| China is located in the southeast edge of the Eurasian plate,squeezed by the Indian Ocean plate and the Pacific plate,with frequent earthquakes and a short history of high-speed railway construction,and has not yet withstood the test of serious earthquakes.China’s high-speed railway construction adheres to the concept of "replacing roads with bridges",and the proportion of bridges on some lines even exceeds 90%.It is inevitable for high-speed trains to run on bridges during earthquakes.For the prevention of train derailment risk caused by an earthquake on the bridge,the design of a high-speed railway bridge still focuses on improving the seismic performance of the bridge itself.The traffic safety index still uses the test and statistical index based on a large number of ordinary railways,which has a limited guiding effect on the seismic design of high-speed railway bridge.The train derailment may still occur when the train runs on the bridge with good seismic performances.Therefore,it is necessary to carry out in-depth research on train derailment risk and provide corresponding design and control means.The simulation of the whole process of train running on the bridge considering derailment caused by an earthquake is very complex.To realize the calculation of the whole process of separation and re-contact between wheel and rail,the calculation program is required to have high calculation efficiency and reliable calculation accuracy.According to the above practical needs,this paper carries out the nonlinear whole process simulation and safety analysis of train running on high-speed railway bridge under earthquake(Nonlinear behavior includes multi-body dynamics,material nonlinearity and wheel rail contact nonlinearity).The main innovative achievements are as follows:(1)By combining the unconditionally stable explicit integration algorithm with the local nonlinearity technology,the multi-partition calculation strategy of the nonlinear train track bridge system is proposed.The unconditionally stable explicit and efficient calculation method suitable for solving the train track bridge nonlinear coupling system is established.Compared with the unconditionally stable implicit algorithm,the new algorithm avoids repeated iteration of the equation with the same integration step setting.Compared with the conditional stable explicit algorithm,the new algorithm greatly relaxes the constraint of integration step size,does not need to use the modal superposition method,and avoids the disadvantage of a large number of matrix multiplication.(2)For the wheel tread,the classical trace method is used to generate the contact trace.However,as for the vertical and near-vertical surfaces on both sides of the wheel,the convex hull point cloud method is introduced to obtain the contact trace at this position.A hybrid search method for the contact point at the extreme position of the spatial wheel-rail using convex hull search is proposed,which prolongs the length of the trace generated by the classical trace method and ensures that the trace method is applicable at the extreme position The analysis shows that this method makes the simulation results of the wheel derailment process more reasonable.(3)According to the geometric characteristics of the rail,the position search of the contact point between the wheel profile and the rail profile is simplified to the relative position detection of the derived curve of the wheel trace and the center of the complex curve of the rail profile.A large number of derived curves of different wheelset yaw angles are calculated off-line to form a look-up table to alleviate the pressure of on-line calculation.A semi on-line efficient search method to improve the search efficiency of spatial wheel-rail contact point is proposed.This method balances the contradiction between the huge time consumption of the online search method and the huge space consumption of the offline search method,and greatly improves the search efficiency of space wheel-rail contact points.(4)Based on multi rigid body dynamics and structural dynamics theories,the numerical model of nonlinear train-track-bridge coupling system is established by using unconditional stable explicit and efficient calculation method and semi-online space wheel-rail hybrid search method,the calculation program is compiled,and the whole process simulation platform of train running on railway bridge under earthquake is built.Compared with classical examples and measured results,the calculation results show that the platform has good calculation accuracy and high efficiency.The results show that by improving the calculation efficiency and the search accuracy of wheel-rail contact points of the complex system and using local nonlinearity technology,the simulation platform realizes the whole process simulation of nonlinear running on high-speed railway bridge under earthquake.(5)Taking the simply-supported girder bridge with slab ballastless track as an example,a large number of calculations are carried out by using the simulation platform developed in this thesis,and the influence law of key parameters on traffic safety is revealed.The statistical results show that the risk of traffic derailment on the bridge under earthquakes is related to the instantaneous impact strength.Based on this understanding,it is proposed to use the apparent deformation rate as the evaluation index of derailment risk.The causes and characteristics of the train derailment in non-longitudinal connected track system are analyzed,and the safety evaluation method based on the visual deformation rate of the train on the railway bridge during an earthquake is established.The physical meaning of the visual deformation rate index is clear,which can be obtained not only through train-bridge simulation analysis,but also only according to the total derivative of track displacement response.Therefore,it can be used for the design institute to judge the derailment risk on the train bridge.68 figures,18 tables,196 references... |
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