Torsional response of frame structures subjected to earthquake wave passage excitation with varying low-frequency contents

The influence of low-frequency contents in seismic waves on torsional response of frames remains systematically unelucidated. Based on structural dynamics theory, this study uses time-history analysis to investigate the effects of low-frequency contents on frame torsional response under earthquake wave passage excitations. Three-dimensional numerical models of planar regular (RFSs) and irregular (IFSs) frames were developed in ABAQUS. By applying wave passage excitations with varying low-frequency contents, peak shear forces in first story corner columns along the excitation direction were calculated. Results show that with sufficient low-frequency contents, peak shear forces in outer corner columns of RFSs and IFSs increase by 31.6% and 85.3%, respectively, under frequent earthquakes. Under rare earthquakes, the corner columns on the wave-facing direction of RFSs and IFSs exhibit 17.9% and 33.9% increases in peak shear forces. These findings indicate that when seismic waves at low-frequency contents are sufficient, the corner columns of RFSs and the outer corner columns of IFSs are susceptible to wave passage effect under frequent earthquakes, while the corner columns on the wave-facing direction of both RFSs and IFSs are susceptible to wave passage effect under rare earthquakes. However, when the low-frequency content is insufficient, the corner columns do not exhibit this effect.