汽车荷载分项系数对桥梁构件可靠度的影响及修正

Analysis and Revision About Influence of Vehicle Load Partial Factor upon Bridge Component Reliability

为了明确汽车荷载分项系数变化对桥梁构件可靠度水平的影响规律,利用校准法对受拉、受弯、大偏心受压(短柱)、轴心受压(短柱)、受剪共5类受力构件,选取0.1,0.25,0.5,1,1.5,2.5六种活恒载效应比,进行了不同汽车荷载分项系数条件下构件的可靠度分析。对于可靠度指标分布不均匀的状况,提出了可靠度修正系数的概念并进行了验证计算,对不同类型构件按照活恒载效应比给出了可靠度修正系数的计算结果。结果表明:汽车荷载分项系数由1.4递增至2.4时,各类构件可靠指标均呈增大趋势;活恒载效应比小于1时,该分项系数每增加0.2,构件可靠指标随之增大0.1~0.3,活恒载效应比大于1时,该分项系数每增加0.2,构件可靠指标随之增大约0.4;活恒载效应比大的构件可靠指标值偏高,且该类构件可靠指标受汽车荷载分项系数的影响也较大;所提出的可靠度修正系数能够调整抗力值以达到目标可靠指标的要求,该系数分布于0.4~1.1之间,各类型构件可靠度修正系数分布规律一致,均随活恒载效应比及汽车荷载分项系数的增大而减小。

In order to figure out the bridge component reliability subjected to the vehicle load partial coefficient changing,five kinds of bearing components including tension,flexural,big eccentric compressive（short column）,axially loaded compression（short column）and shear were examined by calibration method.Reliability analysis of components under six ratios of vehicle load effective to dead load effective of 0.1,0.25,0.5,1,1.5,2.5and different vehicle load partial coefficients.Aimed at the inhomogeneous distribution of reliability indexes,concept of reliability correction factor was proposed and verified by calculation.The calculation results of reliability correction factor of different types of components were given according to the ratio of vehicle load effective to dead load effective.The results show that the reliability indexes become greater with the increase of vehicle load partial factor from 1.4to 2.4.When the ratio of vehicle load effective to dead load effective is less than 1,the increment of reliability index is 0.1-0.3as the partial factor increases by 0.2.When the ratio is more than 1,the increment of reliability index is 0.4correspondingly as the partial factor increases by 0.2.The higher the ratio of vehicle load effective to dead load effective,the greater reliability index for the component.The influence of vehicle load partial factor on reliability index is significant for the component with high ratio.The proposed reliability correction factor can well adjust resistance value to achieve the target requirement for reliability requirement,which ranges from 0.4to 1.1.The distribution laws of reliability correction coefficient are consistent for five kinds of bearing components,which decrease with increase of ratio of vehicle load effective to dead load effective and vehicle load partial factors.