考虑锈蚀黏结退化的钢筋混凝土桥墩抗震性能分析

SEISMIC PERFORMANCE ANALYSIS OF REINFORCED CONCRETE BRIDGE COLUMN CONSIDERING BOND DETERIORATION CAUSED BY CHLORIDE ION INDUCED CORROSION

受氯离子腐蚀作用影响,钢筋混凝土结构的抗震性能在其服役期内会发生退化。以钢筋混凝土桥墩为例,采用OpenSees有限元软件模拟了非锈蚀足尺桥墩的振动台试验以及锈蚀缩尺桥墩的拟静力试验结果,后者引入了氯离子腐蚀作用模型,同时考虑了桥墩的纵筋力学性能衰减以及粘结退化问题。随后基于概率地震需求模型对足尺桥墩的三种纵筋腐蚀工况进行了易损性分析。研究结果表明:采用非线性梁柱单元与零长度截面单元串联方式建立的数值模型能够有效模拟钢筋混凝土桥墩的足尺振动台试验结果和缩尺锈蚀拟静力试验结果;当纵筋腐蚀率较小时,纵筋的性能退化对墩顶最大位移影响不大,但基底剪力和基底弯矩下降明显;轻微破坏状态下,桥墩的抗震性能受纵筋锈蚀的影响不明显,随着破坏程度的加深,纵筋锈蚀对桥墩抗震性能的影响逐渐显著,较小的腐蚀率能导致桥墩的破坏概率发生较为明显的提高。研究内容可为考虑全寿命周期内性能退化的钢筋混凝土结构抗震设计提供参考。

The seismic performance of RC structures declines due to the chloride ion induced corrosion in their life cycles. By means of the software OpenSees, numerical models were built to simulate the test results of a full-scale RC bridge column tested on the shake table and some corroded reduced-scale RC columns tested under quasi-static loadings. According to existing investigations on the model of chloride ion induced corrosion, the degradation of the mechanical property of longitudinal reinforcement and bond deterioration were both considered in the numerical models of corroded RC columns. Then fragility analysis was performed based on the probabilistic seismic demand model for three cases of full-scale RC bridge columns, considering different percentage of the corroded mass relative to the initial mass of the longitudinal reinforcement. The results show that： the numerical model established by parallel connecting the zero-length section element to the nonlinear beam-column element can simulate the test results effectively; when the corroded mass of the longitudinal reinforcement is minor, the maximum top displacement of the column is not sensitive to the degradation of the mechanical property of longitudinal reinforcement, but the maximum base shear force and moment decrease obviously; When the damage degree of the column is slight, the corrosion of longitudinal reinforcement affects the structural seismic performance negligibly. When the damage condition becomes severer, the effect of the corrosion of longitudinal reinforcement is more obvious. A minor corrosion of longitudinal reinforcement increases the damage probability observably. The study can provide a reference for the seismic design of reinforced concrete structures when considering the performance degradation in the life cycle.