Study On Fatigue Behavior Of Urban Overpass Steel Box Girder With Special Shape

Special-shaped steel box girder bridge is widely used in urban interchange because it has fluent structural alignment,which makes the roads of different directions connect each other,perfectly solves the problem of contradiction between bridge deck traffic and ground traffic,and has the advantages of light weight,great spanning ability and short construction period.But it is easy to have fatigue damage because of the cyclic load of vehicle and wind acting on the bridge and the problems of its own during the construction such as welding,section mutation,stress concentration and so on.With the increasing traffic volume and number of heavy vehicles and overloading,the fatigue problem of the steel structure of highway bridges is becoming more and more serious.Based on the background of the special-shaped steel box girder in the connecting section of Shuguang branch and No.2 Bridge of Shuguang Road in Wenling,Zhejiang Province,the influence of the transverse distribution of wheel track and the pavement layer on the fatigue performance of the special-shaped steel box girder is studied and analyzed by ANSYS software.Firstly,the transverse distribution of the wheel tracks on the right turn is measured on the spot.By using the method of camera,the transverse distribution of the wheel track at a certain intersection of larger traffic volume in Wenling is statistically analyzed,and the transverse distribution of the wheel track on the right turn is obtained,and was compares with another two transverse distribution of the wheel track: one was from the "Highway Steel structure Bridge Design Code"(JTG D64-2015),another was given by Cui Bing and Wu Chong based on the field survey of Humen bridge when vehicles were going straight.Secondly,the influence of wheel track transverse distribution on fatigue performance of special-shaped steel box girder is studied.The whole-bridge ANSYS finite element model of background engineering in consideration of diffusion angle without adding a paving layer is established.The fatigue stress variation of the 4 selected typical fatigue structural details under the transverse distribution of three kinds of wheel tracks mentioned above is compared and analyzed,with the fatigue calculation model of the Ⅲ provided by the code loading on the bridge model.Finally,the combination effect of asphalt paving layer and steel deck plate is analyzed.The whole bridge finite element model of background engineering with asphalt paving layer is established to analyze the variation of fatigue stress amplitude of the 4 selected typical fatigue structure details of the special-shaped steel box girder bridge before and after adding asphalt paving layer and the influence of thickness and elastic modulus of paving layer on fatigue performance of the bridge.