Study On Dynamic And Fatigue Performance Of Long-span Suspension Bridge Considering Vehicle-bridge Coupling Effect

In recent years,as widespread construction of long-span bridges and the rapid development of highway transportation,the vehicle-bridge coupling effect of long-span highway bridges appears prominently.Steel-concrete composite bridge deck system has obvious advantages in long-span bridges,and has wide application prospect in suspension bridge.The fatigue state of steel-concrete composite beams is very important for the fatigue state evaluation of suspension bridges during the whole operation period as the main complex stress components.Takeing a steel-concrete composite beam suspension bridge as a project example,the dynamic and fatigue performance considering the vehicle-bridge coupling effect are studied.The main contents are as follows:(1)The finite element model of integral suspension bridge is established by finite element analysis software ANSYS and a 3D three-axle vehicle model is developed which consists of 11 independent degrees of freedom.The irregularity of bridge deck is simulated by MATLAB functions and the vibration differential equation is established and solved.Finally,the vehicle-bridge coupling vibration program is compiled using MATLAB program language.(2)Sensitivity analysis of structural stiffness and temperature variation of suspension bridge dynamic characteristic parameters is carried out.The effects of main cable stiffness,girder stiffness,vehicle speed,vehicle weight,bridge deck irregularity and lateral position of driving on dynamic response of suspension bridge and the impact coefficient of vertical deflection and bending moment of main beam,horizontal displacement of tower top,and suspender force are discussed.(3)The standard segment finite element model of steel-concrete composite beams is established.Static analysis of the stress characteristics of each component of steelconcrete composite beams determines the fatigue details,and the stress concentration factor of each focus is calculated by finite element method.(4)The local traffic volume is predicted by grey prediction based on the historical annual average traffic volume.The fatigue damage degree and fatigue life under three kinds of fatigue vehicle loads,i.e.fatigue load model III in the Code for Design of Highway Steel Structures and Bridges(JTG D64-2015),standard fatigue vehicle of AASHTO code and local fatigue load spectrum of Hebei Province,is estimated and evaluated by using the linear fatigue damage assessment method based on S-N curve(P-M model)and the non-linear fatigue damage assessment method based on continuous damage mechanics(CDM model).(5)Considering the coupling vibration effect between vehicle and bridge,the effects of vehicle load,driving speed,deck pavement deterioration and future traffic volume growth on fatigue damage degree and fatigue life of the structure during operation period are discussed.