PREFABRICATED STRUCTURE

“PREFABRICATED STRUCTURES” A dissertation submitted in partial fulfilment of the academic requirement of Graduation in Architecture.

By Student PARTH SONI Registration Number 0809AR151066 Under the Guidance of ER. GAURAV SONI

School of Architecture IPS Academy, Indore Rajiv Gandhi Proudyogiki Vishwavidyalaya

ACKNOWLEDGEMENT

I with proud privilege take this opportunity to express my heartily gratitude and acknowledge the contributions to all those who enabled me to complete and present this dissertation work.

First of all, I am grateful to my guide ER. GAURAV SONI for guiding me for the proper methodology of the research.

I am thankful to our coordinator AR. NIKHIL HARRY and AR. HARSHIKA S. KEMKAR for their valuable guidance.

I am also thankful to my other faculty members of school of architecture, IPS academy who contributed to my dissertation by their advice.

Moreover, I am thankful to almighty god, my family members and friends for their constant encouragement that leads me to the completion of this work.

I must express my deep gratitude towards our principal PROF. AR. MANITA SAXENA for providing us proper guidance.

I would like to express my eternal gratitude to my parents for their everlasting love and support.

PARTH SONI B. ARCH VII SEM

STATEMENT OF ORIGINALITY & ETHICS DECLARATION

I declare that the research entitled “PREFABRICATED STRUCTURE” is the bonafide research work carried out by me, under the guidance of ER. GAURAV SONI. Further I declare that this has not been previously formed the basis of award of any degree, diploma, associate ship or other similar degrees or diplomas and not has been submitted anywhere else. I hereby, give consent of my dissertation, if accepted, to be available for photocopy and inter-library loan, and for the title and summary to be made to other organizations.

Place: Indore Date:

PARTH SONI B. Arch VII Semester

CERTIFICATE

This is to certify that the Dissertation entitled “PREFABRICATED STRUCTURES” is the bonafide work of Mr. PARTH SONI, in partial fulfilment of the academic requirement for the award of “Bachelors of Architecture Degree”.

This work is carried out by her, under my guidance and supervision.

PROF. AR. MANITA SAXENA Principal

ER. GAURAV SONI Dissertation Guide

School of Architecture IPS Academy, Indore

AR. HARSHIKA SAHAY KEMKAR Dissertation Coordinator

AR. NIKHIL HARRY Dissertation Coordinator Place: Indore Date:

ABSTRACT The study focuses around the major issues of not adopting prefabrication in India, with supporting criteria’s like technological advancement barrier, time constraint, usability, and financial condition of such projects by considering elements, which are structural or non-structural members of structure.

Firstly, to analyse the above factors we have to understand the term prefabricate and distinguish it with similar terms like precast, PEB (pre-engineered building), after that we would discuss the merits and demerits of prefabricated structures, limitations of prefabricated, then study the components of it like claddings, solid slab, hollow core slab, precast beam, precast stair case, precast concrete panels etc.

After explain such terms to get the basic understanding of prefabricated structures, the study will carry forward towards evaluating the factors on the basis of duration and cost in residential building which are as follows: At the last we will give an estimate of situation of residential and industrial prefabricated structure in terms of the usability, durability, and workability and concluding the study by comparing the above aspect and giving reason how prefabricated structure can be efficient constructed in different situation.

1 CONTENT CONTENT NO.

TITLE

PAGE NO.

1. INTRODUCTION................................................................................6 1.1 PREFABRICATED STRUCTURES.........................................................6 1.2 NEED FOR STUDY..................................................................................6 1.3 AIM............................................................................................................6 1.4 SCOPE OF STUDY...................................................................................6 1.5 LIMITATION.............................................................................................7 1.6 METHODOLOGY.....................................................................................7

2. LIERATURE REVIEW.......................................................................8 2.1 TYPES OF PREFABRICATION...............................................................8 2.1.1 OFF-SITE PREFABRICATE-.....................................................................8 2.1.2 ON-SITE PREFABRICATE........................................................................9 2.2 PRECAST VS PEB VS PREFABRICATION.........................................10 2.3 PREFABRICATION IN DEVELOPING COUNTRIES: A CASE STUDY OF INDIA, BY Ryan E. Smith..................................................10 2.3.1 ETHICAL DILEMMAS OF TECHNOLOGY TRANSFER.....................11 2.3.2 TRANSPORTATION.................................................................................11 2.3.3 HUMAN RIGHTS.....................................................................................12 2.3.4 SCHEDULE...............................................................................................12 2.3.5 PRECISION...............................................................................................12 2.3.6 CLIMATE AND VERNECULAR.............................................................13 2.4 CASE-STUDY ON USE OF PRECAST TECHNOLOGY FOR CONTRUCTION OF HIGH-RISE BUILDINGS BY SANDEEP JAIN13 2.4.1 INTRODUCTION (PRECAST AS SOLUTION FOR HIGH DEMAND IN HOUSING)....................................................................................................13 2.4.2 BACKGROUND AND PRESENT SCENARION....................................14 2.4.3 TRANSITION TOWARDS PRECAST.....................................................14 2.4.4 BENEFITS OFFERED BY PRECAST.....................................................14

3. NEED OF PREFABRICATION........................................................16 3.1 Why do we need prefabrication?..............................................................16 3.2 PRINCIPLES(AIMS)...............................................................................16 3.3 ADVANTAGES OF PREFABRICATION...............................................16

2 3.4 DISADVANTAGES OF PREFABRICATION........................................17 3.5 ROLE OF PREFABRICATION IN CONSTRUCTION..........................17 3.6 PREFABRICATION IN INDIA ..............................................................18

4. COMPONENTS AND JOINTINGS.................................................19 4.1 MAJORLY USED COMPONENTS........................................................19 4.1.1 STRUCTURAL COMPONENTS.............................................................19 4.1.1.1 PRECAST SLABS.............................................................................19 4.1.1.2 PRECAST COLUMNS......................................................................20 4.1.1.3 PRECAST BEAMS...........................................................................21 4.1.1.4 PRECAST WALL PANELS...............................................................21 4.1.1.5 PRECAST STAIRCASE....................................................................21 4.1.2 NON-STRUCTURAL COMPONENTS...................................................22 4.2 DESIGN & CONNECTION DETAILS...................................................22 4.3 STANDARD MATERIALS USED FOR MAKING PREFABRICATED COMPONENTS......................................................................................24 4.4 PREFABRICATED STEEL COMPONENTS.........................................31

5. SYSTEM AND MANUFACTURING OF PREFABRICATED STRUCTURE.........................................................................................32 5.1 SYSTEM AND CLASSIFICATION........................................................32 5.2 CONCEPT OF MODULAR STRUCTURE............................................32 5.3 PRODUCTION AND PROCEDURE......................................................33 5.3.1 PRODUCTION PROCEDURE.................................................................34 5.3.2 TRANSPORT............................................................................................38 5.3.3 ERECTION................................................................................................38 5.4 INSTALLATION PROCESS...................................................................40 5.4.1 INSTALLATION OF VERTICAL COMPONENTS.................................40 5.4.2 INSTALLATION OF HORIZONTAL ELEMENTS.................................41 5.5 MERITS AND DE-MERITS OF PREFABRICATED SYSTEM............42

6. LITERATURE CASE STUD.............................................................43 6.1 COMPARISON OF PREFABRICATED STRUCTURE TO A CONVECTIONAL STRUCTURE.........................................................43 6.2 LITERATURE CASE STUDY OF PREFABRICATED RESIDENTIAL BUILDING STRUCTURE ON THE BASIS OF COST AND DURATION OF CONSTRUCTION......................................................44 6.2.1 Project Duration.........................................................................................45

3 6.2.2 Cost Analysis.............................................................................................45 6.2.3 Result and Discussion................................................................................45

6.3 LITERATURE CASE STUDY OF AN INDUSTRIAL PREFAB STRUCTURE ON THE BASIS OF COST AND DURATION OF CONSTRUCTION.................................................................................48 6.3.1 MODELING..............................................................................................48 6.3.2 RESULTS AND DISCUSSION................................................................50

7.1 CONCLUSION.................................................................................51 BIBLIOGRAPHY..................................................................................52 WEBLIOGRAPHY................................................................................52

4 LIST OF FIGURES FIGURE NO.

TITLE

PAGE NO.

Figure 1 off-Site Prefabrication, Amrapali precast, India..............................................9 Figure 2 Different concrete Component which can be prefabricated /precast and erected...................................................................................................................10 Figure 3 Precast roof panels loaded onto a truck to be shipped to another location.......................................................................................................................11 Figure 4 Precast Concrete Structural Elements for a Typical Residential Unit...........19 Figure 5 Precast (a) Hollow Core & (b) Solid Slab Details.........................................20 Figure 6 Typical Precast...............................................................................................21 Figure 7 Precast Beam Details.....................................................................................21 Figure 8 Precast (a) Wall Panels & (b) Claddings........................................................22 Figure 9 Prefabricated RCC Staircase and steel staircase............................................22 Figure 10 Details of (a) Boundary wall, (b) Kerb Stone, & (c) Main Gate.................23 Figure 11 Connection illustration for (a) Beam-Column and (b) Slab to Beam (Source: Paradigm).....................................................................................................................23 Figure 12 Typical Connection Details between In-Situ Shear wall & Hollow Core Slabs.............................................................................................................................24 Figure 13 Typical Vertical Connection Details between Precast Wall Panel to Panel. 24 Figure 14 SIPs..............................................................................................................25 Figure 15 Insulated concrete panel..............................................................................25 Figure 16 colorbond steel and colour coated galvalume sheets...................................27 Figure 17 FRP corrugated sheet and sandwich panel...................................................28 Figure 18 EPS panel and PUF panel............................................................................29 Figure 19 Aerated Cement Sandwich (LEFT), Panel Dry-Wall System (MIDDLE), Aerated Solid Cement Panel (RIGHT)........................................................................30 Figure 20 DOOR AND WINDOW..............................................................................31 Figure 21 Components of PEBs...................................................................................32 Figure 22 Concepts Modular Structure........................................................................34 Figure 23 MODULAR HOME (2015).........................................................................34 Figure 24 Floor plan of double story building.............................................................45 Figure 25 Bar chart showing duration of construction at different stages...................47 Figure 26 Bar charting showing costing of construction at different stages................48

5 Figure 27 plan, elevation and rendered view of CBS model.......................................50 Figure 28 plan, elevation and rendered view of PEB model........................................50

LIST OF TABLES Table NO.

TITLE

PAGE NO.

Table 1 STORAGE OF PRE-CAST CONCRETE PRODUCTS BY STAGE.............38 Table 2 Total Duration for Prefabrication Construction and Conventional Construction ......................................................................................................................................46 Table 3 total cost for prefabrication construction and conventional construction material and labour cost for total project.....................................................................46 Table 4 Data adopted for CSB Model..........................................................................49 Table 5 Data adopted for PEB Model..........................................................................49 Table 6 Comparison of the Self Weight of the models.................................................51 Table 7 Comparison of Cost of Construction...............................................................51 Table 8 Comparison of Time of Construction..............................................................51

6 1. INTRODUCTION 1.1 PREFABRICATED STRUCTURES 

Prefabrication is the practice of manufacturing the parts of an assembly in one location, ready for them to be assembled in another place.

This consists of putting a building from its components such as framework, posts, wall, beams etc. this technology has revolutionized the construction industry.

The products are mass produced in a plant. Once ordered, all the components are delivered to the site where they can be assembled in few days.

With prefabricated construction the components are produced under optimal conditions which are leads to strong, standard and versatile structure.



 

1.2 NEED FOR STUDY

 Construction work to be complete in a short period of time.  To archive standardization in construction work and

uniformity in

construction work.

 Conventional technique of construction is too slow.  Ethical dilemmas of technology transfer if any.

1.3 AIM 

To find out how much time and cost dose a prefabricated structure needs to be erected as compared to a structure of same design in conventional technique.

To find the waste of material and its management in prefabrication and conventional technique.

To find out the possibilities of alteration in design parameters.

To study the effect of prefabrication on social platform like loss of jobs, vernacular architecture, etc.

To study the limitation of prefabrication technology in Indian context.

   

1.4 SCOPE OF STUDY    



The study focuses on use of prefabrication for building construction.

To find out widely used prefabricated components, materials and their jointing available in India.

To find out the method of production of prefabricated slabs and their properties.

Case study of sufficient number of building system will be undertaken to establish a differentiation between prefabrication Techniques and convectional Techniques.

The scope of study is to analyze the prefabrication technologies and the recent works.

7 1.5 LIMITATION   

the study does not include the design aspect.

The study is limited to building systems.

The study is being carried out in an Indian context.

1.6 METHODOLOGY

 Describing different methods of prefabrication.  Collecting data regarding such structures which

are constructed using

prefabricated components.

 Classifying components which come under prefabricated structures and comparing them from convection components.

 Collecting data from existing sources like: 

1) Different types of codes established by recognized organization.

2) Textbooks 3) Internet 4) Existing dissertation reports Merits and demerits of constructing structures using prefabricated components against convection techniques of construction.

 And find out how such structures can be applied in better way.  Finally concluding the above study.

8 2. LIERATURE REVIEW 2.1 TYPES OF PREFABRICATION Prefabrication is a mainly divide into two broad categories.

2.1.1 OFF-SITE PREFABRICATEIn this scheme, prefabricated components are produced at site or near the site of work as possible.

This system is normally adopted for a specific job order for a limited period.

Though there is definite economy with respect to cost of transportation, this system suffers from basic drawback of its non-suitability to any high degree of mechanization and no elaborate arrangements for quality control. Normal benefits of continuity of work is not available in this system of construction. Under this category there are two types that is semi-mechanized and fully-mechanized.

Semi-mechanized



The work is normally carried out in open space with locally available labour force. The equipment machinery used may be minor in nature and moulds are of mobile or stationary in nature.

Fully mechanized



The work carried out under shed with skilled labour. The equipment’s used are similar to one of factory production. This type of precast yards will be set up for the production of precast components of high quality, high rate of production.

Some benefits of prefabrication are follows: 

Greater possibility of quality control



More number of skilled workmen is employed.



Higher degree of mechanization & automation



Products are of higher quality



Testing of these products is easily possible



Rate of manufacturing is higher



Small orders are expensive as compared to large scale demands.



Their sizes are restricted by the transportation vehicle.

9

Figure 1 off-Site Prefabrication, Amrapali precast, India1

2.1.2 ON-SITE PREFABRICATE The work carried out under shed or in open with skilled labour. The equipment’s used are similar to one of factory production. This type of precast yards will be set up for the production of precast components of high quality, high rate of production.



This is the method where components are made on the site; they are manufactured either in the open or in temporary shed.



The rate of manufacture is slower as compared to factory based components



There is always an influence of rain and cold which also affects the curing process.



The temporary site is set for manufacturing is only for one project hence the mechanization level is lower.



The transportation for these big machines is too expensive.



It all depends on the availability of water.



The advantages of site prefabrication include

o No restriction of size of the components o Production time is reduced o Time & money is saved in transportation.

1 Amrapali precast group- http://www.amrapali.in/verticals-precast.asp

10

Figure 2 Different concrete Component which can be prefabricated /precast and erected

2.2 PRECAST VS PEB VS PREFABRICATION Precast is a type of product used in construction processes. A precast unit is a concrete mould that has been cast into a specific shape and cured in a controlled environment. This unit is then shipped to the site and installed as part of a larger structure.

Prefabrication, on the other hand, is the process of manufacturing a structure or unit off-site. Prefabrication can contain precast units, and it usually involves the assembly of various parts in a separate factory. The aim of prefabrication is to remove the construction process from the site and create a more efficient and streamlined progression for construction projects.

Pre-engineered buildings (PEB) are factory-built buildings of steel that are shipped to site and bolted together. What distinguishes them from other buildings is that the contractor also designs the building - a practice called design & build. This style of construction is ideally suited to industrial buildings and warehouses; it is cheap, very fast to erect, and can also be dismantled and moved to another site - more on that later. These structures are sometimes called 'metal boxes' or 'tin sheds' by laymen they are essentially rectangular boxes enclosed in a skin of corrugated metal sheeting.

2.3 PREFABRICATION IN DEVELOPING COUNTRIES: A CASE STUDY OF INDIA, BY Ryan E. Smith2 Prefabrication technology has not transferred as easily when compared with other technologies because it is a production technology or knowledge based and not a consumption technology or product based. Technology transfer of prefabrication is not as pertinent to architects as it is to manufacturers of building products, but we are caretakers of culture in the AEC industry. In many cases we are asked to help with many of the transfers that are occurring by way of global practice or working for multi-national firms that are producing prefabricated components and entire buildings 2 Prefabrication in developing countries: a case study of india, by ryan e. smith

11 for India and elsewhere. Although transfers will continue to occur, especially in the area of prefabrication in building, we should be well aware of how the decisions of U.S. and western architects may have an effect on the ethical dilemmas regarding less developed countries’ development and culture.

2.3.1 ETHICAL DILEMMAS OF TECHNOLOGY TRANSFER “Technology transfer can affect the government, economy, and culture of both the transferring and the receiving nations. It opens too many ethical dilemmas.”

Prefabrication will continue to grow in India as the demand for fast affordable housing increases. However, technology transfer of prefabrication process, including materials and digital tools, can affect the environment, economy and culture of the receiving country negatively. There are risks associated with the transfer of prefabrication technology. The host country may not have the infrastructure, the manufacturing and/or professional prowess to accept it. The negative effects can be social, environmental and/or economical.

2.3.2 TRANSPORTATION The Auroville Earth Institute in 1999 built a prototype-prefabricated house in New Delhi that showed advances in structural capacity during earthquakes. Initially envisioned as a disaster resistant and cost-effective prototype, it was intended that the house would be precast anywhere and shipped by truck to a disaster location. Precast in Auroville, and transported over 2,900 km to New Delhi in a single lorry of 22.5 tons, the prototype was assembled in 66 hours by an 18-man team. The transportation cost alone was equal to the cost of manufacturing the prototype. The model was economically unviable for India. The solution to low cost prefabricated housing must overcome the obstacle of shipping costs. Prefabricating regionally might better serve developing countries. (Fig.3)

Figure 3 Precast roof panels loaded onto a truck to be shipped to another location.3

2.3.3 HUMAN RIGHTS Human rights issues are also of concern with regard to prefabrication technology transfer. As technology made way for mass production and assembly line manufacturing methods in the early part of the 20th century in the U.S., developing 3 Ryan E. Smith

12 countries are using the same process to produce goods abroad today. Along with industrial manufacturing and economic benefits come labour challenges.

Prefabrication presents problems: trading traditional handicraft construction jobs for automation. The culture of local building tradition passed through generations is abruptly discontinued.

Countries with a rich cultural background find it hard to accept drastic changes that involve a great deal of compromises in every field. This may directly affect technological advances, and in the construction field, it hinders the progress of prefabrication as a primary mode of construction. Prefab necessarily involves fewer labourers on site. It therefore renders helpless many households that depend on traditional methods of construction for their livelihood. With a literacy rate of only 61%, the possibility of the construction industry labourers shifting occupation to an office or even an automated factory is bleak. The current labour market is a lot different from what it was the last decade. With an influx of the software industries (in the dotcom boom) and an opening for over a million jobs outsourced from America and Europe, the standard of living among the educated class is increasing. Research by the Boston Consulting Group estimates that the number of jobs in India due to outsourcing will reach 30 million by 2020. India, with its 500 million person labour force, is second only to China in the world. With India continuing to lack in education, questions arise as to how this country will be able to offer equitable opportunity for work in the new technology economy.

2.3.4 SCHEDULE “Some argue that technology has brought humankind many negative effects, including stress-related diseases caused by people’s inability to cope with the world that is moving too fast due to rapid technological progress.�

Regarding construction schedule in less developed countries, specifically India, the concern is how to take advantage of cost reduction while still being able to employ individuals and maintain a cultural lifestyle that is unique to a society.

2.3.5 PRECISION One of the benefits of prefabrication technology is an increase in the quality of the products. Less developed countries such as India employ vernacular materials and methods in construction. The industry in India does not rely on precision, but the lack thereof in order to build everyday structures. Most members of local communities in India are equipped with knowledge of traditional construction.

However, in India, a cultural divide between those that do and those who plan is emerging. This social class structural divide limits the ability for the populous to assimilate alternative methods of building quickly and adopt them into their culture of construction.

13 2.3.6 CLIMATE AND VERNECULAR One of the most significant influences on vernacular architecture is the macroclimate of the area in which the building is constructed. Buildings invariably perform well when built with regard to the local climate rather than a technological trend that may not be as appropriate. The local environment and the construction materials that market can produce govern many aspects of prefab development. Vernacular, by definition, is sustainable, and will not exhaust local resources. For a country that has followed vernacular practices successfully for generations, like India, moving to a concept like prefab may not prove to be climatically as suitable. For example, in many hot regions of India, masonry walls that are heavy and dense conduct heat slowly.

This simple process, called thermal lag, reduces peak cooling loads in summer and peak heating loads in winter. The result is a more comfortable home all year long that produces significant savings in energy. However, in India there are 6 distinct climate zones ranging from cold and dry to warm and wet. Therefore, India’s architecture is varied in its use of materials, style of construction and cultural difference that cannot be generalized. Prefabrication in a technology transfer mode struggles take into consideration these vernacular differences.

2.4 CASE-STUDY ON USE OF PRECAST TECHNOLOGY FOR CONTRUCTION OF HIGH-RISE BUILDINGS BY SANDEEP JAIN4 2.4.1 INTRODUCTION (PRECAST AS SOLUTION FOR HIGH DEMAND IN HOUSING) India is the world’s fastest developing country with an economic growth rate averaging 7.5% for last 5 years. To cope up with this housing necessity, the country needs to build 30 to 35 thousand units of houses per day at least for the next 8 years.

With the rapidly growing population, and to fulfil the aforementioned housing demand, a more reliable, faster, sustainable method of construction is deemed necessary by the construction industry. The concept of “built it fast” in the most economical way has not changed since the beginning; however, new technologies have been developed to suit the modern world construction. One such solution is precast concrete construction technology.

Precast constructions have been a common construction method in United States of America and many European countries. On the other hand, Precast for residential construction has been used in India for only less than a decade, but it has been growing very fast in the past 5 years.

4 Case-study on use of precast technology for construction of high-rise buildings by sandeep jain

14 2.4.2 BACKGROUND AND PRESENT SCENARION From primary structures to small architectural ornaments, precast has become a major part of building construction. In the near future, precast is expected to play a vital role in Indian construction, especially, in the residential building construction.

Over the past 15 years, India has experienced the huge increase in housing demand in a very short period of time, requiring a massive production of residential buildings with the changing face of realty market. The large projects comprising of townships, mass housing, commercial mall, IT parks, SEZ’s etc. are common now a days and will grow exponentially. To build this type of projects at fast rate and affordable with high quality, some builders tried to innovate and bring about transition from the conventional cast-in-situ (CIS) construction and move to precast construction by making building components off-site, and then install them on site. Precast technology, the so-called unconventional method in Indian arena can facilitate both speed and quality and exploit the advantages that projects offer in terms of repetitions and volume.

2.4.3 TRANSITION TOWARDS PRECAST The main practice in India is the cast-in-situ(CIS) reinforced concrete structures. The other construction methodology is using structural steel. In general, most residential and commercial projects are CIS in nature. Steel structures are restricted to industrial projects. The ratio between CIS and steel structures is approximately 70:30. The third construction is using precast concrete.

One of the only real disadvantages to CIS concrete is the high amount of labour it requires. Builders have to go through construction process which all takes time that extends the length of a construction job and results in more hourly pay for work crews, dependency on workmanship, environment and other factors. This further justifies the use of precast technology.

2.4.4 BENEFITS OFFERED BY PRECAST To archive following benefits with the use of precast concrete components there has to be a proper design, use of the correct materials and manufacturing processes with skilled and knowledgeable personnel. Benefits are followed: 

SPEED-TO-MARKET

The advantage of precast is that faster erection reduces the overall construction schedule and overhead costs. Compressed schedules, fewer on-site trades, and eliminating weather delays add up to reduced project costs.



QUALITY & DURABILITY

15 The controlled plant environment has offers easy verification of quality and a dedicated workforce. This means high-quality product can be manufactured every day, regardless of weather. The low water-cement ratio used in precast concrete creates a denser product that does not allow penetration of chlorides and other harmful elements as easily as field-placed concrete. 

INTEGRATED PROJECT DELIVERY

Structural precast components can be erected in a relatively short period of time because they interlock to support one another. Simpler installation requires fewer crew members, which means fewer personnel to manage, fewer trades to pay and fewer trade-related delays. 

ENHANCES SAFETY

Precast products eliminate many of the dangers associated with on-site construction by providing a controlled, off-site fabrication environment. Precast reduces the amount of wet trade work on site, making them cleaner, tidier and safer. 

SUSTAINABILITY

Precast is perfect for today’s focus on preserving resources and protecting the environment though sustainable building practices. It’s a perfect Green Building product. Precast reduces overall life cycle impact on environment compared to other methods as it has lower wastage and high potential to recycle waste. 

OPTIMIZATION & FLEXIBILITY

Precast plants optimize the resource utilization, and produces an improved quality product with reduced tolerances, thinner sections, and engineered solutions. Also, it offers flexibility of space planning by allowing for longer spans which create larger open floor plans and increased flexibility in design. For architects, it can offer variety of different profiles.

16 3. NEED OF PREFABRICATION 3.1 Why do we need prefabrication?5 Prefabrication, in one form or the other, has been in practise since many centuries.

However, the first prefabricated building is known to be constructed in the year 1905.

In the early years, materials such as stone and logs were extensively used, and such a construction was called as ultra-light construction. However, the boom in the prefabrication market occurred after the end of World War I. And since then, massive prefabricated buildings have been constructed, owing to the fluctuating trends in construction industries and demand for homes at cheaper rate, due to tremendous losses suffered in World War 1. The countries at the forefront of prefabrication were United States of America and the Western Europe.

Similarly, the demand for housing grew rapidly in India due more urbanization, people started moving to cities in search of better living standard, which in effect create need of mass housing in India which is a developing country. Major Cities like Mumbai and Delhi need a better and efficient solution for affordable and long-lasting housing solution. Perhaps, a dearth of residential houses and rising prices has forced millions to live in slums in uninhabitable conditions. The slum rehabilitation model for Mumbai has fared miserably with just 13 per cent projects completed in 18 years.

To reduce costs and alleviate conditions of slum dwellers, prefabrication can be implemented.

3.2 PRINCIPLES(AIMS)     

To effect economy in cost To improve in quality as the components can be manufactured under controlled conditions.

To speed up construction since no curing is necessary.

To use locally available materials with required characteristics.

To use the materials which possess their innate characteristics like light weight, easy workability, thermal insulation and combustibility etc.

3.3 ADVANTAGES OF PREFABRICATION     

Self-supporting readymade components are used so the need for formwork shuttering and scaffolding is greatly reduced.

Construction time is reduced and buildings are completed sooner allowing on earlier return of the capital invested.

On-site construction and congestion is minimized.

Quality control can be easier in a factory assembly line setting than a construction site setting.

Prefabrication can be located where skilled labour, power materials space and overheads are lower.

5 Study of prefabrication in India

By Rinkesh patel, Dr.Neeraj Sharma

17        



Time spent in bad weather or hazardous environments at the construction site is minimized.

Materials for scaffolding is stored partly or in full and used Availability of precise structure and expect workmanship.

Work time is reduced.

Fewer expansion joints are required.

Interruptions in connecting can be omitted.

Work is done with a better technology.

Less workers are needed.

Members can be used again.

3.4 DISADVANTAGES OF PREFABRICATION 

Careful handling of prefabricated components such as concrete panels or steel and glass panels are required.  Attention has to be paid to the strength and corrosion-resistance of the joining of prefabricated sections to avoid failure of the joint  Similarly leaks can form at joints in prefabricated components.  Transportation costs may be higher for voluminous prefabricated sections than for the materials of which they are made which can often be packed more efficiently.  Large prefabricated structures require heavy-duty cranes & precision measurement and handling to place in position.  Large groups of buildings from the same type of prefabricated elements tend to look drab and monotonous.  Local Jobs are lost.

3.5 ROLE OF PREFABRICATION IN CONSTRUCTION6 The role of prefabrication in architecture has been lauded for its potential to increase productivity and efficiency while not sacrificing quality. Developing countries, including China, India, Africa and many parts of South America, that are beginning to rely on prefabrication have the potential advantages of realizing housing quickly and affordably; however, greater reliance on manufactured production has possibly more disadvantages than advantages for these cultures. With prefabrication, improved working conditions would seem to be agreeable to everyone: instead of building in the weather, international fabricators supply controlled environments with ergonomically considered equipment – and yet in many fabrication environments, reliance on minimal skills, and a disconnect with the community in which workers live, leaves little room for continued fostering of personal and collaborative skills, culture, tradition and community building.

The potential for prefabrication to be used to create a bland, monotonous landscape is an issue that developed countries construction professionals must grapple with.

Countries such as India are undoubtedly suffering a greater banality in the built environment by embracing prefabrication. Prefabrication is touted as offering a more 6 Study of prefabrication in India

By Rinkesh patel, Dr.Neeraj Sharma

18 sustainable solution to building, but developing counties already rely on vernacular practices for design and construction that require relatively low life cycle energy.

Developing countries continue to embrace technology from their developed country allies. This trend does not seem to see a slowing.

3.6 PREFABRICATION IN INDIA 7 Prefabrication in India came into effect with the foundation of Hindustan Housing Factory in 1950 as a solution to the housing crisis resulted from the influx of refugees from West Pakistan (now known as Bangladesh). The Hindustan Housing Factory pioneered the production of pre-stressed concrete railway sleepers to replace dilapidated wooden sleepers on Indian Railways. This government run company, located in Delhi and now known as Hindustan Prefab limited (HPL), mainly prefabricates precast concrete for various civil and architectural projects throughout India. Prefabricated materials are well-known for their durability and quality in India.

Protection from climatic damages, precision work in computer controlled manufacture in factories and environmental-friendly techniques have attributed to the good quality standards of prefabrication. With an extremely competitive construction industry, construction management with the help of BIM (Building Information Modelling) techniques is being used to pre-plan and visualize the construction process. This makes the construction process leaner and gives scope for prefabrication before the actual site works begins, resulting in lesser wastage.

These building systems are gaining popularity in India due to the need to use very scarce resources optimally. They also have the potential to address the problem of mass housing crisis in India that we face today. L&T owns heavy engineering workshops at Powai (Mumbai), Hazira (Gujarat), Kansbahal(Odisha), Chennai, Vadodara(Gujarat), Kattupalli (Tamil Nadu) which have a combined fabrication area of about 1.2 sq. Meter with over 150,000MT capacity. L&T started a fully precast residential G+23 building project in Parel, Mumbai in 2011. This project will provide a total built up area pf 1.2M sq. ft. 6 building towers. Construction of three towers has been completed in a record time of just 3 months. Speedy construction and design conforming to all IS design codes with less labour intensive operations are the major objectives achieved by this project. The TATA housing group is working on a housing project based on innovative prefabricated technologies. These houses will cost as low as INR 32,000. Tata Group will provide a kit consisting of structural elements which can be erected or assembled.

These houses have an area of 20-30 sq. metres and lifespan of 20 years. The project is still in pilot stage and will soon be implemented across the country. A myriad of prefabrication companies is emerging within India in order to serve the housing demand of one of the most dense, heavily populated, and fastest growing economy in the world. An estimated 12 million low cost housing is required by India at this very moment. A low cost house can be described as a house having an area less than 400 sq. ft. or less.

7 Prefabricated construction for mass housing in mumbai By krish r. villaitramani and dhruv p. hirani

19 4. COMPONENTS AND JOINTINGS

4.1 MAJORLY USED COMPONENTS

Figure 4 Precast Concrete Structural Elements for a Typical Residential Unit8

4.1.1 STRUCTURAL COMPONENTS 4.1.1.1 PRECAST SLABS Main types of slabs used in precast frames are: hollow core slab and solid slab.

The details of hollow core slabs are shown in the Figure 4. The hollow core slabs are prestressed, precast concrete slabs, with hollow portions in the zones of zero stresses. They reduce the overall concrete dead load, concrete requirement and provides for better insulation.

It is possible to achieve larger unsupported spans. Their general thickness used are 150, 200, and 265 mm. These slabs are casted 140m long at a time, with a fixed width of 1.2m. After steam curing the slabs are cut into smaller pieces as per site requirement. They are then delivered to site and installed in position using tower cranes. After installation as per drawings, a thin reinforcement screeding of 5075mm is laid on the top, to seal the joints.

8 Case-study on use of precast technology for construction of high-rise buildings by sandeep jain

20

Figure 5 Precast (a) Hollow Core & (b) Solid Slab Details

Another common type of slab used are solid slab. These slabs are casted on a tilting bad with lateral and longitudinal reinforcement. These slabs are generally used for long span in the common areas and toilets where it is required to facilitate for various MEP services. They are helpful to reduce weight thus easy for site crane handling. It also eliminates the shuttering cost, and helps to attain a superior slab soffit.

4.1.1.2 PRECAST COLUMNS Columns (Shear walls) in precast construction can either be done in CIS or precast. They are most suited in commercial, industrial bay buildings where thicker sections are needed. Precast columns are provided with corbel for simple beam column connections.

Precast also allows for casting of triple height columns, thus faster erection.

4.1.1.3 PRECAST BEAMS

Figure 6 Typical Precast Column Details

21 There are two main categories of beams used in a precast structure. Internal beams are used where floor loading is approximately symmetrical, and external beams are used where floor loading is predominantly non- symmetrical. The use of precast beams with proper designed connections ensure higher structural stability.

Figure 7 Precast Beam Details

4.1.1.4 PRECAST WALL PANELS Precast wall panels and claddings are smart substitute for conventional infill blockwork or brick walls. These walls offer superior finish surface, eliminates the plaster and touch ups, facilitate for desired & accurate openings of doors, windows, ventilators etc. These wall panels also improve the overall lateral stability of the structure.

Figure 8 Precast (a) Wall Panels & (b) Claddings

4.1.1.5 PRECAST STAIRCASE Precast staircase eliminates the complicated-on site shuttering & reinforcement, and provides high quality finish. They can either be a single precast unit containing all flights and landings or separate precast flights & landings.

22

Figure 9 Prefabricated RCC Staircase and steel staircase

4.1.2 NON-STRUCTURAL COMPONENTS Some other elements are precast balconies, canopies etc. and in common areas boundary walls, kerb stones, main gate, etc. are shown in.

4.2 DESIGN & CONNECTION DETAILS The design philosophy of precast concrete construction is based on the buildability, economy, and standardization of precast elements. All loading & restraint conditions from casting to end use of structure are considered in design of precast members & Figure 10 Details of (a) Boundary wall, (b) Kerb Stone, & (c) Main Gate connections. Connections are needed not only to transfer load but also to provide continuity and overall monolithic behaviour of the entire structure. A complete system of precast elements is integrated to form a structure that behaves monolithically with sufficient strength, stiffness & durability to resist seismic & other dynamic loadings.

The connection can be classified into horizontal & vertical joints. Some typical connections details are shown in.

Figure 11 Connection illustration for (a) Beam-Column and (b) Slab to Beam (Source: Paradigm)

23

Figure 12 Typical Connection Details between In-Situ Shear wall & Hollow Core Slabs

Figure 13 Typical Vertical Connection Details between Precast Wall Panel to Panel

24 4.3 STANDARD MATERIALS PREFABRICATED COMPONENTS9

USED

FOR

MAKING

A number of new construction materials are starting to be used as components in prefab housing. Here are two of them: A. Structural Insulated Panels (SIPs) B. Insulating Concrete Forms (ICFs) A. Structural Insulated Panel (SIP) A structural insulated panel (SIP, also called a sandwich panel) consists of a pair of oriented strand board (OSB) or plywood panels with a core of extruded polystyrene (EPS) foam in between, attached with an adhesive. Panels are available in a variety of thicknesses. They are usually produced in 8-ft-tall panels, but they can be customized as per the requirement. Its peculiarity is that the foam in the core is the best insulator and its thickness determine the value of insulation. The foam core forms a continuous energy barrier, and the smaller number of studs leaves less opportunity for heat conduction. SIPs are fabricated to very close (1/8 inch) tolerances, and the edge connections, which vary by manufacturer, are designed to fit snugly together. The best thing about SIPs is their resistance to insects. While the EPS foam core provides no nutrition to insects, it offers an easy way for them to tunnel into the structure. Borate additives can be mixed into the foam during manufacture, providing some amount of insect resistance. De-lamination caused by failure of the adhesive is a major concern because it would affect the ability of structural SIPs to carry load.

B. Insulating Concrete Panel (ICFs)

Figure 11 SIPs

Insulating concrete forms (ICFs) are a prefab construction material which consist of hollow EPS foam blocks that are stacked and glued together on-site, creating a form that is filled with reinforcing bars and concrete. The unique property of ICFs is that the foam blocks are not removed after the concrete hardens; instead, they help insulate the building, while the concrete provides structural integrity. Although ICFs are really a hybrid prefab material, they offer many of the cost and environmental benefits of pure prefab. In comparison with traditional concrete construction, it is faster to stack ICF foam blocks than to build a wood form, and since the foam blocks are not removed, there is much less wastes. It can be also used as sound proof. The concrete must be fluid enough to fill the foam blocks without leaving air voids, which would severely detract from the structural integrity of the finished wall, yet must be solid enough not to exert too much horizontal pressure on the foam, which can cause the

9 Study on Pre-fabricated Modular and Steel Structures

By Prajjwal Paudel, Sagar Dulal, Madan Bhandari, Amit Kumar Tomar

25 forms to fail. Insect can attack this structure so; insect-resistant additives can be mixed into the polystyrene foam.

Figure 12 Insulated concrete panel C.              

Prefab Materials in Market Zincalume Steel Colorbond Steel Aerocon Panels FRP Corrugated Sheets Colour Coated Galvalume Sheets EPS Corrugated Panel CGI sheets UPVC roof Asphalt shingles PUF Sandwich Panel EPS Sandwich Panel Solid Cement wall Panel Dry Wall System using cement boards Different claddings/siding materials

1) Colour Coated Galvalume Sheets These sheets are preferred material for roofing and wall cladding. They combine the strength of steel and corrosion protection of zinc or zinc/aluminium alloy coatings.

These are available in various colours, have appealing aesthetics, long life, durability and easy installation. Colour coated Galvalume sheets of AZ150 class (aluminium zinc coating of 150 grams per sq. meter) with coated alloy of 55% Aluminium, 43.5%

26 Zinc and 1.5% Silicon and of approved colour with top surface coated with 20-25 microns of polyester coating and bottom service coat with 5-10 microns over and above epoxy primer, basic steel conforming to IS -513, ASTM A 792 M / AS 1397 – GALVALUME COATING, ASTM A 924 for mechanical properties and ASTM 755 for paint coating. Overall width of 1120 mm and laid width of 1060 mm, with six crests of 25 mm, spaced at 206 mm centre to centre, and with a stiffening rib (28mm) of 3mm height at the centre of each valley of the sheet, with two anti–capillary grooves with long return leg on either side of each crest.

2) Zincalume Steel This product is high corrosion resistant and thermal efficient hot dipped zincaluminium alloy (55% Al - Zn) coated steel with spangled surface conforming to AS 1397 available in Grade 300 & 550. Thickness of coating conforms to AZ 150 / AZ 200 (AZ 150 - 55% Al-Zn alloy coating of 150 g/m2 minimum).

3) Colorbond Steel The Colorbond steel is comprising of Zincalumer steel substrate as base material and coatings of Zn-Al alloy Coating, Conversion Coating, Universal Corrosion Inhibitive Primer (Nominal 5μm) and Finish Coat (Nominal 20μm) on the front side and similarly with Backing Coat (Nominal 5μm) on the back side. Colorbond steel has good resistance to accidental spillage of solvents such as methylated spirits, white spirit, mineral turpentine, toluene, trichloroethylene, dilute mineral acids and alkalis.

However, all spillages should be immediately removed by water washing and drying.

4) Sandwich Panel These are used for insulation of roofing and walling in the building. It consists of one or both side metal Galvalume sheet and PUF insulation in between. These have high thermal efficiency and significant mechanical strength, which makes it possible to go for larger spans as well as large partition walls.

5) Figure Aerocon 16Panels colorbond steel and colour coated galvalume

sheets

27 Aerocon panels are slim, lightweight wall panels that perfectly substitute plasterboard, plywood, particleboard and brick wall because of their sheer strength. Their low weight, ductility, fire and moisture-resistance properties make them hardy survivors of climatic and accidental disasters. Being pre-fabricated, they are also easy to install and reduce construction time by 80%. Aerocon panels are certified Green product by Indian Green Building Council. The Aerocon panels help to conserve natural resources. Fly ash, which is recycled waste, is utilized in making these panels. No wood is used in the manufacture of this product and little water is required during construction. These panels are also poor conductors of heat, therefore making a building energy efficient. Aerocon panels are available in the following sizes: Size Thickness 600 x 2400 mm 50 and 75 mm 600 x 2700 mm 50 and 75 mm 600 x 3000 mm 50 and 75 mm 6) FRP Corrugated Sheets: Fibre-reinforced plastic (FRP) (also fibre- reinforced polymer) is a composite material made of a polymer matrix reinforced with fibres. The fibres are usually glass, carbon, basalt or asbestos. The polymer is usually an epoxy or a polyester thermosetting plastic. FRPs are commonly used as roofing material as it is light weight, strong and resistive to deforming forces. They are usually rust and termite proof. They have good impact resistance; possess fire retardant properties and resistant to external weather conditions. These are normally available in 0.4 mm to 5.0 mm thickness. They are also available in transparent & opaque varieties. These are extensively used in parking sheds, shelters warehouses and residential and industrial roofing etc. where weight saving is an essential criterion.

Figure 13 FRP corrugated sheet and sandwich panel 7) EPS and PUF Panel

28 Expanded Polystyrene (EPS) Panel comprises of pre-fabricated composite sandwich panels with Expanded Polystyrene (EPS) insulation as core and profiled/plain, colour coated galvanized Steel/ galvalume steel sheet facing on both sides, complete with joint sealants and fixing ancillaries. Expanded Polystyrene is a lightweight closed cell rigid insulation formed by the expansion of polystyrene beads. It has excellent long term thermal and moisture resistance. EPS insulation is reliable, cost effective and compatible with major construction materials.

Polyurethane (PUF) Sandwich Panel is an upgraded material compare to traditional building material, as a kind of new type of multifunctional building material. It consists of steel plate at both side and polyurethane core of different densities inside.

They are bonded with high intension adhesive at high temperature and pressure through auto forming machine a) Thickness Availability: 40 mm, 50 mm, 75 mm, 100 mm, 125 mm, 150 mm, 175 mm, 200 mm.

Figure 14 EPS panel and PUF panel b)      

Benefits of EPS & PUF Panel: Pre-engineered and factory made for precision.

Internationally accepted and meets or exceeds all building code specifications.

Higher energy savings due to very low thermal conductivity.

Flexibility in design and choosing various options on fascia of panels and colours.

All weather proof construction and maintenance free.

Long lasting value with controlled quality, accuracy & speed of construction and caters for better functionality and application.

8) Dry Wall System This system is made of durable galvanized steel, which usually uses gypsum board and calcium silicate board or FCB (Fibre Cement Board) as surface material.

Compared with wooden board, Dry wall system provides safer and resistive wall.

Besides that, compared with bulky brick wall, it can greatly reduce the weight of building. In this system, thermal and acoustic insulation product can also be filled in partition frame to create a safe and quiet environment.

29 Thickness availability: 50mm, 60mm, 75mm, 90mm, 120mm, 150mm, 180mm & 210mm.

9) Aerated Cement Panel Solid cement wall systems comprised of a variety of shapes and wall types. We deal with: Solid wall panel simply refers to walls made of solid concrete. These wall systems require some form of insulation and an interior wall finishing system to complete the building enclosures.

Cement Sandwich panel is a series of building material with fly ash, different polymer beads and sand compound as core material along with low alkali sulphoaluminate cement and calcium silicate board as face panels.

Figure 15 Aerated Cement Sandwich (LEFT), Panel Dry-Wall System (MIDDLE), Aerated Solid Cement Panel (RIGHT)

Thickness Availability: 50mm, 60mm, 75mm, 90mm, 100 mm, 120mm, 150mm, 180mm & 210mm.

D) Roof Options      

PUF Corrugated Panel EPS Corrugated Panel CGI sheets UPVC roof Asphalt shingles Colour Coated Galvalume Sheets

E) Wall Options   

PUF Sandwich Panel EPS Sandwich Panel Solid Cement wall Panel

30  

Dry Wall System using cement boards Different claddings/siding materials

F) Floor Options Generally, cemented solid sheets are used as the flooring materials. Plywood, wooden planks, Marbles, tiles are also the options of flooring.

G) Door and Window’s Frame Hollow metal frames are very good replacement for wooden door/window frames. It can also be provided the looks of a wood frame at a very economical price and have other advantages over wood. The frames are termite proof and weather proof and have a better surface finish than wood. It can be provided with wooden shutters or hollow metal shutter or glass shutter. The shutter can also be provided with rock wool, mineral wool, PUF, Ceramic wool or polystyrene insulation

Figure 20 DOOR AND WINDOW

4.4 PREFABRICATED STEEL COMPONENTS The pre-engineered building is made up of the following components 

Primary Components Secondary Components

31 

Accessories

Figure 16 Components of PEBs10  1) 2) 3) 

PRIMARY COMPONENTS Main Frame Columns Rafters SECONDARY COMPONENTS

Girts and purlins form the secondary components which are used as a support system for walls and panels of roofs. The purlins are used on roofs and girts are used on walls. The main function of the secondary members is that it acts as struts which help in counter acting the part of loads which act on the building like wind and seismic loads and they provide lateral bracings to the flanges in compression of the members of the main frame thereby increasing the capacity of the frame. The secondary components are pre-galvanized or painted at factory with minimum of 35 microns of corrosion protection primer 1) 2) 3) 4) 5)

 ACCESSORIES Anchor Bolts Turbo Ventilator Walking Doors Aluminium Windows Sheeting

5. SYSTEM AND MANUFACTURING OF PREFABRICATED STRUCTURE11 5.1 SYSTEM AND CLASSIFICATION

10 components of PEBs 11 Prefabricated structure CE2046

32 The system of prefabricated construction depends on the extent of the use of prefabricated components, their material, sizes and the technique adopted for their manufacture and use in building. The various prefabrication systems are outlined below.

1) Small prefabrication 2) Medium prefabrication 3) Large prefabrication 4) Open prefabrication system a. Partial prefabrication open system b. Full prefabrication open system 5) Large panel prefabrication system 6) Wall system a. Cross wall system b. Longitudinal wall system 7) Floor system 8) Stair case system 9) Box type system

5.2 CONCEPT OF MODULAR STRUCTURE Cellular structures, cellular modules and modular buildings Modular construction as a concept is not a new idea. The motivation behind this movement is in the promise to gain advantages related to standard procedures.

Different approaches of modularity can be identified. Main possible approaches are: i) manufacturing of identical modules (no customization), ii) mass-customization of modules according to the needs of project in question, iii) manufacturing of free-form unique modules. Architectural possibilities are naturally increasing when going towards higher variability of modules. However, all approaches share the production philosophy where industrialized and standardized production is targeted. A cellular structure is defined as a structural component targeting the minimization of the amount of used material to reach minimal weight and minimal material cost. A honeycomb shaped structure is an example of such cellular structure. Modular construction represents a new kind of skeletal structure (compare Hong et al. 2011).

The basic idea is that the modules can bear the load of the other modules, and thus separate supporting structures are not required. Modular construction is also a special case of modular construction where even multi-storey buildings can be made from volumetric modules, the size of which can comprise a whole dwelling

33

Figure 17 Concepts Modular Structure

Figure 18 MODULAR HOME (2015)12 5.3 PRODUCTION AND PROCEDURE13 The term production of systems is describing a series of operation directly concerned in the process of making or more apply of moulding precast units on the face of it there are very many techniques since almost every type prefabricates requires a specific series of operation in its production.

These techniques however may be grouped into three basic method of production.

These are 1. The stand system 2. The conveyor belt or production line system 3. The aggregate system 1. Stand system 12 Development and Efficiency of Prefabricated Building Components

By Tomas U. Ganiron Jr 13 Prefabricated structure CE2046

34 In the stand system the prefabricates mature at the point where they were moulded While the production team moves to successive stands the bed on which prefabricates.

2. Conveyor belt The conveyor belt system of production splits the whole production process in to a series of operation carried out at a separate successive and permanent point to the heat may be by means of conveyor belt trolleys & crane etc.

3. Aggregate system The word aggregates describe a large, complex permanently installed set of machines and mechanical application which can carry out most of the separate operation involved in casting concrete components.

5.3.1 PRODUCTION PROCEDURE The location of precasting yards consist of storage facilities suitable for transporting and erection equipment’s and availability of raw materials are the critical factors which should be carefully planned and provided for effective and economic use of pre-cast concrete components in construction.

The manufacture of the components can be done in a centrally located factor of in a site where precasting yards set-up at or near the site of work. 

FACTORY PREFABRICATION:

Factory prefabrication is restored in a centrally located plant for manufacture of standardized components on a long form basis. It is a capital intensive production where work is done throughout the year preferably under a covered shed to avoid the effects of seasonal variations high level of mechanization can always be introduced in this system where the work can be organized in a factory like manner with the help of constant team of workmen.

The basic disadvantage in factory prefabricated, is the extra cost in occurred in transportation of elements from plant to site of work sometimes the shape and size of prefabricable are to be limited due to lack of suitable transportation equipment roads controls etc. 

SITE PREFABRICATION:

In this scheme, the components are manufactured at site near the site of work as possible. This system is normally adopted for a specific job order for a short period.

The work is normally carried out in open space with locally a valuable labour force.

The equipment machinery and moulds are of mobile nature.

Therefore, there is a definite economy with respect to cost of transportation. This system suffers from basic drawback of its non-suitability to any high degree of mechanization. It has no elaborate arrangements for quality control.

35 PROCESS OF MANUFACTURE: The various processes involved in the manufacture of precast elements are classified as follows: 1) Main process 2) Secondary (auxiliary) process 3) Subsidiary process 1) MAIN PROCESS: It involves the following steps.

1) Providing and assembling the moulds, placing reinforcement cage in position for reinforced concrete work, and 2) Fixing of inserts and tubes where necessary.

3) Depositing the concrete in to the moulds.

4) Vibrating the deposited concrete into the moulds.

5) Demoulding the forms.

6) Curing (steam curing if necessary) 7) Stacking the precast products.

2) SECONDARY (AUXILLARY) PROCESS: This process is necessary for the successful completion of the process covered by the main process.

1) Mixing or manufacture of fresh concrete (done in a mixing station or by a matching plant).

2) Prefabrication of reinforcement cage (done in a steel yard of workshop) 3) Manufacture of inserts and other finishing items to be incorporated in the main precast products.

4) Finishing the precast products.

5) Testing the precast products.

STAGES OF PREFABRICATED CONCRETE PRODUCT: FLOW DIAGRAM OF STAGES OF PROCESSING

36 CONCRETE

---------MOULD----------------- STEEL

MIXING ---------------- PREPARATION-------- CUTTING

FILLING--------------------

REINFORCING

COMPONENT

COMPACTION

CURING

DEMOULDING

STORAGE

STORAGE OF PRE-CAST CONCRETE PRODUCTS BY STAGE

37 Stage

1 2 3 4 5 6 7 8 9 10 11 12

process Procurement storage of raw materials Testing of raw materials

Operational involved Unloading

Design of concrete mix Fabrication of reinforcement cages Oiling and laying of moulds in portion Placing of reinforcement cages inserts and fixtures Preparation of fresh concrete Transport fresh concrete depouring into moulding etc.

Curing of concrete Stacking of pre-cost element Testing of finished component

Table 1 STORAGE OF PRE-CAST CONCRETE PRODUCTS BY STAGE

5.3.2 TRANSPORT Transport of prefabrication elements must be carried out and with extreme care to avoid any flock and distress in elements and handled as far as possible to be placed in final portion Transport of prefab elements inside the factory depends on the method of production selected for the manufacture.

Transport of prefab elements from the factory to the site of action should be planned in conformity with the trafficable rules and regulations as stipulated by the authouritic the size of the elements is often restricted by the availability of suitable transport equipment, such as tractor-am-tailor, to suits the load and dimension of the member in addition to the load carrying capacity of the bridges on the way.

While transporting the prefab elements in various systems, such as wages, trucks, bullock cards etc. care should be taken to avoid excessive cantilever action and

38 desired supports are maintained. Special care should be taken in negotiating sharp beds uneven of slushy roads to avoid undesirable stresses in elements and in transport vehicles. Before loading the elements in the transporting media, care should be taken to ensure the base packing for supporting the elements are located at specified portion only.

5.3.3 ERECTION It is the process of assembling the Prefabrication element in the find portion as per the drawing. In the erection of prefab elements, the following items of work are to be carried out.

1). Slinging of the prefab elements.

2). Tying up of erection slopes connecting to the erection hooks.

3). Cleaning the elements and the site of erection.

4). Cleaning the steel inserts before incorporation in the joints lifting and setting the elements to correct position.

5). Adjustments to get the stipulated level line and plumb.

6). Welding of deats.

7). Changing of the erection tackles.

8). Putting up and removing the necessary scaffolding or supports.

9). Welding the insorts laying the reinforced in joints.

The erection work in various construction jobs by using prefab elements differs with risk condition, hence skilled foremen, and workers to be employed on the job.

Equipment’s required for erection Equipment’s required for the prefab elements in industry can be classified as.

1) Machinery required for quarrying of course and fine aggregates 2) Conveying equipment, such as but conveyor, chain conveyors etc.

3) Concrete mixers 4) Vibrators 5) Erection equipment such as cranes, derricks, chain pulley etc.

6) Transport machines 7) Work shop machinery for fabricating and repairing steel.

39 8) Bar straitening, bending and welding machines 9) Minor tools and takes, such as wheel barreriour, concrete buckets etc…

10) Steam generation a plant for accelerated curing.

Planning co-ordination It is important to have the precaster erector/installer and builder working together to achieve best performance.

Site Access and storage   

Check for site accessibility and precast panels delivery to site especially low bed trailers Check whether adequate space for temporary storage before installation and ground conditions. (firm ground & levelled) Uneven ground will cause overstress & crack panels.

Planning crane Arrangement    

Plan the crane capacity and lifting gears based on Heaviest weight of precast panels Lifting heights.

Working radius Position of crane in relation to final panel location

Plan other equipment’s  

Boom lift and scissor lift for unhooking installed panels.

Lifting gears

Skilled personnel’s   

Competent crane operators Rigger Signalled etc.

General considerations for crane selection      

Total lifting weight Crane model Crane safe working load (SWL) (i.e.) Based on 15% capacity build in F.O.S. 1.33  Lifting capacity must be 1.5 times the total weight i.e.) F.O.S 1.5 Lifting and swing radius Crane counter weight

40 

Crane boom length is relation to the vertical and horizontal clearance from the building.

5.4 INSTALLATION PROCESS 5.4.1 INSTALLATION OF VERTICAL COMPONENTS 1. Verification of Delivered Panels     

Check the panels delivered for correct marking lifting hook and position etc.

Surface finishing condition Pc Dimension compliance Reinforcement Provision/position Architectural Detail compliance

Setting out   

Check the panels delivered for marking, lifting hook and condition.

Set the reference lines & grids Check starter bars for vertical components before hoisting for installation

2. Setting out Quality control point    

Ensure correct offset line Check shim pedal/plate level and firm Rubber gasket property secured For external wall/column place backer rod.

3. Hoisting, Rigging and Installation        

While tilting provides rubber pad to avoid chip off.

Lift and rig the panel to designated location Adjust the panel in position and secure Lifting of space adding items with balanced centre of gravity.

Ensure horizontal alignment correct Ensure panel vertically to correct plumb Check panel to panel gap consistency Check stability of prop before releasing hoisting cable.

4. Grouting works      

Prepare and apply non-shrink mortars to seal For corrugated pipe sleeve on splive sleeve pour NSGT or proprietary grouts into pipe slab.

Keep installed panels undisturbed for 24 hrs.

Check joint widths are consistent before grouting Grout used should be same grade of components and self-compacting to prevent cracking.

Collect test cube sample for testing for critical element or load bearing

41 

elements

5. Connecting joints      

Cast in situ joints install rebars as required Set up forms for casting joints Do Concreting Remove forms after sufficient strength For external connections sealant shall be used Panel with welded connections welding as required

5.4.2 INSTALLATION OF HORIZONTAL ELEMENTS 1. Setting out     

Set reference line/offset line to required alignment and level of slab/beam during installation Put temporary prop to support the precast slab/beam elements Before Hoisting Chem. Dimensions Check level and stability of shim Check protruding/ starter bars are within the Specified tolerance to prevent any observation during the erection process

2. Hoisting & Installation      

Put temporary props to support slab/beam Lift and rig the elements in designated location Align and check the level before placement The beams shall prop at least 2 location Balcony planter box and shall be supported more than 2 location based on design considerations Check level of precast elements

3. Connections/Jointing      

Precast with cast-in-situ joints place the lap rebars as required Set formwork for casting joints Remove formwork after concrete strength is achieved Supporting beams shall be designed to form part of formwork joints The connecting/lapping rebars tied & secured Same grade of concrete 10 to be used that of panel.

4. Installation using Big canopy  

Big canopy high rise precast concrete construction system This is used for faster and efficient

5.5 MERITS AND DE-MERITS OF PREFABRICATED SYSTEM MERITS

42 

   

Buildings are generally constructed within 70% of the time required by the CBS after approval of drawings. Prefab will thus reduce total construction time of the project by at least 30%. This allows faster occupancy and earlier realization of revenue.

Because of systems approach, considerable saving is achieved in design, manufacturing and erection cost.

Buildings can be supplied to around 90m clear spans. This is one of the most important advantages of PEB giving column free space.

Buildings are manufactured completely in the factory under controlled conditions, and hence the quality can be assured. h) Steel members are brought to site in CKD conditions, thereby avoiding cutting and welding at site. As PEB sections are lighter in weight, the small members can be very easily assembled, bolted and raised with the help of cranes. This allows very fast construction and reduces wastage and labour requirement.

DE-MERITS 

Skilled and artistic work cannot be done in pre-cast buildings



Being a new technology, people are not creative enough to produce artistic work The moment the artisans start working on this aspect, the cost increases Not becoming popular where mass production is not there

 

6. LITERATURE CASE STUD 6.1 COMPARISON OF PREFABRICATED STRUCTURE TO A CONVECTIONAL STRUCTURE14

Prefabricated construction

Traditional methods of construction

Cost

Significantly lower than traditional methods

High cost

Speed

Faster method of construction

Slow as compared to prefabricated construction.

Wastage

Less wastage of materials due to green practices and controlled environment in prefabrication construction

High waste due to in-situ construction practices

Flexibility

Less flexibility due to

More flexible

14 Abhinav Dewangan et al. Int. Journal of Engineering Research and Applications ISSN: 2248-9622, Vol. 5, Issue 11, (Part - 2) November 2015, pp.25-28

43 standardisation of units Quality

Higher quality control due to production under controlled environment

In-situ construction practices are subject to weather changes. They may lead to poor quality construction.

Labour

Less labour intensive due to Computer Integrated Manufacture (CIM)

Skilled personnel and labour required.

Design

Requires heavy detailing with modifications

Requires Specialized computer design

Foundation

Widespread foundations are required Easy to manage and light design work

Erection cost It takes time up to 10-12 weeks for Over all Erection time is less than 6 and time erection and expensive as compared weeks which makes it cost effective to PEB

6.2 LITERATURE CASE STUDY OF PREFABRICATED RESIDENTIAL BUILDING STRUCTURE ON THE BASIS OF COST AND DURATION OF CONSTRUCTION

Figure 19 Floor plan of double story building

6.2.1 Project Duration Project duration of each construction was collected from the similar companies and compares the time of completion period by using Critical Path method with Primavera P6. Table 2gives the project duration of precast and conventional construction of the building

S. No

DESCRIPTION (PREFABRICATED)

DURATION

S. N O 1.

2.

3.

Sub Structure - (Site cleaning, Earthwork, Foundation, Basement, Soil filling& Consolidation.)

Super Structure – (Wall panels framing and Roofing slabs.)

Finishing Works – (Electrical, Plumbing Painting, Tiling, and Windows, Extra items.)

44Duration

(CBS)

22 Days 1.

12 Days

31 Days

DESCRIPTI ON

2.

3.

Sub Structure - (Site cleaning, Earth work, Foundation, Basement, Soil filling & Consolidation.)

Super Structure (Columns, Lintel& sunshade, Beams, Roof slabs, Brick work, Plastering.)

Finishing Works – (Electrical, Plumbing Painting ,Tiling, and Installation of doors & Windows, Extra items.)

Table 2 Total Duration for Prefabrication Construction and Conventional Construction

6.2.2 Cost Analysis

22 Days

52 Days

54 Days

45 This is the main factor which is considered in the project is to find out the comparison of cost analysis of double storey building for the prefab construction and conventional construction. In this analysis we want to consider the resources of labour, material and machineries.

SI NO 1.

DESCRIPTION

COSTS

SI NO 1.

Sub Structure - (Site cleaning, Earth work, Foundation, Basement, Soil filling& Consolidation.)

5,26,000.00 2.

24,23,000.0

2.

Super Structure- (Wall panels framing and Roofing slabs.)

0

3.

Finishing Works – (Electrical, lumping Painting, Tiling, and Installation of doors & Windows, Extra items.)

0

3.

43,51,000.0

DESCRIPTION

COSTS

Sub Structure – (Site cleaning, Earth work, Foundation, Basement ,Soil filling& Consolidation.)

Super Structure – (Columns, Lintel& sunshade, Beams, Roof slabs, Brick work, Plastering.)

5,26,000.00

Finishing Works – (Electrical, Plumbing, Painting, Tiling, and Installation of doors& Windows, Stair case, Extra items.)

44,69,000.0 0

Table 3 total cost for prefabrication construction and conventional construction material and labour cost for total project

6.2.3 Result and Discussion Project duration and cost of the structure was calculated on the basis of data collected from the company. The duration of construction in the prefabricated building was same at the 1st stage as it has to performed on the site itself for construction of super structure. At 2nd stage we can see a major difference in the number weeks required to complete the super structure, for prefabricated structure we require 2 weeks to complete the process while in the7.5 weeks which mean in convection method the hole process takes 75% of more time to complete the similar process. Since, in the case of prefabricated construction elements were already been prepared at the factory and transported on the site which make the process much faster. At 3rd stage we can see from the table that there is similarly condition as of the 2nd stage the CBS takes more 44% more time than the prefabricated system. Since the prefab system require minor finishing touches or does not at all, as they are finished at the factory with all electrical and plumbing fitting.

The figure (25) shows the comparison of project duration for the both prefab and conventional construction in three different stages. As in the figure the sub-structure has taken the same duration for complete the project for both construction of double storey residential building, because of the sub- structure was done by the traditional method. But the category of super-structure has more variations, which the prefabrication construction is completed soon when compare to the conventional construction, because of the super-structure for the prefab was manufactured in factory and installed in site, which reduce the working time. The finishing works also the prefab construction is taken less time duration when compared to conventional.

The total project duration was calculated for both construction and shown in the Figure (25). The figure represents the duration of the prefabrication construction is

1024000.00

46 lower than the conventional construction. The time duration of the project difference is 63 days between the prefabrication and conventional construction.

140

128

120 100

DAYS

80 65 60 40 20 0 CBS PRIFABRICATED STRUCTURE

60 52

54

50

DAYS

40 31

30 22

22

20 12 10 0

CBS STAGE 1

PRIFABRICATED STRUCTURE STAGE 2

STAGE 3

47

Figure 20 Bar chart showing duration of construction at different stages The main factor cost of the project was also analysed in the similar stages as in the case of duration. The sub-structure and finishing work cost was the same as conventional construction because of same method is used to construct in the prefab.

The cost of the project is shown in three different stages. The total cost of the double storey residential building for prefabrication construction is 73, 00,000.00 (seventythree lakh rupees only). The cost of the conventional construction was calculated through the data collected from conventional construction company. The sub-structure and finishing work cost was taken to the prefab construction from the conventional.

So there are no cost variations in both constructions for these stages. But the cost variation was in the super-structure and which is low when compared to the prefab construction for double storey residential building. Total cost of the double storey residential building for conventional construction is 60, 19,000.00 (Sixty lakes and nineteen thousand rupees only).

The figure (26) shows the cost difference for the both prefab and conventional construction in three different stages. As in the figure the sub-structure and finishing works has the similar cost for both construction of double storey residential building, because of the sub- structure and the finishing works was done by the traditional method. But the category of super-structure has more variations, which the prefabrication construction is very high cost compare to the conventional construction, because of the superstructure was done in two different methods as prefab and conventional. The total project cost was calculated for both construction and shown in the Figure (26). The figure represents the cost of the prefabrication construction is higher than the conventional construction. The cost difference is 12, 91,000.00 rupees between the prefabrication and conventional construction.

4469000

4351000

2423000 1024000 526000

526000 RE

5000000 4500000 4000000 3500000 3000000 2500000 2000000 1500000 1000000 500000 0

PR I

FA B

RI

CA TE

D

ST R

UC TU

CB S

COST(IN RUPEES)

48

STAGE 1

STAGE 2

STAGE 3

8000000 7000000 6000000

7300000 6019000

5000000 3000000 2000000 1000000

FA B

RI

CA TE

D

ST R

UC TU

CB S

RE

0

PR I

COST(IN RUPEES)

4000000

49

Figure 21 Bar charting showing costing of construction at different stages

6.3 LITERATURE CASE STUDY OF AN INDUSTRIAL PREFAB STRUCTURE ON THE BASIS OF COST AND DURATION OF CONSTRUCTION 6.3.1 MODELING Parameter

Type/Value Belagavi, Karnataka 40 m 20 m 6m 21.80

Location Total length Total width Clear height Slope of roof Single bay length Column section Purlin section Truss members (Principal rafter, main tie, struts, ties)

4m ISHB 200 @ 40kg/m ISMC 200 @22.1 kg/m 110 x 110 x 15 (Single angle)

The models of the Conventional Steel Building (CSB) and Pre-Engineered Building (PEB) are analysed and designed using STAAD.Pro software. One model each for CSB and PEB was prepared. The details about the models and the data adopted for the study are presented below in Table 4 and Table 5.

Table 4 Data adopted for CSB Model Parameter Location

Type/Value Belagavi, Karnataka

Total length

40 m

Total width Clear height Slope of roof

20 m 6m 5.710

Single bay length Column and Rafters

4m Tapered ISHB 350 to ISHB 300

Purlin section

200x80x5

Table 5 Data adopted for PEB Model The typical plan, elevation and STAAD 3D rendered view of the CSB and PEB models are presented below from Fig.-27 and Fig.-28.

50

51

Figure 22 plan, elevation and rendered view of CBS model

6.3.2 RESULTS DISCUSSION

Figure 23 plan, elevation and rendered view of PEB model

AND

Each of the two models was modelled and analysed using STAAD.Pro and designed using validated MS-Excel sheets. Later, the results obtained for the CSB and the PEB models were compared by using various parameters and the performance of the models was evaluated.

Following are the three parameters considered for the comparison of the results for CSB and PEB models1) Self weight of the Structure 2) Cost of Construction 3) Time of Construction Each of these three parameters was worked out for both the models which are presented below in Table-6, Table-7 and Table-8 respectively. The weight of the connections was assumed as 12.5% of total weight for CSB model and 7.5% of total weight for PEB model.

Table 6 Comparison of the Self Weight of the models Weight of the Components (MT) Model

CSB PEB

Rafter

29.8 14.2

Column

5.1 8.3

Purlin

14.8 8.9

Total SelfWeight (MT)

Connections

6.2 2.3

56.0 33.7

Table 7 Comparison of Cost of Construction

Model

CSB PEB

SelfWeight (kg)

56000 33700

Rate of material per kg (Rs.)

Material Cost (Rs.)

40 43

2240000 1449100

Labour Cost @ Rs.15 per kg (Rs.)

840000 505500

Total Cost of Construction (Rs.)

30,80,000 19,54,600

% saving in Cost for PEB compared to CSB = 35%

52

Table 8 Comparison of Time of Construction

Model

CSB PEB

Geometry of the Structure Working Space Height (m2) (m)

800 800

6 6

Approx. Time of Construction (Weeks)

12 08

7.1 CONCLUSION The total cost and total duration for the double storey residential building have been determined for both prefab and conventional construction. And also, we had known about the advantages and disadvantages of both prefabrication and conventional construction by the survey conducted in similar companies. The comparison showed there is enormous cost difference between the methods, which the prefab is very high when compared to conventional on this type of individual houses. Thus, the main advantages for prefab construction and also it helps when there is labour shortage.

This is main drawback for prefab construction which is not economical to construct in the case 1.

While, in case 2 the total cost and total duration for the industrial building have been determined for both prefab and conventional construction. The comparison showed there is enormous cost difference between the methods, which the conventional is very high when compared to prefab on this type of individual sheds. The main advantages for prefab construction is that it is economical as compared to conventional by 35% secondly, the duration of construction is also less and also it helps when there are labour shortage.

Therefore, we can conclude that there the prefab construction is can be viable choice in the fast moving for better result in terms of construction quality, less duration of construction time with higher level of standard. But, in terms of cost the prefab can some times be economical in case 1 we can see the cost is increased due to higher level of professional required. And in case 2 both cost and duration were less as compared to the convectional building. Thus, we can say that the cost is mainly dependent on the scale of projects and prefab components used for construction, when the project is small the cost increase, and when the project is large the cost decreases significantly. Components also affect the factor of cost since they are transported from the factory to site they should be light in weight and should be compact in size to be easily transported.

53

BIBLIOGRAPHY 1. Prefabrication in Developing Countries: a case study of India by Ryan E. Smith.

2. Case-study on use of precast technology for construction of high-rise buildings by sandeep jain 3. Study on Pre-fabricated Modular and Steel Structures by Prajjwal Paudel, Sagar Dulal, Madan Bhandari, Amit Kumar Tomar 4. Development and Efficiency of Prefabricated Building Components by Tomas U. Ganiron Jr 5. CE2045 Prefabricated structutres 6. Prefabricated construction for mass housing in mumbai Krish R. Villaitramani, Dhruv P. Hirani 7. A Comparative study on the Performance of PEB with CSB considering various parameters by Abhyuday Titiksh1, Abhinav Dewangan, Ankur Khandelwal, Akshay Sharma 8. Comparative Study on Prefabrication Construction with Cast In-Situ Construction of Residential Buildings by N.Dineshkumar, P.Kathirvel 9. A Comparative study on the Performance of PEB with CSB considering various parameters by Darshan Kalantri , Sujay Deshpande , Pavan Gudi

WEBLIOGRAPHY 1.

2.

3.

4.

5.

http://www.amrapali.in/verticals-precast.asp https://www.slideshare.net http://dx.doi.org/10.14257/ijsh.2016.10.6.10 http://www.amrapali.in/verticals-precast.asp https://www.svce.ac.in/departments/cve/downloads/prefabricated %20structures/unit_1.pdf