Vector and Scalar IMs in Structural Response Estimation and Risk Assessment: Part II – Building Demand Assessment

The advantages and disadvantages of using scalar and vector ground motion Intensity Measures (IMs) are discussed for localized seismic response assessment of 3D buildings. Candidate IMs are spectral accelerations, at a single period (Sa) or averaged over a period range (Saavg). Consistent scalar and vector probabilistic seismic hazard analysis results were derived for each IM as described in the companion paper (Kohrangi et al., 2015). The response hazard curves were computed for three buildings with reinforced concrete infilled frames using the different IMs as predictors. Among the scalar IMs, Saavg tends to be the best predictor of both floor accelerations and inter story drift ratios at practically any floor. However, there is an improvement in response estimation efficiency when employing vector IMs, specifically for 3D buildings subjected to both horizontal components of ground motion. This improvement is shown to be most significant for a tall plan-asymmetric building.