Redistributing Forces: Variations of Membrane Tensegrity Shells
Edited by Kenneth Tracy, Christine Yogiaman, Sachin Sean Gupta, Sang Hoon Youm
Engineered Design, Yonsei University Singapore University of Technology and Design
FALL 2019
ED
Engineered Design, Yonsei University Singapore University of Technology and Design
FALL 2019
ED
Redistributing Forces: Variations of Membrane Tensegrity Shells
Redistributing Forces: Variations of Membrane Tensegrity Shells Workshop @ SUTD 2019.10.19-10.23 @ Yonsei University 2019.11.12-11.14
Edited Kenneth Tracy, Christine Yogiaman, Sachin Sean Gupta, Sang Hoon Youm Instructor Kenneth Tracy, SUTD Christine Yogiaman, SUTD Sang Hoon Youm, Yonsei University Student Won Young Choi, Rubin Gui, Ji Hoon Jung, Ga Young Lim, Min Jae Park The workshop was sponsored by Korea Institute of Energy Technology and Planning, Department of Engineering, Yonsei University
Redistributing Forces: Variations of Membrane Tensegrity Shells
This collection of experiments is the result of a short summer workshop conducted in collaboration between the Dynamic Assemblies Lab of Singapore University of Technology and Design (SUTD) and CATLAB of Yonsei University. The workshop explored the possibility of making variations of Membrane Tensegrity Shells (MTS). Tensegrity is a structural principle, coined by Buckminster Fuller in the 1960s, where a discontinuous set of compression elements (usually bars or struts) are opposed and balanced by continuous network of tension members (usually cables or tendons). Because of the compliant structural members and high degrees of deformation tensegrity is rare in buildings; however, similar tensiondriven structures are the basis of mammal, bird, and reptilian bodies. This inherent flexibility may make tensegrity a mismatch for many typical building structures, but new variations of tensegrity (i.e. MTS or membrane tensegrity) offer a unique building typology consisting of compressive struts tensioning an architectural textile membrane. Prior to the workshop, many of the MTS examples and prototypes possessed convex, synclastic curvature made
with linear struts. This workshop explored ways to achieve counter curvature and experimented with curved struts for an enhanced design space for MTS. The experiments yielded surprising variations of the original structures with only subtle variations and patterns created by selectively removing struts. Membrane Tensegrity Shells Membrane Tensegrity Shells (MTS) are a novel class of tensile structures developed by the Dynamic Assemblies Lab. Like most tensegrity structures, these structures primarily leverage tension to transfer loads; however, instead of the discrete cables used in most tensegrity structures, MTS feature a membrane. Replacing linear elements with a membrane provides MTS two distinct advantages: first, the tensile members simultaneously serve as structure and enclosure, and second, the membrane distributes force in a more redundant fashion, allowing for simpler, self-similar 2D configurations of struts. These advantages were previously demonstrated in several other precedents of membrane tensegrity structures, most notably the MOOM Pavilion by Kazuhiro 01
Kojima. MTS is a variation of these previous structures that utilize overlapping struts in two directions to form stiff, stable shells while allowing for large openings. Critical to the stability of MTS is the reciprocal patterning of the embedded rods. Developing methods for strategically patterning the struts form the core of the research. Workshop Approach The workshop’s main approach to achieve its goals was to partially relinquish the tension and thus redistribute the forces to morph the overall shape. Even though the MTS’s workflow involved highly sophisticated integration of digital simulation and analysis, this workshop was conducted using only analog methods. A heuristic approach, enabled by rapid physical hand model production, pushed the workshop participants to explore the broad design space of the structural system within the finite time frame of the workshop. This tactile, highly kinesthetic mode of learning contributed to an empirical understanding of the relevant structural principles. This in turn equipped participants with distinct fidelity over each model’s shape without necessarily depending on the theoretical knowledge behind the complex, nonlinear material formation. The same heuristic approach has been conducted at the start of DAL research in MTS and was a critical tool in the subsequent development of the open-ended
digital design toolkits for MTS structures*1). Over 100 physical models assembled by hand enabled the systematic, empirical study of the structural principles governing the performance of MTS (Figure 1.) To engage the workshop participants in a similar iterative, hands-on process, a kit of 1:20 scaled components that make up a total area of 250m2 was used. These components were lasercut plywood struts designed with a barbed end for attachment and flat pieces of elastomeric textiles. Method 1. Partial Elimination of Compression Struts Generally, tensegrity structures are closed systems where the elimination of any single compression member or a break within a tension member would result in the collapse of the entire structure. However, the MTS maintains structural capacity even when some struts members are removed due to the crossing struts and the use of a membrane instead of cable or a tendon. Thus, the team’s first attempt was to remove some of the struts in order to redistribute the forces, observing to see how the structure would respond. By removing the struts in the central area of the fabric, the area’s tension became loose and the overall shell shape instead relied upon the rods along the perimeter. This resulted in different directions of curvature which depended on the placement of the struts. There are two types of strut
1). Kenneth Tracy, Sachin Sean Gupta, Stella Loo Yi Ning, So Jing Wen, Abhipsa Pal. 2019. Tensile Configurations. ACADIA 19:UBIQUITY AND AUTONOMY [Proceedings of the 39th Annual Conference of the Association for Computer Aided Design in Architecture (ACADIA) ISBN 978-0-578-59179-7] (The University of Texas at Austin School of Architecture, Austin, Texas 21-26 October, 2019) pp. 110-119.
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geometries in the presently developed MTS, a hexagonal type and a cross type. The struts are unitized as a hexagonal shape (three struts at a 60° angle from one another with a common midpoint in plan view) or as a cross shape (two struts at 90° angle from one another with a common midpoint in plan view) and the units overlap to balance the tension forces of the membrane. Within each of the strut units, the struts are overlaid on top of each other. Due to this condition, each strut direction within a unit has a different force characteristic. Before the elimination of the central struts of the structure, the even spacing of these units formed a uniform force distribution,
which resulted in a dome-like shape. The elimination of the central members resulted in breaking away from the overall uniformity. The central region without the struts gets loose in one direction and taut with tension in the perpendicular direction. This results in the structure to become both concave and convex with the membrane in between the struts resolving the counter curvature. The degree of change between positive and negative curvature depends on the degree and location of the strut members’ elimination Method 2. Flipping the surface direction
Figure 1. 3d matrix of tensegrity membrane parameter combinations from SUTD ASD studio
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Flipping the surface where the struts are located was the next step taken to achieve counter curvature. Despite there being a flat spot between the positive and negative curvatures the result was formally quite intriguing. The overlapping of the strut units played an important role in this. Since the strut units are not separated but rather overlapped, the boundary where the two different surface normals converge is not a sharp division but a merging of both surfaces’ strut unit. This in turn provides a smooth transition between the two curvatures. Method 3. Re-positioning the foundation Repositioning the MTS’s foundation on its own is not a way of achieving a counter curving structure; however, when combined with the previous two methods (elimination of struts
and flipping struts from inside to outside the membrane), it turned out to be a valuable tool in terms of finding forms that could balance between extensive and intensive properties. The MTS is a stable and free-standing structure, but the elastic membrane allows the structure to deform and remain in equilibrium. By repositioning the connections to the ground, the canopies can change the form drastically. This flexibility can be used to change footprint, height, and overall curvature in the structures. Method 4. Re-shaping the strut In addition to the previous experiments, we the changed shape of each strut from a straight line to an arc. This change only slightly increased the tension in the system but more significantly provided an architectural and aesthetic depth.
Figure 2. Membrane Tensegrity Shell developed by Digital Assembly Lab
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When the curve of the struts followed the curvature of the membrane, the struts touch the membrane continuously creating a smoother shell with a more uniform shape. If the struts were turned so the curvature protruded into the space under the shell, a pattern similar to carp scales was created. Finally, curving the struts allowed them to be flipped outside the membrane and maintain a similar curvature creating a smooth interior membrane surface with an exoskeleton. Through this variation, we can see the visual/ spatial potential of such subtle changes to the struts. Conclusion: Interplay between extensive and intensive properties The form of the MTS is an interesting result of strong interactions between the extensive properties of the struts and the intensive properties of the force distribution of the membrane. The workshop’s attempt to achieve doubly-curved forms was, in fact, an attempt to modulate these properties to determine how the structure would react and morph according to the changed conditions. The experiments were possible due to the use of a hands-on physical kit instead of a digital method. In a digital environment, it would have been almost impossible to exactly simulate and analyze these complex conditions. These experiments showed the importance of considering both the extensive and the intensive properties when designing a structure, and moreover, the interplay between the two properties, providing intriguing aesthetic results. In the case of the MTS, the use of the membrane and
the overlapping of the strut units provided the tolerance and freedom for the extensive and the intensive properties to react with each other, and as a result, deform the overall geometry accordingly. The next step would be to develop a way to conduct these experiments not only with physical models but also within a digital environment, such as using a real-time digital twin and simulation. About the Authors The Dynamic Assemblies Lab (DAL) at Singapore University of Technology and Design explores emerging technologies through prototyping, simulation, and visualization. DAL’s research focuses on several topics within building performance and digital fabrication including responsive structures, 3D knitting, computational fluid dynamics, compliant mechanisms, fabric formwork, and tensegrity. By developing workflows that leverage these systems, DAL aims to broaden the palette of design possibilities for a more resilient and adaptable built environment. / dal.sutd.edu.sg Sang Hoon Youm is currenlty an Associate Professor at Yonsei University and runs the CAT (Context, Architecture & Techonology) Architecture & Urban Design Lab. The lab seeks to discover alternative urban & architectural spaces as well as experimental design methods. The lab’s architectural study explores the possibilities in between architecture/urban, analog/digital and form/material. His research on boundary spaces between architecture and the city provided a new insight in understanding the contemporary role of architecture in an urban setting. His architectural design and research has been commissioned and exhibited in various locations including MMCA Seoul and MoMA New York. / cat-yonsei.com
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Method 1. Partial Elimination of Compression Struts The team’s first attempt was to remove some of the struts in order to redistribute the forces, observing to see how the structure would respond. By removing the struts in the central area of the fabric, the area’s tension became loose and the overall shell shape instead relied upon the rods along the perimeter. This resulted in different directions of curvature which depended on the placement of the struts.
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Cross Strut Unit
Hexagonal Strut Unit
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Method 2. Flipping the surface direction Flipping the surface where the struts are located was the next step taken to achieve counter curvature. The overlapping of the strut units played an important role in this. Since the strut units are not separated but rather overlapped, the boundary where the two different surface normals converge is not a sharp division but a merging of both surfaces’ strut unit.
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Method 3. Re-positioning the foundation Repositioning the MTS’s foundation when combined with the previous two methods (elimination of struts and flipping struts from inside to outside the membrane), turned out to be a valuable tool in terms of finding forms that could balance between extensive and intensive properties. By repositioning the connections to the ground, the canopies can change the form drastically.
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Method 4. Re-shaping the strut In addition to the previous experiments, we the changed shape of each strut from a straight line to an arc. This change only slightly increased the tension in the system but more significantly provided an architectural and aesthetic depth.
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워크숍 지도교수
케네스 트레이시(Kenneth Tracy), SUTD 크리스틴 요기아만(Christine Yogiaman), SUTD 염상훈(Sang Hoon Youm), 연세대학교
학생
계유빈(Rubin Gui) 박민재(Min Jae Park) 임가영(Ga Young Lim) 정지훈(Ji Hoon Jung) 최원영(Won Young Choi)
발행일
2020년 11월 20일
저자
케네스 트레이시(Kenneth Tracy), 크리스틴 요기아만(Christine Yogiaman), 사친 션 굽타(Sachin Sean Gupta), 염상훈(Sang Hoon Youm)
펴낸곳
열린집
등록
2010년 10월 11일 제 300-2-1-132호
주소
서울 서초구 서초동 1330-3 엔데버빌딩 13층
이메일
ohpress01@gmail.com
[ED] Redistributing Forces: Variations of Membrane Tensegrity Shells [ED] 힘의 재분배: 막 장력 쉘의 변형 Copyright © Dynamic Assemblies Lab, SUTD Copyright © CATLAB, Yonsei University All Rights Reserved 이 책은 저작권법에 따라 보호를 받는 저작물이므로 무단전재나 복제, 광전자 매체 수록 등을 금합니다. ISBN 979-11-952128-4-2 (93600)
Redistributing Forces: Variations of Membrane Tensegrity Shells ???/??
93600
9 791195 212842
ISBN 979-11-952128-4-2
