基于改进可靠度方法的预应力混凝土T梁桥加固效果评估

Evaluation of the Reinforcement Effect of Prestressed Concrete T-Beam Bridges Based on the Improved Reliability Method

摘要: 以一座预应力混凝土T梁桥为研究对象，针对其开裂、锈蚀及局部构造损伤引起的安全储备衰减问题，开展加固前后可靠度评估研究。针对传统可靠度计算中控制对象容易泛化、病害折算路径较为单一、横向分布变化考虑不足等问题，本文以单幅外侧边梁跨中正截面受弯极限状态为评估对象，提出一种考虑损伤退化、横向分布不利化及CFRP加固恢复效应的改进可靠度分析框架。该框架将既有病害影响分别映射至抗力退化、荷载效应放大和参数不确定性变化中，并对预应力筋破坏时平均应力、恒活载效应、横向分布系数及随机变量统计参数进行一致化校核。结果表明：健康状态下桥梁可靠指标为3.85；损伤状态下，传统方法与改进方法计算值分别为3.17和2.79；CFRP加固后分别提高至3.47和3.39，说明加固措施能够有效恢复结构安全储备。研究表明，改进方法能够更合理地反映老旧T梁桥损伤退化、横向受力重分配和加固恢复效应之间的耦合关系，可为同类既有T梁桥加固效果评估提供参考。

Abstract: Taking a prestressed concrete T-beam bridge as the research object, a study was conducted on the attenuation of safety reserve caused by cracking, corrosion and local structural damage before and after reinforcement. Addressing the problems in traditional reliability calculation, such as the tendency for control objects to be generalized, the relatively simple disease conversion paths, and insufficient consideration of lateral distribution changes, this paper takes the mid-span flexural limit state of a single side beam of the bridge as the evaluation object and proposes an improved reliability analysis framework that takes into account damage degradation, lateral distribution deterioration and the reinforcement recovery effect of CFRP. This framework maps the influence of existing diseases to the degradation of resistance, the amplification of load effects and the changes in parameter uncertainties, and conducts consistent verification of the average stress of prestressed steel bars, the constant and live load effects, the lateral distribution coefficient and the statistical parameters of random variables. The results show that the reliability index of the bridge in a healthy state is 3.85; in the damaged state, the calculated values by the traditional method and the improved method are 3.17 and 2.79, respectively; after CFRP reinforcement, they increase to 3.47 and 3.39, respectively, indicating that the reinforcement measures can effectively restore the structural safety reserve. The study shows that the improved method can more reasonably reflect the coupling relationship between damage degradation, lateral force redistribution and reinforcement recovery effect of old T-beam bridges, and can provide a reference for the evaluation of the reinforcement effect of similar existing T-beam bridges.