损伤钢筋混凝土结构氯腐蚀后的疲劳性能劣化规律与机理

The reinforced concrete structures in marine or in deicing environment will be comprehensively damaged by service cyclic load and chloride corrosion environment. The fatigue performance deterioration and mechanism of damaged reinforced concrete structures is not clear yet after the environment actions of chloride corrosion. Taking into account of microdefect sensitivity of structural fatigue strength, the experimental path in this project is selected as “load pre-damaged structures, then suffered environment of chloride corrosion, experiments of fatigue loading was carrayed finally”, which is different from the existing paths, i.e., fatigue loading in corrosivemedium or electrochemical pre-corrosion then fatigue loading. Reinforced concrete members was pre-damaged in different level by loading, then the damaged structures suffered environment action of chloride corrosion, the fatigue performance deterioration and mechanism are experimental investigated finally. Based on the experimental data, the nonlinear analysis model for damaged reinforced concrete structures will be derived and fatigue performance of damaged reinforced concrete structures are anayzed. The fatigue assessment model for damaged reinforced concrete structures will be suggested. The researching achievement here will supply technical supports for fatigue damage assessment, maintenance decision and fatigue life prediction of concrete structures.

沿海或除冰环境的钢筋混凝土桥梁结构在服役期间受到循环荷载和氯腐蚀环境的综合作用。氯腐蚀环境对损伤混凝土结构的疲劳性能劣化规律及机理的影响尚不清楚。不同于现有的无损结构腐蚀疲劳或先电化学腐蚀后疲劳加载的试验路径，本项目考虑到结构疲劳强度对微缺陷敏感的特性，拟采取先荷载损伤结构,再经历氯环境腐蚀,最后进行疲劳加载的试验路径，研究不同损伤程度的钢筋混凝土梁经受氯腐蚀环境作用后，其疲劳性能的劣化规律及钢筋腐蚀机理。基于试验数据,建立钢筋混凝土结构疲劳性能非线性分析模型 并分析钢筋混凝土结构疲劳性能的影响因素.提出结构疲劳状态曲线及评估模型。研究成果将为沿海及除冰环境下混凝土结构的疲劳损伤评估、维修决策和疲劳寿命预测提供依据.

针对钢筋混凝土（Reinforced Concrete, 简称RC）结构的疲劳寿命对微缺陷敏感的特性，本项目对荷载（疲劳荷载或循环荷载）造成的不同程度损伤RC梁经历氯腐蚀环境作用后的剩余静力性能、疲劳性能和氯扩散性能展开较为系统的试验研究，对损伤RC梁中受拉钢筋钝化过程以及不同配筋率RC梁经历疲劳损伤与氯腐蚀综合作用后的剩余疲劳性能进行试验研究。其中，RC梁的初始损伤程度由疲劳或循环荷载幅值（等于荷载上限与下限之差）及循环加载次数表征。试验结果表明，随着荷载幅值增加，初始损伤和氯腐蚀综合作用导致RC梁的剩余力学性能和疲劳寿命显著降低；初始损伤时的循环加载次数对RC梁的剩余疲劳寿命几乎没有影响，但是当荷载幅值大于0.3Pu（Pu为RC梁的静力极限荷载）时，循环加载次数增加对受拉混凝土的氯扩散性具有加速作用；配筋率较高（界限配筋率的77%）且荷载幅值为0.4Pu时，RC梁的剩余疲劳性能呈现明显的非线性特征；荷载损伤对RC梁中受拉钢筋的钝化过程具有加速作用。项目研究成果可为损伤RC梁经历氯腐蚀作用后的疲劳性能劣化提供科学依据，为沿海及除冰环境下RC结构的疲劳损伤评估和疲劳寿命预测决策提供参考。