Geometrical characterisation for structural robustness

Robustness assessment is a widespread problem in the field of structural engineering, which has taken on even greater importance since the attacks of September 11, 2001. Although numerous approaches to the question already exist, there is still today no consensus on which threshold makes a given structure robust or not, nor on the way to calculate this threshold. Moreover, these existing methods are based on a numerical assessment of the structure's aptitude for robustness once its design has been fixed.
This thesis develops a new type of approach to structural robustness, working on geometrical considerations only. It allows the integration of constitutive dimensions of structural robustness at the earliest steps of the design process. Based on graphic statics and strut-and-tie modelling, the method develops a visual robustness indicator showing structural aptitude for force redistributions. When implemented into parametrical software, the approach also turns into an interactive tool that helps project authors to understand the impact of design decisions on the robustness performance sought for.
The method also allows the comparison of design options in terms of the volume of material required for their implementation. The principles of the proposed geometrical method are developed in this thesis for two-dimensional structures. These principles are then illustrated by the analysis of four case studies : two arched structures and two walls.