Amplified seismic loads in steel moment frames under strong ground motion

Abstract

Design of structures with inelastic behaviour under seismic loading conditions is an important issue for engineers. For this reason, amplification factors defined in modem seismic codes are used to reduce the elastic seismic force demand and estimate the actual displacements. Although these factors play an important role in seismic codes, the format and also ratios between them have varied considerably from one code to another. In this paper, the first objective is to investigate the amplified seismic loads in design requirements. Based on this derivation, the second objective is to evaluate their accuracy. For this purpose, considering the increase in the axial load levels on columns, system overstrength factors for Special Moment Resisting Frames (SMRFs) under strong ground motions are examined. The results are presented in as maximum and average maximum axial load amplification factors, plastic hinge rotations and system overstrength factors under selected ground motions.