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Acknowledgement I would like to give my sincere obligations to the almighty, 'Lord Jagannath'. I am extremely grateful to my supervisor Dr. Sean Lu for his inspiration and support during the entire duration of my dissertation. I would like to thank John and Scott for all their support throughout the dissertation by allowing me to use the work shop and allotting space to carry on with the casting experiment. My special thanks to Wang for solving my queries regarding the structural analysis software ANSYS. I will also like to thank my friends Dishant, Manan, Rahul and Stavroula for their timely support during the dissertation period. And I also will like to thank all my classmates and studio mates, all staffs of Architecture Department for their support and smile throughout the year. A special thanks to my family and all the great souls around me for their love and emotions.
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Abstract The advance digital technology in recent times has led the design process to a phase where physical model making has lost its importance. The idea here is to understand the role of model making in the design process and its contribution to the same through live experiments. The aim of the research is to generate a self-form geometry with response to natural forces like gravity by the use of fabric formwork. To analyze the structural performance of the form created, ANSYS simulation has been carried out to give quantitative scientific evidences. The objective of this experiment is to find a selfformed vault shell structure by using fabric form work. Hence, the experiment has been carried out through number of test casts with added parameters like fabric formwork and sewing to get accustomed with the process. A similar geometry of the final double curved vault shell structure is created digitally with 3D modeling tool and the structural simulations are analyzed before drafting the conclusion. The outcome of this research suggests that, model making contributes its value in the design development process and improves the architectural performance. In addition, the fabric formwork creates aesthetically pleasant self-form geometry with proper demonstration of flow of structural forces in the cast with an ability to be used for real site construction work.
Key Words: Natural Form Finding, Design by Making, Self-form Geometry, Fabric Form Work
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Table of Contents 1.
Introduction .................................................................................................................................. 1 1.1
Background ............................................................................................................................. 1
1.2
Issues in present scenario ....................................................................................................... 2
1.2.1 1.3
Gap between the current research strategies and future requirement......................... 3
Objective ................................................................................................................................. 3
1.3.1
Limitations....................................................................................................................... 3
1.3.2
Significance and scope of research ................................................................................. 4
1.4
Methodology........................................................................................................................... 4
1.5
Structure/Flow Chart of Dissertation ...................................................................................... 6
BIBLOGRAPHY ..................................................................................................................................... 8
2.
Literature Review ........................................................................................................................ 9 2.1
Case Study ............................................................................................................................... 9
2.1.1
Antonio Gaudi's Catenary System ................................................................................... 9
2.1.2
Heinz Isler's Shell Structures ......................................................................................... 12
2.1.3
Research at C.A.S.T. ...................................................................................................... 13
2.2
Making and Designing ........................................................................................................... 15
2.2.1
Physical form finding process ....................................................................................... 15
2.2.2
Mock-up model for testing ........................................................................................... 15
2.2.3
Assembly possibilities ................................................................................................... 16
2.2.4
Validating assembly possibilities (Construction) .......................................................... 16
2.2.5
Rapid prototyping of the final product ......................................................................... 17
2.3
Physical form finding process ............................................................................................... 17
2.3.1
Natural form and Geometry ......................................................................................... 18
2.3.2
Physical model vs Digital model .................................................................................... 18
2.3.3
Role of Fabric in Natural Form finding .......................................................................... 19
2.4
Conclusion ............................................................................................................................. 20
BIBLIOGRAPHY .................................................................................................................................. 21
3.
Solution .......................................................................................................................................22 3.1
Introduction .......................................................................................................................... 22
3.1.1 3.2
Adopted Methodology .................................................................................................. 22
Casting................................................................................................................................... 23
3.2.1
Test Casts ...................................................................................................................... 24
3.2.2
Cast I (Double Curve Shell) ............................................................................................ 30 iii | P a g e
3.2.3
Cast II (Double Curve Vault Shell) ................................................................................. 31
3.2.4
Cast III (Support Column) .............................................................................................. 33
3.2.5
Combined Structure ...................................................................................................... 34
3.3 4.
Analysis of Structure with ANSYS .................................................................................................. 37 4.1
Working with ANSYS ............................................................................................................. 37
4.2
Parameters ............................................................................................................................ 39
4.2.1
Material Selection ......................................................................................................... 39
4.2.2
Properties of GFRC (Glass Fibre Reinforced Concrete) used for Simulation................. 40
4.3
ANSYS Simulation .................................................................................................................. 42
4.3.1
Finding Optimum Thickness .......................................................................................... 44
4.3.2
Case I ............................................................................................................................. 46
4.3.3
Case II ............................................................................................................................ 49
4.3.4
Case III ........................................................................................................................... 52
4.4
5.
Conclusion ............................................................................................................................. 36
Conclusion ............................................................................................................................. 54
Conclusion ...................................................................................................................................58 5.1
Knowledge Gained ................................................................................................................ 59
5.1.1
Importance of making - for natural form finding (Self-form generation) ..................... 59
5.1.2
Importance of making - to develop the design ............................................................. 59
5.1.3
Importance of making - to improve the performance .................................................. 60
5.1.4
Fabric Formwork ........................................................................................................... 61
5.2
Role of Simulation ................................................................................................................. 61
5.3
Limitations of Model Making ................................................................................................ 61
5.4
Future Recommendations .................................................................................................... 62
BIBLOGRAPHY ................................................................................................................................... 63
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List of Figures Figure 1-1 Heinz Isler's form finding process for concrete shells by physical model (Source: www.sefindia.org)................................................................................................................................... 1 Figure 2-1 Left, the inverted form finding model of 'Sagrada Familia' and Right, Gaudi's sketch over the photograph from the model (Source: Architectural Science Review, December 2006) ................ 10 Figure 2-2 Left, Original catenary model of Sagrada Familia shows Gaudi's idea of finding form from forces and Right, the structural models of same for actual construction (Source: Sweeney, p 86-87)11 Figure 2-3 Isler's art of form finding with different methods (Photo: Heinz Isler) ............................... 12 Figure 2-4 From model to reality, Isler's development model and the constructed free form structures (Photo: Heinz Isler) .............................................................................................................. 13 Figure 2-5 A funicular fabric form generated by C.A.S.T. (Source: The Centre for Architectural Structure and Technology, Manitoba University, Canada) ................................................................... 14 Figure 2-6 Another thin shell vault developed by C.A.S.T. directly from a single hanging flat sheet of fabric (Source: The Centre for Architectural Structure and Technology, Manitoba University, Canada) .............................................................................................................................................................. 14 Figure 2-7 CNC milled styrofoam moulds for construction of Zollhof Towers (Source: Afify & Elghaffar, 2007) ..................................................................................................................................... 17 Figure 2-8 Fabric-cast beam by C.A.S.T. showing natural structural 'force path' (Source: www.umanitoba.ca/cast_building) ...................................................................................................... 20 Figure 3-1 Details of shell structure casting (Source: Author) .............................................................. 24 Figure 3-2 Casted replica of thin shell with double layer fabric (Source: Author)................................ 24 Figure 3-3 Casting procedure of Y shaped component (Source: Author) ............................................. 25 Figure 3-4 Casted 'Y' shaped component and illustrations showing the assembly possibilities in creating a pattern (Source: Author) ...................................................................................................... 26 Figure 3-5 a. The structure of human leg bone (Source: http://www.daviddarling.info/encyclopedia) b. Casting procedure of twisted column (Source: Author) 26 Figure 3-6 Final cast output of the twisted column experiment (Source: Author)............................... 27 Figure 3-7 Casting procedure of Bubble Shell structure (Source: Author) ........................................... 27 Figure 3-8 Finished outcome of bubble shell cast (Source: Author)..................................................... 28 Figure 3-9 Automatic filtration of excess water from the cast through fabric (Source: Author) ......... 29 Figure 3-10 Test casts showing patterns created with Lycra fabric and sewing (Source: Author) ....... 29 Figure 3-11 Different patterns of sewing on a variety of fabric for experimental casts (Source: Author) .................................................................................................................................................. 30 Figure 3-12 Fabric form work for double curve shell before material application (Cast I) (Source: Author) .................................................................................................................................................. 30 Figure 3-13 Self formed fabric form work for double curve shell structure (Cast I) (Source: Author) . 31 Figure 3-14 Self formed fabric form work for double curve shell structure (Cast II) (Source: Author) 32 Figure 3-15 Double curve vault shell concluding cast (Source: Author) ............................................... 33 Figure 3-16 'Y' shaped support column final cast (Source: Author) ..................................................... 34 Figure 3-17 The final vault shell structure (Source: Author)................................................................. 35 Figure 3-18 Computer generated model of the combined structure (Source: Author) ....................... 35 Figure 4-1 The Base geometry similar to the final cast (Source: Author) ............................................. 37 Figure 4-2 ANSYS start page.................................................................................................................. 38 v|Page
Figure 4-3 Engineering data input page of ANSYS ................................................................................ 38 Figure 4-4 Comparison of physical properties of Glass fibre Reinforced concrete and structural light weight concrete. ................................................................................................................................... 40 Figure 4-5 Physical properties of Glass reinforced concrete put in ANSYS. (Source: www.grconline.com)............................................................................................................................. 41 Figure 4-6 Spraying of GFRC and its results (Source: C.A.S.T.).............................................................. 42 Figure 4-7 Types of geometry to be simulated (Source: Author) ......................................................... 42 Figure 4-8 Structural constraints applied to each geometry (Source: Author) .................................... 43 Figure 4-9 Comparison of Physical properties for Case I, Case II and Case III obtained from ANSYS... 43 Figure 4-10 Stress Intensity comparison for optimum thickness of slab (Source: Author) .................. 44 Figure 4-11 Total deformation comparison for optimum thickness of slab (Source: Author) ............. 45 Figure 4-12 Physical properties of geometry obtained from ANSYS for Case I (Source: Author) ........ 46 Figure 4-13 Total Deflection of the shell structure in Case I, obtained from ANSYS simulation (Source: Author) .................................................................................................................................................. 47 Figure 4-14 Stress Intensity of the shell structure in Case I, obtained from ANSYS simulation (Source: Author) .................................................................................................................................................. 48 Figure 4-15 Physical properties of geometry obtained from ANSYS for Case II (Source: Author) ....... 49 Figure 4-16 Total Deflection of the shell structure in Case II, obtained from ANSYS simulation (Source: Author).................................................................................................................................... 50 Figure 4-17 Stress Intensity of the shell structure in Case I, obtained from ANSYS simulation (Source: Author) .................................................................................................................................................. 51 Figure 4-18 Physical properties of geometry obtained from ANSYS for Case III. ................................. 52 Figure 4-19 Total Deflection of the shell structure in Case III, obtained from ANSYS simulation (Source: Author).................................................................................................................................... 53 Figure 4-20 Stress Intensity of the shell structure in Case III, obtained from ANSYS simulation (Source: Author).................................................................................................................................... 54 Figure 4-21 Comparison of total deflection in all cases (Source: Author) ............................................ 55 Figure 4-22 Comparison of Stress Intensity in all cases (Source: Author) ............................................ 56
List of Tables Table 1 Physical properties of Glass reinforced concrete (Source: http://www.grconline.com/en/grc/propertiesofgrc.html) .................................................................. 41
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1. Introduction 1.1 Background The advancement in digital technology in recent times has led the design process to a phase where physical model making has lost its importance and instead models are treated as a piece of artifact once the final design is done digitally. Since beginning of 21st century, the architectural freedom of creating imaginative shapes has been accelerated with the new innovative techniques of designing and construction, fuelled by CAD/CAM technologies. 'We need form-generation models that recognize the laws of physics and are able to create 'minimum' surfaces for compression and bending as well as tension. And we need to extend the virtual building model to virtual construction - not just conception - so that the way a building is fabricated and erected becomes as important a part of design as its efficient use of materials. This will help us create buildings that will conserve material and energy and hence go some way towards meeting today's pressing need - conservation of our global resources'. [1] Looking back in history, engineers and architects were always inspired and fascinated by the methods of making in reference to physical models and geometrical systems. Form finding models were an integrated part of the design process to derive the geometry and even structural stability. Physics, materiality and the impact of natural forces like gravity were some of the driving forces in design process to create Geometry in the pre-software simulation era. In this way, the architectural form or shape, structural system, material properties and forces of nature share a deep intimacy in a design procedure. Moreover, later being converted to sketches and then in to drawings followed by real construction on the site. Figure 1-1 shows the typical form finding process by Heinz Isler for concrete shells.
Figure 1-1 Heinz Isler's form finding process for concrete shells by physical model (Source: www.sefindia.org)
Anthonio Gaudi's experiment with catenary1 systems for creating masonry compression structures is the most unique way to demonstrate the method of making or model making to solve the 1
'Catenary is the curve assumed by a cord of uniform density and cross section that is perfectly flexible but not capable of being stretched and that hangs freely from two fixed points'. (Source: Merriam-Webster Dictionary)
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complexities in structure. During middle of seventeenth century, Robert Hooks experimented with catenary system mentioned the theorem of inverting a flexible chain which stands as a rigid arch. This also resembles to the sophisticated construction of masonry arches which are very simple compression structures. Heinz Isler's thin concrete shell form finding process during 1960s from his workshop experiments is also another milestone in this area. Looking at architecture from construction or manufacturing point of view, structural elements along with the form and shape play a vital role. Load and forces follow strict rules of mathematics, mechanics and physics. These basic principles add strength and stability to the form. Many major practices of the current time are completely dependent on computers, starting from conceptualization to the creation of the form. The physical model only comes as an artifact once the final design and simulations are over. However, this should not be the way. Looking back to the history, there are many important structures built when architecture was not dependant on technology and have proved to be superior in many cases when compared to the modern day construction.
1.2 Issues in present scenario The recorded history says, starting from 17th century until the middle of the 20th century, the experiments with natural form finding and the use of physical models were an integrated part of architectural design for many engineers and architects. The process of design used to start with making of models for all major design decisions, which are to be described in details in the further chapters. The CAD/CAM technologies have overpowered the initial live experiments which were used to be carried out to start with the designing. A little analysis of past work cultures shows the advantages of such research and also its contribution. The thought of 'How to build?', rarely do contribute to the whole process of designing in the present era. Freeform geometry and shapes are being generated by software without any consideration of any natural force, material properties or construction technique. Any derived form from a software passes through simulation software and again the form is modified to support the structural system and the loop goes on until a software derived form is not generated. Unlike physical models, digital geometry never show the true behavior of what is built. But physical models do come to scenario after the final design is passed through simulation.
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In the present scenario, the work of C.A.S.T.2 is quite promising with their ongoing research on 1:1 casting of the moulds to create prototypes, which gets refined with each new experiment but the use of the natural process of form finding still need to be implemented in the real architectural world, in real construction field .
1.2.1
Gap between the current research strategies and future requirement
Current research does not lead to any real time 1:1 construction with the use of fabric form work and the addition of parameters like sewing or material properties. The exploration in terms of using fabric as form work instead of traditional method which is time consuming, difficult, expensive and need large setups may lead to cheaper construction techniques as well as saving of material without any compromise on the structural performance or quality of construction. The contribution of modern construction techniques will come later which is not a part of this ongoing study.
1.3 Objective This dissertation will focus on the advantage and contribution of model making in the process of designing. The aim is to highlight the process of form finding with response to natural forces to build an optimized structure through the aid of studio experiments and to use 3D simulation software ANSYS to test its structural performance. Furthermore, this dissertation also aims to demonstrates the efficient use of fabric formwork for double curved parametric forms which can yield improved performance benefits, aesthetics and yet economical.
1.3.1
Limitations
It also should be taken in to consideration that these experiments have carried out in a studio within very limited period of time, not in a workshop fully equipped with infrastructure for concrete casting. This adds some limitations to the level of exploration, so the experimentation of form finding has been carried out with small size mock-up models. Three different types of fabric were used for the fabrication to study its impact and response to the natural gravity. Fabric was sewed using a sewing machine before using it for the casting purpose though Geotextile3 is the ideal fabric for this. Again, because of time constraints and lack of facilities, casting plaster has been used for all the casts, which should be GFRC (Glass Fibre Reinforced Concrete) for this type of experiments and are sprayed for casting. Advantage of spraying GFRC is, it can take the exact shape of the mould and
2
The Center for Architectural Structures and Technology is an architectural research laboratory that embraces both the poetic and technical dimensions of architectural design in The University of Manitoba Faculty of Architecture. (Source: www.umanitoba.ca) 3 'Geotextile is a permeable geosynthetic comprised solely of textiles. Geotextiles are used with foundation, soil, rock, earth, or any other geotechnical engineering-related material as an integral part of human-made project, structure or system'. [4] (Koerner, 1998)
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gives optimum construction quality. Casting plaster was chosen for its ease of use and low setting time. Experiments at C.A.S.T. also confirms that any plaster mould can be transferred to 1:1 scale for real time construction [2].
1.3.2
Significance and scope of research
This research will demonstrate the process of natural form finding without any interference of computation but by following the process of model making with response to the natural forces with addition of parameters like fabric formwork, sewing etc. to create complex stable geometry in a very natural situation and economical way. This methodology being practiced 5 decades ago by great engineers and architects has again been carried out in construction laboratory by Mark West in C.A.S.T. (The Centre for Architectural Structures and Technology) in University of Manitoba, Canada, which mainly focused on fabric concrete casting. Whereas the experiments carried out here mainly focuses on the interference of gravitational force on the construction material with some parameters. Alternatively, to create a self-form geometry by methods of model making. Once the form is derived, it can be scanned by using 3D scanner to create a digitized model of the same. This digitized model might take it further for digital manufacturing process like creating moulds in CNC (Computer Numeric Control) system or directly to a 3D printer. The scope and limitations of this will be discussed in the next chapter. The development of this methodology will greatly help many sectors of construction in-terms of easy and economical ways to build.
1.4 Methodology The idea is to understand the role of model making in the initial design process and its contribution to the same through live experiments. To get accustomed with the process, the author decided to do some casting in the laboratory with due consideration of some parameters to it. The objective of this experiment was to find a self-formed vault structure as explained before by the methods of making without any help of drawing or sketch. However, before the experiment it is important to understand the methodology and material behaviors properly. Some test casts with multiple parameters can be done with reference to the literature study done on the development of the same topic. As mentioned under the limitation (Topic 1.3.1 Limitations), the casting material will be casting plaster. With the test casts the author will study the process of self form generation and the response of natural forces and materiality to the geometry or form. Specifically the structural behavior of the self formed geometry is to be studied physically from the test casts and the
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knowledge and experience gained is to be utilized in crafting the final cast in the form of doubly curved vault shell. Fabric formwork4 is the added parameter to the whole process. Rather than following the outcome or recommendation of previous researches on selection of fabric, author decided to use at least two types of fabric to compare the outcome. Lycra fabric is known for its elasticity as well as strength. In addition, the second type of fabric to be used is normal non-stretchable fabric. Therefore, the test casts to be produced will be using both stretchable and non-stretchable fabric and at times a combination of both. The second test parameter to be added is 'sewing' by joining two pieces of fabric. A geometry might be created with the use of this procedure but only test casts will be able to demonstrate it. However, for this case, the visualization of the geometry for creation is also important. Sewing acts like diverting the flow of a stream of water by putting some obstacles on its path. It can add some tension lines to the stretchable Lycra fabric and might create some interesting geometrical patterns. The ultimate aim of the experiment is to generate a self-form geometry with response to natural forces like gravity by the use of fabric formwork. The contribution of natural forces to the final form is to be studied. To analyze the structural performance of the form created, ANSYS simulation has been carried out to give quantitative scientific evidences. A similar geometry of the final cast is created digitally with 3D modeling tool and the structural simulations are analyzed before drafting the conclusion. The simulation results of the model explain the structural stability of the structure. This research is fuelled by the knowledge gained from the investigations and case studies done on the development of the similar research. As form finding and model making procedure is an age-old practice, its development along the time line guides the whole process of experiment. The development and methodology of different eras are studied and compared before doing any test cast. The most important outcome from the case studies is the understanding of how the practices adopted during a particular period has influenced the architecture. And question around every experiment will be, has making any impact on the designing? Does the model making improves the final piece of architecture?
4
Fabric form work uses a flexible textile membrane in place of the rigid formwork panels usually used in concrete construction. (West, 2010)
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1.5 Structure/Flow Chart of Dissertation The entire research is divided into five chapters. First chapter explains the main research question along with the scope of work, its limitations and the research methodology. The second chapter emphasizes on the historical timeline of form finding process in architecture and the currently used processes around the world. This chapter also describes detailed/critical analysis of case studies, which explains the influence of physical model making on design through examples. The knowledge gained from the second chapter are to contribute for the experiments to be done in the next step, which are described in the third chapter. In the solution chapter, the methodology of live experiment and its findings are described. In the fourth chapter, the digital version of the self form geometry has been simulated to showcase it's structural performance. The simulation results are analyzed and discussed if the model making methodology has influenced the performance in any case. The final chapter shows the findings from the experiment to support the main research question and discusses the scope of further research on the related topic. The separated chapters share an integrated bonding to carry out the experiment. The flowchart in the next page demonstrates the bonding of chapters in this current study.
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BIBLOGRAPHY [1] Leach, Neil, Turnbull David and Williams Chris, Digital Tectonics, Great Britain : Wiley-Academy, 2004. [2] West, Mark, The Arrival Of Form, C.A.S.T. (Centre for Architectural Structures and Technology), Unknown Year. [3] West, Mark, Fabric Formwork For Reinforced Concrete Structure and Architecture, C.A.S.T. (Centre for Architectural Structures and Technology), Jan 2010. [4] Koerner , Robert M., Designing with Geosynthetics, New Jersey : Prentice Hall, 1998
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2. Literature Review The concept of using physical models in design development is archaic. Antonio Gaudi is believed to be the father of 'making5', with his unique form-finding model using catenary system [1]. The other few notable names include Heinz Isler and Frei Otto. Heinz Isler in particular is known for building a multitude of thin concrete shells around the world based on physical model. In his own words, 'I would not have been 10% successful if I have not used physical model making for developing these shell structures' [2]. Kenzo Unno is another name who used natural form finding process for concrete walls with the use of fabric. Currently 'The Center for Architectural Structure and Technology', popularly known as C.A.S.T. at University of Manitoba, Canada has taken this research further.
2.1 Case Study The process of form finding started much earlier, and the recorded time line starts from Robert Hooke in the 17th century. In 1675, Robert Hook started the theory of inverted catenary. According to him, "As hangs the flexible chain, so but inverted will stand the rigid arch" [3] (Hayman 1999, p. 9). Hook's theorem shows a high degree of sophistication. Many architects and engineers followed the path of 'making' and created masterpieces around the world, but the process practically started by Antonio Gaudi from his catenary model for the church of Sagrada Familia in Barcelona, Spain. In mid-twentieth century, a great Swiss engineer Heinz Isler, built several hundreds of thin concrete shell structures and followed the methods of natural form finding with his innovative experiments on model making. C.A.S.T. (The Center for Architectural Structure and Technology) in Manitoba University, Canada uses 'making' for the experiments carried out in their laboratory are the blend of technology and yearlong practice of model making. The above covers three different eras of model making and form finding contributing greatly to the methodology adapted in this particular dissertation.
2.1.1
Antonio Gaudi's Catenary System
Based on Robert Hook's catenary theorem, Antonio Gaudi created his unique model of form finding for Sagrada Fimilia in Barcelona. He used hanging chain system with addition of point loads in the form of lead shots. This 1:10 model derived the complete form and structural system of the church. This unfinished 'Residence of God' started in the year 1882. During this unique experiment with catenary system, Gaudi used to capture the development through photographs and later inverted them for the creation of his master piece. This extra ordinary system of designing made him the father of 'making'. 5
Making means model making or physical model making.
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His technique based on very simple catenary system creates very complex yet stable structural system, Strings hung from a rigid support and weighted in response to gravity. The architecture created by him in that era was all seemed to be the work of an analog computer. The parameters for the catenary model of sagrada familia are the anchor point of the hung chain system, the length of the string and tension point where the weight was attached in the form of lead shots. Experimentation of these parameters with the physical model making created such complex geometry and form which is both structurally stable and aesthetically pleasing. This pure tension structure became a pure compression structure when inverted. In this way, this is a great example of structural form finding.
Figure 2-1 Left, the inverted form finding model of 'Sagrada Familia' and Right, Gaudi's sketch over the photograph from the model (Source: Architectural Science Review, December 2006)
Gaudi not only created the form and structure of the Church by model making, he also designed and rendered the interior views of the chapel by drawing directly on the photographic plates over the photographs taken from the model [4]. Figure 2-1 shows Gaudi's original model for Sagrada Familia and his sketch over a photograph from the same model as the final design of the church. The mathematics related to parabolic arch is not so simple and Gaudi used this as an optimum shape for construction. The shape was the outcome of the ratio of the span and height of the arch and was used by him in many of his projects. The large-scale physical model contributed in taking direct measurement in many cases for the construction and the unsolved part gets transferred to graphics for its solution. The experiment and exploration of form finding can be carried out with these kind of models until a pleasant efficient structure is not derived.
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Figure 2-2 Left, Original catenary model of Sagrada Familia shows Gaudi's idea of finding form from forces and Right, the structural models of same for actual construction (Source: Sweeney, p 86-87)
The figure 2-2 above shows the scale of Gaudi's original catenary model along with structural models made for the better understanding of the structural system of the church, which was destroyed during the Nazi civil war. The scale of the physical model can be compared with the human figure in the bottom right corner of the image. Gaudi suspended proportionate weight to the estimated load and it's precise position gave the approximate shape of the vaulting and the direction and also the forms of the column [1]. Hence, Physical models can resolve most of the complicated constraints of construction. This also emphasizes the importance of making large scale physical models during the design development to get the level of accuracy in construction access. However, the author concludes that in this form finding method, the applied weight in form of lead shots acts as a parameter to the whole process with its response to the gravitational force and tension force from strings. However, it creates tension structures, which are very stable for construction, but the strategic positioning of the weight has more influence in the form finding. Nevertheless, this method is useful in creating unlimited number of different shapes, which are purely compression structures when inverted. Gaudi's experiment also points out another feature; for getting the proper level of detailing the size of the model should be proportionate.
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2.1.2
Heinz Isler's Shell Structures
Heinz Isler, the renowned Swiss Engineer known as a structural artist gave a new dimension to the involvement of model making in the design state. Starting from 1950s he was a master of thin concrete shell structures with experimentations on physical model for organic shapes. He used to find the correct form by physical models responding to natural forces and then to test their performance structurally, rather than using any modeling software.
Figure 2-3 Isler's art of form finding with different methods (Photo: Heinz Isler)
His design philosophy was guided by simplicity, purity of concept and physical experiments. In his words, 'one should strive to reduce the number of building components' [5]. With decades of experiment he envisaged his own way to develop the shape of shells naturally, mostly with the use of fabric and self-setting polyester resin, and at times by freezing water over fabric. His specific knowledge on materiality of concrete and construction technique made him unique as an engineer. His experiments were focused on form finding and proving its strength. Most of his researches are influenced by close observation of nature and double curvature organic shapes. Concrete is very strong in compression and weak in tension, so the shells needed to be of perfect form and efficient. In a thin shell of 30-meter span, the stress may vary from 1.5-3.0 N/mm² [5]. His experience and structural knowledge was an advantage. After the form finding process and casting of the physical model, it was being tested in electronic strain gauge to prove its strength. The physical models were measured accurately by a special device, which was a wooden box with calibrated metal bars fixed on opposite sides. A Very careful and error free measurement is important every time to avoid the buckling failure of the shell. In this dissertation, the author will be using ANSYS structural analysis software to prove the optimization of the experiment. With the use of 3D scanner, the exact form can also be easily and accurately converted to digital model for simulation purpose.
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Figure 2-4 From model to reality, Isler's development model and the constructed free form structures (Photo: Heinz Isler)
The image on the left of the figure 2-4 above shows a test cast made by Isler after the form is found naturally and rest two image shows two examples among hundreds of famous shell structures. For Isler, 3 dimensional models have some sort of physical properties as some material is used for it. The material has its own physical properties, strength, thickness and elasticity. And when you see a model, you see it with all your senses and from all sides. Comparing Isler's work with the new concept of designing one can notice that the digital modeling tools of present time can create free and complex sculptural shapes. These are challenging to build and structurally are not efficient, so need lots of complex construction techniques. Unlike Isler's pure shells, here much of the load transfer is accomplished through bending instead of membrane stresses. [6] However Isler's form finding process seems to be monotonous and produces almost similar kind of structure with repetition. With the use of different kind of fabric and addition of some other parameters to his method of form finding, more interesting shapes can be created. But Isler's experiments proved that the structural stability can only be achieved with optimized shapes. The structural clarity and stability in his shell structures are quite prominent.
2.1.3
Research at C.A.S.T.
CAST stands for The Center for Architectural Structure and Technology which is an architectural research laboratory in University of Manitoba, Canada. Their work is quite innovative and inspiring when it comes to fabric form work and even the process of natural form finding. Presently the ongoing research on fabric formwork, concrete casting and form finding process at the C.A.S.T. are quite versatile and could create new milestones in the field. With the initiative of Mark West, this is the first research laboratory in the world dedicated to fabric formwork and fabric formed concrete structures with the collaboration of architects, engineers and industry. In this research, C.A.S.T.'s work will contribute in knowing the advancement of technology and material,
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which are contributing to the methods of making. The prototypes casted at C.A.S.T. show the potential of form finding and demonstrate how it can be done in a very logical and economical way, which follows the principles of nature again as discussed earlier as part of the literature study.
Figure 2-5 A funicular fabric form generated by C.A.S.T. (Source: The Centre for Architectural Structure and Technology, Manitoba University, Canada)
Fabric might be a very potential material for the process of natural form finding and also can contribute to the making method for its properties and also for being economical. With the experiments and suggestions a special kind of fabric having trade name 'GeoTextiles' has been developed which is very economic when compared to the traditional form work. And it has the physical property to withstand a greater amount of load and pressure, making the making of 1:1 prototypes more affordable. The forms created in C.A.S.T. are neither developed in the computer first nor detailed drawings are being prepared while making the prototypes.
Figure 2-6 Another thin shell vault developed by C.A.S.T. directly from a single hanging flat sheet of fabric (Source: The Centre for Architectural Structure and Technology, Manitoba University, Canada)
However ongoing research at C.A.S.T. is not purely natural form finding. But at the same time this also echoes that, making has a big chunk of contribution in creation. The fabric used in all of the castings by CAST is not tailored, means they are not given any curvature but are self formed from geo-textiles. It generates curiosity for the author to apply few parameters like use of fabric with different physical properties and texture and also sew them for a particular pattern and then studying their properties and determine how it affects or contributes to making.
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2.2 Making and Designing Heinz Isler once said, 'You touch it, you feel it, you see it from all sides. And sometimes you hear it, before the model breaks' [2]. Physical models have an edge over digital models in the sense that they are built using real materials and in a real-life scenario, one can foresee any potential problem that may affect the final structure. This will be very helpful, starting from the conceptual stage to the analysis of structures. As it gets built in the three dimensional space it shows real time issues similar to construction site which is convenient to understand and can be resolved in design stage itself. It is difficult to understand complex elements of the designs through drawing and sketches, where physical model gives real experience of the size, scale and complexities of the elements, which is barely achievable on the screen.
2.2.1
Physical form finding process
Architecture is a combination of form and geometry and finding the form is an integrated part of design process which influences the performance of the product in aesthetic, structure or environmental aspects. Hence form finding is important in the process of making of architecture. The form finding can be done in a variety of ways, by making model, by sketching and also with CAD/CAM technologies. As physical form finding process and its contribution to improve the architectural performance is the focus of this dissertation, so the upcoming chapters will elaborate the concept in detail. Specially the role of physical model in making of architecture. The case studies in the previous topic puts some bright light on the topic.
2.2.2
Mock-up model for testing
The contribution of mock up models in the design development is significant to improve the design and performance. Once the design is finalized, the performance of architecture is suppose to be examined, specially for some special design components. Mock ups give real time impression of the design during the design process and develops the design also. A chosen part of the whole design scaled down as per the performance or aesthetic requirement for testing. The scale of the model depends on the testing regimes of the designer. Firstly mock ups show the actual aesthetic sense of the design. It also contributes to the real time construction methodology and contributes to understand the structural performance of the product. Secondly, the physical performance simulations can be carried out before the execution of the final design. Mock up models are generally used or prototypes to study it's behavior and to compare with its design regimes. The 15 | P a g e
outcome and observations of the whole process just refines the design in producing a superior piece of architecture. So, this is another typology of making. Architects like Renzo Piano uses prototyping and testing as an integrated part of their design development. Scaled physical models and relevant testing can lead the process of design to an meaningful outcome.
2.2.3
Assembly possibilities
At the time of rapid prototyping of building or construction elements, the scale factor still remains in consideration. The available manufacturing technologies in the present time are not able to produce building elements in 1:1 scale. There are also some other limitations. One of the critical procedures before fabrication is to break down the final structure to components and building by assembling these components. For instance, a glass facade of a building can be broken into smaller parts as per the optimum available size of material, in this case, the glass used. In every case the assembly procedures and assembly description plays a major role in manufacturing. Thinking about the assembly possibilities in the design stage and incorporating the same in making physical model can give some proper demonstration of the final design output. The assembly should be as simple as possible and should try to avoid complex connections or joinery procedures. 'Making' does not mean model making every time; it can be a process of assembly. A component only can be assembled with very simple connectors to solve the purpose. It can be constructed with various construction methods available. It also can be fabricated using CNC machines and many other techniques available. Manufacturing constraints in making 1:1 scale product results in breaking the whole component into suitable pieces and then assembling it. This makes the whole process easier. One among the test casts as described under topic 3.3.1.2 'Y' shape component, the author tried to make an component based casting which creates an interesting geometric pattern if assembled. Figure 3-3 in the same topic shows the component and it's assembly possibilities.
2.2.4
Validating assembly possibilities (Construction)
Construction is the final stage of making. The elements prototyped in manufacturing methods need to be assembled or constructed to give the final outcome of the design. Again, in the present era, the techniques of construction are equipped with modern machineries. 3D printing, CNC machining and also the use of robotics in the field of construction are going ahead with time.
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CNC milling uses the subtractive construction method, which is economical and also most popular in the current time among digital manufacturing processes. This technique can be used to mill the styrofoam moulds of the required geometry and later used for 1:1 scale casting which can be assembled on site.
Figure 2-7 CNC milled styrofoam moulds for construction of Zollhof Towers (Source: Afify & Elghaffar, 2007)
The construction of 'Zollhof Towers' in Dusseldorf, Germany by architect Frank Gehry is a great example of the same. Total 350 individual concrete facade elements were casted by using CNC milled styrofoam moulds and assembled only on site for construction.
2.2.5
Rapid prototyping of the final product
Computer aided design (CAD) is a standard practise these days, so the development of flexible production of technologies. Computer aided manufacturing (CAM) techniques provide architects an expressive means to manufacture their imagination which is also fuelled by 'file to factory' process. Additive manufacturing technologies like three dimensional printing, layered manufacturing etc. offer an advantage of making scaled prototypes or physical models of any form or shape before it's actual construction for the purpose of testing. These are generally used to represent the final design during the design stage. Still, this is also making.
2.3 Physical form finding process Form finding is often not understood by engineers who are acquainted mainly with the stress and deformation analysis of conventional, rigid forms. Form finding is the optimisation processes, where certain geometric parameters are altered in a deliberate and systematic way, in order to produce a more efficient structure. [2] Form finding of fabric structures is an interactive process which involves both scale model experiments as well as computational analysis for performance calculation.
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Surface geometry of tensioned fabric leads to the self form geometry which mainly responses to the gravitational force of Earth. And such developments can only come from a deep understanding of the optimum structural form of tension structures and an appreciation of the limitations of modelling techniques. Heinz Isler was among the first to elevate experimental form-finding to a scientific level in the mid twentieth century. [6]
2.3.1
Natural form and Geometry
Mother nature is smart. Looking to the natural elements, we understand nature believes in minimalism. Optimised shape and structures seen here are rather complex and beautiful with a pattern which are mostly not identical. Natural shapes created does not follow any function but follows the flow of force. Nature is beautiful and vibrant. We can see and find infinite variety of shapes in it. Natural forms appear simple but are highly complex. Cristian Dumitrescu from Department of Architecture, Politehnica University of Timisoara introduced a term 'Ecotecture' - a term that resulted from the symbiosis between ecology and architecture, meant to find out new architectural forms and structural morphologies based on those offered by nature. The infinity variety of forms offered by nature for different functions and their analysis can represent a permanent source of inspiration for architectural creations. Smart nature not only shows infinite variety of forms but also expresses the laws of their existence [7]. Geometry contributes in developing an architectural form and then to represent architecture. In the first case we can say it describes the design from concepts and in the later case, it plays the fundamental role to transfer the ideas in to paper in terms of drawings. In other words we can say, geometry is the communication between design process and construction methodology [8]. In the age of parametric designs, understanding of architectural geometry is very important. It contributes a lot to the construction aware design procedure.
2.3.2
Physical model vs Digital model
Currently, Computer Aided Design (CAD program) is very popular in built environment to make digital modeling. Earlier, many designers, architects and engineers did a fabulous job with consideration of physical models and the natural forces to find the form even for structural stability. There is a basic difference between physical model and digital model. In digital process shapes/design elements get created in a vacuum without any physical properties or responding to
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any natural forces like gravity or natural material properties. However, in case of physical models above mentioned factors automatically get considered. According to Heinz Isler, 'The model not only gives a visual aspect but also shows the general statistical behavior. Weak points become obvious. Stiffness can be felt. And most importantly models offer solutions. Often you also realize when finishing actual model, how the next one, a better one will look like' [9]. Why to make hands dirty when 3D models of builds can be created easily with the help of computers! This might have captured the thought of many architects with the start of digital age, so the deformation. Still, the role of the architectural physical models will never diminish.
2.3.3
Role of Fabric in Natural Form finding
The concept of using fabric in construction is not age old. During the mid-twentieth century silk fabric was basically used in the underwater construction as it is erosion resistant and also used as formwork for foundations. Heinz Isler used fabric for finding optimized natural forms for shell structures. He used self-setting polyester resin for membrane models The ongoing research in Manitoba University by C.A.S.T. related to fabric form work has opened up many possibilities, especially for designers and also for construction industry. For example, specially developed geotextiles which costs less than 1 USD per square meter [10] may become the optimum material for form works in future. Use of fabric as formwork has got many advantages over the traditional formwork with scaffolding systems. This is quite economical and does not need complex techniques. According to Mark West, fabric form work may cost 1/10th of the conventional form work. It is also easier to create complex parametric forms easily. The fabric formed concrete is also of superior quality in compared to other casting system as the fabric allows the excess water out of the concrete because of its porosity resulting in a compact casting and superior cement rich surface finish. The advantage of fabric is that it deforms with the load responding to the gravitational force. This creates optimum structural form clearly showing the tension and compression forces. This also contributes to the material consumption, again reducing the construction cost.
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Figure 2-8 Fabric-cast beam by C.A.S.T. showing natural structural 'force path' (Source: www.umanitoba.ca/cast_building)
For example, the above shown concrete beam by fabric formwork by C.A.S.T. shows an optimized form in comparison with traditional rectangular or square cross section beams. This is economical by minimizing both the casting material and shuttering work and at the same time aesthetically pleasing. These types of forms only can be explored by the method of making with fabric parameters or it can be said, 'free form of fabric formwork can fit any architectural whim'.
2.4 Conclusion After doing all this research, reading and analyzing the methods of making and form finding adopted by many architects and engineers around the world, starting from the early twentieth century to the present time, the author concludes that: Structural free form geometry can be achieved naturally but it is important to understand the flow of forces in a physical model to understand its structural behavior. Natural form finding does not require any detailed engineering analysis or mathematical calculation. Alternation of geometry and some other external parameters in a deliberate way can generate aesthetically pleasing and structurally efficient structures. Following the flow of forces to find a self form geometry may end-up in creating monotonous structures, so some experiment should be carried out in exploring the possibilities of adding external parameters to create interesting geometry. But they should be implemented sensibly. Fabric can be used as an inexpensive and light weight form work material to create self form geometry. Permeability of fabric results in a quality cast with the removal of excess water and air bubbles from the concrete. The texture of fabric creates interesting unusual surface patterns of concrete adding a high aesthetic value to the cast.
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BIBLIOGRAPHY [1] Sweeney James Johnson and Sert Josep Lluis, Antoni Gaudi. UK and Commonwealth : The Architectural Press London, 1960. [2] Lewis W. J., Chilton J. C., Choo, B. S., and Popovic O., Structural Morphology towards the New Millennium. Nottingham: School of Architecture, University of Nottingham, 1997 [3] Heyman Jacques, El esqueleto de pierdra: mecanica de la arquitecture de fabrica. Madrid: Instituto Juan de Herrera, 1999. [4] Huerta Santiago, Structural Design in the Work of Gaudi. Architectural Science Review, Volume 49.4, pp 324-339, University of Sydney, 2006. [5] Chilton John, Heinz Isler (Engineer's contribution to Architecture). London : Thomas Telford Publishing, 2000. [6] Thomas Katie Lloyd, Material matters (Architecture and Material Practice). New York : Routledge, Taylor & Francis Group, 2007. [7] Dumitrescu Cristian, Natural Forms - Alternative forms in Architecture. International Colloquium, Nottingham, 1997 (p. 196-200) [8] Leopold Cornelie and Matievits Andreas, Studies of Geometry Integrated in Architectural Projects. Journal for Geometry and Graphics, Volume 5, 2001 (p. 181-182) [9] Isler Heinz, Is the Physical Model Dead? International Colloquium, Nottingham, 1997 (p. 270-271) [10] West Mark, Fabric-Formed Concrete Structures, C.A.S.T. (Centre for Architectural Structures and Technology), Unknown Year. [11] West Mark, Fabric Formwork For Reinforced Concrete Structure and Architecture, C.A.S.T. (Centre for Architectural Structures and Technology), Jan 2010. [12] West Mark, The Arrival Of Form, C.A.S.T. (Centre for Architectural Structures and Technology), Unknown Year. [13] West Mark, Thin-Shell Concrete From Fabric Molds, C.A.S.T. (Centre for Architectural Structures and Technology), University of Manitoba Faculty of Architecture, 2009.
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3. Solution 3.1 Introduction This chapter discusses the research and the methodologies carried out to understand the contribution of 'Making' to the design development, it shows how optimum forms can be defined by this age old method of model making. It also explores the option of fabric form work with some added parameter with live demonstrations. Selected casts, among all of the test casts done to understand the procedure are explained here and analyzed. A building is formed of many components and can be measured on different performance factors like aesthetical, environmental, economic or even structural. To narrow down the research because of time constraints, this dissertation focuses on architectural structural performance of the natural derived geometry that is an economical and convenient way of construction.
3.1.1
Adopted Methodology
The research started by gaining knowledge on how model making has been influenced or developed after the unique experiment of Gaudi and at the same time how it has evolved over past ten decades. Reading about pottery from a book and making a pot on a potter's wheel with wet clay can't be compared! So, let's spin the potter's wheel and make the hands dirty! As a first step or should we say learning steps, few test casts were casted. In the process attempt was made to add some parameters like playing with geometry and understanding the evolution of self form structures. The outcome of these casting experiments leads to the final form finding of a double curved vault shell with the use of fabric form work and it's support structure, a 'Y' shaped fabric form work casted column. The architectural performance of the casted elements only can be experienced. Due to time constraints proper scientific tests were not carried out to give performance results as values. But 'numbers' are essential to prove structural performance, so the further structural analysis by software simulation. In the next step, the Geometry generated by the methods of making is measured in terms of dimensions and deflections in both the directions. A digital model has been created with the use of Rhinoceros 3D modelling software. This creates the base geometry for simulation analysis for structure. For the comparison purpose, there should be a set of similar structure with some geometrical variation. Keeping an eye on the time constraint, the author decided to prepare three digital options to compare them. Both the curvatures created across the span and across the width 22 | P a g e
were manipulated and three different geometry were created to experience the structural behaviour. If the curvature changes, the geometry goes through a vast change over and how it responses structurally and contributes to architecture are discussed in the next chapter (4. Analysis of Structure with ANSYS).
3.2 Casting The methodology adopted here is to create or cast some natural geometrical forms with the use of casting plaster, a variety of fabric and sewing. The method of sewing and different fabrics acts as an added parameter to the whole form finding process. Understanding the material properties and material behaviour is quite important to get something built in real three-dimensional world, unlike in the virtual world of computers. A very simple example to explain why the method of making is critical and informative, if a slab is created with the use of software and supported by four columns at four corners and two of any consecutive columns are removed, the slab will remain at same position until the simulation process is run in any advanced software. In addition, material properties need to be applied properly to get accurate simulated results. However, if it is built in real, one must have to think about which material to use, how to make form works and even how to cast it. The process is very similar to the real construction techniques which always put some sort of challenges before being executed. Similarly, with the removal of columns or any support, it crashes instantly. It does not mean that author is purely against the simulations but do they really contribute to the design in the initial stage to find a self-forming form? Does it show the real time challenges that might come during the construction of any complicated form? The answer to these questions is being given in this chapter by demonstrations. The understanding of compression and tension is quite important in carrying out this kind of live experiments. Kenneth Frampton says, ' There is an expressional transparency between structure and forces within the structure'. Understanding the principle comes from knowledge and experience. As discussed in the first chapter, the ongoing research will try to contribute to the structural performance by creating a shelter with naturally occurred funicular geometries. Concrete casting is a labour intensive production process and need some proper infrastructure and facilities. With limited resources and time, the initial experiments for this research started with some small-scale casts.
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3.2.1
Test Casts
3.2.1.1 Shell structure Replica Illustrating one of Heinz Isler's thin shell concrete form finding process, here a different procedure has been adopted to find a natural form. 'Lycra fabric', known for its flexibility and strength has been used for this cast. Lycra in two layers has been sewn here with the pattern shown in figure 3-1 and filled with casting plaster. Then this is hung from a flat surface from four corners. It is noticed that the portion of the fabric filled with casting plaster has a different natural deformation responding to the edges of sewing.
Figure 3-1 Details of shell structure casting (Source: Author)
The fabric here is highly flexible but the thread used for sewing is rigid, so the sewing lines became rigid and created a non-stretchable edge on the stretchable fabric. As the square piece of fabric has four tension points at four corners, the gravitational force creates the deformation to the plaster filled part. This resulted in a naturally formed shell structure as shown in the figure 3-2 below.
Figure 3-2 Casted replica of thin shell with double layer fabric (Source: Author)
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Finally, this casting creates a pleasant looking structure and it seems to be structurally stable. However, as the four legs of the pattern create a narrow passage and the central area is opened up, the plaster has been deposited in that part, making it the thickest. This might not be structurally stable for large scale and also the consumption of material will be more when compared with Isler's thin shells, where as shells are considered as to be material-efficient structural systems.
3.2.1.2 Y Shape Component The Lycra fabric used in the previous cast has a very fine texture and is very flexible. Another type of Lycra fabric with lesser elasticity and rough texture replaced the previous one. Hexagons are considered as most stable geometrical patterns, so little bit of brainstorming created a 'Y' shaped pattern as shown in the Figure 3-3. Assembling two of the shapes created an interesting interlock able pattern as illustrated in Figure 3-4 in the next page. Figure 3-3 also shows the sewing pattern on fabric before the casting. Here, the rectangular fabric was supported at four edges and the fabric got the natural deflection by gravity. Three parameters contributed to this shape, the edge support, the Lycra fabric and the sewn pattern.
Figure 3-3 Casting procedure of Y shaped component (Source: Author)
Figure 3-4 in the subsequent page shows the final cast and the virtual assembly of it to create the final pattern. The pattern created on the surface seems to be quite interesting. These kind of casting can demonstrate the assembly possibilities in various ways which we discussed earlier in the literature review.
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Figure 3-4 Casted 'Y' shaped component and illustrations showing the assembly possibilities in creating a pattern (Source: Author)
3.2.1.3 Twisted Column Human bone is a fine example of structural stability and nature's minimalism. To replicate the Tibia and Fibula of human legs, the pattern shown in the Figure (3-5 a) was sewn and poured with plaster. The mould is then twisted by 90 degrees during the setting process of casting plaster as shown in the figure 3-5 b. The outcome was quite interesting when the fabric was removed. It creates two twisted columns joined at top and bottom with a void at the centre. This seems to be quite stable structurally and also reduces the material cost, which can be used as a column. Except structural stability the form also gives advantage to aesthetics with its sculpture like appearance. Figure 3-6 shows the final cast.
Figure 3-5 a. The structure of human leg bone (Source: http://www.daviddarling.info/encyclopedia) b. Casting procedure of twisted column (Source: Author)
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Figure 3-6 Final cast output of the twisted column experiment (Source: Author)
3.2.1.4 Bubble Shell When a piece of rectangular fabric is hung with support at two edges, then it forms a barrel vault like structure, which is very stable structurally when inverted. Two sheets of rectangular fabric were sewed at longer sides and other two sides were left open. Circular wooden plates were bolted from both the sides, sandwiching the two layers of fabric. This creates an irregular pattern on the fabric with connected branches. The mould was hung from the shorter side and plaster was poured from both the ends. The liquid plaster spread throughout the fabric and created a tensional vault like structure. Once dried, the wooden circular limiters and fabric were removed. Figure 3-8 in the next page shows the final cast in this method which has been inverted creating a stable compression structure.
Figure 3-7 Casting procedure of Bubble Shell structure (Source: Author)
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Figure 3-8 Finished outcome of bubble shell cast (Source: Author)
3.2.1.5 Conclusion From the above-described test casts and few other casts done as a part of this research, following conclusions can be drawn: Casting with double layer fabric may not be economical and structurally stable for large structures and for large-scale projects. The column casting can be done with similar methodology to create interesting structural forms. The casting might be in-situ or precast with very easy and economical form work. Rigid and strong fabric should be used rather than Lycra fabric. The geotextile used for all the castings at C.A.S.T. seems to be better option as it is rigid and economical. Small scale casting experiment does not contribute much and may show some errors. The deflection of fabric was very nominal for small scale casts even after the material load. The fabric formwork contributes to the quality of concrete. Figure 3-9 in the next page shows how the excess water is filtered out easily even in a very small scale casting. Only surplus water is soaked out, not the mixing material. C.A.S.T.'s experiments also claim this as described in the previous chapter resulting in an improved quality of concrete as well as smooth cementious surface.
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Figure 3-9 Automatic filtration of excess water from the cast through fabric (Source: Author)
The texture imprinted from the fabric in all the moulds gives the option to use it for aesthetic purpose rather than using expensive and laborious construction methods. Interesting patterns can also be created as shown in Figure 3-10 below. These casts shown in the figure are among few other test casts.
Figure 3-10 Test casts showing patterns created with Lycra fabric and sewing (Source: Author)
Sewing can effectively be used as an added parameter to the whole form finding process to significantly alter the geometry. Figure 3-11 in the next page, shows some patterns sewed in a variety of fabric for experimental casts in this research.
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Figure 3-11 Different patterns of sewing on a variety of fabric for experimental casts (Source: Author)
These conclusions are not based on any scientific logic but are derived by pure observation, which were drawn from the process of model making in this particular experiment. The knowledge gained in the above exercise leads to the final form finding and casting for this research.
3.2.2
Cast I (Double Curve Shell)
To cast a funicular6 vault shell, a rectangular fabric was laid flat with support only at four corners measuring 750x1500 millimetres. Without any support on the edges, the fabric deflected and created a funicular double curvature surface. This is a natural form, formed with stress constraints of fabric used. If inverted, it is a compression shell structure. As a next step, six tension points (three on each side) were added to the shorter edge. This resulted in creating three tension ridges by dividing the rectangular fabric into four parts and also the depth of deflection for each individual section reduced significantly as compared to the original form. Figure 3-12 shows the final formwork for the same before casting. The deflection of each double curvature surface was quite less. This whole process created the natural formwork to be used for further casting with anticipation that the fabric will gain more deflection naturally once the plaster/casting material is applied over it uniformly.
Figure 3-12 Fabric form work for double curve shell before material application (Cast I) (Source: Author)
6
Having the form of or associated with a cord usually under tension is called Funicular (Source: Merriam Webster Dictionary).
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Figure 3-13 Self formed fabric form work for double curve shell structure (Cast I) (Source: Author)
Figure 3-13 above shows the deflection of the fabric after the application of one layer plaster, which is very negligible. Only with the first layer of material application, the overall form looked to be unstable because of the deflection curve on the shorter span. Very gentle push from the bottom part resulted in cracks on the surface. Even the structure seemed to be fragile with very little shake. Secondly, it was not aesthetically pleasant. These observations led to create another developed formwork.
3.2.3
Cast II (Double Curve Vault Shell)
In the next step, another mould was created by increasing the size of the spread fabric. With the same frame size as used in the previous cast, the fabric formwork showed more deflection as compared to the previous one. However, this time, four tension points (two on each side) were added to the shorter edge instead of six in total. This resulted in creating two tension ridges by dividing the whole rectangular fabric into almost equal three parts with significant deflection in both the directions. The central ridge also got deflection at centre, as there were tension points only on the edge and no support throughout. Figure 3-14 shows the final formwork. A significant variation of deflection can be noticed here as compared to the previous fabric formwork.
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Figure 3-14 Self formed fabric form work for double curve shell structure (Cast II) (Source: Author)
The preliminary shape of fabric changed its shape when the first layer of plaster is applied. The weight of casting material led the fabric to gain deflection and rigidity resulting in final freeform geometry. Here casting plaster was uniformly applied throughout by hand. Image (Figure 3-14) shows underneath the fabric formwork, after the fabric has taken the load of the casting plaster. The deflection was significant unlike the previous cast. It suggests that the geometry deflected naturally, which seems to be the optimum one. Later, reinforcement in form of steel wire mesh was added for the rigidity of the structure and another thick layer of plaster was applied. The final geometry created, as shown in the figure 3-15 in subsequent page, was removed from the rigid formwork and inverted. Once inverted, the vault became a rigid compression structure with very prominent patterns of fabric which also shows the flow of force along the structure. The textured fabric used for the form work also crafted a pleasant texture all over the surface.
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Figure 3-15 Double curve vault shell concluding cast (Source: Author)
This is a funicular vault, which can be used as a roof element or for shelters, which is both structurally stable and aesthetically pleasing. The built structure claims its structural stability only by observation. However, the structural stability is being tested in the next step with software simulation to get results.
3.2.4
Cast III (Support Column)
The second experimental casting has been done to create a column by fabric formwork and sewing. The first test cast for the 'Y' shape column was only 15 centimetres high and did not show any sign of the natural form finding. In the previous chapter (Chapter 2, 2.1.1) as we learnt, Gaudi's 1:10 scale catenary model of sagrada familia church proved the importance of scale while making design development models. Smaller scales do not represent the true form of geometry as well as complicacies of real construction methods as well as the flow of forces. This time, the fabric formwork for the support structure was 45 centimetres high and has a diameter of 7 centimetres. The base of the fabric mould was supported firmly and tension was applied to both the wings. Before pouring the plaster from top, the base was rotated by 90 degrees, similar to the test cast of the bone structure (Refer to Figure 3-6). While pouring liquid plaster through the fabric, the natural deflection of the formwork was experienced. The weight of the poured material resulted in more deflection at the column base, similarly to a tree trunk. Later the fabric formwork was removed from the dried cast, and the author noticed that the base of the column is firm and the column can stand by its own. This is naturally formed by the pressure of 33 | P a g e
the material and shows structural stability. The 90-degree twist applied to the formwork of the column was also prominent and it adds some aesthetic value to the casted element. It was also noticed that the formwork left a firm imprint of the texture of fabric, which enhances the aesthetics of the casted column. Figure 3-16 below shows the final cast as a freestanding support column.
Figure 3-16 'Y' shaped support column final cast (Source: Author)
The boxed images in the figure above shows the level of detailing achieved by fabric form work and by twisting. And also the stability of the self form geometry as the column is self standing.
3.2.5
Combined Structure
The vault shell as casted in the previous topic (3.2.3 Cast II - Double Shell Vault Structure) and the support column (Chapter 3, 3.2.4 Cast III - Support Column) can be combined in creating a shelter as shown in the Figure 3-17 in the next page. An illustration at the bottom left corner of the same image shows a combination of multiple structures which creates an interesting pattern of roof structure. Figure 3-18 shows a computer generated model of the same. The structure seems quite stable from the appearance and also from the physical properties according to the observations.
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Figure 3-17 The final vault shell structure (Source: Author)
Here comes the next procedure to test its structural performance digitally with software simulations. The aim was to create a similar digital model and then investigating its structural performance to get the most structurally stable object as well as a lightweight structure by keeping eye on optimum thickness of the slab to save a considerable amount of materials. The ANSYS simulation will add the quantified data to the performance of the architectural structural element.
Figure 3-18 Computer generated model of the combined structure (Source: Author)
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3.3 Conclusion Author's experimentation with physical models pointed out many advantages which are quite important for the designing stage as well as for a well conceived architecture; While working on a physical model, the designer can play with form in real time. The geometry can be manipulated instantly and the difference can be compared immediately. This results in quicker decision making for the form finding process. In this particular experiment, the structural behaviour of element was studied easily while making the casts. Geometry is observed better while working and playing with physical models. This interactive mode of working by model making leads to invention rather than analyzing a particular shape or form. Large scale mock-ups brought the complex construction methodologies in front, involved in conversion of small scale to full scale. The sense of aesthetics can be realised from large scale models. Small scale casts did not represent the proper design so the design ideas. The physical behaviour of the structure noticed properly with large scale mock-up. The flow of natural forces can be experienced physically. In this particular case in creating the vault, the fabric form work always found a form by itself in response with the gravity to be in equilibrium. Model based work flow contributes to the in depth design analysis and optimization. Physical models helps in better visualization of the design as a whole. Visible progress of the design process and problem solving can be experienced with the process of making.
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4. Analysis of Structure with ANSYS In the previous chapter the process of natural form finding has been described and demonstrated. A question arises, is the shell structure casted with the natural deflection of fabric form work most stable? To answer this question, the author decided to go for the structural simulation analysis with ANSYS 12.1 version. ANSYS is an advanced engineering simulation software mainly used for structural performance and fluid dynamics, having mainly industrial use [www.ansys.com]. The developed digital model as described in the previous chapter is to be simulated here to notice the structural performance with Static Structural(ANSYS). The digital model created in Rhinoceros is to be imported in (.igs) format to ANSYS for the purpose. Image 4-1 below shows the digital model similar to the vault shell casted as demonstrated in the previous chapter (Chapter 3, 3.3.3 Cast II - Double Curve Vault Shell).
Figure 4-1 The Base geometry similar to the final cast (Source: Author)
4.1 Working with ANSYS Figure 4-2 shows the typical start page of the software. The material to be assigned can be found under 'Engineering Data' of Static Structure (ANSYS). Here the material properties can be changed as well as new materials can be added as shown in the figure 4-3.
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Figure 4-2 ANSYS start page
Glass reinforced concrete (GRC) is not available in the present ANSYS library, so the properties of concrete has been changed as per the physical properties of GRC provided by a particular manufacturer. The parameters which are added and the properties of GRC has been discussed in the further topics for better understanding.
Figure 4-3 Engineering data input page of ANSYS
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After the material assignment, the next step in ANSYS was to import the geometry or digital model for simulation. By opening the 'Geometry' tab, the .igs file created before was imported and geometry generated.
4.2 Parameters The geometry imported to ANSYS has no physical properties unlike any physical construction. The geometry imported should only be in the form of surfaces without any thickness so that further parameters can be added to get accurate simulation results as per the requirement of the software. The geometry generated in ANSYS is converted to mesh for optimized surface transformation. This creates polygons on the object surface. The Surface to be simulated is given the required thickness. Material assignment was the next step done, this has been described in detail in the next topic (Chapter 4, 4.2.1 Material Selection). The next step was the allotment of support points. As the final simulation is to be run for the surface of the slab which has been simply supported at 8 points by 4 'Y' shaped columns. The contact between the column and slab creates a surface which has been selected as support points. The columns do have fixed support at the base. By allotting of material and thickness to the object, the slab gained its own weight as dead load. Optimum thickness of the slab is also decided after some procedure, as it contributes a lot to material consumption. The same has been described in the following topic (Chapter 4, 4.2.3 Finding Optimum Thickness). The slab measures 1500 x 750 millimetres but as the deflection curve changes in each geometry, the surface area also varies for each slab and this causes the difference in the weight of the slab. So the dead load of each slab are not equal and this also affects the structural performance. Density of GFRC used here is 2000 kg/m続. Detail of the physical properties of GRC has been discussed in the next part (Chapter 4, 4.2.2 Properties of GFRC used for Simulation).
4.2.1
Material Selection
The material property carries an important role in the construction methodology as well as for the stability of the structure. Light weight materials are generally suitable for the casting of thin shell structures. Some research on different materials and material properties concluded to two materials, Light weight concrete and Glass fibre reinforced concrete (GRC or GFRC). Though from case studies of casts of C.A.S.T., it was mentioned that GRC is the most suitable material as it can be sprayed evenly on a surface and results in a thin shell structure. But here the author decided to compare the structural behaviour of both the materials side by side.
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Physical properties of light weight concrete was readily available from the material information technology
software
'Granta'
and
physical
properties
of
GRC
were
obtained
from
www.grconline.com which is described in detail in the next topic. Figure 4-4 below shows a comparison of physical properties of both the materials.
Figure 4-4 Comparison of physical properties of Glass fibre Reinforced concrete and structural light weight concrete.
Though both the materials are of same density but there is a big difference in compressive yield strength. The load bearing capacity of GFRC is more than structural light weight concrete if they both are of same thickness, With the increase of thickness of the slab for the latter case, the structural strength can be achieved but will compromise with material consumption. So, GFRC is the material for light weight vault casting and also for considerable material consumption. The high structural strength in compact thickness was the reason of its selection over any other concrete. GFRC is contains high strength glass fibres in a cementitious matrix. The reduced thickness, results in light weight construction with increased structural strength over any other concrete.
4.2.2
Properties of GFRC (Glass Fibre Reinforced Concrete) used for Simulation
GFRC or GRC (Glass fibre reinforce concrete) was chosen over the structural lightweight concrete for the simulation purpose in ANSYS. Different manufacturers provide different physical properties for GFRC. Here the author has used the physical properties available at www.grconline.com which shares information and knowledge on GFRC or GRC manufacturing. Table 4-1 in the next page shows the Properties of GRC available at source and highlights the information used in ANSYS for the simulation.
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Table 1 Physical properties of Glass reinforced concrete (Source: http://www.grconline.com/en/grc/propertiesofgrc.html)
Figure 4-5 below shows the physical properties of the Glass fibre reinforce concrete used for the simulation of all the digital models in ANSYS.
Figure 4-5 Physical properties of Glass reinforced concrete put in ANSYS. (Source: www.grconline.com)
The most important figure is the Compressive Yield strength which means, the maximum load at a point should not be more than this which is 80 MPa7 in this case as per the material properties.
7
MPa represents Mega Pascal. SI derived unit for pressure is Pascal which is equivalent to 1 Newton per square meter. 1 Mega Pascal = 10â ś Pascals
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The glass reinforced concrete is considered to be casted by mechanical spraying. The spray concrete results in enhanced quality of construction and also reduces the overall thickness of the cast as well as gives an uniform thickness throughout. The spraying results in providing high strength to the cast and also getting the exact shape of the fabric formwork with natural deflection. Figure 4-6 obtained from C.A.S.T. shows the typical concrete spraying and the obtained mould from it.
Figure 4-6 Spraying of GFRC and its results (Source: C.A.S.T.)
4.3 ANSYS Simulation The original geometry (Figure 4-1, Page 37) created in reference with the casted vault has been differed by changing the deflection curvature. This is considered as the base geometry and two other digital geometry were also created with the same reference. The base geometry is considered as Case III in this analysis chapter. In option two (Case II), as shown in the figure 4-7, the deflection of the curvature has been reduced to create a different geometry. As the first option (Case I), the deflection of the curvature has been considered as zero when compared to the original one.
Figure 4-7 Types of geometry to be simulated (Source: Author)
These three geometries have been simulated and compared before getting any conclusion in the further steps. In all the simulation, the physical properties of the structures like material, thickness, weather condition, applied live load etc. are kept constant.
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Figure 4-8 Structural constraints applied to each geometry (Source: Author)
Figure 4-8 above shows the structural constraints added to the geometry. As the vault is supported by four 'Y' shaped columns at four corners, the slab is simply supported at eight connecting surfaces of the column and the column bases are considered as fixed support. Standard Earth gravity (9806.6 mm/s² or 9.8 m/s²) is considered as natural external force on the slab. Suppose this structure will be used as a shelter and considering the slab to be built in United Kingdom, we have to consider the live load in form of snow only. For extreme conditions, the height of the snow deposited is taken as 1.5 meter and this will add an extra pressure of >0.3 Mega Pascal (MPa). To be in safer side, 0.5 MPa of uniform pressure has been added under 'Static Structural' in ANSYS.
Figure 4-9 Comparison of Physical properties for Case I, Case II and Case III obtained from ANSYS
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Figure 4-9 on page no. 43 shows a comparison of the physical properties in all three cases. Total deformation and stress intensity has been calculated and considered for all the three options and are discussed individually before the comparison of structural performance in the conclusion.
4.3.1
Finding Optimum Thickness
Thickness of the slab to be casted is very important in terms of structural stability, material consumption and aesthetics. Referring to the casting works at University of Manitoba (C.A.S.T.), the GFRC spraying resulted in 1 inch or 30 millimetre thick casts. But to get the optimum thickness for the casted geometry in this particular experiment, the author decided to go for ANSYS simulation. By taking 30 millimetre as reference, three simulations were done with thickness of the 20 millimetre and 40 millimetre for the base geometry (Case III).
Figure 4-10 Stress Intensity comparison for optimum thickness of slab (Source: Author)
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Figure 4-10 on the previous page shows the simulation results for the 'Stress Intensity' of the same geometry but with different thicknesses of 20mm, 30mm and 40mm. The maximum stress should not be more than 80 MPa as per the material properties. The comparison of maximum values shows that for the slab with 30mm thickness, the value lies closer to 80 MPa with a number of 60.532 MPa. The value goes much above the limit for the 20 mm thick slab. Though the minimum stress intensity value is obtained from 40 mm thick slab, it does not create an optimum structure with extra use of construction material.
Figure 4-11 Total deformation comparison for optimum thickness of slab (Source: Author)
Figure 4-11 above shows a comparison of total deformation occurring for all the cases. Total deformation is minimum for the thickest slab which is obvious. But the differences of deformation is very negligible in all three cases. The slab with 30 mm thick can be considered as optimum structure based on the analysis of stress intensity previously. 45 | P a g e
4.3.2
Case I
In the first case, the geometry has no longitudinal deflection. The deflection of geometry or slab along the longer span has been considered as zero. With the uniform thickness of 30 millimetre, the mass of the roof becomes 129.14 kilogram. Figure 4-12 below shows the screenshot of physical details of the whole structure obtained from ANSYS like thickness, assigned material, the size of the roof slab, volume and mass of the slab etc.
Figure 4-12 Physical properties of geometry obtained from ANSYS for Case I (Source: Author)
Being a rigid material and with high density, the total deformation of the geometry in this case seems to be quite low as per the simulation results from ANSYS. As shown in the figure 4-13 in the next page, it can be seen that the deformation is highest at the central part of the vault slab with a value of 2.4957 millimetres. Being supported at eight points, there is no deflection at all four corners of the slab. Though the value is very negligible at central part, we can compare it with the values, which are going to be obtained from the simulation of other two geometries in further steps.
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Figure 4-13 Total Deflection of the shell structure in Case I, obtained from ANSYS simulation (Source: Author)
Compressive strength of the GRC is 80 MPa as mentioned earlier (Chapter 4, 4.2.2), so the total stress intensity should not be more than that for a stable structure. As shown in the figure 4-12 above, the Stress intensity is 103.51 MPa at certain points. Though the value is close to 50 MPa at most of the cases, still it is failing at the junction points with columns. From the simulation results it is clear that the roof is not stable with a thickness of 30mm. The simulation result after increasing the thickness of slab geometry from 30mm to 40mm though solved the structural problem but do result in more material consumption as well as increasing the construction cost. The optimum thickness of the slab has already been discussed earlier (Chapter 4, 4.3.1). The simulation of other two geometries might contribute to the solution in further steps. In figure 4-14 the intensity of stress can be seen over the structure. The simulation image also indicates that values are significantly high around the three ridges. Ridges are creating convex surfaces here and they are considered as stable structures.
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Figure 4-14 Stress Intensity of the shell structure in Case I, obtained from ANSYS simulation (Source: Author)
The simulation resulted in increasing the thickness by 10 mm to create a structurally stable structure though the deflection is very negligible with nearly 2.5 mm maximum at the central part. At the same time as the longer span is straight, it may cause problem in self drainage of snow in winter days and might create problem for the structure. The impact of manipulation of geometry are to be observed in further steps.
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4.3.3
Case II
In this case the geometry has been manipulated as described in the previous topic. A deflection of 60 millimetres at centre of the slab along the longer span has been added. This created an interesting double curvature geometry like a bow from side with the deflection of central ridges.
Figure 4-15 Physical properties of geometry obtained from ANSYS for Case II (Source: Author)
Figure 4-15 shows the physical properties of the slab for the second option. With the same thickness of 30 millimetre but the manipulation of the curvature resulted in the increase of the surface area as well as mass.
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Figure 4-16 Total Deflection of the shell structure in Case II, obtained from ANSYS simulation (Source: Author)
Figure 4-16 above shows the ANSYS analysis for the total deflection of the slab. The deformation has been reduced to 1.7652 millimetres, compared to the 2.4957 millimetres in the previous case. The simplest modification in geometry resulted in this. The result was expected because, following the principles of geometry and also as discussed in the second chapter, the concave structure becomes a compression member when inverted and gives better resistance to the bending moment when compared to a geometry parallel to ground. Here the 60 millimetre longitudinal deformation at centre of the slab created a gentle curve and when inverted, it became a rigid compression structure.
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Figure 4-17 Stress Intensity of the shell structure in Case I, obtained from ANSYS simulation (Source: Author)
The simulation result for the stress intensity indicates in figure 4-17 that the maximum value is again more than 80 MPa. At certain points the stress intensity is 81.704 MPA as maximum, so the structure will fail. Again, with the increase in thickness of the vault the stress intensity can be reduced up to the limit. But it is noticeable that, with a nominal deflection, the intensity of stress has reduced significantly. It indicates that more deflection might give the slab more structural strength.
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4.3.4
Case III
In case III, the deflection of the longitudinal curve has been increased to 150 millimetres. This creates a proper vault shell and adds some aesthetical value to the structure. In all these three cases the curvilinear geometry along the shorter span has remain unchanged.
Figure 4-18 Physical properties of geometry obtained from ANSYS for Case III.
The variation of geometry can be noticed from Figure 4-18, obtained from ANSYS. The deflection resulted in an increases surface area of the vault as well the weight of the slab has been increases to 133.9 kilograms.
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Figure 4-19 Total Deflection of the shell structure in Case III, obtained from ANSYS simulation (Source: Author)
Simulation image for the total deformation of the vault indicates that the maximum deflection is 1.2795 millimetre at the central part, lowest among all three cases. This is the shape of the selfformed cast which is obtained from the physical casting experiments. The geometry was naturally formed by the fabric with response to the gravity as well as the self weight of the structure. It is also noticeable that the deformation area is less. Figure 4-19 above shows the ANSYS static structural simulation images of total deformation for case III.
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Figure 4-20 Stress Intensity of the shell structure in Case III, obtained from ANSYS simulation (Source: Author)
Figure 4-20 above shows the stress intensity simulation for the same geometry. The resistance to the load has been increases significantly in this case. The maximum stress at certain points is 60.532 MPa, where as the maximum value should not be more than 80 MPa. It means the structure is much stable. A simple parameter to the geometry resulted in self-forming of this vault.
4.4 Conclusion The ANSYS simulation added some quantitative data to this experiment. The structural performance analysis was based on the total deflection and the value of stress intensity. The aim was to find out the minimum deformation of the geometry and safe stress intensity value under the limits of maximum load carrying capacity as per the physical properties of the GFRC used for the purpose. The manipulation of geometrical parameter as described earlier (Chapter4, 4.0.0) resulted in three different structures and with similar physical conditions the structural simulation was done. The comparative analysis of all three geometries for total deflection and Stress intensity are shown in Figure 4.21 and Figure 4-22 respectively.
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Figure 4-21 Comparison of total deflection in all cases (Source: Author)
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Figure 4-22 Comparison of Stress Intensity in all cases (Source: Author)
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Figure 4-21 in the previous page shows a comparison of total deflection occurring in each case of the simulated geometry. The value of deflection is though very negligible in each case, Case III got the minimum deflection of 1.2795 millimetres and it is maximum at the central part of the slab. Figure 4-22 in the previous page shows the comparison of stress intensity for all three options. The compression strength of GFRC is 80 MPa, it means at any point the maximum stress intensity should not exceed this to make the structure stable. As achieved and described earlier (Chapter 4, 4.2.2) the optimum thickness of the vault slab is 30 millimetre. The base geometry (Case III) which replicates the casted double curve vault shell only shows the value of maximum stress intensity less than 80 MPa, which is 60.532 MPa. So it can be said that Case III is the optimized structure and the geometry is self formed in response to the gravitational force and material properties of the fabric form work. The analysis of values obtained in all three cases as described earlier says, Case III is the optimum structure to carry the load with minimum thickness which results in material saving as well as economical.
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5. Conclusion The aim of the study was to know the contribution of model making in the improvement of the design process. The role of fabric form work in developing a self form geometry and testing it through simulation to understand it's structural behaviour was one of the objectives. The experiment presented in the process of finding a self-form vault shell responding to the natural forces and material behaviour and how it has improved the geometry in creating a stable structure, after comparing them through simulation tools like ANSYS which also supports the role of making in the design process. Decades long study of development in the field starting from Antonio Gaudi to C.A.S.T. has contributed a lot to the process of making and form finding. The knowledge gained from studying the process of making the prototypes by C.A.S.T. gave the basic idea on how to carry forward the research with making procedure. Isler's experiments contributed in knowing the flow of forces in a physical model and in understanding the tension and compression structures. From the catenary model of Gaudi, the role of scale while making model was understood. An implementation of gained knowledge from these case studies resulted in creating all the rest casts and the final vault shell and understanding the theory behind the process of making as well as its contribution to the whole process. Due to time constraints and available facilities, the scale of the casts and method to be adopted was decided. A full size cast though was not possible but large scale plaster casts lead towards the solution. The structural performance cannot be just claimed by making a model. It needs some proper analysis and quantitative data. Heinz Isler, used to do manual structural analysis of the test cast of his found form before preparation of drawings. Here in the present essay, ANSYS software simulation methodology has been adopted for the final analysis of the geometry. The outcome of this research suggests that, model making contributes to the design development process in a logical way and improves the architectural performance. Also, fabric form work creates aesthetically pleasant self-form geometry with proper demonstration of flow of structural forces in the physical model with an ability of practical use. Model making surely fuels the designing process to create superior architecture in terms of both aesthetics and performance.
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5.1 Knowledge Gained
5.1.1
Importance of making - for natural form finding (Self-form generation)
Geometry always plays a key role in the process of designing and geometric principles contribute to the structural system. One can consider it as primary source to create architecture. Self form geometry with fabric form works are not only aesthetically pleasing but also structurally efficient which has been proved in the current research through experiments. These forms are also durable as the forces flow in a natural way and contributes economically to the construction or manufacturing. The test casts as described in chapter 3 (3.2.1) are casted without any drawing, but the results were encouraging as in a variety of self-formed geometrical forms were derived. The form of shell structure replica (3.2.1.1) was found naturally responding to the gravitational force, material dead load and fabric formwork. The double curve vault shell casted (3.2.3) demonstrates the process precisely. The fabric form-work supported at particular points creates a self-form geometry when casting material is applied. This creates a tension structure and when inverted, it becomes a pure compression structure which is structurally stable.
5.1.2
Importance of making - to develop the design
Many among the current practices prefer simulation, as model making results in time consumption and seems to be economical. But the outcome never responds to the forces of nature, material properties and real time construction challenges which can only be achieved if the design develops through physical models. The whole process seems to be time consuming and also has economical limitations but it solves the critical structural problems in response to the various forces and even material properties by making the whole process lot easier. And the form found is achieved with the responses of natural forces and phenomenon. Intensely expressive architecture can be created by methods of model making. Innovative designs do approach when the development process is carried out through the process of making. While working on initial design models, improvements do come even before the completion of one stage. And this lead to the next better ones. The same has been experienced during the current research while making the double curve vault shell. In previous chapter (Chapter 3) while attempting to get a self-form geometry for the same (Chapter 3, 3.2.2 & 3.2.3), it was realized that the structure of initially found form is not going to be the optimum one even with the application of initial layer of plaster. This piloted to an improved design in terms of a double curve vault shell
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(Chapter 3, 3.2.3) where the application of fast layer of casting ensured of some logical response to the natural forces and a stable structural element which later proved by the quantified data from ANSYS simulation. At the same time, the fabric form work can be used to create elegant shapes.
5.1.3
Importance of making - to improve the performance
Physical models do show similar problems as of a constructed building in terms of both performance and construction methodology, these can be understood with proper observation. Models not only give the visual aspects but also reflects the general statistical behaviour. The design development combined with human imagination and physical models leads to superior and invaluable solutions. The performance of a design can be investigated in terms of aesthetics and structural stability. The question of aesthetics is always tricky as it varies from person to person. To measure the performance, there is a requirement of quantified data which can be achieved by software simulations for stress analysis, after the natural form finding process is done. Form finding results in establishing a stable structural geometry. The structural behavior can be studied instantly while making the model. In other words, models do generate logical structural geometry. The design process completes by Form Finding, Structural Analysis and Manufacturing. Here in this case, the optimized thickness for the slab was generated through ANSYS static structural analysis. Later, the stress intensity and total deflection values contributed as quantified data to prove the structural performance of the self form double curve vault shell. Alternated simulations carried in Chapter 4 (4.3.2, 4.3.3 & 4.3.4) also verified that the self form geometry as casted (Chapter 3, 3.2.3) is structurally stable. At the same time, the fabric form work used also creates an interesting aesthetical pattern. Easier and economical construction procedures with aesthetic sense can also be considered under enhanced performance. Design development by physical models give solutions to critical manufacturing constraints as the structure is built in real three dimensional world with materials having some physical properties as the whole structure can be seen from all sides and experienced before its design execution.
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5.1.4
Fabric Formwork
Fabric form work has the potential to be used in the construction field for economical form works but it needs certain expertise in the field. Understanding the reaction of fabric is very important in creating casts with fabric form work and also in creating patterns. As described earlier (Chapter 3, 3.2.1), fabric formwork acts as a parameter to the natural formfinding process. This also contributes to the structural performance by filtration of excess water in concrete and also the air bubbles. A variety of fabric used in test casts resulted in creating different patterns and surface textures. Sewing can be another external parameter added to this in diverting the flow of forces as well as maintaining the equilibrium of forces.
5.2 Role of Simulation Performance is always investigated by a quantified data and need a scientific proof. In this particular research, the structural stability of the self form geometry only can be seen and assumed on basis of certain rules, physical calculations and observations. But the ANSYS simulation run on the basis of parameters of geometry achieved by physical making adds the quantitative value to the structure and justifies the natural principles of flow of forces as seen on the funicular vault shell. Here, other than giving structural values like stress intensity and maximum deflection, the optimized thickness of the slab was also calculated by ANSYS which results in lesser material consumption.
5.3 Limitations of Model Making Finding form by natural forces or developing a design by physical models seems to be time consuming and a tedious task to many designers. Most of the architectural practices depend on computer software to develop the form and then to simulate it to achieve the performance goals. With this methodology, in most of the cases the flow of forces which is very important for self-form geometry is interrupted but it seems to be quicker way to derive forms. Experiment with model making need specific infrastructure in terms of space, tools, materials, man power etc., which again seems to be a costly affair according to many practices. But the methodology solves many critical constructional issues before the execution of work with considerable economical saving and time consumption, even redesigning of the whole.
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5.4 Future Recommendations Live experiments with casting concrete need some sort of infrastructure and amenities. Man power and time consumption are the other factors to be considered. So this research can be carried further in a group so that a number of prototypes with bigger scales can be made for detailed observations. A similar geometry with different parameters can be casted and physical testing can be performed to know its structural behaviour. The reinforcement will be a constraint in the casting these freeform natural shapes. The conventional method might be a laborious process. But with the advancement of technology in the current time, it is not impossible to get some sort of solution. Fibre can be used as flexible reinforcements or with the use of CNC the reinforcement can be moulded. The digital technology used in Architecture now a days, basically were developed for automobile and aero space industry. So at certain cases Architecture moulds itself in to the criteria of another field, like an compromise. The ongoing research on the field has very little contribution to the designing industry.
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BIBLOGRAPHY
[1] Iwamoto Lisa, Digital Fabrications (Architectural and material Techniques). New York : Priceton Architectural Press, 2009. [2] Kolarevic Branko and Klinger Kevin, Manufacturing Material Effects (Rethinking Design and Making in Architecture). New York : Routledge, 2008. [3] Bechthold Martin, Innovative Surface Structures (Technologies and Applications). New York : Taylor & Francis, 2008. [4] Rahim Ali, Contemporary techniques in Architecture. London : Architectural Design , Vol. 72, No 1, January 2002. [5] Hrsg. Rainer Barthel, Diesta Eladio, Form Und Konstruktion. Technische Universitat Munchen, 2001. [6] Mette Anne, CONCRETELY. www.concretely.blogspot.com [Online] [Cited: 5 August 2011] [7] Pedersen Louise and Talisten Jonas, Structure as Architecture. Master’s Desertation, Lunde University, Sweden, 2007. [8] Lee Kwang Yeul, Frei Otto, Bodo Rasch, Finding Form: Towards an Architecture of the Minimal, Unknown Year. [9] Mele Tom Van and Block Philippe, A Novel Form Finding Method for Fabric Formwork for Concrete Shells, Proceedings of the International Association for Shell and Spatial Structures (IASS) Symposium 2010, Shanghai, China, November 8-12 2010. [10] Linkwitz K., Formfinding by the “Direct Approach” and Pertinent Strategies for the Conceptual Design of Prest ressed and Hanging Structures, University of Stuttgart, Germany, April 1999.
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