横向非等高双柱式桥墩抗震性能研究

Study of Seismic Performance of Transversely Unequal-Height Double-Columned Piers

为研究墩高差对横向非等高双柱式桥墩抗震性能的影响,以某山区3×(5×30)m梁桥为背景,建立OpenSees全桥有限元模型,采用增量动力分析方法(IDA),输入地震动,分析不同墩高差下墩柱关键截面的弯矩~曲率关系、曲率、墩顶位移以及曲率与位移关系。结果表明:地震荷载作用下,当墩高差在10m以上时对系梁位置处桥墩截面延性影响较大,随墩高差增加,与横向等高双柱式桥墩相比,墩顶截面延性有所减小,墩底截面延性增加较大;受墩高差影响,墩底与系梁位置处桥墩曲率在屈服后对地震动强度变化更敏感;墩顶位移总体与墩高差成反相关,墩高差对墩顶位移的影响在峰值加速度PGA=0.5g后差异较大,PGA由0.5g增加到1.0g时,随墩高差增大,墩顶位移减小量逐渐变小;受墩高差影响,横向非等高双柱式桥墩破坏模式差异显著。

To study the influence of pier height difference on the seismic performance of transversely unequal-height double-columned piers, a beam bridge with spans of 3×(5×30) m in the mountainous region was taken as the study background. The software OpenSees was used to establish the finite element model of the overall bridge, to which the ground motion was input by the incremental dynamic analysis (IDA)method. The relations of bending moment and curvature, curvature, pier-top displacement and the relations of curvature and displacement of the key pier column sections were analyzed, in the contexts of different pier heights. The results show that when exceeding 10 m,the height difference will exert great influence on the section ductility in the piers at the locations of tie beams, under seismic loads. As the pier height difference increases, ductility in the pier-top cross section decreases, but the ductility in the pier-base cross section significantly increases. Due to the influence of pier height difference, the pier curvatures in the pier base and at the locations of the tie beams after yielding are more sensitive to the undulation of ground motion intensity. The pier-top displacement is, at large, inversely proportional to pier height difference. There appears great variation of influence of pier height difference on the pier-top displacement, when the peak ground acceleration is 0.5g. When the peak ground acceleration rises from 0.5g to 1.0g, the decreasing amount of the pier-top displacement gradually drops, as the pier height difference increases. Due to the existence of pier height difference, the damage mode variation of transversely unequal-height double-columned piers is distinct.