地震动输入方向对结构扭转振动的影响

选取2009年姚安MS6.0、2014年鲁甸MS6.5地震的水平结构强震记录进行谱分析，结果均显示17 Hz、2.1 Hz为该结构第一、二振型的自振频率，且第二振型出现扭转现象。对比两次强震记录发现，鲁甸MS6.5地震作用下结构的扭转振动远超姚安MS6.0地震。利用SAP2000建立该结构的有限元模型，分别以实际入射角度输入场地强震记录并进行时程分析，其结果与强震记录谱分析结论一致。由于输入地震动的强度、频谱相近，因此判断其输入方向是影响结构平面扭转振动的主要原因。

The Influence of Input Ground Motion Direction on Structure Torsional Vibration

We examine structure strong motion observation records from the Ludian MS6.5 and Yao’an MS6.0 earthquakes, as recorded by a structure seismic response array in Yunnan province. Fourier spectrum analysis shows that 1.7 Hz is the natural frequency of the first vibration mode, and 2.1 Hz is the natural frequency of the second, which is a torsional mode. Comparing strong motion records of the two earthquakes, we infer that the torsional vibration of Ludian is much stronger than Yao’an. In addition, we establish a 3D finite element model using SAP2000, selecting strong motion records as input motion to simulate the seismic performance of structure. Time history analysis shows that the structure’s performance is consistence with Fourier spectrum analysis. In summary, we think that the input motion angle is an important aspect to the torsional vibration of structure.