NUMERICAL SIMULATION STUDY AND RESILIENCE ASSESSMENT OF STEEL ECCENTRICALLY BRACED FRAMES WITH REPLACEABLE LINKS

Abstract

Earthquake demand parameters, EDP, such as displacement, velocity and acceleration are meaningful to engineers. In general, most decision-makers are non-engineers and do not understand these parameters. This study uses a procedure stipulated in FEMA P-58 to convert the earthquake demand parameters derived from nonlinear time history analysis into performance measures that are more meaningful to the decision-makers.This conversion of EDPs is better known as the performance-based design. In compliance with FEMA P-58, this study performed structural design and nonlineartime history analysis, and then assessed the seismic performance of ten different prototype buildings with K-type steel Eccentrically Braced Frames (EBFs) as primary seismic force resisting system. Among the ten EBFs, nine EBFs are new designs, and one existing 23-story EBF building that underwent a Mw6.3 earthquake in Christchurch, New Zealand. Next, an intensity-based assessment using nonlinear response history analysis is carried out in an open-source finite element analysis software - OpenSees. The assessment results help evaluate the building’s seismic resilience performance using a FEMA companion tool known as PACT. Ultimately, PACT converts the EDP into performance measures such as repair cost, repair time, unsafe placarding, and environmental impacts. This study uses the existing EBF building performance assessment to validate the performance assessment of this study. Overall, PACT results predict a 75% probability that both the repair cost and the repair time on average will be less than or equal to 8.0% of the total repair cost and the total repair time, respectively, for the nine EBF design with replaceable link beams. Hence, these results suggest the EBFs design adhering to the current seismic code specifications are resilient if replaceable link beams are used.