考虑碳化和氯离子累积效应的梁桥时变可靠度

Time-dependent reliability analysis on reinforced concrete beam bridge considering carbonization and chloride accumulation effect

摘要:

为探究多因素影响下钢筋混凝土桥梁的性能退化情况,对其抗力及可靠性时变演化过程进行研究.分析碳化、混凝土表面氯离子累积效应、荷载以及裂缝对氯离子侵蚀的影响.根据Fick第二定律和路径概率方法得到不同服役期时钢筋锈蚀率的无条件概率密度分布,进而得到不同服役期对应的抗力概率密度分布,并采用三参数Burr XII分布模型对其进行拟合.采用蒙特卡洛方法对不同服役期桥梁的可靠度进行计算,研究碳化和混凝土表面氯离子累积效应对钢筋锈蚀概率、桥梁抗力及可靠性的影响.结果表明:随着服役时间的增加,桥梁的抗力及可靠性逐渐降低,抗力的离散性逐渐增大；考虑碳化和累积效应后,桥梁的抗力及可靠性会降低,碳化和累积效应对桥梁可靠性的影响主要体现在服役后期.在对服役期较长的桥梁进行可靠性评估时应注重考虑碳化和氯离子累积效应的影响.

Abstract:

To investigate the performance degradation of reinforced concrete bridges under multiple factors, the time-dependent evolution process of its resistance and reliability was studied. The effects of carbonization, chloride accumulation, load, and crack on chloride ion erosion were analyzed. According to Fick’s second law and the path probability model, the unconditional probability density distribution of corrosion rate at different service periods was obtained, and then the probability density distribution of resistance corresponding to different service periods was obtained. The three parameter Burr XII distribution model was used to fit it. The Monte Carlo method was used to calculate the reliability probability of the bridge in different service periods, and the effect of the carbonization and chloride accumulation on the probability of corrosion of steel bar as well as the resistance and the reliability of the bridge was studied. The results show that the resistance and reliability of the bridge gradually decrease with the increase of service time, and the dispersion of resistance increase gradually. The resistance and reliability of the bridge reduce when the effect of carbonization and chloride accumulation is considered. The effect of carbonization and chloride accumulation on bridge reliability is mainly manifested in the later stage of service. The influence of carbonization and chloride accumulation should be considered when evaluating the reliability of a bridge that has been in service for a long time.