Vulnerability of structural systems

A structure is vulnerable if relatively small damage leads to disproportionately large consequences. A structure which is unacceptably vulnerable in any one way is not acceptably robust. A theory of structural vulnerability has been previously reported by the authors. The purpose of the theory is to identify particular failure scenarios by analysing the connectivity of the structural form. In this paper vulnerability theory is applied to three-dimensional frames and, in a preliminary way, to structural dynamics which is crucially important in assessing impact damage in for example progressive collapse. The concepts are illustrated through examples. The vulnerable failure scenarios may then be examined by conventional response analysis and/or by systems reliability theory and risk assessment. The theory is also applicable to structural damage assessment or for assessing structures under unforeseen terrorist attack.