Effect of moving resonance on the seismic responses under far-field and near-field earthquakes

Abstract

The variation of the earthquake frequency content, which is known as spectral non-stationarity, is a feature of earthquakes that leads to different structural responses. The moving resonance phenomenon takes place when the ground vibration frequency content and the structural frequency content are very similar and have a strong correlation. The present study aims to explore the occurrence of moving resonance (MR) on SDF structures. At first, the frequency contents of far-field and near-field records are analyzed in MATLAB using the Meyer wavelet transform. Then, the OpenSees finite-element software is employed to analyze the structural responses with two nonlinear models of steel. Finally, the quantitative effect of moving resonance on the seismic response of the structure is examined by identifying possible structural features in terms of moving resonance occurrence based on the amplification factor parameter. Moving resonance times are determined using the correlation coefficient concept. The results show that when the fundamental periods of the SDF system are in a small range, the type of record has a significant impact on the moving resonance. In larger periods, the far-field and near-field records have the same influence on the occurrence of MR.