Stability of gridshells

Description of the research

The buckling of gridshells is of practical interest for engineers who want to assess the safety and reliability of structures. Some post-buckling analysis have been applied to the gridshell of the Solidays festival. They demonstrate that these structures have a ductile behaviour, even with the assumption of accidental yield of some members  (Tayeb 2013). These calculations are however time-consuming. Simpler indicators can be used to assess the stability of gridshells during early stages of design. The current literature provided the designers with little insight on the actual influence of the forces induced by the beams deformation on the buckling capacity of gridshells.

Studies by Lefevre et al. and Mesnil et al. have shown  that the pre-stress due to the shaping process of elastic gridshells has little impact on their stability. In pseudo-funicular grid-shell, the pre-stress consists of compression forces, and the bearing capacity decreases (Mesnil et al. 2013&2015). In gridshells mapped on arbitrary surfaces, both tension and compression can result from the form-finding process. The pre-stressed structures can thus in some cases be more stable than unstressed ones (Lefevre et al. 2015).

The methods developed can be extended to other kind of residual stress fields. As an example, residual stresses are present in some steel structures because of the fabrication process (think of cold bending techniques). The stability of steel structures is currently under investigation for non-conventional patterns. The first results concern the kagome grid pattern, which is shown to have promising properties, as it outperforms quadrangular gridshells without cable bracing (Mesnil et al. 2017).