Symposium of the International Association for Shell and Spatial Structures - IASS

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Evolution and Trends in Design, Analysis and Construction of Shell and Spatial Structures. Proceedings IASS 2009. A Symposium under the auspices of the International Association for Shell and Spatial Structures (IASS), Laboratorio Central de Estructuras, Centro de Experimentación de Obras Públicas (CEDEX), and the Universitat Politècnica de València (UPV)

The 50th Anniversary Symposium of the International Association for Shell and Spatial Structures (IASS), wich was celebrated at the Universitat Politècnica de València in September 2009, has brougth together a wide group of engineers, architecs, researches and educators able to contribute with their work, experience and perspectives to the understanding of the evolution and exploration of future trends in the field of shell and spatial structures.

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39 etc... : Heinz Isler's infinite spectrum of new shapes for shells
(Editorial Universitat Politècnica de València, 2009-11-25T08:32:07Z) CHILTON, John
The first Congress of the International Association of Shell Structures (now IASS), held in Madrid in 1959, was the occasion when Heinz Isler's innovative methods for determining the shape and constructing reinforced concrete shells first became widely known. Although he had introduced his ideas at smaller conferences as early as 1955, his Madrid paper `New Shapes for Shells' (Isler [1]) was presented in front of some of the most eminent shell designers of the day. This paper included a diagram showing 39 alternative shell forms with the abbreviation "etc." at the bottom right-hand corner indicating that Isler believed there were many more possibilities yet to be revealed. Contemporary accounts of the discussion describe how his presentation completely astounded the assembled audience, which included renowned engineers such as Torroja, Esquillan and Arup. On the 50th anniversary of his presentation the content of the original paper and subsequent debate are reviewed. Isler's form-finding and analysis was unassisted by modern digital design aids yet he was able to create efficient and economical structures of great elegance. His design and construction methods will be described and some examples of his shells, both built and unbuilt will be presented. The paper concludes with a brief discussion of the influence that Isler's unconventional design philosophy, methods and extremely graceful shells have had on the development of free-forms in architecture over the last 50 years and hopefully will continue to have into the future.
50 years in the Design of Towers and Masts. From IASS Recommendations to Current Procedures
(Editorial Universitat Politècnica de València, 2009-11-25T09:44:30Z) SMITH, Brian
Up to the 1970s there were no recognized design procedures for the analysis and design of guyed masts. This was recognized in the industry in the early 1960s, when there was a rapid growth of these structures to accommodate the growth in radio and television broadcasting. Accordingly a Working Group of the IASS (WG4) was set up to examine the behaviour of these structures and to produce Recommendations for their design and analysis. These Recommendations were published in 1981 and they have formed the basis for the production of national and international codes for these structures since that date. The Recommendations contained innovative ideas at that time, including the treatment of relative structural reliability, the use of dynamic response procedures and the statistical treatment of wind actions. Such procedures have been adapted since in many design codes outside the field of towers and masts. This paper reviews the development of design procedures for both towers and masts, the background to the Recommendations and explains how these have been developed and applied in national codes (Australia, Canada, United Kingdom) and latterly in the published Eurocode for Lattice Towers and Masts.
About the freedom of free forms
(Editorial Universitat Politècnica de València, 2010-01-26T13:17:06Z) ANDRES, Oscar A.
This paper deals with the arrival of freedom at the world of structures giving birth a new generation of forms: the free forms. Its purpose is to analyze, to discuss and to comment critically this singular fact as well as their implications on the designers' task. It is more a philosophical than a technical paper. For centuries man has imagined new forms for their structures but he has not been always able to analyze and to build them. Before the arrival of the electronic calculus, the representation and analysis of structural forms could be limited to those ones belonging to the Euclidean Geometry. The computers broke those limitations and they gave wide freedom to the designers to conceive a new generation of forms; these new forms were called "free forms". Nowadays any form imagined can be represented, it can be analyzed and it can be built. Nevertheless not any imagined form can become a structural free form. Perhaps it could be a beautiful sculptural form, but not necessarily a structural one. For being a structural form, the inescapable laws of the mechanics must be satisfied. Moreover a structural free form can become an architectural free form just only when aesthetical, functional, environmental and social requirements, among others, are accomplished. Freedom has widened the horizons of creativity for the designers' task. Simultaneously new responsibilities have come altogether with this freedom. Today free form designers face permanent challenges; designers must be familiar with the menus of new and multiple tools created by the modern technology and they must be trained to make the right use of them. They must handle those wide menus in order to select the most appropriated options to generate, to model and to analyze the new free forms. At the same time they must select the most appropriated new materials and techniques to build these free forms. Finally, designer must be fully conscious of the high impact of their engineering and architectural works on the people and physical environment without forgetting their commitment to the society.
Accurate solution of some I-beam optimization problems
(Editorial Universitat Politècnica de València, 2009-12-11T22:45:14Z) GORDEIEV, Vadym
The problem of proportioning an assembled steel I-beam made of three sheets is wellknown. It is included in nearly every course of study where the analysis of steel components is involved. In the presented case we consider finding the depth of a beam with a predefined modulus of resistance, based on the condition that the cross sectional area should be minimum. Such a depth of the beam is generally called optimum. At the same time, the minimum depth of the beam, which can be found from the stiffness conditions, can be considered in addition to its optimum depth. Such a problem is generally solved by empirical approaches with no strict formulation nor a proper mathematical analysis. The paper poses the problem as that of parametric mathematical programming with inequality constraints which appear as the condition of strength in bending, the condition of strength in shear, and the stiffness condition. Several variations which differ in the functional relationships between the depth of the beam¿s web and its thickness have been analyzed.
Adaptive planar structures
(Editorial Universitat Politècnica de València, 2010-02-24T11:37:32Z) WEILANDT, Agnes
Panes and shells as only in-plane loaded structural elements play an important role in lightweight structures. However their great bearing capacity will be reduced significantly when their homogeneous stress distribution is disturbed. These disturbances can be caused for example by cuttings or constraints. Present research to reduce the disturbances by form optimization of the cuttings or by adding local bracing elements can only respond to particular loading conditions. Adaptive structures are a new innovative alternative for the optimization of panes and shells. With the use of sensors, control units and actuators they can register different external stimuli and adapt to them. This allows an optimal reaction to different loading conditions and so a reduction of the disturbances in the homogenous stress distribution.
Advanced form-finding for cable dome structures
(Editorial Universitat Politècnica de València, 2010-02-24T08:29:31Z) LEE, Jaehong; TRAN, Hoang Chi; LEE, Kihak
A numerical method is presented for form-finding of cable domes. The topology and the types of members are the only information that requires in this form-finding process. Dummy elements are used to transform the cable dome with supports into self-stressed system without supports. The eigenvalue decomposition of the force density matrix and the Singular value decomposition of the equilibrium matrix are performed iteratively to find the feasible sets of nodal coordinates and force densities which satisfy the minimum required rank deficiencies of the force density and equilibrium matrices, respectively. Based on numerical examples it is found that the proposed method is very efficient, robust and versatile in searching self-equilibrium configurations of cable dome structures.
The Almuñecar aquarium textile roof
(Editorial Universitat Politècnica de València, 2010-02-24T08:36:08Z) LLORENS DURAN, Josep Ignasi
The Almuñecar Aquarium is a 3000 m2 underground installation that shows Mediterranean fauna on two levels below the Kuwait Square next to the market and near the City Hall of the andalusian town of Almuñécar (Spain). The Aquarium emerges to the surface by means of its control building, staircase and lift, all arranged around an open courtyard. We designed a textile roof in order to protect this courtyard from direct sunshine and rain. As the only part of the building that shows above is the membrane, it has also been envisaged as an eye catcher in order to attract visitor's attention. Two water ponds reflect the white and lofty membrane set in front of the backdrop of white apartment buildings.
Analysis and experiments for form finding of the SCST structures
(Editorial Universitat Politècnica de València, 2010-02-18T10:46:48Z) DOH, Jeung-Hwan; KIM, Jin-Woo; PARK, Moon-Ho
This paper is focused on the form finding of three kinds of SCST structures that are constructed with bolt type joint by gusset plate, bolt type joint, and ball type (Mero type) joint by means of cable-tensioning. The cable-tensioning method for SCST structure is a innovative, fast, and economical construction method in the special construction site or field condition, the cable-tensioning is performed with the strand in the bottom chords of space structures. In this paper, the unit shape of test models consist of uniform pyramids, from the planar structures on the ground, the space structures are shaped and erected into its final curved space structures by cable-tensioning. The cable-tensioning is applied along the diagonal direction, the circumference line direction, or the middle line direction of the each SCST structures. The feasibility of the proposed cable-tensioning technique and the reliability of the established geometric model were confirmed with finite element analysis and experiments for a small-scale test models. Through the experiments in the three types of SCST structures, within the yield limit of the members, a planar layout can be deformed to desired space shape by means of cable-tensioning. As a results, the proposed cabletensioning technique could be applied the form finding of the various SCST structures, so we can know the behaviour characteristic of the joint for each types in form finding for practical design purposes. For a special site condition of construction field, this cabletensioning technique should be an economic and reasonable construction method compare to conventional construction method including the heavy crane and scaffold.
The analysis of load relieving system using sliding cable element
(Editorial Universitat Politècnica de València, 2009-12-15T12:52:05Z) WU, Y. J.; CHEN, Z. H.
A new structural concept load relieving system is introduced which replaces unaffordable strain by reasonable deformation. A new kind of FEM element cable sliding element is also refer to. Its elementary presentation is given, which has arbitrary number of sliding nodes and satisfies uniform strain assumption. A typical load relieving system model is established applying the sliding cable element and studied under 2 representative load cases. As the results of analysis are reasonable, the correctness and validity of sliding cable element and its application in load relieving system can be proved. Furthermore, the strategy of simulating distributing load by applying concentrated forces on separate nodes of sliding cable element is proved feasible.
Analysis of moisture state of recycled coarse aggregate and its influence on compression strength of the concrete
(Editorial Universitat Politècnica de València, 2009-12-15T13:07:46Z) Pelufo Carbonell, María José; Domingo Cabo, Alberto; Ulloa Mayorga, Vivian Andrea; Vergara Acuña, Needy Nayiv; Dpto. de Ingeniería de la Construcción y de Proyectos de Ingeniería Civil; Escuela Técnica Superior de Ingeniería de Caminos, Canales y Puertos
This article analyzes the impact of the moisture level of recycled coarse aggregate additions to concrete on its compression strength, with the goal of finding a logical development process that can be reproduced at an industrial level and provide acceptable results for concrete production. This study takes into account the reality in the process of the production of concrete; while many authors suggest the use of recycled coarse aggregates in a saturated state to ensure the desired ratio water to cement in the concrete, in reality, the aggregates are introduced unsaturated. The main objective of this study is to observe and analyze the behaviour of recycled coarse aggregate in concrete, so that it is not stigmatized by the extra work involved in its use. The concrete was produced using three states of the recycled coarse aggregates. In the first one, the aggregates were added in their natural state, taking into account the total water in the dosage; in the second one, aggregates were added after being submerged in water for 10 minutes and drained for 10 minutes; and in the last one, the aggregates were added in their natural state, taking into account its absorption when adding the water. In order to evaluate the recycled coarse aggregates¿ resistance to compression at 28 days, four percentages of replacement of the recycled coarse aggregates, 0%, 20%, 50% and 100% were established among the concretes studied. The study finds that to define the resistance of a concrete, the effective ratio of water to cement plays a very important role; basically, the high absorption of recycled aggregates directly affects the quality of the concrete. The results showed that the values of compressive strength increased as the replacement percentage of the recycled coarse aggregates increased when the aggregates were added in their natural state, not considering their absorption in the mixed water. The opposite result was obtained when the aggregates were added in saturated state, reflecting a significant decrease in the resistance of the concrete as the replacement percentage of recycled coarse aggregates increased.
Analysis of Normal Lines for Structural Grids
(Editorial Universitat Politècnica de València, 2010-01-27T13:28:17Z) KAMERLING, Wim M. W.
For free-forms the structural grid affects the design of the envelope as well as the design of the structure. Due to the complex geometry of the surface the directions of the normal lines will vary. The diversity of the directions of the normal lines affects the design of the envelope and structure, especially in case the surface is connected directly, without secondary structure, to the members of the structural frame and the structural members have to be curved and twisted. Comparing several structural grids shows the effect of the grid for the directions of the normal lines and the design of the structural elements.
An analytical model for Tensairity girders
(Editorial Universitat Politècnica de València, 2009-12-14T11:32:56Z) LUCHSINGER, Rolf H.; TEUTSCH, Uwe
An analytical model for the deflection of a symmetric, spindle shaped Tensairity girder under homogenous load is proposed which can be solved analytically. The results are compared to FEM predictions for a specific Tensairity girder. Further simplifications of the analytical solution lead to a simple relation for the deflection of the Tensairity girder, which reveals the importance of the elasticity of the chords relative to the air pressure in the inflated hull. Such simple models are crucial to understand the basic principles of Tensairity and provide the engineer with easy rules to estimate the load-deflection behaviour of this new light weight structure.
The application of folded plate principles on spatial structures with regular, irregular and free-form geometries
(Editorial Universitat Politècnica de València, 2009-12-22T08:21:40Z) TRAUTZ, Martin; HERKRATH, Ralf
The two main folding plate principles of pointed folding plates forming an facet texture and longitudinal folding plates forming the typical fold texture imply different fields of application in architecture and structural engineering. This Paper presents a method of developing the folding plate principles on spatial structures also with irregular and freeform geometries. Hereby algorithms of triangulation, originally applied in finite elements analysis, are used for discretisation and form-finding of the textures of folded plate shells
Application of pushover analysis in estimating seismic demands for large-span spatial structure
(Editorial Universitat Politècnica de València, 2010-02-18T10:45:09Z) ZHANG, Weijin; QIAN, Jiaru
Pushover analysis has been widely adopted in the seismic analysis of low- and medium-rise structures. It needs to be studied whether it is accurate for large-span spatial structure. In this paper, pushover analysis of a large-span spatial structure, Beijing A380 hangar structure at Capital International Airport is introduced. The modal load pattern is adopted to perform pushover analysis for the hangar structure. The pushover analysis results are compared with nonlinear response history analysis results. It is concluded that pushover analysis is accurate enough for large-span spatial structure, provided the modal participating mass ratio is larger than about 0.65.
Application of the tensegrity principles on tensile textile constructions
(Editorial Universitat Politècnica de València, 2009-12-28T13:44:18Z) PEÑA, Diana Maritza; LLORENS, Ignasi; SASTRE, Ramon
This study tries to contribute in a particular way to the application of the tensegrity in architectural spaces, in this case sports spaces through a new proposal that generates an external ring in tensegrity with a central dome, free of any interior support, by formfinding a continuous membrane pattern with discontinuous struts in double layer that find their equilibrium through the tension of the membrane. In the following examples one can observe that traditional tensegrity tendons are replaced by membranes, which is the main contribution of this work that finds geometry and its constructive method of the different prototypes with the help of software like AutoCAD and WinTess (a software development by Ramón Sastre), which verifies the structural equilibrium.
Application of vibration method for estimating tension force of stay cables in 2002 World-cup stadiums in Korea
(Editorial Universitat Politècnica de València, 2010-02-24T10:10:58Z) CHANG, Kug Kwan; CHUN, Young Soo; JIN, Byung Chang
This study is to consider the character of cables in six World-Cup stadiums constructed in 2002 and to inspect problems on measurement natural frequencies interpretation and application of existing theory. Because stay cable structures should be controlled by the tension force of cable under the construction, and managed to maintain geometric balance without loss of the tension force after construction. it is very important to develop the method which is able to measure the tension force easily, quickly and reliably in the field. The result of experiment shows it is possible to determine the tension force with an accuracy of 8% by taking the cable bending stiffness. However, if single mode of vibration is used, the tension force of the real cables could be overestimated, and the estimated tension force with experimental results would not be reliable.
Applications of a "Virtual" Force Density Method
(Editorial Universitat Politècnica de València, 2010-02-09T07:42:02Z) BASSO, Paolo; DEL GROSSO, Andrea E.; PUGNALE, Alberto; SASSONE, Mario
The Force density Method [FDM], since Linkwitz and Schek¿s first development [8] in 1970¿s, has been well known as a powerful tool for analytical form-finding and static analysis of self-stressed structures like tensile membranes and cable networks [12]. Actually force density is always associated to a real stress state of the structure under a field of applied forces that, combined with other boundary conditions (constraints, etc.), allows the shape to evolve and improve). The approach proposed in this paper enables the technique to become more versatile so that it is possible to extend its application to different kinds of problems. In particular, changing the connection matrix and introducing virtual forces, morphogenesis can be related to general spatial frame structures looking at geometrical requirements as form and function irrespective of the applied stress field. As a demonstration of the capabilities of this tool, three different applications on current issues in free-form architecture are tested by means of a commercial NURBS based software and a VB based algorithm. One of these applications concerns the preliminary design of the roof structure of Ponte Parodi project, by UNStudio Amsterdam, a multifunctional building to be located on the waterfront of Genoa, Italy.
Applications of hybrid string structures in large-span architectures
(Editorial Universitat Politècnica de València, 2010-02-17T13:33:51Z) DING, Jie-min; WU, Hong-lei; Zhang, Zheng
Along with rapid progress of large-span architectures in China, hybrid string structures which have excellent load-bearing performances as well as great ability to adapt innovative architectural forms, are being applied extensively in large-span architectures by engineers. In this paper, conceptual design, structural system and arrangement and optimization of hybrid string structures are discussed in several fine project cases, including theme pavilion of World Expo.2010, canopy of Fuzhou south railway station, Quanzhou Gym and Beijing University Gym, which hopes to provide references to similar projects.
Appraisal of two early twentiech century composite masonry-concrete structures: the Civic Theatre in Schio (Italy 1907) and Carraresi's Castle in Padua (Italy, XIII century)
(Editorial Universitat Politècnica de València, 2009-12-18T12:24:49Z) DA PORTO, Francesca; VALLUZZI, Maria Rosa; STIEVANIN, Elena; MODENA, Claudio
In this contribution two examples of buildings constructed using composite masonryconcrete are illustrated: the Civic Theatre in Schio (Vicenza, Italy) and the Carraresi's Castle in Padua (Italy). Their reinforced concrete (R.C.) elements were built at the beginning of the 20th century, a few decades after the invention of reinforced concrete. The theatre, in the original 1907 project, had already been conceived as a composite structure. The castle of Padua, built in the XIII century, has undergone a series of historical transformations, including the introduction of the r.c. elements in the north wing at the beginning of the twentieth century. Both are early examples of the use of the first patented technique for building r.c. structures: the Hennebique system . The Civic Theatre in Schio soon after its construction underwent a decline in its activity, until the complete closure and disuse at the end of the Seventies. The castle of Padua at the beginning of the 19th century, during the French domination, was transformed into a prison. Then, in 1990, the structure ceased to function as a prison and went through about twenty years of disuse which led to the current damaged conditions. The restoration and reuse of both of these structures, thanks to their cultural and architectural value, was proposed and supported by many historians, experts in architecture and fellow citizens. Therefore, both the Municipalities of Schio and Padua are planning to develop projects for their reuse. However, the change in the use and current norms require a series of studies and analyses in order to collect enough information for safety assessment. The comparison between the structure of the theatre and that of the castle is useful in order to gain more knowledge as to the materials and structural behaviour of these early r.c. structures, which nowadays present several problems mainly related to the degradation of the materials and to inadequate choice of structural solutions. In this work, the main results and key observations made during inspections and in situ and laboratory tests are presented. On the basis of collected information, inspections and tests carried out, the level of knowledge achieved could be considered adequate (Confidence Factor of 1,20, according to O.P.C.M. 3431 and EN 1998-3:2005 EC8) for both buildings. Following investigations, the results of the tests were used to check structures according to the original method of calculation (Hennebique system), to the Admissible Stresses method and to the Ultimate and Serviceability Limit State method. The safety assessment, required by changes in the use and by current norms, showed that both structures examined need strengthening repairs. Thus, in general, it is possible to say that most of the historic R.C. buildings need repairs to verify nowadays safety requirements.
Architectural engineering and beyond
(Editorial Universitat Politècnica de València, 2010-02-24T11:41:36Z) TEUFFEL, Patrick
Various design drivers influence the architectural engineering design process, such as architectural criteria or multiple environmental impacts. Most of these conditions are time dependent, which leads to the challenge that the building system should be able to respond to or interact with these circumstances, in order to create high-performance systems. This leads to the overall framework of "adaptive" or "bionic" systems: in natural systems the integration of several disciplines and functions is self-evident. In contrast to traditional technical artefacts the understanding of natural systems makes clear, that the distinction between different disciplines leads not to optimum results - in natural systems, which are optimized over millions of years, the integration and adaptation of different function is selfevident. Understanding these systems is a major scientific interest, since we can learn about their uses as structural or functional devices. Further on highly interesting is the adaption of thermal systems or functions which can influence the building physics of buildings. The framework of this paper is to develop new concepts with a holistic and sustainable approach and this can be achieved by the consequent introduction of adaptable building systems. Buildings and construction industry are one of the main consumers of energy in the world, but these new concepts will lead to environmental friendly, sustainable solutions by reducing the mass and energy demands of our built environment. Apart from reducing the embedded energy by using lightweight systems it is aimed to develop zero emission buildings, e. g. by using smart skins to control heat and light transmission through the building envelope. The objective of this idea is to study these concepts and to develop them further, in order to save our environment. The paper presents examples where the concept of adaptation can improve the performance of building systems at different aspects.

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