A vector intensity measure to reliably predict maximum drift in low- to mid-rise buildings

An optimal intensity measure (IM) should be able to predict the structural response with minimum dispersion, which is called efficiency, and also independently of other ground motion characteristics, such as earthquake magnitude (M) and source-to-site distance (R), which is called sufficiency. Using an optimal IM can play an important role in reliable seismic performance assessment of structures. The present study is aimed at investigating the efficiency and sufficiency of vector-valued IMs for predicting maximum inter-storey drift ratio (MIDR). The IMs considered in this study include response spectral acceleration at the fundamental period of the structure, Sa(T-1), as a common scalar IM, the vectors (Sa(T-1), epsilon(Sa)) and (Sa(T-1), N-p) as well-known vector-valued IMs, and ten other vector-valued IMs. These ten IMs consist of two components, with Sa(T-1) as the first component and different parameters that are ratios of scalar IMs as the second component. By investigating the desirable features of an optimal IM, (Sa(T-1), Sa(T-1)/PGV) is proposed as an optimal vector-valued IM for the prediction of MIDR demand on low- to mid-rise reinforced concrete moment-resisting frame structures. To make the proposed IM predictable, a ground motion prediction equation (GMPE) is determined for Sa(T-1)/PGV by using the existing GMPEs.