考虑抗力与恒载相关性的钢筋混凝土梁桥限载取值研究

Research on Truck Weight Limits for Short to Medium Span RC Beam Bridges Considering Correlation of Resistance and Dead Load Effect

为给按不同时期规范设计的中、小跨径钢筋混凝土梁桥限载合理取值提供参考,依据《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTJ 023-85、JTG D62-2004、JTG 3362-2018)中对应的混凝土受弯构件承载能力极限状态设计表达式,提出一种考虑抗力和恒载效应相关性的中、小跨径钢筋混凝土梁桥限载取值分析方法。该方法引入抗力与恒载效应相关系数,应用Rosenblatt变换公式构造由独立标准正态随机变量表示的结构功能函数,并建立基于验算点法(JC法)的公路桥梁限载系数反演分析模型,在此基础上,针对按不同时期规范设计的钢筋混凝土梁桥,以规范目标可靠指标为基准、设计活恒载比值为基本参数,分别计算不同抗力和恒载效应相关系数对应的限载系数,并按限载等级一级计算与JTJ 023—85、JTG D62—2004、JTG 3362—2018规范对应的典型车辆总重限值。计算结果表明:抗力与恒载效应相关性对中、小跨径钢筋混凝土梁桥限载取值影响较大,在相同的限载等级和设计活恒载比值下,相关系数越大,典型车辆总重限值越大;提出的限载分析方法和典型车辆总重限值可作为中、小跨径混凝土梁桥限载标准与超重车辆认定标准制定的参考依据。

This paper studies the reasonable truck weight limits for short to medium span RC beam bridges designed in accordance with the specifications of different periods,and an analytical method to determine truck weight limits for short to medium span RC beam bridges is presented,using the ultimate limit state equations in the Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts(JTJ 023-85,JTG D62-2004 and JTG 3362-2018).The correlation of resistance and dead load effect is also considered in the analytical model.Based on Rosenblatt′s transformation,the performance function is first constructed in terms of uncorrelated standard normal random variables and correlation coefficient of resistance and dead load effect,and then the back-calculation method for determining truck weight limits for highway bridges is established using the Checking Point Method(JC method).Furthermore,the truck weight limit factors corresponding to different resistance and dead load effects are calculated based on the target reliability index adopted by current bridge design code and the design live to dead load ratio.The gross weight limit values of typical truck corresponding to specifications JTJ 023-85,JTG D62-2004,and JTG 3362-2018 are determined under level 1 safety class.The results show that the correlation coefficients of resistance and dead load effect have a significant influence on truck weight limits of RC beam bridges.For the same safety level and live to dead ratio,the gross weight limits of typical trucks increase with the correlation coefficient of resistance and dead load effect.The proposed truck weight limits analytical method and typical gross weight limits can serve as a reference for the development of standards for determining truck weight limits and identifying overweight vehicles for short to medium span RC beam bridges.