钢筋锈蚀率的概率模型及时变可靠度分析

氯离子引起的钢筋锈蚀是导致钢筋混凝土结构性能劣化的主要原因,因此有必要对钢筋锈蚀率的计算进行详细研究。考虑钢筋锈蚀过程中各影响因素的不确定性,将钢筋初锈时间和保护层开裂时间作为随机变量,首先分3种情况建立钢筋锈蚀率的计算模型;然后通过Monte Carlo模拟对锈蚀率进行概率分析,确定锈蚀率的概率分布类型和统计参数,最后根据收集的试验数据建立钢筋混凝土受弯构件剩余承载力与钢筋锈蚀率的关系,对受腐钢筋混凝土受弯构件进行时变可靠度分析。研究表明:钢筋锈蚀率服从正态-正态双峰分布;暴露时间越长,钢筋未锈蚀和混凝土保护层未开裂的概率越小;构件可靠度随时间的增加明显降低。

A probability model for rebar corrosion loss and time-dependent reliability analysis of RC member

Chloride-induced corrosion of reinforcing steel bar is a major factor that affects structural performance of reinforced concrete structures. It is important to acculately calculate the corrosion loss of the reinforcing steel bar. A probability model for corrosion rate is developed in this paper， in which both the time of corrosion initiation and the time of concrete cover cracking are treated as random variables which are related to uncertainties in the process of reinforcing steel bar corrosion. Statistical analysis of the corrosion rate is conducted by Monte Carlo simulation and the statistical parameters and distribution type of the corrosion rate are determined. Finally， an expression to depict the relationship between the resistance of the RC flexual member and the corrosion rate of the reinforcing steel bar is proposed based on the collected experimental data in literatures, and time-dependent reliability analysis of corroded RC member served in marine environment is performed. The analysis results show that the corrosion rate loss of steel bar follows a bimodal probability distribution. The probabilities of having no corrosion and no cover cracking reduce with the time increasing. The reliability indexes reduce significantly with time due to chloride-induced corrosion.