The performance-based seismic response of special steel MRF: Effects of pulse-like ground motion and foundation safety factor

Abstract

This study aims to investigate the effect of near-fault pulse-like earthquake ground motions as well as the foundation safety factor, on the performance-based seismic response (PBSR) of special steel moment-resisting frame (MRF). The Beam on the Nonlinear Winkler Foundation (BNWF) approach was employed for modeling the soil-foundation system. In this regard, values of 2, 3, and 5 were considered for the foundation vertical safety factor (FSv). The PBSR of the MRF has been assessed under 32 far-fault (FF) ground motions as well as 55 near-fault (NF) pulse-like records, through Incremental Dynamic Analyses (IDAs). The effects of extracted pulses and residual components of near-fault records were investigated as well. Results show that regardless of the earthquake record type, FSv has no considerable effect on the performance-based drift demand in the structure. However, larger settlement and rotation of the foundation are expected when a small FSv is accounted for. This leads to difficulties in providing the Immediate Occupancy (IO) performance objective for structures with operational performance levels. The effect of the input record type on the median foundation settlement is also inconsiderable. As well, a similarity was observed between the seismic performance of the structure under the residual components and the far-fault records. What’s more, neither the extracted pulses nor the residual components of near-fault earthquake records can represent the original near-fault pulse-like records. Also, the residual component plays an important role in the structural responses under low-intensity earthquake events.