Estimation of peak floor responses of special concentrically braced frames under orthogonal seismic effects for seismic loss analysis of nonstructural components

Abstract

Estimating seismic demands and the consequent damage to nonstructural components (NSCs) is very critical within the performance-based earthquake engineering (PBEE) framework. NSCs are usually classified based on their sensitivity to floor responses of acceleration, velocity, or displacement. There have been heuristic approaches for estimating orthogonal seismic effects by combining the responses dependently obtained from seismic analysis in two principal directions. However, the approaches were examined for seismic demands of structural components while little attentions were devoted to seismic demands of NSCs. FEMA P-58 provides a specific rule to estimate the orthogonal seismic effects for NSC seismic demands. However, its accuracy in evaluating NSC losses remains unexamined. This paper explores the effectiveness of three popular combination rules in seismic loss estimations for acceleration- and velocity-sensitive NSCs. The probabilistic-based combination rules proposed by the authors before were used for a comparison purpose. Incremental dynamic analyses are performed on six special concentrically braced frame (SCBF) buildings with various heights and torsional irregularities under unidirectional and bidirectional record sets. Based on the peak floor acceleration and peak floor velocity values obtained using combination rules, the seismic losses of NSCs are estimated following the FEMA P-58 framework. The findings indicate that, using the original combination rules, the mapping between the accuracies of peak floor response (PFR) and loss estimation is highly nonlinear and the overestimated PFR values would enlarge the overestimation in NSCs’ losses by up to 30 %. The developed probabilistic-based combination rules provide a sound performance in NSC loss estimations.