| Orthotropic steel bridge decks are widely used in long-span bridges because of their light weight,high strength,convenient manufacturing,and convenient construction.However,steel bridges that use them as deck structures have fatigue disease cases during service.Increasingly,these fatigue diseases have seriously affected the normal service and driving safety of steel bridges.Once the fatigue disease occurs,it is usually difficult to repair and requires interruption of traffic.The repair cost is also very expensive.Among the many fatigue vulnerable parts of the orthotropic steel bridge deck,the fatigue disease that occurs at the weld between the longitudinal rib and the roof is the most harmful.For this reason,this paper selects the weldingseam between the longitudinal rib and the top plate of the orthotropic steel bridge deck as the object of concern.For this reason,this paper selected the weld seam between longitudinal rib and roof of orthotropic steel bridge deck as the object of concern,studied the fatigue performance of the welding details under wheel load through finite element numerical simulation,optimized and analyzed the selected structural parameters with the structural stress safety and economy as the optimization objective.The main research contents are as follows:(1)Analyze the stress mechanism and fatigue damage mode at the weld between the longitudinal rib and the top plate,determine the important fatigue failure form at the weld between the longitudinal rib and the top plate,and compare the main traditional fatigue assessment methods and fracture mechanics methods based on the SN curve Carry out analysis,give the method and idea of studying the fatigue performance of the welding detail.(2)Establish a segment model through the ABAQUS software,simulate the longitudinal rib and the top plate weld,formulate the loading mode and loading condition of the segment model,and extract the top plate and longitudinal rib weld under different loading conditions through calculation and analysis The corresponding stress longitudinal history curve is obtained,and the most unfavorable loading conditions of the welding details are given according to the curve,and the fatigue life assessment is carried out for the situation where the fatigue crack starts at the welding toe of the top plate,combined with the PM linear damage accumulation criterion.(3)Based on the theory of fracture mechanics,the method and steps for numerical simulation of the crack growth of the fatigue crack initiating at the welding root of the panel are given,the crack size is drawn,and the fatigue crack propagation process at the root of the roof welding is simulated through ABAQUS and Franc3d software,and the calculation Corresponding stress intensity factor in each expansion step,according to the critical crack size combined with Paris formula,the fatigue crack growth life evaluation of welding details is carried out.(4)Comprehensively consider the structural force safety and economic benefits,optimize and analyze the selected structural parameter values based on the response surface method,and compare the calculated results in the experimental design with the fitted predicted values to verify the effectiveness of the fitted function The optimization goal is to minimize the fatigue stress at the weld toe and the root of the weld between the top plate and the longitudinal rib,and the structural quality,and obtain the optimal value and combination of the structural parameters according to the fitting function. |
