多支座大跨度结构随机地震响应分析

A Random Seismic Response Analysis of Multi-Support Bridge

首先用有限元离散实际的多支座支承的大跨度结构，在对其响应分析时考虑了相干性损失和相位差。同时在频域里推导了位移和内力响应的功率谱矩阵表达式，这些表达式可以直接应用于工程实际。最后通过计算一受多支座支承的大跨度结构的内力功率谱，得出了一些有益的结论。

Multi support long span bridges are being increasingly built in China, sometimes in regions where earthquakes occur. We apply finite element method to analyzing their random seismic response. Considering the loss of coherency among ground supports and the ground motion phase lags, we derived eq.(13) as the power spectral density (PSD) of the displacement response and eq.(22) as that of the internal force response. We took two different apparent wave velocities 2 000 m/s (Fig.2) and 300 m/s(Fig.3). In both figures, span was taken to be from 30 m to 60 m. In both figures, PSD of internal force response increases with increasing span. In Fig.4, the span was taken to be 50 m. The long span bridges basic natural frquency is of the order of 1 Hz. In Fig.4, the excitation frequency was taken to be from 0 to 14 rad/s; when the excitation frequency is low, the PSD must be computed by considering loss of coherency (solid curves in Fig.4); when the excitation frequency is high, there is no need to consider loss of coherency.