Collision Effect And Control Of Main Approach Bridge Of (120+3×180+120)m Highway Railway Bridge

Long-span continuous steel truss bridge for both highway and railway will produce large longitudinal displacement under strong seismic action,which will cause the collision effect of the main approach bridge at the expansion joint.Therefore,it is necessary to study the collision effect and take appropriate control measures.In this thesis,a(120+3×180+120)m continuous steel truss girder for highway and railway is the engineering background.Considering the influence of the constraint effect of the seamless steel rail and the temperature change,the impact effect of the main approach bridge is analyzed,and the magnetorheological damper(MR damper)is used to control the impact effect of the bridge under the earthquake,so as to reduce or avoid the impact of the main approach bridge.The main research contents are as follows:(1)MIDAS/CIVIL is used to establish the integrated model of beam and rail and the model without rail constraint,and its dynamic characteristics are analyzed and compared;Input different seismic loads and analyze the impact effect of the main approach bridge at the expansion joint;Change the overall temperature of the system and analyze the impact of extreme temperature changes on the impact effect.The results show that the period of the beam-rail integrated model is smaller than that of the model without rail constraint,and the integrity is stronger;The seamless rail restraint can effectively reduce the number of collisions of the main approach bridge and reduce the peak impact force;When the temperature is high,the initial gap of the expansion joint is small,and the impact effect increases.When the temperature is low,the initial gap of the expansion joint is large,and the impact effect decreases.(2)By comparing and analyzing the advantages and disadvantages of different MR damper mechanical models,Spencer’s phenomenon model is selected and simulated by MATLAB/SIMULINK to verify its mechanical properties.The results show that the mechanical model can well describe the hysteretic performance of MR damper,and the validity of the simulation model is verified.(3)The simulation model of the collision unit is established in SIMULINK,and the collision process of the main approach bridge is simulated according to the calculation data of the finite element model.The simulation model of the MR damper is added to the collision model of the main approach bridge to obtain the simulation model of the control system,and the control process under different control strategies is simulated.(4)Under the action of different seismic waves,the impact effect of MR damper on the main approach bridge is analyzed.Five different control schemes are obtained by changing the input current of MR damper through different strategies.The best control scheme is obtained by comparing the impact effect of the main approach bridge without MR damper.The results show that semi-active control is better than passive control,and fuzzy control has the best damping effect;At high temperature,five different control schemes still have good control effect.