Optimal vector-valued intensity measure for seismic collapse assessment of structures

The present study is aimed to investigate the ability of different intensity measures (IMs), including response spectral acceleration at the fundamental period of the structure, S (a) (T (1)), as a common scalar IM and twelve vector-valued IMs for seismic collapse assessment of structures. The vector-valued IMs consist of two components, with S (a) (T (1)) as the first component and different parameters that are ratios of scalar IMs, as well as the spectral shape proxies E > (Sa) and N (p), as the second component. After investigating the properties of an optimal IM, a new vector-valued IM that includes the ratio of S (a) (T (1)) to the displacement spectrum intensity (DSI) as the second component is proposed. The new IM is more efficient than other IMs for predicting the collapse capacity of structures. It is also sufficient with respect to magnitude, source-to-site distance, and scale factor for collapse capacity prediction of structures. To satisfy the predictability criterion, a ground motion prediction equation (GMPE) is determined for S (a) (T (1))/DSI by using the existing GMPEs. Furthermore, an empirical equation is proposed for obtaining the correlation between the components of the proposed IM. The results of this study show that using the new vector-valued IM leads to a more reliable seismic collapse assessment of structures.