随机地震动场多点激励下宽幅大跨桥梁结构地震响应研究

为了研究随机地震动场多点激励作用下宽幅大跨桥梁结构的地震响应,基于二维相干模型,考虑地震波非平稳性合成桥址各支承点的人工地震加速度时程波,采用多项式拟合法在时域内对各支承点处的人工合成加速度波进行校正,并对校正前后加速度波的响应谱进行比较校验;随后以某大跨自锚式悬索桥为例,利有限元软件中线性时程分析模块,将所合成的加速度地震波施加于结构,对比研究一致激励与随机地震动多点激励下宽幅大跨桥梁结构的地震响应。分析表明,考虑二维相干和地震波非平稳性合成的各支承点地震加速度时程波可采用多项式拟合法进行基线漂移现象的校正,同时应对修正前后加速度波的反应谱进行比较校验;对于大跨且横桥向支承点相距较远的桥梁结构应考虑横桥向地震波的非一致性。

Seismic Response of Wide Long-span Bridge Structure under Multi-point Excitations of Random Ground Motion Field

In this study, we used the dynamic time history method to analyze the seismic response of bridge structures. The time history analysis method, which has higher accuracy than the response spectrum method, can identify various kinds of responses and can also consider various factors in the calculation and analysis, including the coherent effects, multi-dimensional inputs, and multi-dimensional responses. The primary problem in applying the dynamic time history method is how to simulate ground motion acceleration. In the artificial acceleration wave, the velocity and displacement of the seismic wave deviate from the baseline. At the end of the seismic wave, the velocity and displacement time history are not zero, which generates a baseline drift of the seismic wave. As such, it is necessary to revise the seismic response before analysis and to eliminate the influence of the baseline drift phenomenon. At the same time, the response spectrum of the acceleration wave before and after correction must be checked and compared. In this paper, based on a 2D coherent model, we analyze the seismic response of a wide long-span bridge structure under multi-point excitations of a random earthquake motion field. We use the polynomial fitting method to adjust them in the time domain. We use the response spectrum to check the seismic wave, which is corrected before and afterwards. Then, taking a large-span self-anchored suspension bridge as an example, we use the linear time history analysis module in the finite element analysis software and the synthetic seismic wave to analyze and compare the seismic response results under uniform and multi-point excitations. The results indicate that the artificial acceleration wave must take into account the baseline drift phenomenon, and the polynomial fitting method can be used to adjust the waves. In addition, the seismic waves corrected before and after must be checked against the response spectrum. For large-span and wide bridge structures, the non-uniformity of transverse seismic waves must be taken into account.