Study On Running Safety Of High-speed Railway Rigid Frame Bridge Under Earthquake Condition

Sichuan Tibet railway is an important part of the external transportation channel in Western China,and the most difficult railway project in the history of human engineering construction.Sichuan Tibet railway crosses a wide area and many high-intensity seismic belts.There are many near fault or cross fault bridges along the railway.The seismic activity has caused great hidden danger to the bridges along the railway and the traffic safety on the bridges.Therefore,it is of great significance to study the safety of train operation on bridge under earthquake action for Sichuan Tibet railway.In this paper,aiming at a double deck steel truss hybrid rigid frame bridge on Sichuan Tibet railway,a refined train track bridge coupling vibration analysis model is established by using the general finite element software ABAQUS.The vibration response laws of different positions of the double deck steel truss hybrid rigid frame bridge under various earthquake types and earthquake intensities are analyzed;the safeties of driving on the bridge at different speeds and different earthquake intensities are studied.The main research contents and conclusions are as follows:(1)Through "built-in embedding","tie connection" and "MPC rigid arm connection",the connection of multiple steel components and concrete components in composite bridge is accurately simulated.According to the generated random irregularity curve,the spatial coordinates of rail grid node are modified by secondary development of Abaqus-Python,and the random irregularity of rail is imposed,The spring element is selected to simulate the primary and secondary suspension accurately;Based on the secondary development,the batch fastener between rail and bridge is established,and the Hertz contact between wheel and rail is set by using normal pressure interference table and static dynamic friction index attenuation formula;The key problems such as self balance of train and bridge are solved by means of static rotation technology and lengthening rail outside the bridge;Finally,a refined train track bridge analysis model is established in ABAQUS.(2)First of all,the design response spectrum is generated by self-made table.On this basis,the measured seismic wave is downloaded from the PEER website in combination with the natural vibration period of the structure,and the original seismic wave data is post processed with Seismo Signal software;At the same time,Artificial seismic wave is generated in SIMQKE＿GR;Finally,the seismic data for this study are obtained.(3)The “Acceleration-Input” mode is used to calculate the seismic response of the structure,and the seismic response law of the double deck steel truss hybrid rigid frame bridge is obtained;The results show that the maximum lateral and longitudinal acceleration responses of the bridge appear in the middle of the second span,and the maximum vertical acceleration appears in the first span;The horizontal dynamic displacement in the middle of the first span is the smallest,while the vertical dynamic displacement is the largest.(4)Compared with the limit value of the code,the acceleration and amplitude of the bridge caused by the train are very small,and the difference of the bridge response under different speed is small.When there is no seismic action,the derailment coefficient of train on the bridge will increase,and the influence of vehicle speed on the maximum derailment coefficient is significant;The results show that the train derailment coefficient increases significantly under earthquake,and the maximum derailment coefficient increases faster with the increase of earthquake intensity.The maximum wheel load reduction rate is positively correlated with the train speed.When there is earthquake,the wheel load reduction rate is more sensitive to the vehicle speed,and the wheel rail separation will occur when the train leaves the bridge at 160km/h and 200km/h under the earthquake.(5)In the case of no earthquake,there is no obvious difference in the acceleration response of each train.The acceleration response of vehicle body is positively correlated with vehicle speed,and the faster the vehicle speed is,the more sensitive the vehicle acceleration is to vehicle speed.The results of seismic vehicle bridge calculation show that the seismic action will change the variation law of vehicle body acceleration with time when driving on the bridge.The response of vehicle body vibration acceleration under seismic action is more sensitive to vehicle speed,and the maximum vibration acceleration of vehicle body increases approximately linearly with the increase of seismic intensity.When the earthquake intensity is0.20 g and the vehicle speed is 200km/h,the peak value of the lateral acceleration of the vehicle body is close to the limit value of 0.10 g,while the peak value of the vertical acceleration of the vehicle body has exceeded the limit value of 0.13 g.From the perspective of the vehicle body acceleration,when the earthquake intensity reaches 0.20 g,the train should cross the bridge at a speed lower than 200km/h.