疲劳荷载作用下锈蚀预应力混凝土梁时变可靠性分析与寿命预测

Based on mechanism of fatigue failure of corroded prestressed tendons, a parameter characterizing deterioration of fatigue properties will be proposed for corroded prestressed tendons. High-precision geometrical models will be established for corroded prestressed tendons by using the three-dimensional laser scanning technique. The evolution of geometrical characteristics of prestressed tendons with the increasing corrosion degree will be analyzed, and a time-dependent probability distribution model for the parameter characterizing deterioration of fatigue properties will be obtained. Stochastic stress-strain relationship will be developed for corroded prestressed tendons with fatigue damage by tension tests after experiencing a certain cycles of fatigue loading. Based on the previous study on flexural fatigue behavior of corroded prestressed concrete beams, the degradation and failure mechanism for shear fatigue behavior of corroded prestressed concrete beams will be investigated, and the mechanism for transfer between two kinds of failure modes will be proved.The fatigue damage accumulation criterion, the damage constitutive and the failure criterion for concrete, steel bars and prestressed tendons will be given and introduced, and then a whole-process analysis method will be put forward for structural response of corroded prestressed concrete beams under fatigue loading. Taking into account the spatial-temporal variability of geometric characteristics and mechanical properties of corroded prestressed tendons, the potential failure modes, a time-dependent reliability analysis method for prestressed concrete beams under fatigue loading will be developed by means of the probability density evolution theory and/or the Monte Carlo method. Meanwhile, the coupling mechanism between corrosion of stirrups and longitudinal reinforcement will be studied, and the influence of coupling effects on the evolution of geometric characteristics, the degradation of fatigue properties of prestressed tendons and the fatigue reliability of corroded prestressed beams will be investigated.

从锈蚀预应力筋疲劳破坏机理入手，提出疲劳性能退化表征参数。采用三维激光扫描技术建立锈蚀预应力筋高精度几何模型，探索锈后预应力筋几何特征演化规律，建立疲劳性能退化表征参数时变概率分布模型。通过先疲劳后静力拉伸的方法，建立疲劳损伤锈蚀预应力筋随机本构。在锈蚀预应力混凝土梁弯曲疲劳性能研究的基础上，重点研究锈后剪切疲劳性能的退化和破坏机理，探明两种破坏模式的转换机制。引入混凝土和钢筋/预应力筋的疲劳损伤累积准则、损伤本构以及破坏准则，提出疲劳荷载作用下锈蚀预应力混凝土梁结构响应的全过程分析方法。综合考虑锈蚀钢筋/预应力筋几何特征、力学性能的时空变异性以及破坏模式，借助于概率密度演化理论和蒙特卡洛方法，发展疲劳荷载作用下锈蚀预应力混凝土梁的时变可靠性分析方法，为结构全寿命设计理论的发展奠定基础。同时，研究箍筋与纵筋间的偶接作用机理，探明偶接作用对几何特征演化、疲劳性能退化乃至锈蚀梁疲劳可靠性的影响

预应力混凝土结构广泛应用于桥梁、海洋平台、核电站安全壳等重要工程结构，承受静载作用的同时，长期承受重复荷载和环境作用。预应力筋/钢筋锈蚀是其性能退化、提前发生破坏的主要原因。项目对锈蚀预应力筋锈蚀后几何特征和力学性能及锈蚀预应力混凝土梁疲劳性能的随机演化开展了系统研究，提出了时变可靠性分析和疲劳寿命预测方法，为混凝土结构全寿命设计与维护理论的建立奠定了基础。.疲劳拉伸实验表明，锈蚀预应力筋/钢筋往往在横截面积最小且存在明显锈坑处发生疲劳断裂，疲劳寿命的降低不仅与横截面积的减小及其纵向不均匀性有关，还与锈坑处应力集中密切相关，为此提出疲劳性能退化表征参数即锈坑处应力综合影响系数K。采用时间连续、状态分离的马尔科夫链模拟锈坑演化过程，通过三维激光扫描建立锈蚀预应力筋/钢绞线高精度几何模型，探明锈后预应力筋几何特征演化规律及钢绞线中丝与边丝几何特征演化的相关性，获得横截面积纵向不均匀性系数R和锈坑处应力综合影响系数K的时变概率分布模型。.锈蚀预应力筋静力拉伸和疲劳拉伸的数值试验与物理实验相结合，探明预应力钢丝和钢绞线力学性能退化规律。随着钢筋锈蚀和疲劳损伤的发展，强化段缩短乃至消失，强度降低、离散性增大，弹性模量基本不变但离散性增大；经统计分析建立力学性能指标的随机过程模型，在此基础上，发展了静力拉伸和疲劳损伤预应力钢丝/钢绞线的随机本构关系。.开展了锈蚀预应力混凝土梁弯曲疲劳和剪切疲劳的实验研究，揭示了受力性能退化规律和破坏机理，探明了弯曲破坏和剪切破坏两种模式的转换机制。引入混凝土和钢筋/预应力筋的疲劳损伤累积准则、损伤本构以及破坏准则，提出疲劳荷载作用下锈蚀预应力混凝土梁结构响应的全过程分析方法。综合考虑锈蚀钢筋/预应力筋几何特征、力学性能的时空变异性以及破坏模式，借助于蒙特卡洛方法，发展了疲劳荷载作用下锈蚀预应力混凝土梁的时变可靠性分析方法以及基于概率的疲劳寿命预测方法。