Journal of the International Association for Shell and Spatial Structures

Published by International Association for Shell and Spatial Structures
Online ISSN: 1996-9015
Publications
Article
The optimization problem related to the tessellation of free-form grid shells is presented in this paper. This kind of structure is generally composed of a supporting grid that defines the geometry of a large number of cladding elements that are always different from each other. From the construction point of view this means that each single piece needs to be designed and produced “ad hoc”, then marked and positioned with the aid of an assembling table. In order to reduce the heterogeneity of grid shell elements, several optimization strategies, referring both to evolutionary and gradient-based techniques, have been tested and compared. All the free-form geometries are defined and handled with a commercial NURBS based software, while the development of all the optimization procedures has been made thanks to the VB based programming language implemented inside the NURBS based software. Due to the smoothness of the solution domain of this specific problem, gradient based procedures seem to be the most efficient for the rapid convergence to the optimal solution. Finally a multiobjective procedure, that involves static analysis combined with the discussed geometrical optimization, is proposed in view of future developments.
 
Two-axes tracker. Conceptual design 
b: Conceptual design. Rotation Axes 
Plan Layout. 
Conceptual design. Scale model. 
Prototype. General view. 
Article
The population growth and development in underdeveloped countries has led to a rise in the demand for energy and the fact that conventional energy sources cause damage to the environment means that the sustainable future must be based on alternative energy sources. This paper describes an application of movable structures for alternative energy sources. We present the design of a movable structure-mechanism for an innovative two-axes solar tracker with a ratio between generated and consumed energy which is less than half the usual one for two-axes trackers. The device has minimum height (minimum environmental impact, easy assembly) and is strong and reliable.
 
Article
Sandwich shells have recently emerged as aesthetically pleasing, efficient and economical structural systems, with a number of applications. They combine the advantages of sandwich layer technology together with those of shell action. With different materials and thicknesses used in the sandwich layers, their performance characteristics largely remain un-quantified and there are no guidelines at present for their design. This research paper provides verification, through finite element modeling and testing, for the application of this technology to dome styled dwellings with research currently being conducted into the further application to roofing and floor structures.
 
Article
p. 560-568 A new method of computational morphogenesis for the shell structures with free curved surface is proposed, where not only the shape of shell surface but also the topology of the curved surface can be obtained at the same time. For the topology optimization, the optimization process for the shell thickness is used, where the topology of the curved surface with a multi-connecting surface is dealt with as a limit in which the shell thickness vanishes. For mathematical expression for the shape of the shells, NURBS (Non Uniform Rational B-Spline) is used, by which the number of unknowns can be effectively controlled while the high degree of freedom for the expression of the shape of shell surface as well as the shell thickness are kept. This paper shows the fundamental formulation of the proposed method for the optimization problem for both the shape and the topology of the free-form shell, followed by numerical examples in which the effectiveness of the proposed scheme is investigated through the application to several existing shell structures.
 
Article
The efficient and lightweight structural concept Tensairity can be used for a variety of applications, ranging from large span structures to temporary constructions. Tensairity structures provide features few conventional structures have, such as a fast assembling/dismantling, collapsibility, and a compact storage and transport volume. These are all aspects ideal for mobile and temporary applications. However, this structural concept would be even more appropriate for these kinds of structures if it would be capable to be folded or rolled together without having to disassemble anything, which a basic Tensairity girder is not able to. This paper presents the research of deployable Tensairity structures. Various foldable alternatives for the continuous compression element in a standard Tensairity beam are investigated experimentally. Several proposals for a flexible compression element are evaluated and discussed. The influence on a promising mechanism, the foldable truss, of different parameters such as the amount of hinges and the presence of pretensioned cables, is also studied and discussed. Finally, all these results are summarized and they will then provide the basis for further research for a proposal of an optimised deployment mechanism for the deployable Tensairity structure.
 
A quadrilateral mesh origami.
A perturbation within the solution space. Each form is rigid-foldable.
Freeform Miura-ori with a rigid motion.
Rigid foldable models with trivial symmetry. (a)MARS (b)Single-curved Miura- ori.  
Article
p. 2287-2294 In general, a quadrilateral mesh surface does not enable a continuous rigid motion because an overconstrained system, in which the number of constraints around degree-4 vertices (three for each vertex) exceeds the number of variables (the number of hinges), is constructed. However, it is known that the developable double corrugation surface, called Miura-ori, produces a rigid deployment mechanism. The rigid-foldability of Miura-ori is due to the singularity in its pattern, where a single vertex is repeated. We generalize the geometric condition for enabling rigid motion in general quadrilateral mesh origami without the trivial repeating symmetry. To ensure the existence of a finite motion, we derive the identity of functions from the formula for degree-4 single-vertex origami. This yields a variety of unexplored generalized shapes of quadrilateral mesh origami that preserve finite rigid-foldability in addition to developability and flat-foldability.
 
Seismic hazard map of Iran (GSHAP [7])  
Article
This study deals with a new application of shell structures called modular shell system in seismic areas. This structure consists of an assemblage of tubular and cupola units. These structures are built using reinforced concrete and have been proposed for reconstruction after the Bam earthquake. A complete three-dimensional modal spectral analysis, including both horizontal and vertical ground acceleration components, with all probable load cases, is carried out. The results show that this structural concept behaves well under seismic loading. Nevertheless, more attention should be given for opening frame regions. Due to the profound and efficient structural performance of shell concept, the shell system is suggested as a housing system for areas where the local site effect increases the high seismic risk.
 
Article
Torroja excelled as a designer, as a docent, as a code-maker and as a founder of technical associations. Nothing was conceded to improvisation. Every outcome of his thought was the mature fruit of deep reflections; of precise knowledge of the problem's formulation and its boundary conditions. Moreover, he did not stop thinking till he found not only one, but different possible alternatives.
 
Article
MycoCreate 2.0 is a spatial structure with load-bearing components made of mycelium-based composites, built for the 2022 Biomaterials Building Exposition at the University of Virginia, and has been initially conceptualized for the 2021 IASS Innovative Lightweight Structures Competition. Mycelium-based composites are lightweight, renewable, and biodegradable biomaterials obtained from mycelium, the root systems of fungi. There is a growing interest in mycelium-based materials from the architecture community, mainly due to their sustainable features. With MycoCreate 2.0, we employed a computational form-finding strategy for funicular, component-based structures fabricated with mycelium-based materials and an affordable and sustainable fabrication strategy to minimize waste. In addition, we tapped into the structural aspects of mycelium-based composites, their lightness, and biodegradability while easing the breathing and compaction of the material within the formworks.
 
Article
Carlos Lázaro presented a report on the lASS technical activities at the 2011-2012 annual event. The lASS policy on Technical Activities was approved by the Executive Council in 2008. The Executive Council agreed for a three-year extension of this policy in the meeting that took place at the 2011 Symposium in London, extending it from 2012-2014. The Technical Activities Committee Session was motivated by several objectives. Some of these objectives were to improve the knowledge of the Association by the Symposium delegates, to present the lASS website and Working Group (WG) web pages, and to identify the Organized Sessions for delegates who could be interested to attend one or more of them. Experts who were interested by the activities of a WG were included as its members to participate in such activities.
 
Article
This paper proposes a new deployable structure for huge flat constructs such as a Solar Power Satellite (SPS). The SPS, which was proposed by Dr. Peter Glaser in 1968, is a working concept to construct huge solar cell panels in space, the scale of which ranges from several hundred meters to kilometers. The present study focuses on some problems related to transportation and construction of such structures and proposes a new method to fold and deploy them two-dimensionally. We assume that the plane is divided into some small square panels, and propose a new method to lay them one on top of one another two-dimensionally, with masts made of a scissors mechanism, tilted rotational axis, and springs. The tilted rotational axis is originally used to rotate a panel two-dimensionally in a local coordinate system, and to stretch a spring for stabilization of an unstable scissors mechanism. The first half of this paper presents a numerical analysis of its stable structure. The second half shows a three-dimensional simulation of its rigid body motion as an unstable structure without springs, where the thickness of panels and size of joints are taken into consideration.
 
Article
This paper focuses on the use of graphic statics in both the two and three-dimensional layout of structures, and in the purely geometric panelization of architectural surfaces. The paper will present an in-house computer program for graphic statics including an untangling algorithm, a topology optimizer based on the Newton method with constraints and discrete step as well as an optimization procedure based on virtual work. In the second section, we show how graphic statics can be generalized to 3D to enable form-finding of 3D funicular structures. In contrast to other form-finding techniques like the force density method, this method is straightforward to use in the design of structures that have both compression and tension forces. We demonstrate the utility of this approach via examples of form-finding of a bridge with a tensioned curved deck supported by a spatially curved compression arch. Finally, we will show how graphic statics can be used in a purely geometric context to lay out flat panels on architectural surfaces of arbitrary topological complexity. Since graphic statics relates the equilibrium of forces in a 2D truss structure to the orthogonal projection of a 3D plane-faced polyhedron (the discrete Airy function), it is possible to use 2D equilibrium to define and control 3D plane-faced architectural surfaces. This approach provides an intuitive method for engineers, normally more familiar with equilibrium than pure geometry, to understand and rationalize architectural surfaces. Using this approach, we show how graphic statics can be used to derive, explore, and reason about architectural planar panelizations. Unlike variational approaches to surface planarization, it is straightforward to handle a surface of any topology; pentagons, octagons etc. are treated just as easily as quads and triangles. We also believe this approach allows clearer reasoning about the limitations and design degrees-of-freedom of different panelization strategies. Copyright © 2018 by C. Hartz, A. Mazurek, M. Miki, T. Zegard, T. Mitchell and W. F. Baker.
 
Article
This paper presents a study on the mechanical behaviour of thin membranes modelling the common 32-panel soccer balls. Most soccer balls are fabricated of synthetic flat panels subject to an internal pressure. Unlike most tensile structures such as tents, balls form closed surfaces, which are expected to comply strict conditions, most importantly regarding geometry. In this paper we perform a parametric study on a series of ball configurations, including a few commercially available ball types. The roundness and the stress distribution are numerically evaluated and compared in terms of the model parameters and the pressure.
 
Article
Due to increase of requirements on accuracy of structural analyses, practically applicable computational tools for reliable determination of the real structural performance of bridges are needed. A method is proposed for the true full 3D analysis which can be applied to achieve the real spatial behaviour of concrete bridge structures taking into account rheological phenomena and changes of structural systems. Particularly, the effects of shear lag, shear performance of webs of box girders, warping torsion, warping of cross-sections, distortional effects, state of stresses in the singular regions, the real prestress loss, etc., can be correctly determined. The method combines conventional approaches (based on the elementary beam-type assumptions) for calculating the time development of the internal forces due to rheological phenomena and changes in the structural system during construction and routine commercial FEM software intended for calculating spatial shell structures. The method is capable to give the true 3D prediction of structure behaviour by using only commercially available software. The primary advantage of the proposed method is its ease of application which allows the true 3D performance to be determined from simple calculations. The method offers the designers of concrete bridge girders an ideal design tool. The correct 3D simulation can lead to more efficient and economical designs.
 
Article
Evolutionary Structural Optimization (ESO) method is one of the powerful and promising techniques for pursuing the optimal structural form. Although it is easy to carry out the calculation of ESO, there have been remained some weak points in its evolutionary process, by which inefficiency of calculation is caused or unreasonable solutions are generated. The authors have already proposed a new method through the usage of the contour lines, which is named Extended ESO method, in order to remove such defects of the original ESO as well as to enable the structures to not only be scraped off but also grow up toward the final optimal structures. In this paper, extension for 3-dimensional structures of the Extended ESO method is proposed and the effectiveness of the proposed scheme is shown through some numerical examples as well as the application to the actual structural design project.
 
Article
Whizdom 101 is a new high-end fully integrated and digital mixed-use development comprising both commercial spaces and residential towers. The centre of the commercial space is covered by the big roof, a 50m span freeform steel roof covered with ETFE, forming an aerated and relaxing space for the pedestrians. Several shapes and structural systems have been explored at early stage of the project to best integrate the roof in its environment. The resulting shape is a quiet and smooth surface providing shade and natural ventilation to the spaces below. Although complex, the geometry was generated to fully take into account the buildability - all the steel members were translated in a language of plates and single radii, comprehensible for the fabricator. Initially made of conical surfaces, the edge beams sections geometry was rationalized through parametric modelling in order to be only made of cylindrical surfaces which are developable and therefore easy to fabricate.
 
Article
The "Modern Architecture's Thin Shells Adventure" started in the twenties, when the reinforced concrete was still developing and a new "air" - Modernity - was born. At that time, and during the following decades, it was very difficult to design thin shells because computers, as we know nowadays, did not exist and the existing tools to calculate such shells were very complicated. Also it was difficult to guarantee the right structural behaviour of this new structural form, being slender, light and big in size. This was the reason why in the 1930's Eduardo Torroja developed the reduced model test to check the structural behaviour of this new structural form. In 1941 the Spanish engineer Ildefonso Sánchez del Río presented, at the Eduardo Torroja Institute, his own and innovative system design for shell structures. During three decades he built a lot of thin shells using his system design, like the Oviedo Sport Palace (100m span) and the Pola de Siero Market, which were published in the covers of the IASS bulletin.
 
Article
If designers ask for the dos and don 'ts concerning the geometry of membranes, it is hard to give a clear and simple answer. This paper gives a complete overview of the possibilities for the manipulation of membranes. It is presented in a matrix with 84 icons representing the 84 ways to manipulate a membrane. The overview aims to be a helpful instrument for designers and researchers working with membranes.
 
A finite element model of a four-layer thinwalled origami tube with the symmetric Kresling pattern 3.2. Model Settings A total of 44 finite element models have been established for the axial crush testing and analysis of the origami tubes with the Kresling pattern, as listed in Table 1. The mass of each tube is also listed in Table 1. The model number is nD(F)Kβ. Brass is mainly used as the structural material, where n
Material parameters for five different materials
Article
Origami structures have been widely used in various engineering fields due to their desirable properties such as geometric transformability and high specific energy absorption. Based on the Kresling origami pattern, this study proposes a type of thin-walled origami tube the structural configuration of which is found by a mixed-integer linear programming model. Using finite element analysis, a reasonable configuration of a thin-walled tube with the Kresling pattern is firstly analyzed. Then, the influences of different material properties, the rotation angle of the upper and lower sections of the tube unit, and cross-sectional shapes on the energy absorption behavior of the thin-walled tubes under axial compression are evaluated. The results show that the symmetric thin-walled tube with the Kresling pattern is a reasonable choice for energy absorption purposes. Compared with thin-walled prismatic tubes, the thin-walled tube with the Kresling pattern substantially reduces the initial peak force and the average crushing force, without significantly reducing its energy absorption capacity; moreover, it enters the plastic energy dissipation stage ahead of time, giving it a superior energy absorption performance. Besides, the material properties, rotation angle, and cross-sectional shape have considerable influences on its energy absorption performance. The results provide a basis for the application of the Kresling origami pattern in the design of thin-walled energy-absorbingstructures.
 
Article
Overall objective of this research is to evaluate the importance of geometric nonlinearity in the structural behaviour and design of shallow truss roofs, depending on their geometric configuration and on their material as well as cross-sectional properties, and eventually to propose simple analytical criteria for assessing whether linear analysis can be safely adopted for design. For that purpose, the simple von Mises truss model is analytically and numerically investigated, with emphasis on the interaction between geometric nonlinearity at the system level and buckling, material nonlinearity and imperfections at the member level. The obtained results are compared to the criterion proposed in Eurocode 3 for adopting first order analysis for the design of steel structures. Interesting findings are reported that can then be extended to more complex reticulated shells. Copyright © 2016 by Maria A. Livanou and Charis J. Gantes. Published by the International Association for Shell and Spatial Structures (IASS) with permission.
 
Article
Location of Project: Barcelona, Spain Structural Type:thin shell roofProject Scale:1.9 m by 3.55 m in planArchitect:Lisa Ramsburg and Albert ChaoStructural Engineer:Edward M. Segal and Powell DraperConstruction year:2019
 
Article
The purpose of this paper is to present a complete design study of foldable and unfoldable curved tensegrity systems with all the involved steps: generation of the curved tensegrity truss, implementation of finite mechanisms, structural analysis and folding/unfolding. Three criteria are required to introduce the finite mechanisms and self stress saving throughout the folding procedure. The new tensegrity configurations which meet these criteria are classified and illustrated with respect to three parameters: direction of truss beams, surface's mean curvatures and direction of articulation axes. Several configurations are then presented.
 
Article
The paper discusses the construction of the world's first full-scale prototype of an adaptive shell structure. The 10m × 10m double-curved structure, consisting of a multi-layer wood laminate, has three freely positionable supports. High-speed, real-time positioning of the supports allows for the manipulation of stress fields within the shell as well as of vibrations and deformations of the structure. The paper focuses on the potentials of adaptivity for shell structures and the construction process of the prototype.
 
Article
This research outlines a new computational workflow for the design and optimization of patterned, perforated surface structures. Well-designed surface structures can be highly efficient on their own, but their potential for structural efficiency can be notably improved by deliberately introducing specific aperture patterns. Patterned surfaces can also be used to produce more stimulating architectural environments, and even those of increasing complexity can be realized thanks to recent developments in digital fabrication. With this said, designers currently lack a streamlined and rigorous approach for the exploration of patterned surface structures. This research aims to address this issue by advancing a recent work that employs NURBS-based isogeometric analysis to integrate structural analysis into an accessible CAD modeling platform. Specifically, this paper proposes an adaptive pattern optimization framework formulated to save designers appreciable computational time. Not only does this framework offer a way to quickly visualize various design solutions, but it also provides the designer an important opportunity for design interaction and control over design evolution, in turn lending itself as a versatile tool for the exploration and conceptual design of patterned surface structures.
 
System force distribution and peripheral telescopic bars' application cases
Digital model erection
Assemblage of small-scale physical model
Physical model erection
Article
Adaptive structural systems possess the ability of geometrical and mechanical adjustment with regard to changing functional, loading, or environmental conditions. In particular, gridshells following bending-active principles in their deformation behavior, require a comprehensive approach in dealing with aspects of form-finding and adaptive structural behavior. The respective framework provides systems of multi-curvature configurations with transformability capabilities that are implemented through a step-by-step process of an initially non-deformed planar grid. In the current paper an adaptive bending-active plate gridshell is proposed. This is a proposal of a structural concept and not of a specific structural/architectural solution. It consists of an array of paired elastic member stripes, which combined with interconnecting telescopic bars and cables of variable length connecting the supports, operate the necessary deformation in providing the system’s planar expansion and erection. The topology of the structure and its configurability are initially digitally investigated. Twelve different cases have been developed, based on control parameters of the supports’ displacement and the telescopic tubes’ length modification. A particular system configuration has been realized in a small-scale model, and further investigated following a sequential nonlinear static Finite-Element Analysis (FEA), in its form-finding and load-deformation behavior. Copyright © 2018 by the International Association for Shell and Spatial Structures (IASS).
 
Article
This paper presents recent advances in the field of multilayer textile cladding systems with a focus on the latest findings. Primary topics are the special characteristics of textile materials in building envelopes in relation to thermal insulation, vapour issues and changing weather conditions as well as the acoustic evaluation of such ultralight systems, and the ambitious demands of acoustic insulation and spatial acoustics. The results are completed with evaluations to the performance for fire protection and natural lighting.
 
Article
The benefit of an increase of the stability limit of a structure in consequence of a modification of the original design may largely be lost through deterioration of the postbuckling behavior. Therefore, it may be useful to concentrate on design changes that result in a significant improvement of the postbuckling behavior without decrease of the stability limit. It is shown that the possibility of converting imperfection-sensitive structures into imperfection-insensitive ones by adding tensile members is not restricted to academic examples such as the von Mises truss. An arch bridge serves as the demonstration object. The reason for disregarding the option of adding compressive members to the original structure is to exclude the possibility of buckling of these members.
 
Article
Theoretical studies are introduced on static stability, dynamic stability, and dynamic failure mechanisms of reticulated shells; and studies on wind-induced response analysis of flexible tension structures, including the consideration of the possible aeroelastic effects, are described.
 
Article
This paper presents practical aspects and recent advances in computational methods for the design of membrane structures. Form finding and cutting pattern generation as crucial steps in the design process will be discussed. The updated reference strategy as form finding methodology will be developed from a rigorous continuum mechanical formulation. The method can be applied to any finite element discretization of cable and membrane structures subjected to prestress or other external loading. Cutting patterns of textile membrane structures are generated by the inverse engineering method. It is based on an optimization approach, which is also embedded in a full continuum mechanical description. Based on the description of the specific methods for form finding and cutting pattern generation, actual developments for both methods will be shown in detail. In case of the inverse engineering method, the control of equal edge length for associated patterns or the patterning of highly curved structures are examples for important and practically relevant enhancements.
 
Article
The use of inflatable wings for unmanned aerial vehicles over their fixed-winged counterparts has many advantages. However, there are difficulties associated with predicting the profile of the inflatable wing, which makes achieving a desirable aerofoil profile non-trivial. This research aimed to formulate a design methodology which would determine the uninflated geometry for an inflatable aerofoil profile, accurately fitting that of a target or prescribed profile. The aspects omitted from the scope of this work includes the aerodynamic performance and stiffness of the inflated aerofoils. The resulting uninflated geometry is suitable to construct a physical model. The methodology proposed incorporates numerical shape optimisation on finite element models. A series of structured numerical experiments determine robusticity of the established methodology by altering the thickness of the target aerofoil profile and increasing its complexity. For each case, the methodology successfully satisfied its aim, producing accurate fits between the inflated numerical model and the target aerofoil profile. When validated, the inflated shape of the numerical model proved to predict that of its corresponding physical model accurately for both simple and more complex geometries.
 
Article
Shells, though potentially efficient structural systems, are difficult to build because of their complex shapes. The paper presents a new design and manufacturing process for wood-sandwich roof shells. These are complexly shaped multifunctional construction elements that are manufactured off-site. The proposed manufacturing process treats wood as a modern composite material. Thin wood strips and foams combine into structural sandwich panels that can then be joined into a roof shell. The geometrically complex panels are generated by a combination of subtractive Computer-Numerically-Controlled machining processes and manual lamination. Infrastructure elements can be embedded into the sandwich build-up in order to enhance the functionality of the roof as a building envelope. Numerical tools are proposed that allow the determination of manufacturing-related parameters in the digital design environment These inform the architectural and structural design in the early design phases. The new manufacturing process for wood/foam sandwich shells is verified through the design and manufacturing of prototypes. Design guidelines are presented as the practical basis for architects and engineers to incorporate new types of roof shells into architectural projects.
 
Article
The paper presents a complete study of the work done by Pier Luigi Nervi for the design and construction of a series of concrete hangars between 1935 and 1940. This research is enclosed in the framework of the exhibition entitled "Pier Luigi Nervi, il modello come strumento di progetto e costruzione" that gathers researches from Università degli Studi di Bologna, Università di Roma Tor Vergata and Politecnico di Milano. The exhibition was used as a starting point for a general discussion about the meaning of the logical passage that leads engineers and architects from physical scaled models to numerical structural models. The Politecnico di Milano contributed to re-writing the first experiences of Pier Luigi Nervi and Arturo Danusso in the structural modeling. Scaled models, nowadays substituted by finite element methods, were widely used in the past, for the understanding of the structural behavior of complex structures. Unfortunately, many of these masterpieces have been destroyed during the years (as happened to the two original models tested by Pier Luigi Nervi and reproduced for the exhibition). In the last part of the paper, based on numerical results, the structural behavior of these hangars is deeply discussed, underlining all the principal strengths and weaknesses of these complex structures.
 
Article
This paper introduces the Swivel Diaphragm: an innovative type of retractable ring structure constituted by straight and angulated elements. Compared to other similar mechanisms for example, Retractable Plates or Deployable Reciprocal Frames, the Swivel Diaphragm can offer the additional advantages of pure rotational motion around fixed external supports, simplicity of components and the possibility of different designs that employ the same number and type of elements. In addition, this paper evaluates the potential of deployable grids using modules of the Swivel Diaphragm. Key words: Retractable Plates, Foldable Structures
 
Article
Seismic response of lattice shell roofs with substructures is complicated, because these roofs have large numbers of parallel vibration modes, and their amplitude changes drastically along the rise/span ratios and the stiffness ratios between domes and substructures. Under limited condition, however, their response characteristics are considered to become relatively simple. In this paper, simple response evaluation method of domes and cylindrical shell roofs with substructures are proposed using response amplification factors approach. Firstly, the response characteristics of raised roofs with various depth/span ratios and substructure stiffness are numerically discussed with simple arch model. Then response of lattice domes and cylindrical shell roofs are investigated, and simple acceleration response evaluation method using response amplification factors is delivered. The proposed method can be used as equivalent static loads for design, and compared with precise analyses with CQC method.
 
Article
Finding efficient forms and section profiles for a deploying structure is a challenging design problem traditionally approached through trial and error. Alternatively, heuristic search algorithms can be used to pursue an optimized geometry and design the section profiles. This paper proposes a methodology for the design and optimization of a deploying structure for minimum self-weight using a Simulated Annealing algorithm. The design variables are 1) geometric variables that define the system throughout deployment and 2) the section profiles of each element. The constraints include 1) geometric requirements that ensure proper deployment and 2) section profile specifications defined by design code. This methodology will be demonstrated for a deploying pantograph, but could be employed for the design of other deployable structures, including retractable roofs, movable bridges, and expandable shelters.
 
Article
Moore-Penrose generalized inverse method is applied to kinematic analysis of a large space antenna composed of a reflective mesh, a cable network and a deployable toroidal truss that also acts as the supporting structure. Dynamic equations of deployable space truss structures are formulated using dependent Cartesian coordinates of idealized truss joints as variables. By integrating the constraint equations into the dynamic equations, a group of revised dynamic equations with no coefficients is formulated. The number of these equations is the same as the number of the structure's unconstrained degrees of freedom. The constraint violations of numerical solution are corrected using a new active correction method. To a deployable toroidal truss structure for large mesh antenna, a new mathematic algorithm is developed to formulate the constraint equations and the relevant Jacobian matrices. A numerical example is presented to demonstrate the effectiveness of the analytical process. It is concluded that dynamics simulation can be an effective design tool to analytically verify deployment of large mesh reflectors.
 
Article
Digital television (DTV) antennas are often mounted on tall guyed masts; these are relatively flexible structures and will deflect and rotate under wind loading. Rotation of a DTV antenna will alter the population coverage and time availability of the broadcast signal. This paper presents a methodology for the assessment of the effect of guyed mast rotations under along-wind loading on the performance of broadcast antennas. The method is illustrated by application to Winter Hill Mast (north of Manchester) which, at the time of the study, has the greatest population coverage of any TV broadcast structure in the Arqiva portfolio.
 
Article
Based on the hexahedron module, a space deployable truss antenna is presented in the paper. The parabolic antenna can stow and deploy associated with the stretch and shorten of the diagonal members. The deployable power is acted by the tension spring in the diagonal rod, and no need for extra force. The geometrical relation of the whole structure's rods is complex, so it is necessary to analyze the geometrical constraint of the structure from the deployed configuration to the stowed one. From the results of the structural analysis, the structure presented in this paper is practical.
 
Article
Top-mounted antennas cantilevered above guyed masts are vulnerable to increased levels of dynamic response due to turbulent buffeting from wind. In addition to the effects of gusts acting on the antenna itself wind-induced vibration of the flexible mast below can further excite the antenna, producing a whip-like action capable of generating large dynamic bending stresses at the base the antenna. While the dynamic sensitivity of cantilevered antennas is not explicitly recognized in most guyed mast design standards, it has been linked to at least one major guyed mast collapse. In the current study, the dynamic response of guyed masts with top-mounted antennas is investigated numerically using frequency domain analytical methods for a range of mast and antenna configurations. The results indicate that the mast-antenna system is highly coupled, with dynamic behavior depending on a number of factors including the relative stiffness, mass and span lengths of the mast and antenna, as well as on the overall structural characteristics of the guyed mast assembly. Furthermore, cantilevered antennas deemed to be slender relative to the mast below were found to exhibit significantly higher levels of dynamic response than those typical for the mast as a whole. In large part, the increased dynamic response could be attributed to elevated resonant participation of vibration modes dominated by flexural motion of the antenna.
 
Article
Scissor mechanisms are frequently used for deployable structures and many studies have been conducted on the subject. Most of the studies consider scissor units as modules in the design process. An alternative approach is to utilize loops as the modules for design. In this paper, the design alternatives of single degree-of-freedom planar linkages comprising anti-parallelogram loops using the loop assembly method is presented. First, scissor mechanisms are reviewed. Next, the types of four-bar loops and the resulting linkages in the literature are introduced and those which are yet to be explored, anti-parallelogram being one of them, are identified. Then the loop assembly method and the examples in the literature are reviewed. As a method to form as many alternatives as possible, symmetry operations are proposed. Suitable frieze symmetry groups utilized for obtaining the assemblies are explained and the anti-parallelogram loop patterns are derived. Next, the single degree-of-freedom linkages are obtained from the loop assemblies. Finally, a selection of the resulting linkages with novel properties are presented. This study shows that loop assemblies are efficient in systematic type synthesis of scissor linkages, some types of which could not be foreseen by using units as modules.
 
Article
Unfolding double-curvature surfaces is a problem that is widely encountered in engineering and increasingly met in architecture and digital fabrication processes. In the context of building construction, the process used to unfold the complex surface matters more than the unfolded result. Mastering the process of developable surfaces is fundamental to the construction method in order to keep the resulting geometry faithful to the initial one, to increase structural efficiency and material savings. The interest in unfolding a surface lies in its feasibility, in order to build surfaces with materials that can be elastically bent. This study is based on geodesic curves on surfaces and involves a process including parameters such as the number of geodesics and the division of these geodesics depending on the curvature of the surface, to be as close as possible to the initial surface. The algorithm approximates the initial surface by building developable strips between two successive geodesic curves.
 
Article
In this paper, artificial bee colony (ABC) to obtain the decent solutions that the authors proposed is applied to the structural morphogenesis for RC (Reinforced-Concrete) free-form surface shell with arbitrary boundary shape. The 'decent solutions' have relatively high evaluation solutions that maintain the diversity of the design variable space, including the global optimal solution and local optimal solutions. In this paper, we focus on an opening of RC free form surface shell structures considering design and functionality, and the structural morphogenesis procedure that considers constraints of the excessive bending moment caused by the presence of an opening in the shell is proposed. Numerical results demonstrate the efficacy of a structural morphogenesis procedure that simultaneously considers shell shape, thickness, and opening as design variables. Furthermore, it is shown that proposed structural morphogenesis using decent solutions search method can support a designer's idea of architectural forms having a relationship between shape and mechanical behavior at the initial stage of design.
 
The maximum normal force, shear force and bending moment of the arches in the case of different loads and different suspension systems
Article
This paper introduces special arch-supported tensile structures, based on a new invention, which makes possible building structures with clear spans longer than allowed by existing technologies. The invention converts random roof loads (wind and snow) into uniform, symmetric arch loads using a unique suspension system, based on the well known principle of block and tackle. The bending moment in the supporting arches can be minimized by using this suspension system. Procedures developed by the author make possible to analyse arch-supported tension structures with this special suspension system numerically. The main steps of the numerical analysis of such structures are topology generation, determination of the theoretical shape of the membrane or cable net (an equilibrium shape that corresponds to a required stress-distribution), determination of the "real" construction shape (that corresponds to member lengths, material constants and prestress in the suspension cables), and load analysis. Dynamic relaxation-based procedures developed for these stages of the analysis are introduced briefly. Numerical examples are presented to answer questions about the usefulness of the system. The results of the nonlinear analysis show that the invention can be effective in minimizing moments in the supporting arches.
 
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A new approach is presented for evaluating seismic responses of arch-type long-span structures. The responses are estimated using a series of pushover analyses utilizing multiple load patterns as linear combinations of dominant modes. The representative displacement and acceleration are defined in a general manner without resort to the base shear or roof displacement. The eigenmodes of initial elastic structure are assembled to the equivalent static loads to take the snapshot of the deformed structure at its maximum deformation. The damping due to plastic energy dissipation is evaluated through equivalent linearization for inelastic systems. Accuracy of the proposed method, especially for force and stress responses, is demonstrated in the numerical example of an arch-type long-span truss.
 
Article
Closed-form equations for determination of reactions and internal forces of linear-elastic symmetric arches with constant cross-sections are derived. The derivation of the equations was initially made for segmental, threehinged, two-hinged, and hingeless arches. Not all derived equations are simple, but still not excessively complex to apply, and they reveal several new insights into the structural behavior of arches. The first is an extremely simple approximate equation for horizontal reactions of a hingeless arch under self-weight, which could be also applied with excellent accuracy to catenary and parabolic arches, and with a desirable level of accuracy to two- and three-hinged arches with a relatively wide range of geometries. The second insight is an approximately linear relationship between reactions and between internal forces of arches with different structural systems, which helps understand the global structural behavior of arches in a new way and enables inference of some other insights presented in the paper. The third insight reflects the relationships between normal force distribution and its eccentricity in different types of arches. Finally, the fourth insight regards the comparison of behavior of arches under the self-weight with those loaded with uniformly distributed load along their span.
 
Top-cited authors
John Ochsendorf
  • Massachusetts Institute of Technology
Olivier Baverel
  • École nationale supérieure d'architecture de Grenoble
Tomohiro Tachi
  • The University of Tokyo
Axel Kilian
Jean-François Caron
  • École des Ponts ParisTech