Abstract
A system is robust if it can withstand arbitrary damage. There are many practical ways to design in robustness, but there is as yet no accepted theory of robustness. Reliability theory is a useful tool for examining the probability of failure for a preโdefined type of loading; however lowโprobabilityโhighโconsequence events may be missed. One insight into the lack of robustness is gained by identifying how a system is vulnerable. A system that is vulnerable in any one way is not robust. Like robustness, vulnerability has been defined differently in different contexts. The purpose of this paper is not to argue for particular definitions of robustness, vulnerability or risk, but rather to review a โtheory of structural vulnerabilityโ developed by the authors and to show how it can be used in practice to improve the robustness of a system. The theory is one of form and connectivity. The purpose is to identify weak links within a structure as vulnerable failure scenarios. These can then be used with the probability of actions causing them to produce a measure of structural reliability and risk.