行波效应对大跨钢桁拱桥地震易损性的影响

Influence of Traveling Wave Effect on Seismic Vulnerability of Long-Span Steel Truss Arch Bridge

以某主跨长为490 m的大跨有推力上承式钢桁拱桥为研究对象,分别采用一致激励与行波激励2种激励模式,基于能力需求比模型与增量动力分析,建立拱上立柱及拱肋弦杆典型构件易损性曲线及概率差值曲线,分析行波效应对该桥地震易损性的影响。结果表明:2种激励模式下,拱顶区域与拱上立柱相交处的上弦杆、拱顶短立柱均为易损构件;与一致激励相比,行波激励下拱肋上弦杆易损构件总数量由10个增至22个,即内、外侧上弦杆数量分别由8和2个增至13和9个;行波激励下拱肋1/4和3/4附近区域的上弦杆也变为易损构件;行波效应对拱顶区域上弦杆易损构件的中等损伤超越概率影响显著,一致激励下的分析会明显低估响应结果;拱桥在峰值加速度0.5g的罕遇地震行波激励下,中等损伤超越概率仅为3%,拱肋弦杆基本保持在弹性或处于轻微损伤状态。

Taking a long-span deck-type thrust steel truss arch bridge with the main span of 490 m as the research object,two kinds of excitation modes including uniform excitation and traveling wave excitation were adopted respectively.Based on the capacity demand ratio model and incremental dynamic analysis,the vulnerability curves and probability difference curves of the typical components of arch column and arch rib chord were established to analyze the influence of traveling wave effect on the seismic vulnerability of the bridge.The results show that under the two excitation modes,the upper chord at the intersection of the arch vault area and the arch column and the arch short column are vulnerable components.Compared with the uniform excitation,the total number of vulnerable components of the upper chord of the arch rib under traveling wave excitation increases from 10 to 22.That is,the number of inner and outer upper chord increases from 8 and 2 to 13 and 9 respectively.The upper chords near 1/4 and 3/4 of the arch ribs also become the vulnerable components under traveling wave excitation.The traveling wave effect has a significant influence on the exceedance probability of medium damage for the vulnerable components of the upper chord in the vault area,and the analysis under uniform excitation will obviously underrate the response results.Under the traveling wave excitation of rare earthquake with the peak acceleration of 0.5g,the exceedance probability of medium damage of the arch bridge is only 3%,and the conditions of the arch rib chords are basically elastic or slightly damaged.