Evaluation of seismic parameters of steel moment resisting frames based on “FEMA P-695” under near-field rotated ground motion

Abstract

Behavior factor (R) is one of the seismic design parameters that considers nonlinear performance of structures during an earthquake. In most of the seismic design codes, behavior factor has been used for considering nonlinear performance of structures in linear analyses. The purpose of this study is an evaluation of seismic parameters of structures under far-field and near-field ground motions (rotated to fault strike‑normal and fault strike‑parallel) based on the method presented in FEMA P‑695 and comparing the results with those in the code. Thus, five intermediate steel moment resisting frames with 4, 7, 10, 15, and 20 stories were considered. The capacity curve of each model were obtained by Displacement- based Adaptive Pushover Analysis. All of the nonlinear analyses were conducted by OpenSees. The results state that the behavior factor due to the ground motions used in this study decreases as the structure’s height increases. Average of difference of behavior factor in far-field ground motions and average of behavior factor in near-field ground motions is 6.5 percent and the reason is that the behavior factor in far-field ground motions is greater. Also, the behavior factor in fault strike-parallel near-field ground motions (SP) is greater than fault strike-normal near-field (SN) and the average of this difference for different structures is almost 4 percent.

Keywords

• behavior factor (r factor)
• displacement modifier factor
• displacement-based adaptive pushover analysis
• fema p-695
• overstrength factor