Dynamic Response Analysis Of Long Span Railway Hybrid Beam Cable-stayed Bridge

Based on the engineering background of a long-span railway hybrid beam cablestayed bridge,the structural dynamic characteristics of the long-span hybrid beam cablestayed bridge are studied in this paper.Through dynamic time-history analysis,static wind stability study and vehicle-induced vibration calculation of the cable-stayed bridge with mixed beam,the internal force displacement response of the bridge under multiple working conditions was mastered,and the mechanical properties of the bridge were summarized,providing a design idea for the cable-stayed bridge with mixed beam.The main work of this paper is as follows:1 This paper briefly introduces the general situation of bridge development,sums up the current situation and deficiency of bridge seismic problems,static wind stability,vehicle induced vibration research.The spatial simulation model of hybrid beam cablestayed bridge is established by using the finite element software.2 The natural vibration characteristics of the hybrid beam cable-stayed bridge are analyzed,and the appropriate seismic waves are selected to analyze the dynamic timehistory of the bridge under the action of longitudinal,longitudinal + vertical,transverse and transverse + vertical earthquakes.The internal force displacement response extremum and time-history curve of the bridge are calculated,and the dynamic response under four different earthquake load conditions is compared.It is found that the seismic excitation in a single direction mainly causes the displacement response of the internal force in that direction,but has little effect on the other two directions.At the same time,the internal force response of the bridge tower is the most prominent in the whole bridge no matter it is unidirectional excitation or two-dimensional combination excitation.Therefore,when designing and checking the seismic performance of the bridge,it is necessary to pay special attention to the internal force response at the bottom of the bridge tower.3 The aerodynamic model of the bridge section is established by FLUENT software,and the variation trend of the three component force coefficient of the bridge section under different wind speed and wind attack angle is studied.By applying wind load to the finite element model,the displacement response of the main beam and the bridge tower under the equivalent static wind load is studied.The results show that when the wind angle of attack is 0 °,when the wind speed reaches 60 m / s,the static wind instability of the bridge does not occur,which shows that the static wind safety of the bridge can be guaranteed.4 The simulation model of wheel rail and train is established by using SIMPACK multi-body dynamics analysis software.The high interference track irregularity spectrum of Germany is used as the external excitation source of wheel rail.Three calculation conditions of train passing through the bridge at 120 km / h,140 km / h and 160 km / h are selected to calculate the wheel rail force time history function when the train is running.The train load is applied to the finite element model to obtain the displacement response of each key section of the bridge structure under each working condition.By comparing the relevant provisions of the code,the hybrid beam cable-stayed bridge meets the requirements of the dynamic response code in normal use.At the same time,through the comparison of the dynamic response of the joints on both sides of the steel-concrete joint section,it is found that the acceleration response of the joints on both sides is slightly different under the train load due to the change of the stiffness on both sides of the steelconcrete joint section,which may have a negative impact on the fatigue response of the steel-concrete joint section under the long-term load,so attention should be paid in the subsequent detection.