Seismic Damage Evaluation of Unanchored Nonstructural Components under Combined Effects of Horizontal and Vertical Near‐fault Ground Motions

With consideration of seismic resilience, damage of nonstructural components (NSCs) attracts significant attentions. Most previous studies focused on dynamic behaviors of NSCs under horizontal excitations. Near-fault earthquakes, however, have strong vertical ground motion components, but few studies assessed their influence on seismic damage of NSCs. In this study, the seismic responses of unanchored NSCs under near-fault earthquakes with strong vertical components are investigated. Response history analyses of steel moment frames with different heights under near-fault earthquakes are performed and the derived floor acceleration responses are taken as the inputs of unanchored NSCs. The sliding and rocking responses of NSCs under horizontal and vertical excitations are used to quantify the influence of near-fault earthquake characteristics. The results highlighted that bidirectional excitations (horizontal & vertical) would elevate the uncertainty in the sliding demands of NSCs and more likely to induce the occurrence of overturning failures for slender NSCs. The relation between rocking demands of NSCs and common intensity measures like PFA would be weakened due to the presence of vertical excitations.