碰撞对山区高墩桥弹塑性动力响应的影响

摘要

为了研究碰撞对山区高墩桥动力响应的影响,以某一大跨度高墩桥体系为原型,充分考虑了碰撞过程中的刚度变化、能量耗散以及桥墩的非线性行为,基于OpenSess平台建立了两种典型桥跨结构的弹塑性动力分析模型.在此基础上,利用所选的天然地震波和人工地震波对比分析了碰撞效应对山区高墩桥弹塑性动力响应的影响.研究结果表明:碰撞会对高墩桥结构的动力响应产生较为明显的影响,特别是场地条件较差时,其最大改变率为15.86％,桥墩与主梁的连接方式会进一步改变碰撞对桥墩变形的影响程度;相邻结构动力特性差异越大,高墩桥体系发生碰撞的概率就越大,但碰撞次数的增加可能会对桥墩变形起到限制作用,降低桥墩的响应,在确定山区高墩桥体系相邻结构周期比时,既要考虑相邻结构动力特性差异对碰撞概率的影响,还应考虑其对碰撞效应的影响;高墩桥的梁-桥台碰撞主要受地震动作用大小的影响,地震动的强度和相邻结构动力特性的差异均会对梁-梁碰撞产生影响,在对高墩桥进行减撞防撞设计时,应针对不同的碰撞位置采取不同的措施.%To study the effect of pounding on the seismic response of high-pier bridge in mountainous areas,the elastic-plastic dynamic analysis models of two typical bridge structures were established by using the OpenSees framework,based on the prototype of a real high-pier bridge. The variation in stiffness,energy dissipation during the pounding process,and the non-linear behavior of the piers were fully considered in the models. Additionally,the effect of pounding on dynamic responses of a high-pier bridge was analyzed by using the selected natural and artificial ground motions. The results show that pounding can significantly affect the structural responses,especially for poor site conditions,and the maximum change rate is 15. 86％ . Moreover,the method of connecting the pier and beam further influences the effect of pounding on the pier displacement; A larger difference in dynamic characteristics of adjacent structures corresponds to a larger probability of collision;however,the increasing frequency of pounding may reduce the responses of piers,owing to the restriction effect on the pier deformation. Thus,when selecting the period ratio of adjacent structures,it is necessary to consider its effect on not only the probability of pounding,but also on the degree of effect of pounding. In comparison,beam-abutment pounding is mainly affected by the intensity of ground motions,whereas the beam-beam pounding is influenced by both the intensity of ground motions and the difference in dynamic characteristics of adjacent structures. Therefore,in seismic design,to reduce the pounding of high-pier bridges,it is suggested that different measures should be adopted for different pounding positions.