Advances in digital and computational design alongside fabrication have facilitated the visualisation and development of complex architectural concepts driving equally novel structural solutions. Engineers accommodate this demand by designing bespoke structural members that are built-up from thin panels, which are increasingly required to be warped to achieve the desired form. The current work focuses on the behaviour of such thin-walled members under shear loads, with a particular focus on such warped panels, primarily using numerical finite element (FE) models that are validated with published experimental results.

It was observed that FE models of isolated simply-supported web panels do not consistently withstand the design load predicted by the current code recommendations for the web resistance in shear; yet, this design load is achieved when the flanges are modelled explicitly. The influence of the flange on the shear resistance is presently attributed to three mechanisms: (1) the elastic critical buckling stress of the cross-section under shear being greater than that of a simply-supported web panel when the restraint provided by the flange is accounted for; (2) at ultimate limit state, the flange providing a membrane restraint to the web panel that further increases the shear resistance of the web, and (3) sufficiently thick flanges directly contributing to the shear resistance of the cross-section. Revised shear buckling curves are developed herein for isolated flat webs under shear; their strength is enhanced by accounting for the flange contributions described.

The structural behaviour of panels warped in the form of a hyperbolic paraboloid (hypar) is then explored, since this geometry often features as a result of parametric modelling. The hypar has been frequently implemented when designing long-span roof structures owing to its aesthetic appearance and efficient response to out-of-plane loading through membrane action. Yet, the hypar has been less keenly studied at the elemental scale under in-plane loading. A nonlinear mechanical model is developed to understand hypar panels under shear loads, wherein the hypar is treated as a deliberate imperfection applied to a flat plate. The model provides insights into the geometric characteristics that govern the out-of-plane instability witnessed from the onset of loading and the parameters that drive the strongly stable post-buckling response. Design recommendations are developed using the revised shear buckling curves through imperfection curves that are calibrated to the plate curvature, which accurately and reliably predict the ultimate resistance of the warped panels in shear.