Document Type : Original Article
Authors
1
Assistant Professor, Department of Civil Engineering, Faculty of Engineering, West Tehran Branch, Islamic Azad University, Tehran, Iran
2
MSc in Earthquake Engineering, Department of Civil Engineering, Faculty of Engineering, West Tehran Branch, Islamic Azad University, Tehran, Iran
10.22065/jsce.2023.393483.3093
Abstract
One of the uncertainties in the seismic evaluation of structures is how to select random seismic records and how to consider the orientation effects of horizontal components of ground motions in the time history analysis. The rotation of the recorded components can increase the seismic characteristics such as peak ground acceleration, response spectrum shape, or earthquake energy. Therefore, the effects of this issue on the most critical scenarios of seismic response of important structures are questionable. This study has evaluated three rotation methods proposed by previous studies, i.e., principal axes, maximum direction, and fault-normal and fault-parallel orientation, based on the data available in the Iranian Strong Motion Network. Then, the effects of these methods are assessed on the seismic response of two building types, low-rise and medium-rise regular steel moment frames, using the nonlinear time history analyses. According to the results, if the structure principal axes are along with the most critical orientation of the accelerometer installation, the magnification of the seismic response can be expected, especially in near-fault structures. So that for the studied structures, , two structural response parameters including the maximum base shear and maximum inter-story drift ratio are increased between 10 and 120 percent under different rotated ground motions, depending on the earthquake type and the applied method of record rotation and also depending on the building height and its distance to the fault. According to the results, the selection of the most critical rotation method was a complicated and time-consuming process. Based on this research results, it is proposed to give priority to the rotation method which maximizes the value of peak ground acceleration and specific energy density of the seismic record to reduce the calculations of identifying the critical scenario for the rotation method of seismic ground motions in the time history analysis method
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