公路正交异性钢桥面疲劳荷载计算模型与实际交通荷载匹配性研究

Research on Matching of Fatigue Load Calculation Model and Actual Traffic Load in Highway Orthotropic Steel Bridge Deck

针对正交异性钢箱梁桥面系构件提前发生疲劳损坏的问题,以军山长江公路大桥为例,研究公路正交异性钢桥面疲劳荷载计算模型与实际交通荷载匹配性问题。通过交通实际组成分析,发现设计规范规定的疲劳荷载验算计算模型Ⅲ对应的车型(五轴车)与实际交通代表车型不符(实际代表车型为六轴车)。进而采用有限元数值模拟计算的方法,对两种车型(五轴车和六轴车)荷载作用下钢箱梁结构受力情况进行分析,发现实际代表车型作用下最不利截面处的最大应力幅较计算模型Ⅲ车型提高25%~47%,相应的疲劳寿命为原设计的1/2~1/3,这是导致钢箱梁结构虽然设计上满足规范要求,但是提前发生疲劳破坏的重要原因。因此建议钢箱梁设计过程中,根据实际交通组成情况选择合理的正交异性钢结构桥梁桥面系构件疲劳荷载验算模型。

Aiming at the fatigue damage problem of the deck members of orthotropic steel box girder in advance,in this paper the Junshan Yangtze River Bridge is taken as an example,the matching problems between fatigue load calculation model and actual traffic load in highway orthotropic steel bridge deck are studied.Through the analysis of the actual traffic composition,it is found that the fatigue load checking calculation modelⅢ(five-axle vehicle)stipulated in the design specification is not consistent with the actual traffic model(the actual representative vehicle type is six-axle vehicle).Then,the finite element numerical simulation method is applied to analyze the stress of steel box girder under the load of two kinds of vehicle(five-axle and six-axle).It is found that the maximum stress amplitude of typical fatigue details under the actual vehicle type is increased by 25%~47%compared with the calculation modelⅢ,and the corresponding fatigue life is 1/2~1/3 of the original design fatigue life,and this is the important reason for the structural design of steel box girder to meet the requirements of the standard,but the fatigue damage occurred in advance.Therefore,it is suggested to select a reasonable fatigue load checking model for deck system members of orthotropic steel bridges according to the actual traffic composition in the design process of steel box girder.