Effect of moving resonance on the seismic responses under far-field and near-field earthquakes
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ORIGINAL PAPER
Effect of moving resonance on the seismic responses under far‑field and near‑field earthquakes Jalal Akbari1 · Saeed Rozbahani2 · Mohsen Isari3 Received: 11 May 2020 / Accepted: 3 September 2020 © Springer Nature Switzerland AG 2020
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. Keywords Seismic response · Wavelet transform · Moving resonance · Far-field and near-field earthquakes · Spectral nonstationarity
Introduction When structures are subjected to multiple severe earthquakes, significant variations in their response are observed. This effect of ground motion randomness on the variation of structural response is defined as record-to-record variability (Vamvatsikos and Cornell 2002). For a set of records that are scaled to match with a specific design response spectrum, the peak inter-story drifts calculated from analyses * Jalal Akbari [email protected] Saeed Rozbahani [email protected] Mohsen Isari [email protected] 1
Civil Engineering, Bu-Ali Sina University, Hamedan, Iran
2
Laboratory of Earthquake Engineering and Structural Health Monitoring of Infrastructures (LEESHMI), Bu-Ali Sina University, Hamedan, Iran
3
Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
have very wide ranges. The reasonable values of dispersion for the inter-story drifts could be 0.3 or more (Cornell et al. 2002). As well, because of this wide dispersion in response history results, the accuracy of the estimation of the structural response predictions could be poor if a small number of ground motions are used. Although several investigations were characterizing the contribution of record-to-record variability on the dispersion of response history results, there were significantly fewer attempts to analyze the sources of this variability and to predict
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