Parametric Collapse Performance of Low-Ductility Concentrically Braced Frames with Reserve Capacity

Abstract

In moderate-seismic regions, cost-effective steel building design solutions such as the R=3 and ordinary concentrically braced frame (OCBF) systems do not consistently provide reliable life-safety protection. The collapse performance behaviors of these systems are not thoroughly substantiated by experimental or historical evidence. Thus, a numerical study consisting of 2 conventional and 216 parameterized variations of a prototype seismic force–resisting system (SFRS) was developed to (1) investigate low-ductility braced frame failure mechanisms and collapse performance capabilities; (2) quantify the influences of key design parameters on probabilistic collapse capacity; and (3) provide the basis for development of a robust and socioeconomically viable design alternative for low-ductility concentrically braced frame (CBF) systems. Collapse probabilities were assessed through numerical simulations of ground motion excitations using incremental dynamic analysis (IDA), and variations in collapse probabilities were quantified with respect to five design parameters using an ANOVA model. The results indicate that the collapse probabilities of low-ductility CBF systems can be substantially reduced through design parameters that promote favorable failure hierarchies and provide deliberately engineered reserve capacity.