大跨曲线与直线刚构桥水平双向多点地震反应分析对比

Analysis and Comparison of Horizontal,Two-Directional and Multi-Support Seismic Response of Long Span Curved and Straight Rigid-Frame Bridges

利用多维多点激励的反应谱法对某大跨曲线刚构桥进行了水平双向多点地震反应分析,与相同结构尺寸的直线桥进行对比分析。结果表明:多点激励对于桥墩受力是有利的,减少了桥墩顺桥向响应,且对横桥向响应影响不大;直线桥和曲线桥在水平双向多点激励下桥墩受力相差不大。多点激励对主梁的地震响应是不利的,较大地放大了主梁的地震响应,尤其对主梁的扭矩放大作用很明显。另外,由于一致激励时,直线桥主梁受力幅值相对较小,相比曲线桥受多点地震激励的影响更加显著。该类桥型抗震设计时,由于主墩为抗震设计的薄弱部位,无论直线桥还是曲线桥,可不考虑多点激励对桥梁的影响。此外,对于常见的大跨曲线刚构桥(曲率半径大于300m),可按展开的直线桥进行抗震设计。

The response spectrum method of multi-directional and multi-support excitation is used to analyze the horizontal,two-directional and multi-support seismic response of a long span curved rigid-frame bridge and the analysis of the seismic response is compared to that of a straight rigid-frame bridge with same structural dimensions.The results of the analysis and comparison show that the multi-support excitation is beneficial to the force conditions of piers of the bridge,can reduce the response of the piers in the longitudinal direction,does not have much influence on the response of the piers in the transverse direction and the force conditions of both the straight and curved bridges under the horizontal,two-directional and multi-support excitation do not differ greatly.However,the multi-support excitation is not beneficial to the seismic response of the main girder,because it amplifies the response of the girder,particularly significantly the torsion moment of the girder.Moreover,since the amplitude values of the force conditions of the main girder of the straight bridge are relatively small at the time identical excitation takes place,the influence of the multi-support excitation on the straight bridge is more obvious as compared to that of the curved bridge.For the seismic design of a long span rigid-frame bridge,whether it is curved or straight,the influence of the multi-support excitation may not be considered because the piers of the bridge are always the weak parts in the seismic design.Besides,for the common long span curved rigid-frame bridges（with curvature radii greater than 300 m）,the seismic deign of the bridges can be carried out in accordance with an unfolded straight bridge.