| With the rapid development of urban rail transit in our country and the increase of urban metro network,the impact of vibration caused by metro is becoming increasingly severe.In the simulation calculation of subway vibration,the two-dimensional model is widely used due to its advantages such as less freedom and lower computational cost,but it also has disadvantages such as the inaccurate accuracy of some indexes and the inability to reflect the three-dimensional spatial characteristics of track structures.With the development of computer performance,the traditional two-dimensional model is gradually replaced by a refined three-dimensional rail coupling model.However,on the issue of simulating the aboveground structure vibration caused by subways,the model is too large and the computational cost is too high when simulating some large-scale system dynamics models,and its efficiency of problem solving will be greatly reduced.Considering the above issues,this paper conducts a series of studies on the calculation accuracy,parameter values,and vehicle load simulation methods of two-dimensional and three-dimensional models based on the rail structure of steel spring floating slabs in subways.The rationality of the model is verified by field tests.Finally,the two-dimensional model optimization is proposed based on the accurate three-dimensional simulation method.The main research work of the thesis is as follows:(1)Using ABAQUS finite element software,two-dimensional plane vibration model and three-dimensional spatial coupling analysis model are established respectively.The two-dimensional finite element model of the track-tunnel-soil is established based on the principle of plane strain,using shell elements.The vehicle load is fitted by empirical analysis.The three-dimensional model is based on the spatial dynamic finite element method and vehicle-track coupling dynamics theory.The vehicle dynamics model is simulated using multi-rigid body motion system connected by spring damping system.The track,tunnel and soil models are simulated by using space solid element,and wheel-rail contact is simulated based on Hertz contact theory.The measured irregularities are taken as the excitations,and the boundary of the model is simulated by the infinite element method to reduce the influence of the reflection of the vibration wave at the boundary.On this basis,the spatial coupling dynamic model of the vehicle-track-tunnel-soil is established.The reliability of the two-dimensional plane model and three-dimensional space coupling model was verified by relating the existing literature and measured data.(2)Using the two-dimensional track-tunnel-soil vibration analysis model to study the vibration characteristics of subway.In order to ensure the calculation accuracy,the grid density and model size of the 2D planar model are firstly confirmed by research:the grid density should be less than 1m,the model width should be greater than 120m,and the model depth should be greater than 70m.On this basis,the influence of the track structure parameters and vehicle speed on the vibration characteristics of the track structure is analyzed.(3)Using the vehicle-track-tunnel-soil vibration analysis spatially coupled finite element model to study the vibration characteristics of the system.Firstly,the influence of the three-dimensional model mesh density and the model size on the calculation results was confirmed:When the maximum mesh density is less than 2m,the model width is greater than 120m,and the depth is greater than 70m,the accuracy of the model can be met.On this basis,the influence of the track structure parameters and the train speed on the vibration characteristics of the system is analyzed.(4)Through the dynamic test of the track structure of urban rail transit underground lines,the vibration characteristics of track and tunnel are studied in driving conditions.In the dynamic test,the vertical accelerations of rails,floating slabs,tunnel walls,and vertical displacements of rails and floating slabs were mainly measured.The dynamic response of the system in driving conditions was obtained by statistically analyzing the test data in the time domain and frequency domain.(5)Relating the results of on-site dynamic test,the simulation results of 2D plane model,3D separation model and 3D coupling model were compared and verified.For the three-dimensional separation model,the wheel-rail force and fastener reaction force based on the three-dimensional coupling model were used as excitations.The simulation results of the three-dimensional separation model and the three-dimensional coupling model were compared with the dynamic test results.The results showed that when using the wheel-rail force as the excitation,the calculation results of the "separation" model and the coupling model are basically the same;when using the fastener load as the excitation,the low frequency range within 100 Hz of the acceleration fits well with the measured data,while the vibration attenuation in the middle and high frequencies is large.For the two-dimensional model,when the wheel-rail force obtained by the traditional empirical formula is used as the excitation,the calculation results are often larger than the three-dimensional results in the same parametrical condition;the frequency domain components calculated by the traditional empirical formula are relatively single,and the results are greatly different from the measured ones;when the 3D coupling model whole process wheel-rail force simulation results,single-point wheel-rail force simulation results and fastener reaction force simulation results are applied as excitations of the 2D model,the study shows that the accuracy of the vibration response is significantly higher than that of the vibration response obtained by using traditional wheel-rail force fitting formulas.The improved two-dimensional model can better simulate the vibration transmission law of subway vibration tracks.When the whole process wheel-rail force simulation results are used as excitation,the calculation accuracy of the two-dimensional plane model is most significantly improved. |
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