在役桥梁承载能力检算系数的可靠性校准

Reliability-based Calibration of Load Capacity Checking Factors of Existing Highway Bridges

为建立与现行桥梁设计规范相适应的在役桥梁承载能力鉴定方法,应用可靠性理论对承载能力检算系数取值进行了校准.根据在役桥梁承载能力检算表达式,引入桥梁结构或构件技术状况评定等级等效于承载能力可靠性分级的假定,以承载能力的可靠性分级标准为依据,详细分析了不同技术状况评定值与承载能力折减系数的关系,提出了基于现行桥梁设计规范的承载能力检算系数建议值.考虑到实际结构或构件抗力分项系数与理论值的差异,给出了承载能力检算系数的修正方法.研究结果表明,对于按现行规范设计的桥梁,若满足目标可靠指标的要求,不同受力状态构件承载能力检算系数的最大值为1.0;按原规范承载能力检算表达式计算的校准值与规程建议值吻合良好.

In order to establish a method,which is consistent with the current bridge design Specifications,for load rating the existing bridges,load capacity checking factors are calibrated based on reliability theory.Firstly,according to the load capacity checking expression of the existing bridges,the assumption that the condition levels of bridges structures or components are equal to reliability-based levels of load capacities is adopted.On the basis of reliability-based rating scales of load capacities,the relations between various condition levels and reduction coefficients of bridges are analyzed.And then the suggested values of load capacity checking factors consistent with the current bridge design specifications are presented.Finally,the correction formula is provided to modify the checking factors by considering the differences of resistance factors between actual values and theoretical values.The research results indicate that the maximum value of load capacity checking factors are 1.0 for various components designed with current specifications which satisfy the target reliability index;The checking factors calibrated by checking formats based on previous specifications are consistent with these adopted in current specification for load capacity rating of highway bridges.