一般大气环境下锈蚀钢筋混凝土梁的时变可靠度分析

Time-dependent reliability analysis of corroded reinforce concrete beams in the atmospheric environment

根据一般大气环境下锈蚀钢筋混凝土梁中的钢筋截面损失时变模型和抗剪、抗弯承载力退化模型,建立了考虑其随机性的极限状态方程。基于概率守恒原理分析得到满足该极限状态方程的概率密度演化方程,并引入吸收边界条件,提出了梁时变可靠度的计算方法。以受对称集中荷载的锈蚀钢筋混凝土简支梁为例,展示了目标函数的概率密度演化过程,并讨论了配置不同直径箍筋和不同厚度保护层时的时变可靠度。结果表明,在保证梁具有足够初始抗剪强度和抗弯强度的前提下,适当增大保护层厚度和箍筋直径(具有相同配箍率)能延缓混凝土构件力学性能的退化。通过和100万次蒙特卡洛模拟结果的对比可知,选用本文方法能在以付出较小计算代价的前提下,获得计算精度良好的分析结果。

The limit state equation with random parameters is established based on the time-dependent model of reinforcement material performance and the degradation probabilistic model of shear strength and bending strength in corroded reinforced concrete beams under atmospheric environment.The probability density evolution equation which satisfies the limit state equation is obtained based on the principle of probability conservation,and the calculation method of time-dependent reliability for the degradation strength of beams is proposed by introducing absorbing boundary conditions.The probability density evolution process of objective function is shown and the time-dependent reliability of different diameters of stirrups and different depths of concrete cover is discussed by taking a simply supported corroded reinforced concrete beam subjected to symmetrical concentrated loads as an example.The results show that the degradation of mechanical properties of concrete members can be delayed by appropriate increasing the concrete cover depth and the stirrups diameter under the precondition that the beam has enough initial shear strength and bending strength.By comparing 1 million Monte Carlo simulation results,it can be seen that the proposed method can obtain the results with good calculation accuracy at less computational cost.