Form-finding of elastic gridshells

Abstract

Elastic gridshells are obtained by elastic deformation of an initially flat grid into a three-dimensional shell-like geometry and were first implemented in architecture in the 1970's. Their mechanical behaviour, which includes aspects of both a continuous shell and a network of elastic rods, is complex to model. To date, a limited number of elastic gridshells have been constructed around the world. Yet, gridshells are extremely efficient structures. They can cover long spans with low self-weight and allow for a variety of aesthetical shapes. Elastic gridshells present the additional advantage of being simple and rapid to construct. Despite these outstanding qualities, efficient design tools are not currently available to help form-find elastic gridshells. Numerical tools previously applied to their design are computationally costly and resort to simplifications that can lead to an incomplete understanding of the mechanical behaviour of the structure. It is particularly challenging to predictively model the initial elastic deformation of elastic gridshells. This thesis presents a study of the elastic shape transformation undergone by an originally flat grid into a three-dimensional configuration. Our focus is on explorative experiments using scale physical models towards identifying and better understanding avenues of form-finding elastic gridshells. In parallel, a new numerical tool based on the Discrete Elastic Rods method, whose development was motivated by the current work, is used to model the behaviour of our elastic gridshell. The numerical tool is implemented in form-finding numerical experiments similar to the ones developed using physical models. Finally, the results from the laboratory experiments and the numerical simulations are compared and found to be in good agreement. These findings suggest the Discrete Elastic Rod method can be a powerful tool for form-finding and design evaluation of elastic gridshells. Keywords: Elastic gridshells, elastic deformation, actuation, form-finding, physical scale models, Discrete Elastic Rods method.