracies of timber and log-processing equipment; • risk assessment and working out of corrective actions subsequent to the results of equipment status control; • maintenance engineering and equipment repair; • feasibility study of further equipment service by taking into account forecasting of its technical condition with revealed defects involving the use of numerical scheme [10]. It is necessary to note that log frame construction is practically controllable without additional disassembling if upper and lower front gates are open. Therefore evaluation of technical status of mutually arranged parts of feeding and cutting

mechanisms represents no difficulty, excluding lack of improved methods of immediate control. The analysis of GOST 10294 has made possible to highlight some drawbacks of typical checkouts. Accordingly, most significant of them, in estimating horizontality of lower feeding rollers axes and location of lower feeding rollers in one horizontal plane could be considered as: • complication in basing the level on a narrow tested surface of a straightedge; • under considerable vibrations and inertial loads inclination of footing and frame may exceed measurement limits of the level. An invention is proposed in order to get through revealed troubleshooting. It refers to the field of measurements of rectilinear surfaces (flat and cylindrical) deviation from horizontal position and can be applied to increase measurement accuracy of these deviations by means of block levels of common accuracy in different branches of engineering. It is especially good for assessment of mutual parallelism of the feeding rollers axes on basing and guiding devices in wood-working machines and log frames. This technique includes level adjustment in a horizontal position on the tested surface with the help of special inclinometer. It differs in the fact that departure from horizontality measurement is carried out by means of detection device, while the level is used only for identification of horizontal position of inclinometer base.

Figure 1: Inclinometer Special inclinometer (Figure 1), placed on the tested surface, consists of two pivotally connected plain-parallel bars, one of which is a support block – 5, and another one is inclinable block – 4, it serves as a support for level –1. For setting in horizontal axis an adjusting screw – 3 is used. For measurement of inclination angle – indicator depthometer is used.

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Depending from measurable value, Lб – a baseline from the pivot axis to indicator axis is determined. The following technique [8] permits to decrease: • random inaccuracy in measuring device basing; • time and labour input needed for multiple metering in order to get average result with the given accuracy and reliability. Journal of Applied Engineering Science 15(2017)2, 428

Olga Tarasova - Investigation of feeding rollers alignment in a horizontal plane

According to the analysis and the invention, which was mentioned above, new techniques and facilities have been developed (Devices 1 and 2, represented in diagrams 1 and 3). They permit to estimate position of the rollers in a horizontal plane immediately without equipment

disassembling. Besides, they give an opportunity to consider inaccuracies of the installation, including existence of radial beats of the rollers by means of conducting measurements within mutually perpendicular planes.

Table 1: Horizontality of the axes of lower feeding rollers GOST 10294-90 Verification Scheme

Proposed Verification Scheme

Tolerance 0,4 for length 1000 mm;

1 –feeding roller shaft, 2 – linker, 3 – level

To conduct measurements it is necessary to make key lines on a shaft or a tooth wheel with graduation of 90 º, with setting point pairs 1 – 3 and 2 – 4, and mark a stationary part of the base or a floor to determine the moment of the accurate wheel (roller) shut down against points, marked on the wheel i=1…4 (Figure 2).

where: 1 – control bar, 2 – linker with supports, 3 – flat springs, 4 and 5 – left and right rollers necks,6 – indicator head, 7 –adjusting screw, 8 – level

h11=АГ + АМ + АR;

(1)

In order to exclude inaccuracies of production, Ам device is flipped through 180º (or replace onto another neck) and repeat the measurements. At the same time, roller axis deviations do not change, while inaccuracy of the linker changes its sign. h13 = АГ - АМ + АR;

(2)

When h 11 and h 13, sum up, АМ excludes h11+ h13= 2(АГ + АR) where АГ + АR=(h11+ h13)/2 (3)

Figure 2. Scheme of point pairs 1 – 3, 2 – 4 arrangement for readings and the point of the wheel (roller) shutdown

At setting the roller into position 1 – 3, Device 1 (table 1) is mounted on the necks on front lower feeding roller and adjusted on level horizontality by an adjusting screw. Indicator h, for Device 1 is shown in Table 1and the data for h11, h13, h31, h33,h22, h24, h42, h44 are represented in Table 2 and 3. They include deviation from horizontal axis АГ, inaccuracies of linker formation АМ and inaccuracies, connected with radial beat of necks АR:

Journal of Applied Engineering Science 15(2017)2, 428

For error exception from radial beat АR the roller is flipped through 180º and the device is mounted into position 3 – 1, so the measurement А31 is conducted: h31=АГ+АМ - АR;

(4)

After the device has been flipped through 180º, the measurements are repeated. At this, deviations of roller axis АГ and АR do not change, while the deviation of the device changes its sign. h13 = АГ-АМ-АR;

(5) Σ h11+ h13= 2(АГ - АR)→АГ - АR = (h31+ h33)/2 (6)

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Olga Tarasova - Investigation of feeding rollers alignment in a horizontal plane

roller is flipped through 90 º. The results of the given research are based on the estimation of log-processing equipment condition at the OAO “Woodworking manufacturing plant”, YoshkarOla, Russia. They are represented in Table 2.

Summarizing (3) and (6), radial beat excludes (АГ + АR) + (АГ - АR) =2 АГ - АR + АR = 2АГ → 2АГ =( h11+ h13 + h31+ h33)/2→ АГ=(h11+ h13 + h31+ h 33)/4 (7) After that the whole series of measurements is repeated in the plane 2 – 4. For this purpose,

Table 2: Horizontal axes inclination of lower feeding rollers measurement results Plane

Measurement Read-ings

1–3

2–4

Front / Rear lower feeding roller/ h

Average

h11

h13

h31

h33

h22

h24

h42

h44

11.383 /11.367

10.783 /10.933

10.833 /11.213

10.883 /11.117

11.65 /11.533

11.213 /11.183

11.567 /11.383

10.967 /11.117

h 0.6/0.434 Deviation from horisontal-ity

0,05/0,096

АГ1-3=(h11+ h13 + h31+ h33)/4 0.3/0.265

0.437/0.35

0.6/0.266

АГ2-4=(h22+ h24 + h42+ h44)/4 0.52/0.308

Average meaning of deviations from horizontality (Аг) = АГ1-3/ АГ2-4 = 0.41/0.276 mm

The suggested device enables to set rollers arrangement with a sufficient accuracy as well as the existing deviation from their horizontality (parallelism), which equals (Аг)̅=|ΔГПВΔГЗВ| = 0.41-0.276=0.144, scaled to standard length equals 2 mm, that 5 times exceeds the standard rate. Mutual parallel misalignment of feeding rollers in horizontal and vertical planes may serve

as one of the reasons for industrial timber production with crooking and flexion. Application of the new way of measurement based on the technique, mentioned above can also help to evaluate deviations of rollers’ axes in a horizontal plane with the help of Device 2, represented in the Table 3. The measurement results are given in Table 4.

Table 3: Arrangement of lower feeding rollers axes in one horizontal plane GOST 10294-90 Verification Scheme

Proposed Verification Scheme

Tolerance 0,4 for length 1000 mm;

1 and 2 – necks of front and rear lower feeding rollers, 3 – straightedge, 4 – level

190

Device 2, where:1 and 3 – necks of front and rear rollers, 2 – stop, 4 – proof bar, 5 – level support, 6 – level, 7 – adjusting screw

Journal of Applied Engineering Science 15(2017)2, 428

Olga Tarasova - Investigation of feeding rollers alignment in a horizontal plane

Table 4: Measurement results of inclinations of lower feeding rollers axes arrangement in one horizontal plane Deviation from horizontality, mm

h1-3

h2-4

Average deviation value ( h1-3 + h2-4)/2

Right side

11.45

11.05

11.275

11.6

11.5

11.55

11.41

0.275

Left side

10.85

11.05

10.95

11.1

11.0

11.05

11.0

0.1

Deviation from horizontality (Аг=) hП - hЛ

0.325

0.5

0.41

0.187

Plane 1 – 3

Plane 2 – 4

Average value

It was found that actual deviation from horizontality equals 0.41±0.09 on the roller length of 700mm, modified to standard condition of 1000 mm accounts for 0.51.mm, which is just above the standard value of 0.4 mm. CONCLUSION 1) Methods, proposed in the given research, along with calculation examples permit to achieve (by means of immediate control) consistent results of accuracy of mutual arrangement of feeding mechanism parts and to determine availability of deviations from parallelism in a vertical plane and, above all, respective horizontality. 2) Thanks to simplicity of construction these devices could be produced on any woodworking plant, providing 0.05 mm accuracy. 3) The main advantage of the recommended devices is the opportunity to evaluate woodworking equipment rollers arrangement in a horizontal plane even if a considerable deviation exists and far exceeds the limits of machinist level measurements, which is applied for estimation of equipment conditions. REFERENCES 1) Eklund, (2000), U Influencing factors in sawing accuraly in a bandsawill, Holz Roh – und Werkst. 2) GOST 2140-81 visible defects, of wood. Classification, terms and definitions, methods of measurement (1981), Mosсow, 118р. 3) GOST 5524 – 75 Saws for vertical gang mills, (1975), Mosсow, 10р. 4) GOST 10294 – 90. Woodworking equipment, Journal of Applied Engineering Science 15(2017)2, 428

Deviation from parallelism on vertical plane | h1-3 - h2-4|

Vertical two-storey saw frames. Basic parameters. Standards of accuracy (1990), 9р. 5) GOST 20911 – 89. Technical diagnostics. Terms and definitions, (1989), Mosсow, 9р. 6) GOST 25338 – 82. Woodworking equipment. Accuracy and rigidity test. General requirements, (1991), Moscow, 7р. 7) Tarasova O. G. Issledovanie i sovershenstvovanie standartnyh sposobov kontrolja i povyshenija kachestva piloprodukcii: dis.... kand. tehn, nauk. – М. 2011. – 259 p. 8) Pat. 2538480 Rossijskaja Federacija MPK V27B 27/00 G01C 9/24 Sposob dlja ocenki gorizontal’nosti ploskih i cilindricheskih poverhnostej / Bojarskij M.V., Tarasova O.G. №2012153655/13; Bojarskij M.JuV., zajavl. 11.12.2012; 10.01.2015 Bjul. № 1. 9) RPI 6.1-00, Rukovodjashhie tehnicheskie materialy po opredeleniju rezhimov pilenija na lesopil’nyh ramah (1987), Arhangel’sk: CNIIMOD. 10) Tarasova, O.G., S.V. Shlychkov, (2016), Vlijanie defektov tehnicheskoj sistemy na parametry proizvodimyh pilomaterialov, Remont, vosstanovlenie, modernizacija. № 1, p. 13–17. 11) Tehnologicheskie rezhimy RPI 6.1-00. Podgotovka ramnyh pil (1982), Arhangel’sk, CNIIMOD. 12) Vuorilehto, Jaakko. (2002) Quelity yield capability of a breakdown sawing process, Jaakko Vuorilehto, Forest Prod. J, 52№4, Р. 77-81. Paper sent to revision: 17.11.2016. Paper ready for publication: 25.04.2017.

191

Original Scientific Paper

doi:10.5937/jaes15-12935

Paper number: 15(2017)2, 429, 192 - 202

TRANSIENT SIMULATION OF IMPULSE WIND EFFECT ON A TALL SHIPYARD FRAME STRUCTURE Goran Radoičić* Public Utility Company Mediana, Niš, Serbia Miomir Jovanović University of Niš, Faculty of Mechanical Engineering, Niš, Serbia This paper presents the importance of a dynamically checked design of the shipbuilding portal rotating crane geometry regarding wind load. The dynamic character of wind load is mathematically introduced by a harmonic function of excitation and logarithmic wind speed profile. Structural analysis on the nonlinear model of the crane is carried out using the finite element method. The dissipation function is described by using an adequate model of structural damping. Combining the tracking and transformation methods, the eigenvalues of the FEM model of the observed structure were extracted. This research provides a faithful mechanical model of the crane for transient analysis in which structural elasticity is verified on the real structure. Through several case studies, the paper indicates a greater danger of a multi-wave wind gust at the steady state of wind speeds statistically recorded in relation to a single-wave wind gust at the extremely recorded speed. Based on the conducted dynamic simulations of wind action a new design criterion is suggested – the conditional quotient of structural geometry. Key words: Dynamic response, Engineering design, Modelling, Simulation, Wind load IN BRIEF ABOUT WIND The impact of hurricane on high buildings or cranes which do not have the survival mode in the rest position, can directly endanger their integrity and stability. One such characteristic structure is a tall Shipyard level-luffing Crane (SC) with a horse-head section that is constantly faced with complex environmental load conditions. This crane has an expressed risk of collapse due to its broad vertical flat area exposed to the load of changeable wind and a tall structure of height H in relation to the portal basis b×d that is about ten times smaller than the height (this refers to one of the dimensions – dim. b, in the direction of the wind). The gusts of strong wind frequently lead to galloping oscillations, resonance and collapse of structures. Apart from crane height, orographic factors have a significant influence on a structure which multiplies the wind effect. On the basis of the research [01] a reference can be made to a number of recent breakdown events of cranes and other big construction facilities over the world. Extreme gusts of strong wind are rare * Public Utility Company, “Mediana” Niš, Mramorska 10, Niš, Serbia; doicic@jkpmediana.rs

occurrences but should still be taken into consideration in the design of tall cranes and other shipyard and marine structures. One should strive towards better geometric criteria in the design of level-luffing cranes that would lead to a more efficient response of the support structure on extreme recorded environmental loads, especially to unfavourable combinations of natural phenomena at which their collapses occur, [02], [03]. Wind is observed as a phenomenon with a constant effect because of its large period of oscillation, i.e. small frequency, so that it is modelled as a constant load in civil-engineering calculation. However, this constant wind effect on structure can cause, and it often does cause, the resonant vibrations as the consequence of the interaction between the structure and wind flow. There are two key reasons for it: underpressure due to airflow turbulence in certain zones around construction, and so-called “flutter” or “follower force” as a nonlinear load that depends on structural deformation (example: airplane wing). Thus, one can conclude that the wind load is variable with the same eigenfrequency of the structure which leads to resonance (example: Tacoma Narrow Bridge, [01]). 192

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

The wind force is decomposed into two components – the horizontal and the vertical. The horizontal component of the force is induced by the vortexing of air in the vicinity of the body or crane support structure. This force component is particularly expressed for bodies without the aerodynamic profile. Contrary to that, the vertical component of the wind load occurs due to the air flow with the relative speed vr. This force component acts on the vertical surface of the crane at an angle of (90-a)o. The vertical force component leads to the galloping vibration effect on the observed machine. This aerodynamic vertical force component can be labelled as Fav. It also has two components, and these are: Fd – the component in the direction of velocity vr, named the drag-force, and Fl – the component that is perpendicular to the direction vr, named the lift force, [03]. In this research, two important assumptions are adopted: the vertical force Fav has a harmonic nature and the incidence angle is a=00. The wind load model requires the modelling of

interactive effect between the air flow and structure, as well as a nonlinear formulation with a very small time step (“follower forces” are not conservative forces). A comprehensive (better) method of modelling should harmonize a wind flow model defined by the Euler formulation and model of support structure described by the Lagrangian formulation. Therefore, the oscillation period of wind in this research is assumed on an approximate three-minute duration of sustainable wind flow at the reference speed, that also represents the oscillation period of the structure (resonance effect). RELEVANT METEOROLOGICAL REFERENCES The observation of wind sustainability varies by the region of tropical cyclones so that the oneminute regime is characteristic for North Atlantic Ocean and Eastern Pacific Ocean, and the tenminute regime for South-West Indian Ocean and Australian Region [04] – Table 1.

Table 1: Some of the most intense cyclones in the last few years [04] North Atlantic Ocean Wilma 2005

Eastern Pacific Ocean 295 km/h

South-West Indian Eunice 2014-15

Patricia 2015

325 km/h

Australian Region 240 km/h

The measured maximal wind speeds in Croatia [05] confirm a known fact that we can clearly distinguish the climate wind in continental areas in relation to coastal areas and islands. However, the specific positions of bridges: Pag, Krk, and Maslenica, in relation to the surrounding orography, cause higher ten-minute wind speeds of even above 40 m/s and maximal wind gusts of above 60 m/s. In the calculations of the impact effect of wind on the chosen crane, two quantities of the reference wind speed are taken into account as follows: 35 m/s and 45 m/s, because such and even higher impact speeds were statistically recorded on the Balkan Peninsula.

Monica 2005-06

250 km/h

Where: [M] is the inertial matrix, [C] is the damping matrix, {fext} is the vector of external forces, ɺ is the {fint} is the vector of internal forces, u generalized velocity vector, {ɺuɺ} is the generalized acceleration vector, t is the moment in time in which one of the sizes is observed. Geometric nonlinear structural analysis requires the calculation of stress in the current structural configuration, and the integration of those stresses in the current structural continuum tV, with the aim of obtaining internal structural forces. Therefore, it can be written as:

{}

(2)

THEORETICAL FRAMEWORK The exploration of transient responses of a discrete finite element system, such as the FE model of a shipyard level-luffing crane, is based on the formulation in Eq. (1). t

t t t t [M ] {ɺɺu}+ [C] {uɺ } = {f ext }− {fint }

Journal of Applied Engineering Science 15(2017)2, 429

(1)

where [B] is the matrix of deformation-displacement (defining the linear members of the deformation field) of the FE model. The time integration method was chosen for the following reason. In the research, the Newmark time integration was used as an implicit integration method whose a time step was 0.001 s. The decision was taken 193

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

on the basis of the material of the considered structure (steel), excitation force and the range of oscillation. The dynamic balance of the geometrically nonlinear system from Eq. (1) could still be developed for time t+Δt as: (3) where: [KT] is the tangential stiffness matrix, Δ is the increment of a size, k is the iteration. The matrix [KT] allows for the assessment of the elastic forces along with the increase in displacement at time t+Δt. The matrix [KT] is calculated according to:

bar mechanism form with articulated connections between elements and rocker. The payload of the crane is 25/15/5 tones to reach of 27/37/40 m, respectively. The central mast has the height of 30 m. The mechanisms for movement are set within a rotating platform on the mast. A frame pylon structure is set above the mast and platform. The basic members of the level-luffing mechanism on the pylon are shown in Figure 1 (rod, boom, rocker). The drive mechanism for level-luffing has a spindle which acts on the basic boom. The boom system is balanced by using a structure in the form of a four-bar mechanism – an arm and a balancer with a counter-weight of 21 t in mass. The overall rotating crane structure is equilibrated with a weight of 100 tones that is set on the platform.

(4)

where all quantities of the current structure are given in time t, as follows: t[KL] is the linear stiffness matrix, t[Kσ] is the geometric stiffness matrix, [H] is the Hooke’s matrix, [BNL] is the matrix that yields the nonlinear part of the strains, and [σ] is the stress state given in the matrix form. MODELLING OF A CRANE FRAME STRUCTURE For the purpose of transient simulation used to determine the behaviour of a high frame structure, a model of SC was designed with 225 finite elements and 135 nodes with 810 degrees of freedom. The model accurately represents a real existing structure (Figure 1). On the basis of the experimental investigations of dynamics of frame structures [06] and [07], the authors experimentally determined the safe coefficient of structural damping. This coefficient (G) takes a value between 0.05 and 0.06 for tall cranes and similar machines. The MSC NASTRAN software was applied for structural modelling as well as geometrically nonlinear dynamic analysis of the designed model. A new model of stiffness was experimentally proven (verified) on a real structure – the levelluffing crane (SC) in the Pula shipyard (Croatia), [08]. The max. height of SC is 67 m, the max. reach is 40 m, the dimensions of the portal basis are b1×d1=6×8 m, the mass of the crane in total is 400 tons. The level-luffing system has a four194

Figure 1: The first mode shape (eigenfrequency w1=0.3147 Hz) of the shipbuilding crane

The elasticity of the developed finite element model of SC was verified by using the experimental results from the examination in the Pula shipyard. On that occasion the elasticity of the top of the jib, that is, the path of the rocker top was determined by optical levelling method. In this manner, the quality of modelling was checked. The results of experimental investigation are given in Fig. 2 and they show their analytical, numerical and experimental stacking. In Figure 2, the dotted symbols of rectangular shape point to the measured values during the operation of the crane with a load. This experiment was carried out using an optical method. At the same figure, the black full curve shows a numerical envelope of the rocker top translations under the load of 12 tons in mass, calculated using the finite element analysis. The slightly brighter full curve gives us the theoretical trajectory of the rigid body mechanism i.e. starting positions Journal of Applied Engineering Science 15(2017)2, 429

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

of the top of the crane rocker. The experimental and numerical results of the rocker top deflection differ by 10% maximally throughout the full range of level-luffing, [09]. These deviations are mainly nonlinear in nature. They are caused by the rheological changes in the geometry of the track on the sea shore as well as manufacturing errors in making large-scale members of the crane steel structure.

Figure 2: A verification for the experimental and theoretical elastic characteristics [09]

DEVELOPMENT OF A WIND LOAD MODEL To analyse the behaviour of a high crane structure under the influence of strong wind, the authors selected a level-luffing crane at the shipyard Uljanik in Pula which is constantly exposed to the effects of air without its opportunity for self-protection i.e. switching to a safe-position. This shipyard crane has a multi-body structure. It contains several sub-structures such as: pedestal, tower, rotating platform, control cabin, counter-weight, pylon, boom (jib), rod, level-luffing mechanism and rocker. When creating models, most of the sub-structures can be modelled using frame and beam type of elements. The aforementioned element types can be considered sufficiently aerodynamic so as to approximately neglect the influence of the aerodynamic force due to swirling, thus it will not be taken into consideration in the direct transient analysis. Only the aerodynamic force Fav is taken as a time-variable exterJournal of Applied Engineering Science 15(2017)2, 429

nal load with a harmonic nature caused by wind gusts under the angle of incidence a compared to the normal of exposed (vertical) crane area. The wind force, in this research, was calculated in two ways, first as a static force in order to define the boundary conditions of static stability, and then as a dynamic perturbance force under the wind gusts to define the dynamic reserve of the crane structure. The force of the wind which acts on the exposed surfaces of the crane in their gravity centres, varies with the height of the crane whose maximum value is 67 meters from the ground. In the direct calculation procedure, the whole structure of the crane is divided into seven parts – individual areas Ai where i=1÷7 indicates the serial number of surface (Figure 3). Because all surfaces are placed vertically, the same angle of incidence may be adopted and that as a=00 for each of the individual forces of wind Fi (It means: the force acts normally on the surface). When dimensioning the support structure of the crane, the force of wind pressure on the structural members is considered as a steady load. Figure 3 and Table 2 show the heights Zi of the gravity centres Ti for each of the elementary surfaces Ai. Table 2 provides the descriptions and shape coefficients Cs for all used element shapes. The individual force of wind Fw(i) from Eq. (5) describes a steady state of the wind on an elementary surface Ai of the structure, taking into account the standards [10], [11] and [12] as well as research [13]. (5) Where: Ra=1.225 kg/m3 is the air density for dry air at the temperature of 150C; Cs is the shape coefficient (taken according to the until recently valid standard SRPS U.C7.113); Ai [m2] is the exposed surface of the each observed structural element (elementary surface at height zi); v=U(z) [m/s] is the wind speed at each observed height z, taking into account the geographic terrain roughness z0; a=00 is the angle between the direction of the wind effect and the normal to the surface of the observed element of the structure (if the wind acts perpendicularly on the surface then a=00, cosa=1). To calculate the vertical wind profile at a given height z, the logarithmic profile model, in accordance with the standard [14] and conditions of a 10-minute speed averaging U(Href) at a refer195

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

ence height of Href=10 m used here. The logarithmic wind speed profile is defined as: (6) Where U(z) is the current wind speed at the height z and U(Href) iz the averaged wind speed at the reference height Href=10 m at the exposure of T=10 min, i.e.: (7) As well as: Href=10 m – the reference height; ka=0.4 – the von Kármán constant; z0=0.0010.01 m, adopted z0=0.01 m – the terrain roughness parameter for coastal areas with onshore

wind based on Panofsky and Dutton 1984, Simiu and Scanlan 1978, Dyrbye and Hansen 1997, [14]; z – the height of the point of incidence upon which the wind force acts; k – the surface friction coefficient. Based on the Overview of temporary and approximate reference wind speeds in the former SFRY with a return period of 50 years [15] as well as the works [16] and [05], the reference (basic) wind speed is adopted: U1(10)=v1,ref=35 m/s, i.e. U2(10)=v2,ref=45 m/s. Thus the expressions are obtained for determining the logarithmic wind speed profile at the height z in the function of two selected reference speeds U1 and U2 (Table 2): (8)

Figure 3: Crane model with elementary surfaces, wind speed (Eq.(8)) and wind force (Eq.(5)) respectively from left to right, depending on the height of surface gravity centres z and reference speed U(Href) Table 2: Calculation of the wind speed U(z) and wind force Fw(U) i

Exposed surface Ai [m2]

Height zi [m]

Element shape (for each of Ai)

Shape coef. Cs [-]

Wind speed U1(z) [m/s]

Wind speed U2(z) [m/s]

Wind force Fwi(U1) [N]

Wind force Fwi(U2) [N]

37.94

02.66

Rectangular cross section (beam)

2.0

28.2934

36.3772

37205.16

061502.42

67.86

14.48

Circular cross section (cylinder)

1.2

36.8748

47.4104

67820.31

112111.12

38.80

29.23

Steel plate

2.0

40.4322

51.9842

77700.12

128443.05

12.94

34.18

Truss structure

1.6

41.2245

53.0029

21551.15

035625.37

32.82

40.42

Rectangular cross section (beam)

2.0

42.0737

54.0947

71169.81

117648.06

15.30

49.52

Rectangular cross section (beam)

2.0

43.1020

55.4169

34819.54

057558.82

13.73

53.08

Truss structure

2.0

43.4536

55.8689

31758.40

052498.57

196

Journal of Applied Engineering Science 15(2017)2, 429

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

The developed finite element model of the shipyard level-luffing crane as a typical representative of the high structures was used to transient analysis where the recommended coefficient of the wind static force growth was not available. The real nature of the strong wind in the Western Balkans region, based on a multi-annual monitoring by the meteorological stations, was included in the calculation of the function of time Fh(t), Eq. (9). Such analyses are closer to the actual development of the situation (recurrence) in the given off-shore locations and they represent a safer guarantee for the crane owner to preserve its stability. The strong wind has a wave shape presenting a time function. Although the wind has a random character, a certain recurrence, such as the terrain directing of the air flow on the coast caused by seasonal cycles in nature and environmental, can occur. Therefore, as a

general model of dynamic analysis of structures, the transient structural analysis of the effect of wind load was used. Also, the excitation forces (and speeds) were taken from the official meteorological evidence for the observed period. The authors’ choice of the wave function of excitation which acts on the crane structure is an adverse wind effect with one or more short and strong harmonic gusts of the wind. The wave function which describes the dynamic character of the wind is mathematically presented in Eq. (9) as an individual force Fh for an individual surface A and angle of incidence a: (9) Where Fw is the steady wind force as a static effect and fw(t) is the harmonic function of the wind excitation.

Figure 4: (a) Simplified scheme of the portal with the support elements, (b) sine excitation with one wind gust, (c) sine excitation with three wind gusts, (d) axial forces in the finite element E-71 (support) of the derived portal with basic dimensions: b×d=6×8 m Journal of Applied Engineering Science 15(2017)2, 429

197

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

Since the wind exposed crane surface is divided into seven parts, seven discrete harmonic functions of the force can be formulated for each of these areas, Eq.(9). To observe the behaviour of the structure caused by the wind, the function of influence has to be expanded by the initial calm state due to the lack of the wind and the function of the calm state after the wind has passed. This multi-function has several parts in the total

simulation time of 80 seconds. The synchronous function of the wind excitation fw(t) is composed of three interconnected elementary functions fn(t), n=1÷3, Eqs. (10)-(11). In the time of simulation, the segment t1÷t2 of the excitation function fw(t) has a harmonic (sine) shape f2(t), with one (1H, Fig. 4(b)) and three (3H, Figure 4(c)) wind gusts (H – harmonic).

Such a choice of harmonic functions aims to show the importance of the retroactive effect of the wind that attacks a high structure with more gusts by causing its dynamic response. These functions have the same step, i.e. period of oscillation and a different number of wind gusts (1H and 3H). The effect of the modelled functions of wind on the crane causes: a) large horizontal displacements of some elements of the structure such as a rocker, b) a large increase in the reaction force of the supports important for evaluating the dynamic stability of the entire structure.

then performed on the redesigned FE model of the SC with a modified portal geometry i.e. a new portal basis of dimensions: b2×d2=8×8 m. A modal analysis aimed to determine the new lowest (resonant) eigenfrequency whose current value is w1(6x8) = wmin(6x8) = 0.3149 Hz was the first carried out. The transient analyses for both wind speeds and excitation forces i.e. both load types were conducted after that. For both load cases 1H and 3H, the wind gust with one, Eq. (10), and three, Eq. (11), uniform impacts, and the same critical gust period T1=3.18 s is simulated after the period 0-30 s without wind (function f1(t)). Reference cases of accidents at high and heavy frame structures with resonant characteristics under the influence of natural dynamic phenomena are used in the paper to further the understanding of the unpredictable nature of strong wind. One such accident was the collapse of Falcon Crane Liverpool (39 m in height), [01], under the gust of wind at speed of 82 km/h in the duration of 1 sec. The most critical case of analysis was a gust of strong wind, at the lowest eigenfrequency of vibration of the structure, that elastically moved the structure in the direction of the wind action – the observed direction (Fw) in Fig. 1. This case of load leads to resonant oscillatory behaviour of the crane. The critical i.e. lowest eigenfrequency for both cases of geometry

ANALYSIS OF EXTREME INFLUENCE RESULTS Procedure: Dynamic response of the elastic supports of the crane is observed here. More precisely, the dynamic stability of the crane is observed under the strong wind influence at one gust (1H) and three gusts (3H). One gust of wind (1H) occurs at the reference speed v=45 m/s while three wind gusts (3H) occur at the reference speed v=35 m/s. The initial analysis was conducted on the derived crane structure solution named PULA-2 with the basic dimensions of the portal b1×d1=6×8 m. Dimension b1=6 m extends in global x-direction i.e. the wind direction (Fw, Fig. 1). Procedure after redesigning: New analyses were 198

Journal of Applied Engineering Science 15(2017)2, 429

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

of the crane portal (b1×d1=6×8m; b2×d2=8×8m) was computed by modal analysis: w1(6x8) =wmin(6x8) (6x8)=0.3147 Hz and w1(8x8)=wmin(8x8)= 0.3149 Hz. The reaction forces in the supporting members E-70 and E-71 (marked in Fig. 4(a)), as well as elements E-59 and E-60 on the opposite side of the portal (unmarked in Fig.4(a)), remained negative during the action of the static wind force. On that occasion, the members were under pressure. This response of the structure at the static load of the wind showed the sufficient static stability of the structure. The dynamic response of the crane structure was obtained by transient analysis. The analysis was carried out on a faithful structural dynamic model of the crane. The intensity of strong wind force is labelled as Fwi and excitation function is written in Eqs. (10)-(11). Parameters of numerical integration take the following values: the integration step is 0.03 s and the number of output sets is 2667. The lowest eigenfrequency of the structure was taken for modelling a periodic nature of the strong wind which would be the worst case of load. In both cases of the analysis (1H and 3H), dynamic instability of the initial crane portal of dimensions b×d=6×8m occurred sooner or later during the simulation (curve A and B, Fig. 4(d)) and thus caused the overturning of the crane. One can see from the diagram (curve B, Fig. 4(d)) that even a wind speed of less than 35 m/

s at more gusts causes almost the same effect on the structure – instability as well as the faster speed v=45 m/s at one gust. The change of force is shown in the diagram only for the element E-71 because it has the biggest magnitudes of forces so that this element is very sensitive to the wind action – disturbance of stability. The reference wind speeds are different because the higher speed v=45 m/s corresponds only to one wind gust (function 1H) while the lower speed v=35 m/s to three wind gusts (3H), which is a possible real situation in the Balkan peninsula area. The wind excitation force functions 1H and 3H are complex and have a sine shape whose step (period) corresponds to the resonant eigenfrequency w1(6x8=0.3147 Hz for the basic construction with the portal of dimensions b1×d1=6×8m, i.e. wmin(8x8)=0.3149 Hz for a modified geometry of the portal b2×d2=8×8m of the elastically supported crane in the direction of three global axes, Fig. 4(a). Figure 5 shows the curves C and D obtained by the transient analysis of the redesigned crane structure, which represent the forces in the supports (only shown are forces in the element E-71). The magnitudes of forces are significantly reduced by redesigning so that one can talk about preserved stability in both cases of load at different speeds of an extreme airflow (if a randomly chosen extreme ambient resonance effect of the wind is acceptable).

Figure 5: Reaction forces in the finite element (elastic support) E-71 of the redesigned portal with new basis b2×d2=8×8m and two variable wind loads 1H and 3H (No loss of stability!) Journal of Applied Engineering Science 15(2017)2, 429

199

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

By comparing the results of the transient analysis under wind influence with the static analysis without wind influence, we get the quantity of dynamic coefficients Kd, Eq. (12), for the four selected finite elements in order from E-212 to E-215 which represent the portal legs, where: FE,mindyn is the minimal dynamic pressure axial force (the biggest axial force) in the leg elements of the initial portal basis b×d=6×8m which calculated by transient analysis; FEstat is the static force in the leg elements calculated by nonlinear static analysis of the portal with the initial basis 6×8m (without wind influence). (12)

and E-215 are placed in front and directly exposed to the wind effect (they are raised under the influence of the wind). The wind models are denoted as: 3H at wind speed of 35 m/s, and 1H at speed of 45 m/s, Figure 6. Through more case studies of wind effect on tall cranes, a better adjustment of the height, shape and basic position can be implemented. One can notice that the initial model of the portal 6×8m (in Figure 1) has a ratio of the crane height H and basis b (in fact the basis b1): (13) while the redesigned model of the portal 8×8m (with the greater depth b2=8 m) has the ratio:

The elements E-212 and E-213 are placed behind the surfaces exposed to the wind effect (the wind presses them), and the elements E-214

(14)

Figure 6: Structural dynamic coefficients expressed through the finite elements of the portal legs (E-212 to E-215) for: the derived (basic) portal geometry with basis b1×d1=6×8m – on the left side, and the redesigned portal geometry with the new basis b2×d2=8×8m – on the right side

In Fig. 5 we can see that the redesigned geometry of the crane portal (H/b2=7.64) provides the dynamic stability in the given wind load conditions. Otherwise, the unstable states (when lifting the legs of the portal) at the same wind effects and a smaller width b of the portal (H/b1=10.188, Fig. 4) are obtained. As a temporary criterion for portal designing, the authors recommend a “soft” criterion for the design of crane’s height and portal basis in the case of tall crane structures, i.e.:

observed case, we can see that the extreme wind consequently causes the dynamic coefficients above expected values. The dynamic coefficients go to Kd=2.21 (Figure 6, for speed of 45 m/s) after the redesigning. It points to the need for further improvement of the portal geometry (redesign) and structural aerodynamics in order to reduce the dynamic coefficients limiting it up to 1.5. CONCLUSION

(15) We can assess the success of design by using the obtained dynamic coefficients. Thus, in the 200

By these comparative analyses, the dynamic stability of a tall shipbuilding crane subjected to an extreme environmental (local) wind effect is checked. Thereby, suitability of the crane portal Journal of Applied Engineering Science 15(2017)2, 429

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

design for adverse natural wind effects is considered. The comparison was conducted by a quasi-static and transient dynamic model of the wind influence. The dynamic coefficients obtained as a consequently changed design of the basic (portal) structure of the CS are observed here. On the basis of these comparative analyses some rules can be established: 1. The best design of tall cranes implies the choice of geometry that fully corresponds to a wind load in the observed environment. This means that the starting point for the analysis is the wind effect – a realistic timetable of speeds and directions of air flow registered on the selected locality in a 50-year period. 2. Before a structure (tall crane) is made, its design has to guarantee the checking of the dynamic influence of the wind which changes in line with the height of the exposed surface against which the wind acts with repeating impact periods. In these situations, the case study FEM transient analyses can be useful. 3. One of the most adverse random natural wind effects on tall structures is the wind gust at an oscillation period corresponding to the lowest eigenfrequency period of the structure (resonant effect). 4. Using numerical simulations, this paper shows a greater threat of the combined load of more consecutive average maximal recorded wind gusts at a resonant schedule in comparison with a short-term gust at the maximal recorded wind force. 5. The extreme dynamic coefficients caused by a resonant repetition of the wind gust are reduced by changing (increasing) the portal basis b×d, as shown in the paper (Fig. 6). 6. Case study simulations at extreme wind effects are an important class for checking the dynamical stability of structures and they represent the highest safety guarantees for people and material goods. 7. Influence of the wind variability on different geographic areas requires individual design as anachronistic and costly category. A universal element of design can be a new parameter of the drive class of cranes – an extreme wind for which the structure is designed. Namely, it can be a standard wind speed (m/s) denoted as: Wind-30, Wind-40, Wind-50, ..., Wind-100. Journal of Applied Engineering Science 15(2017)2, 429

8. What is gained by redesigning the global structural geometry? Answer: A decrease in the dynamic coefficients (Figure 6). 9. Simulations based on transient analyses introduce a more realistic wind influence than quasi-static analyses, which corresponds better to the requests of the modern design. REFERENCES 1) Ristić, N. (2009), “Hazard wind influence and collapse structure”, Science and Practice, University of Niš, Faculty of Civil Engineering, 178–181. 2) Hajdin, N., Zloković, Đ., Vukobratović, M. and Đorđević, V. (-), “Active structures”, Proc. Conf. Mechanics, Material and Constructions, Serbian Academy of Sciences and Arts, 83(2), 419–434. 3) Bošnjak, S., Zrnić, N. and Dragović, B. (2009), “Dynamic response of mobile elevating work platform under wind excitation”, Strojniški vestnik – J. Mech. Eng., 55(2), 104–113. 4) https://en.wikipedia.org/wiki/List_of_the_ most_intense_tropical_cyclones 5) Bajić, A. (2011), “Spatial distribution of expected wind speed maxima in the complex terrain of Croatia as a basis for wind loads calculation”, Ph.D. Dissertation, University of Zagreb, Croatia. 6) Radoičić, G. and Jovanović, M. (2013), “Experimental identification of overall structural damping of system”, Strojniški vestnik – J. Mech. Eng., 59(4), 260–268. 7) Jovanović, M., Radoičić, G., Petrović, G. and Marković, D. (2011), “Dynamical models quality of truss supporting structures”, Facta Universitatis – Series: Mech. Eng., 9(2), 137–148. 8) Jovanović, M. (1990), “Supporting structure level luffing system and driving mechanisms resistance of portal-jib cranes optimization”, Ph.D. Dissertation, University of Niš, Niš, Serbia. 9) Radoičić, G. and Jovanović, M. (2015), “Dynamic response of heavy-lifting shipyard machines to resonant environmental load conditions”, Facta Universitatis – Series: Working and Living Env. Protection, 12(3), 341–358. 10) Standard Det Norske Veritas DNV-RP-C104, 2012. 201

Goran Radoičić - Transient simulation of impulse wind effect on a tall shipyard frame structure

11) Standard EN 1991-1-4-2005+A1-2010. 12) Standard ISO 4354:2009, Wind actions on structures, https://www.iso.org/ standard/38882.html 13) Rama, G. (2014), “An automatized in-place analysis of a heavy lift jack-up vessel under survival conditions”, Facta Universitatis – Series: Mech. Eng., 12(2), 107–121. 14) Standard Det Norske Veritas DNV-RP-205, 2005. 15) Popović, O., Bogner, M., Simonović, A. and Stupar, S. (2011), About Chimneys, ETA, Belgrade, Serbia.

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16) Zarić, M. (2014), “Storm and hurricane gusts of Košava – blizzard and snowstorm in the northern and northeastern regions of Serbia”, RHMZ of the Republic of Serbia, Belgrade, January-February. Paper sent to revision: 15.01.2017. Paper ready for publication: 20.04.2017.

Journal of Applied Engineering Science 15(2017)2, 429