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The current paper describes a spin-off investigation from the initially published international research project [1] [2] , which is looking into the design and development of single-meridian grid deployable structure. As a part of the collaborative international project between South Korea (Project Leader), Japan and Denmark, expandable bars of two...
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... the position of pinned supports (one degree of freedom) A and B are fixed the structure can not make any mechanical movements. When a pair of expandable bars is introduced to the system (Figure 3), the system now gains four degrees of freedom; two translational, and two rotational. A method based on the constraint Jacobian matrix is to calculate the DOF of it. ...
Citations
... However, it was disregarded that when a structure is folded, the joints can prevent the SLE's to close on a straight line. Developing and analysing bistable scissor structures is still a contemporary research subject in civil engineering, as can be seen from the large number of recent contributions (Gantes, 2004;Kawaguchi et al., 2019;Lee et al., 2015;Lee et al., 2016;Arnouts et al., 2018;Arnouts et al., 2019;Arnouts et al., 2020), without aiming for exhaustivity. ...
Pre-assembled scissor structures can be transformed from a compact bundle of elements to a fully deployed configuration, offering a considerable volume expansion. Intended geometrical incompatibilities during transformation can be introduced as a design strategy to obtain bistability, which allows instantaneously achieving some structural stability in the deployed state. Because of these incompatibilities , some specific members bend during transformation, resulting in a controlled potentially tunable snap-through behaviour. Geometric design methodologies were proposed in the literature to obtain a compatible geometry (i.e. with all of the beams straight) in the folded and the deployed configurations. However, most of these approaches do not consider finite hub sizes or introduce extra incompatibilities in the geometry by adding hub legs. In this contribution, deployability conditions are derived taking the finite hub size, i.e. the spacing between the connections of the different beams to the hub, into account to make triangulated bistable scissor modules fully geometrically compatible in the folded and the deployed configuration.
... By consequence, both the service state as well as the transformation phase have to be considered in the design. Although analysing bistable scissor structures is a contemporary research topic [12][13][14][15][16][17][18][19], existing applications in civil engineering are rare, largely due to this complex structural behaviour. ...
... , inc forces (15) with n forces the number of applied forces. ...
Lightweight bistable deployable structures can be designed to be transportable and reusable. They instantaneously achieve some structural stability when transformed from the compact to the deployed state through a controlled snap-through, as a result of intended geometric incompatibilities between the beams. Due to their transformable bistable nature their design requires assessing both their non-linear transformation behaviour, as well as their service state in the deployed configuration. The requirement of a low peak force during transformation can be shown to oppose the high stiffness requirement in the deployed state; their design can therefore be formulated as a multi-objective non-linear optimisation problem. In this contribution, a size and shape optimisation method is elaborated by choosing the best material combinations, the optimal geometry of the structure and beam cross-sections. The originality of this contribution is the use of a multi-objective evolutionary algorithm to structurally optimise bistable scissor structures taking into account the deployed state as well as the transformation phase. First, the method is applied to optimise a single bistable scissor module. Next, a multi-module bistable scissor structure is optimised and the single module and full structure based approaches are critically compared.
Deployable bar structures are made of lightweight materials, and that is one of the reason why they do not require high transportation costs, are easy to assemble (by unfolding) and disassemble (by folding) and are able to successfully respond to many requirements when in the shortest possible time it is necessary to provide architectural structures for various purposes. In this paper, the deployable bar structures are analyzed with the aim of forming a universal multifunctional space which could be used as a facility for temporary housing, healthcare, education and similar purposes. Due to the fact that geometric shape of a certain space significantly determines the function of that space, and the way it is used, detailed analyses of the geometric shapes of these structures have been conducted. Comparison of the forms explored so far with the existing architectural deployable bar structures has resulted in two distinct geometric forms: singly curved (barrel vault) and doubly curved (dome). It was concluded that the application of these forms in the form of freestanding modules provides limited opportunities for organizing functional content due to the specific locations of certain connections between elements, as well as the complicated design process. This is one of the reasons for rare application of these structures in architecture. The proposal of a multifunctional Universal module which consists of unified singly curved modules in combination with doubly curved and prismatic forms came as a result of the conducted analyses. Proposals for forming more complex architectural spaces of higher capacity provide a wider range of applications of these structures and opens new possibilities for their use.
