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Authors:Deepshikha Nair, Yuki Terazawa, Toru Takeuchi Abstract: International Journal of Space Structures, Ahead of Print. Curved gridshells are excited not only in the horizontal direction but also experience large anti-symmetric vertical accelerations when subjected to horizontal earthquake ground motions. In addition to the coupled response, gridshells exhibit closely spaced modes and substructure-roof interaction. Nevertheless, previous studies have proposed elastic horizontal and vertical equivalent static seismic forces considering these complex dynamic response characteristics. These are determined from the input horizontal acceleration at the substructure’s roof level, an assumed acceleration distribution, nodal roof masses and amplification factors derived from the dynamic characteristics of the dome and substructure. To extend this methodology to nonlinear substructures with displacement-dependent damping devices, this paper investigates the applicability of ductility reduction factors (or Rμ factors) to estimate the inelastic response spectra and an alternative equivalent linearisation approach to compute the peak horizontal acceleration of multistorey substructures with buckling-restrained braces. This is achieved by modelling the curved roof as a rigid mass for the substructure model, and using its idealised base shear-roof displacement relationship obtained from modal pushover analyses. The peak horizontal acceleration of the substructure is then used to obtain the equivalent static loads of the curved roof using amplification factors, and the accuracies are verified against the results from nonlinear response history analyses. It was confirmed that the Rμ [math]factors combined with the roof amplification factors provide a simple way to estimate the peak roof response with sufficient accuracy for preliminary design of domes with multistorey substructures having low post-yield stiffness. Citation: International Journal of Space Structures PubDate: 2022-06-13T02:05:07Z DOI: 10.1177/09560599221097834
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Authors:Tamás Baranyai Abstract: International Journal of Space Structures, Ahead of Print. Elasticity ellipses or central ellipses have been long used in graphic statics to capture the elastic behaviour of structural elements. The paper gives a generalisation the concept both in dimensions and in the possibility of degenerate conics/quadrics. The effect of projective transformations of these quadrics is also given, such that the entire mechanical system can be transformed preserving equilibrium and compatibility between its elements. Citation: International Journal of Space Structures PubDate: 2022-03-08T11:51:05Z DOI: 10.1177/09560599221081013
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Authors:Nizar Bel Hadj Ali, Omar Aloui, Landolf Rhode-Barbarigos First page: 81 Abstract: International Journal of Space Structures, Ahead of Print. Clustered (continuous) cables reflect an advantageous solution for reducing the number of tensile elements in engineering systems. During the tensioning or activation of tensile structures, such as cable structures, membranes and tensegrity structures, the deficiency of having to control too many elements can be overcome by employing clustered cables. The use of clustered cables has been shown to alter the structural behavior of tensile systems by modifying the force distribution in the systems. This effect has been showcased under the assumption of frictionless sliding of the cable elements across nodes or pulleys. However, friction can have also impact on the behavior of the system. In this paper, a new Finite Element formulation is proposed for the static analysis of tensile structures with clustered cables. The proposed formulation accommodates sliding-induced friction by the consideration of the Euler-Eytelwein equation as well as geometric nonlinearities. It is found that the sliding-induced friction can significantly modify the force distribution in the system. The applicability and importance of the proposed formulation is demonstrated through the analysis of two examples from the literature. Citation: International Journal of Space Structures PubDate: 2022-04-11T11:16:16Z DOI: 10.1177/09560599221084597
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Authors:Ping Liu, Xin-Feng Yang, Dan Li First page: 107 Abstract: International Journal of Space Structures, Ahead of Print. The present paper investigated the characteristic of the vibration of a membrane structure under impact load based on a series of experiments. Eight cases with different pretension forces by varying the pretension load in the lateral direction were carried out. The impact loads were applied on the center position of the membrane. The results of frequency, vibration amplitude, and damping ratio were discussed. It is shown that there is a main vibration mode with different main frequencies in the vibrations and the duration is the same under the different impact loads. The frequency is linear to the pretension force, and the amplitude of the vibration decreases by an exponential function determined by the parameter of the damping ratio. When the pretension force exceeded a threshold (6.2% of strength), the maximum amplitude and vibration duration tend to be a fixed value. Citation: International Journal of Space Structures PubDate: 2022-01-25T08:20:00Z DOI: 10.1177/09560599211064111
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Authors:Seyed Mobin Moussavi, Hana Svatoš-Ražnjević, Axel Körner, Yasaman Tahouni, Achim Menges, Jan Knippers First page: 119 Abstract: International Journal of Space Structures, Ahead of Print. This paper presents the use of a computational design algorithm in combination with robotic fabrication and sensing to augment the design and construction process for non-standardized material. Although reusing reclaimed material can significantly reduce the environmental impact in building construction, current design processes are not set up for this shift in thinking. Contrary to conventional practices, designing within the constraints of available material means that geometry and topology cannot be fully pre-determined. This paper introduces a design methodology for corrugated shell structures from folded sheet metal of variable geometries and properties, in which the design goal adapts to available material. It follows a two-fold approach of digital algorithm development and scanning and physical prototyping for robotic fabrication. The scanned materials database is classified based on object geometry data and material properties; such as thickness, type of metal, and spring-back values for fabrication purposes. Together with a target surface, it is an input for a generative design algorithm consisting of surface generation and optimization. The surface generation tries to approximate the target through a translation of search algorithm results for object placement into a 2D mesh graph which is then linked to 3D particle spring based form-finding. The optimization consists of evaluation of structural, fabrication, and design criteria, with finally user selection. Robotic fabrication included object recognition, metal sheet folding and consideration of different metal spring back behavior. These methods were tested on a single curved arch surface and applied to a double curved cantilever canopy as a final demonstrator. The algorithm results showed a generation of different corrugated shell topologies based on iterated object placement. As a demonstrator, a part of the selected canopy was robotically fabricated from local industrial leftovers. Citation: International Journal of Space Structures PubDate: 2022-03-07T10:04:45Z DOI: 10.1177/09560599221081104
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Authors:Barbara Ruschel Lorenzoni, Fabio Pinto da Silva First page: 135 Abstract: International Journal of Space Structures, Ahead of Print. In digital design, rigid flat materials commonly hinder the fabrication of complex-curved geometries. A fabrication approach based on the socalled bending cut patterns or “kerf-bending” can be used to improve the ability of a material to bend. This bending method relies on a complex mechanical behavior, requiring an accurate evaluation of the resultant surface. By mastering the geometric effects, some adjustments can be made to the project so that the result better approximates the designer’s intentions. This study focused on geometric accuracy of MDF kerfbending, including target-geometry design, cutting, bending, 3D scanning and analysis. It demonstrated that depending on the arc bending radius, the sample with a defined cut pattern may become excessively tensioned, protruding to the outside, or without enough stiffness to conform to an ideal shape. Experiments have validated this methodology and obtained a stable and precise half-cylinder by selecting the most adequate radius range for the material and parameters adopted. Citation: International Journal of Space Structures PubDate: 2022-03-14T08:04:40Z DOI: 10.1177/09560599221081015
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Authors:Marina Konstantatou, William Baker, Timothy Nugent, Allan McRobie First page: 150 Abstract: International Journal of Space Structures, Ahead of Print. This research paper introduces a theoretical framework for the design and analysis of compression-and-tension grid-shells in static equilibrium where the states of self-stress function as design freedoms. This is based on a synthesis of reciprocal discrete Airy stress functions in the context of graphic statics and the Force Density Method (FDM). Specifically, the former is a direct method for generating 2-dimensional global static equilibrium whereas the latter allows for its 3-dimensional implementation. As a result, creative design explorations can take place directly within the equilibrium space without the need for iterative convergence algorithms to obtain equilibrium. The use of reciprocal Airy stress functions in conjunction with the lower bound theorem gives insight and explicit control with regards to the states of self-stress as design and analysis freedoms which can define the structural form and its load path. Citation: International Journal of Space Structures PubDate: 2022-03-12T12:18:06Z DOI: 10.1177/09560599221081004
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Authors:Philip J Wicks First page: 165 Abstract: International Journal of Space Structures, Ahead of Print.
Citation: International Journal of Space Structures PubDate: 2022-04-01T07:17:08Z DOI: 10.1177/09560599221084135
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First page: 168 Abstract: International Journal of Space Structures, Ahead of Print.
Citation: International Journal of Space Structures PubDate: 2022-03-14T10:02:52Z DOI: 10.1177/09560599221089050
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Authors:Alexander Sehlström, Karl-Gunnar Olsson, Chris JK Williams First page: 94 Abstract: International Journal of Space Structures, Ahead of Print. Discontinuities in the Airy stress function for in-plane stress analysis represent forces and moments in connected one-dimensional elements. We expand this representation to curved membrane-action structures, such as shells and cable nets, and graphically visualise the internal stresses and section forces at the boundary necessary for equilibrium. The approach enhances understanding of the interplay between form and forces and can support design decisions related to form-finding and force efficiency. As illustrative examples, the prestressing needed for three existing cable nets is determined, and its influence on the edge-beam bending moment is explored. Citation: International Journal of Space Structures PubDate: 2021-12-28T08:09:01Z DOI: 10.1177/09560599211064104