Abstract
Abstract Free-edge gridshells represent the majority of built gridshells. Indeed, the gridshell reference geometry usually needs to be trimmed in order to provide building access or to insert the gridshell within an existing building, giving rise to one or more elastic boundaries. Despite the current design practice, so far a very limited number of scientific studies has been devoted to investigate the influence of elastic boundaries on the overall structural behaviour of gridshells. This paper focuses on the effects of the orientation of the boundary structure with respect to the grid direction. This is done by studying the buckling behaviour of an ideal single-layer steel gridshell, for different grid layout (quadrangular, hybrid, triangular) and orientation. The results of the parametric study demonstrate that the sensitivity of free-edge single-layer gridshells to the free-edge orientation strongly depends on the grid pattern. In particular, isotropic gridshells have shown an almost negligible influence of the free-edge orientation in terms of buckling load, in opposition to orthotropic gridshells. Moreover, the change in free-edge orientation induces significant variations of the global structural stiffness for all the layouts, resulting in possibly unacceptable displacements in service conditions.
Highlights
Gridshells belong to the family of lightweight form-resistant structures [1], together with tensegrity structures [2, 3] and Gridshell structures are highly prone to buckling phenomena, as testified by catastrophic collapses such as the one of the Bucharest Exhibition Hall dome in 1963
The behaviour of the hybrid gridshell adopted as case study is more similar to the triangular one, it can be classified as isotropic, but it is expected that orthotropic behaviour could emerge for lower values of the cable axial stiffness
If the free edge orientation doesn’t have a relevant influence on the gridshell ultimate behaviour, at least for isotropic gridshells, on the other hand the reduction of the initial stiffness when the free edge is not aligned with the grid directions is expected to have a significant influence on the structural behaviour in service
Summary
Gridshells belong to the family of lightweight form-resistant structures [1], together with tensegrity structures [2, 3] and Gridshell structures are highly prone to buckling phenomena, as testified by catastrophic collapses such as the one of the Bucharest Exhibition Hall dome in 1963. All the cited studies have been carried out by referring to gridshells with horizontal spring-plane and rigid supports. Gridshells of this kind represent a minority and are limited to research pavilions [7, 26] - horizontally constrained at the ground level - or roofs - rigidly constrained along their perimeter to the underlying structure - such as the Neckarsulm dome [8] or the British Museum Great Court roof [27]. Despite the current design practice, “this kind of elastic boundary has not been extensively investigated, and studies are needed in each design to know how and if the supports improve the buckling resistance” [13]
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