中文摘要：

针对软土地区拓宽桥梁抗震研究的不足,以珠三角地区某一不等跨连续梁桥为工程背景,在考虑桩—土联合作用效应的前提下,引入纤维模型弹塑性梁单元,利用有限元程序Midas/Civil对旧桥模型、两种场地土条件下的拓宽桥梁模型进行了弹塑性地震响应分析.研究了不同地震波输入方向结构关键位置的位移响应,结构塑性铰的出现时间、位置和破坏模式.研究表明：软土场地拓宽模型的地震响应位移极值最大,约为砂土场地拓宽桥梁位移极值的1.15倍;在分级纵、横向地震荷载下,软土拓宽模型桥墩最早出现塑性铰,更容易发生破坏,且破坏时间更早.通过对比原桥模型和拓宽模型表明,结构拓宽不利于抗震,建议今后对拓宽桥梁提高抗震验算要求.

英文摘要：

In view of the deficiency of seismic research on widen bridge at soft soil area, the paper, based on an unequal span continuous beam bridge at Pearl River Delta, took pile-soil effect into consideration. Fiber inelastic beam element, finite element program Midas/civil is used to do elastic-plastic seismic response analysis on existing bridge model and widen bridge model under two field soil conditions. The paper researched displacement response of the structure＇s key position corresponding with different input direction of seismic wave, the occurrence moment, position and failure mode of plastic hinge. Researches showed that the seismic response displacement extreme of widen bridge at soft soil field was the biggest, which was nearly 1.15 times of it at the sand field. Under hierarchical vertical and lateral seismic loads, plastic hinge firstly occurred at pier of widen bridge at soft soil field, where failure happened easily and the failure moment was earlier. By contrasting existing bridge model with widen bridge model, structure widening was bad for aseismatic action, the paper suggested that seismic checking requirements of widen bridge should be enhanced.