The influence of the indicator η on the collapse capacity of structural systems has been investigated in this article. Eta has been introduced recently as an indicator of spectral shape which has strong influence on the structural nonlinear response. In this article, a closed form formula has also been developed to predict the collapse capacity of structures as a function of their structural behaviour parameters. The collapse fragility of a given structure can be determined for different hazard levels by adjusting the single fragility which results from a general set of ground motion records. The results of a seismic collapse risk analyses of a four- and an eight-story reinforced concrete test structure have confirmed the consistency of the proposed simple approach which is valid for period range of 0.25–3.0 s and the ductility range of 4–12.
