山区桥梁排架抗震能力评价方法

摘要

Bents are widely used as bridge columns in mountain areas.The seismic failure mechanism of the bents is complex under transverse seismic actions.Also,no practical seismic analysis method is available to evaluate the seismic behavior of the bents.A practical seismic analysis method for RC bridge bents in mountain areas was proposed based on the quasi-static and dynamic time-history analysis.The failure mode of the pier and the deformation capacity of the bent were analysed by using the fiber column element and shear strength model for column section.Then,the failure mode and deformation capacity of the bent under different ground motion intensity were revealed according to the time-history analysis.The seismic behaviors of 2 bridge bents in one bridge in mountain areas were evaluated by the proposed method. It is found that the axial load of the piers in the bent will be changed significantly as a result of the transverse seismic action.Before yielding of the pier,the variation range of the axial load increases as the lateral displacement increases. After yielding of the pier,the range will change no more and the variable axial load would lead to shear failure of the piers.The results provide reference to the seismic design and analysis of bridge bents.%排架在山区桥梁工程中应用广泛，其横桥向地震破坏机理复杂且缺乏工程实用的抗震分析手段。通过拟静力和动力时程分析给出了山区桥梁排架抗震能力评估的一般性方法，借助纤维梁柱单元并结合截面抗剪强度模型，首先基于静力分析手段确定了排架桥墩可能的破坏模式及排架变形能力。在此基础上通过动力时程分析，揭示不同地震动强度下排架的破坏模式和变形能力。以某山区桥梁2个排架墩为例，将建立的评价方法对排架横桥向抗震能力进行评价。结果表明：横桥向在地震作用下，排架桥墩承受显著的变轴力作用，桥墩屈服前，随侧向位移增大，桥墩轴压变化范围逐渐增大，桥墩屈服后轴压变化范围基本稳定；且变轴力易引起排架桥墩发生剪切破坏。该方法可为桥梁排架结构抗震设计和评估提供参考手段。