氯离子侵蚀作用下的典型钢筋混凝土梁桥时变抗震性能分析

Time-dependent seismic performance analysis of typical reinforced concrete girder bridge under chloride-induced corrosion

  • 摘要: 为研究氯离子侵蚀作用下钢筋混凝土(reinforced concrete, RC)桥梁抗震性能的退化规律,基于Duracrete模型和现有材料劣化的研究成果,确定了纵筋、箍筋、保护层混凝土和核心混凝土力学性能的时变劣化模型;以一座三跨RC连续梁桥为例,采用OpenSees平台建立了不同服役时间下的桥梁分析模型,通过比较不考虑钢筋极限拉应变劣化、采用三种不同的劣化关系模型考虑钢筋极限拉应变劣化这四种情况,分析了氯离子侵蚀作用对桥梁结构抗震能力和地震需求的影响。分析结果表明:在氯离子侵蚀作用下,钢筋极限拉应变的劣化明显比钢筋屈服强度的劣化更为严重;考虑钢筋极限拉应变劣化时,桥墩截面极限曲率的退化更为显著,曲率地震需求明显增加,导致墩柱曲率能力与需求比更小,桥梁结构的抗震性能受到变形能力劣化的显著影响,因此若不考虑钢筋极限拉应变劣化,会使得对桥梁结构全寿命周期内抗震性能的评价结果偏于不安全;此外,三种劣化关系模型的适用性各不相同,墩柱曲率能力与需求比的退化程度也存在较大的差异,需要根据研究应用的场景进行选择。因此,选用合适的劣化关系模型,在RC梁桥时变抗震性能评估中考虑钢筋极限拉应变的劣化特性是很有必要的。

     

    Abstract: This study aims to investigate the life-cycle seismic performance degradation behaviour of reinforced concrete (RC) bridges under chloride-induced corrosion. Based on the Duracrete model and existing research results, the time-dependent deterioration models for the mechanical properties of longitudinal reinforcement, transverse reinforcement, cover concrete, and core concrete are determined. A three-span continuous RC bridge is taken as an example, and its nonlinear analysis models corresponding to different characteristic time points are established by the OpenSees platform. Four analysis cases are investigated to study the effects of chloride-induced corrosion on the bridge's seismic capacity and seismic demand. Among these cases, one involves the omission of considering the deterioration of ultimate tensile strain of reinforcing steel, while the remaining three consider this deterioration using three diverse degradation models. The results show that: in the presence of chloride-induced corrosion, the degradation of the ultimate tensile strain of reinforcing steel manifests markedly more severe than the deterioration observed in its yield strength; the bridge suffers a more significant decrease in ultimate curvature, a greater increase in curvature demand, and a lower curvature demand-to-capacity ratio of pier when considering the deterioration of ultimate tensile strain of reinforcing steel; disregarding the degradation of the ultimate tensile strain of reinforcing steel would render the life-cycle seismic performance evaluation results of bridge structures unreliable and unsafe; additionally, the applicability of these three deterioration models varies, and there are significant differences in the degree of degradation of curvature demand-to-capacity ratio among these models. Therefore, the choice among these three models should be grounded in the research application scenario. As a result, it is necessary to consider the deterioration characteristics of the ultimate tensile strain of reinforcing steel in the time-dependent seismic performance evaluation of RC bridges.

     

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