采用混合体系的预制拼装桥墩抗震性能分析

Analysis of seismic performance of a hybrid prefabricated bridge pier system

为提升预制拼装桥墩在地震作用下的延性和耗能能力,构思一种结合整体现浇桥墩与预应力节段拼装桥墩体系的混合体系预制拼装桥墩。介绍混合体系预制拼装桥墩的设计思路、构造和力学行为特征,分析其三水准性能目标。建立桥墩的三维实体有限元分析模型,并通过参照试验结果进行验证。从混凝土应变、预应力行为、滞回特性和接缝开合等角度,分析不同形式桥墩在循环荷载下的抗震性能。选取底部节段高度、初始预应力水平、预应力布置方式等关键设计参数,探讨其对混合体系拼装桥墩和预应力拼装桥墩抗震性能的影响规律。研究结果表明:混合体系预制拼装桥墩与预应力拼装桥墩相比,可同时利用接缝非线性行为和底部塑性铰机制来抵抗地震作用,其初始弹性刚度和水平承载力更大,具有更强的延性和耗能能力;混合体系预制拼装桥墩底部节段的长细比大于1.2时,随着长细比的增大,位移延性降低,残余位移增大;初始预应力水平对2种桥墩水平承载力、位移延性、初始弹性刚度等的影响有差异,对于混合体系预制拼装桥墩,40%的初始预应力水平较为合适;混合体系预制拼装桥墩的预应力束在截面边缘布置可减小接缝位置混凝土的损伤,同时可有效提高桥墩的水平承载力。研究结论可为预制拼装桥墩的抗震设计和性能优化提供参考。

In order to enhances the ductility and energy dissipation capacity of the prefabricated bridge piers during earthquakes,a novel prefabricated hybrid bridge pier system,which combines a monolithic cast-in-situ pier system with a prefabricated post-tensioned pier system,was designed.The design idea,construction,and mechanical behavior of the prefabricated hybrid bridge piers were introduced.Their performance objectives were analyzed under three levels of ground motions.Three-dimensional finite element models of the piers were established,and the numerical results were verified by comparing them with previous test results.The seismic performances of different types of piers were analyzed in terms of concrete strain,prestressingbehavior,hysteretic characteristics,and joint openings of the models under cyclic loads.The influences of three design parameters,namely base segment height,initial prestressing level,and prestressing layout on the seismic performance of the piers were studied.The results show that compared with conventional prefabricated post-tensioned piers,the proposed hybrid piers have greater initial stiffness,lateral carrying capacity,ductility,and energy dissipation,owing to the anti-seismic abilit,provided by the joint rocking behavior and the plastic hinging mechanism at the base segment.As the slender ratio of base segment rises from 1.2,the proposed hybrid piers exhibit a decreasing displacement ductility and a growing residual deformation.The initial prestressing level has different influences on the lateral carrying capacity,displacement ductility,and initial stiffness of the two types of piers.For the proposed hybrid piers,the ideal prestressing level is around 40%.The prestressing at the section edge of the hybrid piers can effectively mitigate the damage to the concrete near the joint,and enhance the lateral carrying capacity.This research can provide a reference for the seismic design and performance optimization of prefabricated bridge piers.8 tabs,14 figs,22 refs.