Satorasti Report IASS 2004

IASS 2004 – MONTPELLIER, FRANCE – J. LLORENS – ETSAB/UPC 1

IASS 2004 “SHELL AND SPATIAL STRUCTURES FROM MODELS TO REALIZATION”. MONTPELLIER, FRANCE Prof. Dr. Josep Llorens School of Architecture of Barcelona E-mail: [email protected] http://www.upc.es/ca1/cat/recerca/tensilestruc/portada.html From the 20 to the 24th of September 2004, the International Association for Shell and Spatial Structures Symposium was held in Montpellier, France organized by the University Montpellier II and chaired by Prof. R. Motro. As usual, the IASS Symposium was an opportunity to get up to date information on the topics covered by the event. 5 Conference rooms were running simultaneously dealing with form-finding, shells, prospective, geometry, membranes, tensegrity, morphology and design, projects, nature, computer aided design, computation, concrete, structures, wood, surfaces, conceptual design, cables, movable, space frames, dynamics, technology, optimisation, grids, models, wind, composites, instability and glazed structures. Some presentations concerning tensile structures and membranes dealt with: − Developments of membrane structures in China − Tensegrity − Lighting performance − Wind loading − Computational fluid dynamics − Biaxial test protocol − Rigidizing a membrane mould with polyester − Textile junctions − Rostock Zoological Garden aviary − Rapid deployment military shelter system − Temporary grandstand canopy − Roofing the “Palacio de Mineria” courtyard − A large membrane roof for the Babtist Church of Fortaleza − A tensegrity lighthouse − Multi-layered tensile membranes − Intelligent kinetic structures


Invited Lectures Tien T. Lan: “Developments of membrane structures in China” Membrane structures have developed rapidly in China during the recent years at a rate of 15-20%. Distinguished projects are the Shangai, Yizhong and Yizou Stadiums, Qinghuangdao Gymnasium, Chengdu Aquatic Paradise, Changsha Theatre, Shenzhen Trade Fair, Boan Auditorium and Nanning International Convention Centre.

Gas station in Tianjin Theoretical research has also been carried out in the field of pre-tensioned membranes. For patterning, a new method has been proposed introducing the compensation before flattening and the fluid-solid coupling wind vibration analysis has been improved by a digital wind tunnel method. It is expected that membrane structures wilt be applied extensively in China and the cooperation with the world will steadily increase. Technical Papers R.H.Luchsinger, A. Pedretti, P. Steingruber & M. Pedretti: “Lightweight structures with Tensairity”. A new lightweight structural concept: Tensegrity was presented. The basic idea is to use low pressure air to stabilize compression elements against buckling. The basic Tensairity structure is a beam with the properties of a simple air-beam as lightweight, fast set up and compact storage volume with the load bearing capacity of conventional steel girders. As a first demonstration a small car bridge with 8 m span and 3,5 tons maximal load was built. Two parallel cylindrical Tensairity beams 50 cm in diameter each were the supporting structure. The membrane was standard PVC coated polyester fabric. Steel cables 6 mm in diameter were used. A carbon sandwich was used for the compression element. The beams were covered with wood


plates to drive on. Working pressure was 400 mbar. Each complete Tensairity weighed 98 Kp. The equivalent HEB steel girder would had weighed 320 Kp. Tensairity demonstration bridge J. Mundo Hernandez, R. Rutherford & J. Chilton: “Lighting performance of fabric membrane structures: behaviour and effects on visual perception”. Daylight and artificial lighting affect the perception of any membrane structure, the illuminance inside the building, its thermal performance and the comfort of the occupants. These characteristics are the result of the translucency, lightness and small thickness of the materials. Previous research in this area was summarized. As a conclusion, it was stated that the lightweight membrane skin can provide large amounts of daylight, converting the building in an environmentally sensitive space. This characteristic could be an advantage if the fabric membrane is appropriately chosen according to the desired internal environment, the purpose of the building and the environmental conditions of the site. The Amenity Building of the Inland Revenue Centre in Nottingham was mentioned as an example. Inland Revenue Centre, Amerity Building, Nottingham


J. Burton & P.D. Gosling: “Wind loading pressure coefficients on a conic shaped fabric roof. Experimental and computational methods”. A research was presented concerning a square based conic shaped roof. It had a 14x14 m base, rising 4,5 to a 2,5 m diameter ring, the whole supported by three column heights: 3,8 and 14 m. The pressure coefficients were obtained for each arrangement from a series of wind tunnel test. This experience showed how the results can be misrepresented by trying to over-simplify the results. Computational Fluid Dynamics (CFD) was mentioned but the comparison was not undertaken. The representation compromises the accuracy A.M. El Nokaly, J.C. Chilton & R. Wilson: “Computational fluid dynamics (CFD) modelling of airflow around conic tensile membrane structures”. Accurate predictions of airflow in and around buildings are essential for the thermal conditioning. This presentation described a study of the airflow patterns around and under conic tensile membrane structures using CFD modelling covering open and semi-enclosed spaces. The reason was to investigate the use of the structures topology to assist in passive cooling and achieve higher comfort levels of covered spaces by membrane structures in hot climates. The results were validated using wind tunnel experiments. They showed that the increase in the height of the cone improves ventilation. They also indicate the need for further research in this area.

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Max = +0.66 Min = -0.72

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.000.00

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Max = +1.75Min = -1.41

-1.60-1.40-1.20-1.00-0.80-0.60-0.40-0.200.000.200.400.600.801.001.201.401.60


Tested models Contours of velocity magnitude B.N. Bridgens & P.D. Gosling: “A new biaxial test protocol for architectural fabrics”. The aim of this paper is to present a biaxial test protocol to generate response surfaces to describe in-plane biaxial fabric behaviour. Biaxial tensile testing of a plane cruciform specimen was carried out using a purpose built test rig. The fabric was conditioned such that the behaviour measured was not the initial behaviour but the typical behaviour of an in-situ fabric. The effect of load history on the response of the fabric has been investigated. As a result, the PTFE/glass-fibre fabric showed a very discrete response envelope, the behaviour dominated by crimp interchange with little extension of the stiff glass yarns. In contrast, the polyester yarns were more easily extensible giving a greater range of possible strain states. Biaxial test rig R. Houtman, E. Moncrieff & A.D.C. Pronk: “An art pavilion made by rigidizing a membrane mould with polyester”.


The concept and engineering design for an art pavilion in Eindhoven was described. The surface was made of glass fibre reinforced polyester and the mould of PVC coated polyester membrane. The manipulation of form-active surfaces made it possible to use membranes as a mould. The way the artist made his model and how it was used as a starting point was presented. Further, the form-active structure was calculated and patterned to make the fabric mould and finally the polyester surface was engineered and built. Balloons in nylon stocking rigidized using textile junctions K. Leitner: “Models of new folded plate structures of timber boards and the textile junction”. It is a major challenge for realizing folded timber board structures to find a simple flexible junction of its segments so that the plate can be easily folded. To overcome this, a textile junction was developed in a triple layer material and tested in a model of folded plate structure. The fast on-site assembly was an advantage of the folding technique and the textile junction. No additional structural elements were needed and therefore, a great architectural quality was achieved. Double-curved honeycomb structure using Double-curved honeycomb structure using textile junctions textile junctions V. Bayer, K. Wagener & C. Wolkowicz: “Development and realization of a freeform tensegrity structure”. The design of an aviary for the Rostock Zoological Garden was described. The concept was not to present the animals only, but to excite interest in science in general. From this philosophy arose the idea to design an aviary with a special


structural concept. Another design constraint was to keep the cage itself free from any structural element. That’s why the cage had a ground plan of a 6,30 x 8,30 m and an elevation of 6,45 m, the entire structure a 11 x 12,45 m ground plan and 9 m height. The bars were planned as steel tubes and cables based on stainless steel wires arranged in a tensegrity system with none connected compression members. The main problem was to find a self-stressed state such that each node of the structure was a state of equilibrium and all cables had tension forces. The first stage was to find stability. In the future, structural details will be developed and analyses will be verified by experiments. Front and side view of the aviary N. Burford: “Rapid deployment military shelter system”. The design and construction of a 6 m span rapid deployment military tent was presented. It has a length of 10 m and a height in the centre of 3 m. The structural system comprises four lightweight trussed arches pre-stretched and composed by a thin rib reinforced and restrained from bending by a shaped web of pre-stretched polyester fabric. The arches are arranged in parallel and support a mechanical pre-stressed anticlastic membrane weighing less than 90 Kp, the shelter can be carried by only four people and erected in less than 10 minutes providing a lightweight and stiff structural support system.

General arrangement of the components of the truss


C. Gengnagel: “Temporary grandstand canopy” A modular structure has been designed to provide weather protection to seating for major public events. It is constructed from a series of bays, 6 m wide with a 13 m free-span cantilever, supporting a mechanical pre-stressed membrane cover. The bays are supported by aluminium trusses separated by tubular aluminium purlins and sway bracing. The system benefits from having only a minimum number of components that can be transported flat, a simple and quick assembly process that can be carried out from ground level and the ability to erect the entire structure quickly and safely with only two people. Fig. 11 – Front and side view of the aviary J.G. Oliva-Salinas: “Adaptability of a tent construction to a historical building in Mexico City”. To cover the 26x26 m courtyard of the “Palacio de Mineria” in Mexico City a 35x35 m tent construction was adopted. It consists on a radial composition with a circular skylight in the middle. A fabric roof was selected because the cover had to be easy to erect and dismantle and lightweight to rest on the old building. It also had to suffer from the sinking effects characteristics of Mexico City. Moreover, if the roof was dismantled, the courtyard had to recover its original architecture as an open space and any structural element for the cover had to disappear. Fig. 14 – Cross section Final view of the tent


R.M.O. Pauletti & R.A.A. Alvim: “A large membrane roof for the Baptist Church of Fortaleza The membrane roof of the Baptist Church of Fortaleza, Brazil, was described. It was composed by a 70 m long, 50 m wide double asymmetric conoidal membrane hanged from two masts, 20 m tall, hinged at their lower ends and connected to the membrane by two upper rings, 2 m in diameter, 17 m height. Roof area amounts to about 2900 m2, a national record and the first case of a fully computer-assisted design process within Brazil. Inauguration of the membrane roof C. Wolkowicz, V. Bayer & A. Stahr: “A tensegrity light house”. A sculpture of high aesthetic and artistic value that constituted at the same time an innovative construction was presented. It was a light house made of discontinuous floating luminescent bars connected by a continuous network of tension members in a similar way Kenneth Snelson did. Three units consisting of three bars and nine cables connected by an upper and louver basic polygon are put on top of each other in a way that the bars of the upper unit are placed in the middle of the upper polygon cables of the lower unit. As compression bars, commercial fluorescent tubes were used. They were previously tested up to the breaking point: 800 N. Cables were made of steel and textile nodes were developed. The effort and accuracy that was necessary was remarkably.


Tensegrity light house Posters M. Mollaert: “Multi-layered tensile membranes” This poster showed the capability of tensile membrane structures of obtaining specific shading, thermal, ventilation, acoustic, lighting or structural properties by means of multi-layering. There exist numerous possibilities to combine structural as well as non-structural layers. They increase the complexity and require full compatibility between individual components. Several applications were shown: cushion systems, freely hanging inner textiles and separated tensioned layers. To design multi-layered tensile membranes, “multiphysics” simulation tools and good insight in the different phenomena are needed. Structural and constructive intuition should be complemented with the building physics aspects. Cushions. Expo Hannover 2000 Assembly tent (B. Rasch & J. Bradatsch)


M. Mollaert, T. Van Mele, P. Block & N. De Temmerman: “Intelligent kinetic structures: architectural organisms as a concept”. Focussing at flexibility, a combination of scissor elements and structural fabric integrating Pleated Pneumatic Artificial Muscles was developed at the Vrije Universiteit Brussel. Doing so, they created an architectural organism with a skeleton, skin, muscles, tendons and may be later even a brain. They tried to derive a principle from this, providing direction to further research and taking the first step towards the integration in different, move complicated, transformable constructions and in kinematic architecture in general. The poster presented also an overview of the world of dynamic architecture.

Computer simulation of an architectural organism The collection of extended abstracts and full papers are available at: R. Motro (ed), 2004 “Shell and Spatial Structures from Models to Realization” Editions de l’Espéron, Montpellier ISBN 2-912261-22-8

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Satorasti Report IASS 2004