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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Effects of member loss on the structural integrity of tensegrity systems
(Editorial Universitat Politècnica de València, 2009-11-19T11:23:15Z) ABEDI, Karim; SHEKASTEHBAND, Behzad
Tensegrity systems are statically and kinematically indeterminate systems. It may be mistakenly believed that this inherent redundancy provides a large measure of safety against collapse. However, a number of members are critical to system integrity, with the loss of any of them likely to produce serious strength reductions. Furthermore, when these members are lost suddenly, their forces are shed into the structure in a dynamic manner, leading to yet more severe damage. This paper presents a numerical investigation into the static and dynamic response of plane tensegrity systems due to the gradual and sudden member loss. According to the results of this study, in some cases, the dynamic effect of member loss caused the occurrence of progressive collapse. It was shown that in several cases, static analysis cannot provide a correct and realistic picture of the behavior of the damaged tensegrity system and would lead to a significant overestimate of the load carrying capacity of the structure. The conclusions drawn from such a study can in turn, lead to the suggestion of some simple guidelines for the design of such systems.
Triangles and Quadrangles in Space
(Editorial Universitat Politècnica de València, 2009-11-25T08:18:32Z) MIURA, Koryo
In some space missions, the highest priority of the structural design is given to the geometry of the surface which has to be packaged and then deployed in space. Large space antennas and large solar cell arrays are such examples. It is interesting to note that basic geometric forms play a major role in conceiving novel concepts of these space structures. In this presentation, the author introduces two concepts of deployable space structures that are symbolized with groups of triangles and quadrangles, respectively.
From large natural draft cooling tower shells to chimneys of solar upwind power plants
(Editorial Universitat Politècnica de València, 2009-11-25T08:23:15Z) KRAETZIG, Wilfried B.; HARTE, Reinhard; MONTAG, Ulrich; WOERMANN, Ralf
Natural draft cooling towers (NDCTs) presently form the world-largest RC shell structures, solar updraft power plants (SUPPs) will do this in future. The paper starts with explanations of the working principles of NDCTs and SUPPs. In industrialized countries with strong legal emphasis on sustainable power production technologies, NDCTs are widely spread, while SUPPs represent future solar power generation concepts in the world¿s tropical areas, using solar irradiation as power plant fuel. Consequently, the paper elaborates on recent German NDCTs, under them the world-highest tower shell. The design of such highefficient RC tower shells will be explained including their critical response characteristics. The paper then changes to future SUPPs, describing the structural components of their solar chimneys, followed by a sketch of some of their critical response characteristics. The aim of this presentation is to draw the readers¿ attention to extremely large shell structures (Mega-shells), present and in future, and to demonstrate their close structural mechanics relationship to each other.
Saving the blue planet (How membrane and spatial structures can preserve our precious water resources
(Editorial Universitat Politècnica de València, 2009-11-25T08:23:41Z) LEVY, Matthys
Water covers 70 % of our planet's surface and is vital to its survival, but water is becoming an increasingly rare resource. The conundrum is that the earth's population continues to expand, but the amount of potable water is becoming severely limited. Aggravated by the effects of global warming, fresh water is evaporating into the atmosphere at faster rates and is cycling back to earth where it is not necessarily needed; a small amount that dissipates into the atmosphere is lost forever. As engineers and designers, we are equipped to create structures that contain water efficiently and help prevent its evaporation. Spatial structures and tensioned membrane structures are ideally suited to this task. This paper explores both the problem of water scarcity and the potential solutions for protecting this most vital of resources.
A conceptual approach to shell buckling with emphasis on reinforced concrete shells
(Editorial Universitat Politècnica de València, 2009-11-25T08:28:42Z) MUNGAN, Ihsan
Author's own experimental and theoretical researches on buckling of shells of revolution are summarized with special emphasis on the conceptual approach behind them. Effect of the biaxial stress states is depicted in form of interaction diagrams. Design formulas based on these concepts and computations carried out for reinforced concrete hyperboloidal cooling tower shells allow the erection of very large and thin cooling towers which meanwhile have reached the 200m limit in height.
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.
Silos and tanks in research and practice: state of the art and current challenges
(Editorial Universitat Politècnica de València, 2009-11-25T08:32:28Z) ROTTER, J. Michael
Silos and tanks are probably the commonest form of large engineering shell structure in service, but their placement on industrial sites and out of the public eye often leads them to be neglected by researchers and the public alike. The high rate of structural failure in these structures is a strong indication of the extensive range of issues that must be understood by the designer and the complexity of their behavior. This paper outlines some of the most critical aspects of the loading, structural behavior and failure modes of silos and tanks, and points in many places towards the need for additional research to permit better regulation of these very varied and complex structures.
Full Scale Experiences with Flow Funnel
(Editorial Universitat Politècnica de València, 2009-11-25T08:32:47Z) KALDENHOFF, Martin
This article describes some experiences with flow funnel in large concrete silos with a large discharge eccentricity. Some in-situ measurements were made (full-size experiments) and the results are described here. As a consequence of the experiments described here, the eccentric discharge funnel flow model of the Eurocode EN 1991-4 has been incorporated into the new DIN 1055 Part 6 standard for pressures on silo walls. Finally some reference calculations are described which give some understanding of the variation of the main parameters in this funnel flow model and show the influence of these parameters on the bending moments developing in concrete silo walls.
Influence of patch-load metal silos with corrugated walls
(Editorial Universitat Politècnica de València, 2009-11-25T09:43:00Z) AYUGA, Francisco; GONZALEZ-MONTELLANO, Carlos; GALLEGO, Eutiquio; FUENTES, Jose Maria; RAMIREZ, Alvaro
Silos are widely used in food industries to store different types of agricultural products. Loads exerted by the stored material on silo walls are critical in the design of the shell structure. Eurocode standard represents these loads by means of symmetrical pressure distributions and unsymmetrical pressure distributions, this latter named patch-load. In this paper, the structural effects of the patch load are investigated. A 3D FEM model has been developed to model cylindrical flat bottom silos made of corrugated steel walls. Firstly, silos were modelled only with the effect of the symmetrical pressure distributions. The structural effects at this stage were compared to those obtained in a second stage, where the patch-load was introduced in the model. The purpose of this research work was to understand the structural effects of the patch-load as described in the Eurocode, as well as validate analytical expressions to determine these effects more easily.
Hurricane failures of tanks for the oil industry
(Editorial Universitat Politècnica de València, 2009-11-25T09:43:25Z) GODOY, Luis A.
This paper presents an overview of recent research aimed at understanding the behavior of aboveground steel tanks under wind loads, carried out by the author and by other researchers in this field. The tanks considered are representative of those constructed for the oil industry, with radius to thickness ratios of the order of 1500, and height to radius ratios less than one. The paper discusses the buckling behavior of isolated tanks, and the buckling of tanks which are part of a group in a tank farm. The behavior of tanks with a fixed roof is shown with reference to failures occurred during the recent hurricanes in the Caribbean and the US Gulf. Finally, advances in modeling techniques are discussed, including computational buckling analysis and reduced stiffness methods.
Masts and Towers
(Editorial Universitat Politècnica de València, 2009-11-25T09:43:45Z) STØTTRUP-ANDERSEN, Ulrik
The analysis and design of masts and towers requires special knowledge and experience, especially when it concerns guyed masts. The special problems related to these structures are underlined by the many collapses during the years. The basis of design for such antenna supporting structures are sometimes many and often mutual contradictory, and the overall structural layout may have a dramatically effect on the loading on the structure. The loads are mainly meteorological from wind and ice and combination of these, and the dynamic nature of the wind has to be taken into account as masts and towers are more or less sensitive to dynamic loads. This paper gives a brief introduction to the problems related to the design, as well as several practical examples are mentioned. The aesthetic elements are becoming more and more important for antenna supporting structures and are also mentioned. The IASS Working Group No. 4 Masts and Towers is the only international forum for the exchange of knowledge and experience within the field of masts and towers, and this Working group is briefly mentioned in the paper.
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.
Felix Candela's Legacy
(Editorial Universitat Politècnica de València, 2009-11-25T12:24:35Z) GARLOCK, Maria E. Moreyra; BILLINGTON, David P.
Félix Candela was a world-renowned engineer, builder, and structural artist of thin-shell concrete-roof structures in the mid 20th century. Although a native of Spain, his exile to Mexico at the end of the Spanish Civil War provided the New World locale in which he created all his major works. Through an examination of his self-proclaimed favorite structures (Miraculous Medal Church, Restaurant at Xochimilco, the Bacardi Rum factory, and the Chapel at Cuernavaca), plus his first hyperbolic paraboloid shell (Cosmic Rays Laboratory) and his umbrella shells that comprised the bulk of his work, we give insight into Candela¿s ideas and genius. In this way the legacy of such structural artists provides an essential part of engineering education and of the means for greatly improving the practice of structural design.
Computer analysis and design of concrete shells roofs
(Editorial Universitat Politècnica de València, 2009-11-25T12:24:59Z) SAMARTIN, Avelino; ABEL, John F.
This paper is a preliminary version of Chapter 3 of a State-of-the-Art Report by the IASS Working Group 5: Concrete Shell Roofs. The intention of this chapter is to set forth for those who intend to design concrete shell roofs information and advice about the selection, verification and utilization of commercial computer tools for analysis and design tasks. The computer analysis and design steps for a concrete shell roof are described. Advice follows on the aspects to be considered in the application of commercial finite element (FE) computer programs to concrete shell analysis, starting with recommendations on how novices can gain confidence and competence in the use of software. To establish vocabulary and provide background references, brief surveys are presented of, first, element types and formulations for shells and, second, challenges presented by advanced analyses of shells. The final section of the chapter indicates what capabilities to seek in selecting commercial FE software for the analysis and design of concrete shell roofs. Brief concluding remarks summarize advice regarding judicious use of computer analysis in design practice.
Construction methods and quality control for concrete shell roofs
(Editorial Universitat Politècnica de València, 2009-11-25T12:26:10Z) MIHAILESCU, Mircea; SUNDARAM, R.
Concrete shells are moldable to any shape and can be made aesthetically beautiful. This paper discusses the suitability of various methods of concrete shell roof construction, necessary precautions and quality guidelines. Good construction practice for concrete shell roofs is also highlighted.
Recent developments of cooling tower design
(Editorial Universitat Politècnica de València, 2009-11-25T14:13:17Z) HARTE, Reinhard; WITTEK, Udo
Natural draught cooling towers (NDCT) are the characterizing landmarks of power stations. They contribute both to an efficient energy output and to a careful balance with our environment. In the last decade the building of new power plants stagnated all over the world. Nowadays the German power suppliers have started an extensive renewal program, where old units will be replaced by new ones, which will be much cleaner and more efficient. Besides innovative boiler techniques the sustainable and reliable design and construction of cooling towers are focussed both by research and industry. The goal is to determine and implement strategies that insure an adequate level of safety and durability at the lowest possible life-cycle cost. Further, the implementation of new European and German codes for the design and proof of reinforced concrete structures required a revision of the VGB Guideline ¿Structural Design of Cooling Towers¿ (BTR ¿ Bautechnik bei Kühltürmen), which since many years served as the theoretical and practical tool to design and build cooling towers all over the world. In 2005, a revised version has been elaborated, where the partial safety concepts acc. EC 1 and EC 2 and the respective German codes have been considered, and where the application of nonlinear design tools and the requirements with respect to sustainable durability have been improved (VGB 2005 [11]). The paper presents the main features of this new VGB-guideline. Further it gives an overview over running and planned cooling tower projects in Germany, with special focus on technical innovations. Finally it summarizes some results of actual research projects, exploring the effects of progressive damaging and high-performance concrete on design, stability and durability of cooling tower shells.
Monitoring of full scale tensegrity skeletons under temperature change
(Editorial Universitat Politècnica de València, 2009-11-26T14:07:37Z) KAWAGUCHI, Ken'ichi; OHYA, Shunji
Strain change in the members of full-scale tensegrity skeletons has been monitored for eight years. The one-day data of one of the tensegrity frame on the hottest and the coldest day in the record are reported and discussed.
Benefits of using haptic devices in textile architecture
(Editorial Universitat Politècnica de València, 2009-11-26T14:07:46Z) SANCHEZ, Javier; SAVALL, Joan
The aim of this paper is to introduce the use of haptic technologies in the design of tensile membranes structures. In the last years, haptic devices have become very popular and have been used in many applied fields as product design, medicine, architecture or art between others. By means of haptic devices, the user can interact with virtual objects via the sense of touch. The benefits of using haptics in the design of tensile membrane structures are explained in this paper. Using this technology, the designer can easily define complex equilibrium shapes and try different design alternatives in a very short time. An application has been developed to test the benefits of using haptics in textile architecture.
Living with the sun: using canopy structures in Mexico and the UK
(Editorial Universitat Politècnica de València, 2009-11-26T14:07:58Z) MUNDO, Julia; RODRIGUEZ, Salvador; MENDOZA, Marisela; BAKER, Richard
"Sometime too hot the eye of heaven shines"- especially in Mexico - "and often is his gold complexion dimmed" - especially in the UK. Meeting these challenges becomes ever more urgent as we burn fossil fuels into which the sun poured his energy long ago, thereby changing our climate - and meanwhile our population expands (Shakespeare [1]). To explore how fabric membranes may help to meet these very different challenges, two tensile membrane structures have been studied, one in Mexico and one in the UK, with their very different temperatures, humidity and, above all, solar radiation. This study analyses these two different architectural approaches in two different climates from the users' point of view, especially their perceptions of thermal and luminous comfort during winter and spring seasons. The research follows a post-occupancy evaluation methodology designing and distributing a questionnaire for visitors and employees. The first membrane structure is at a retail space, Palmas Plaza, in Puebla, Mexico (19º N). It features a six-coned canopy structure covering 6000 m2, houses restaurants as well as shops. The fabric membrane structure was designed and built by SM Ingeniería y Diseño in 2004-05. The second membrane structure is at a retail space in Rotherham, UK (53º N). A 900 year old market place whose existing building dates back to the 1750¿s, posed the challenge of installing a roof lay in creating minimal intrusion and impact on the existing structure. As a result, the roof was designed to be supported on six free standing masts, entirely independent of the existing buildings. The canopy structure was designed by Architen Landrell [2]. Both structures are used all year round: their environmental performance at different seasons is thus important to the users, and affects their perceptions. Hence, this study will, in the future, explore users¿ environmental perceptions of the case study buildings during Summer time. Galileo [3] said that the sun, with all those planets depending on it, still finds time to ripen a bunch of grapes. Inspired by this happy thought, we have also looked at the forwardlooking Alpine House in Kew Gardens designed by Wilkinson Eyre [4]. Here the need is for movable membranes that can provide sun and shade as the seasons, conditions and the plants' needs vary. It was found from the users¿ perception of Palmas Plaza and Rotherham market that the membrane structures perform well in terms of luminous comfort and ventilation but not so well for thermal comfort, aesthetics or functionality. The Alpine House seems to perform well in all environmental factors and aesthetics of the movable membranes (Table 1). The potential of canopy structures to generate green energy through the exposure to solar radiation is also discussed: new materials and technologies allow harnessing energy from the available solar exposed surface. It was found that they can generate up to 534 MWh/yr in Mexico and 156 MWh/yr in the UK.
A Deployable Mast for Adaptable Textile Architecture
(Editorial Universitat Politècnica de València, 2009-11-26T14:08:12Z) DE TEMMERMAN, Niels; MOLLAERT, Marijke; DE LAET, Lars; VAN MELE, Tom; GULDENTOPS, Laurent; HENROTAY, Caroline; DEBACKER, Wim; PADUART, Anne; HENDRICKX, Hendrik; DE WILDE, Patrick
Proposed here is a concept for a deployable mast with angulated scissor units, for use in adaptable temporary architectural constructions. The adaptable structure serves as a tower or truss-like mast for a temporary tensile surface structure and doubles up as an active element during the erection process. The mast consists of scissor-like elements (SLE¿s) which are an effective way of introducing a single D.O.F.(degree of freedom) mechanism into a structure, providing it with the necessary kinematic properties for transforming from a compact state to a larger, expanded state. The scissor units used here are not comprised of straight bars, but rather consist of angulated elements, i.e. bars having a kink angle. Although primarily intended for radially deployable closed loop structures, it is shown in this paper that angulated elements can also prove valuable for use in a linear threedimensional scissor geometry.

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