多维地震激励下人字形桥梁地震模拟振动台试验研究

Shaking table tests for Y-shaped bridges under multi-dimensional seismic excitation

为研究人字形桥梁在地震作用下的动力响应,以某人字形桥梁为原型,制作了一座相似比为1∶20的模型桥梁,采用El-Centro波对其进行了不同地震烈度的多维激励地震模拟振动台试验和有限元分析。研究结果表明:随着地震烈度的增加,模型结构自振频率降低阻尼比增大;桥墩墩顶顺桥向加速度响应基本不受竖向地震分量影响;计算桥墩墩底应变响应时进行水平双向地震激励即可满足要求;梁体跨中竖向加速度响应,主梁和分支梁间的伸缩缝宽度取值,伸缩缝处的碰撞响应等均与地震波输入维度有关。因此,对于人字形桥梁在进行抗震设计时应针对不同的设计目的对其进行选择性的多维地震激励。

In order to study sesimis responses of Y-shape bridges under earthquake,based on a existing Y-shape bridge,a scale 1 /20 model of Y-shaped curved bridge was constructed,El-centro waves were used to make a shaking table test with different earthquake intensity and multi-dimensional seismic excitation. Besides,the finite element analysis were also conducted for this model bridge. The research results showed that when the earthquake intensity is enhanced,the fundamental frequency of the model bridge decreases and its damping ratio increases; the longitudinal acceleration response of pier＇s top is not affected by the vertical earthquake excitation; the horizontal bidirection earthquake excitation can meet the requirement when calculating the strain response at bottom of a pier; the vertical acceleration response of the mid span,expansion joints width between the main beam and branch beams and pounding response at expansion joint are related to seismic wave input dimension; therefore,when designing Y-shaped bridges,multi-dimensional seismic excition should by chosen according to different design purposes.