应用Monte Carlo-JC法评估FRP加固RC梁受弯承载力可靠度

Application of Monte Carlo-JC method to the reliability assessment of flexural capacity of RC beams strengthened with FRP

将Monte Carlo随机抽样方法与JC法相结合(称为Monte Carlo-JC法),利用Matlab软件自带的随机数发生器编制了程序,针对ACI 440.2R-02设计指南(称为ACI指南)中的FRP抗弯加固条款进行了较为系统的可靠度评估。可靠度分析结果表明:混凝土强度fc′、CFRP片材配筋率fρ及CFRP片材性能是影响抗力比值均值和标准差的3个主要因素;可靠度指标的平均值随着折减系数的增大而逐步减小,且随着荷载效应比值Ln/Dn的增大而减小。对所有可靠度指标进行统一考虑,得到整体抗弯设计指标0β为4.40,可见该指南的可靠度水平偏高。基于对抗力折减系数的参数研究结果,无论钢筋的应变水平如何,建议取固定值0.90。在所有相关设计指南中,ACI指南最具有代表性,对该指南的可靠度评估具有普遍意义。

The JC method combined with Monte Carlo simulation procedure （called Monte Carlo-JC method） was applied to conduct a systematic reliability assessment of flexural capacity of FRP reinforced concrete beams designed by the report ACI 440. 2R-02 （called ACI guideline）. Several programs were made by utilizing the inherent random number generators of Matlab software. The results indicate that the concrete strength f＇e, CFRP reinforcement ratio ρr and CFRP mechanical properties are the most significant influencing factors on the mean values and the standard deviations of the strength ratio M/（ФMn）. The results show that the averaged reliability indexes decrease with increasing the resistance reduction factor Ф and load effect ratio Ln/Dn. The global reliability index for flexural design was found to be 4.40, based on all reliability indexes. The reliability level of ACI guideline is rather conservative. The resistance reduction factor Ф is suggested as a fixed value of 0. 90, regardless of the strain level of the tensile steel reinforcement. ACI guideline is the most typical one among all current relevant guidelines. The reliability assessment of this guideline is of general significance.