Response And Optimization Of CRTS ? Ballastless Track Structure Under Earthquake

At present,the total mileage of Chinese high-speed railway has exceeded 22,000 kilometers.In the meantime,China is located in the most active earthquake area in mainland.By comparing the high-speed railway network and the seismic belt,most of high-speed railway will inevitably pass through the seismic belt.It is easy to cause the track slab to be seriously damaged when the ballastless track slab is impacted by the strong earthquake load,and it will directly affect the safe operation of the train.In this paper,the time-history analysis method is used to analyze the seismic response of CRTS II ballastless track slab in time domain and frequency domain,and an optimization is proposed for the earthquake isolation of track structure.The main contents of this paper are as follows:1.The calculation method of structure seismic response was summarized,and the differences between static analysis method,response spectrum method and time-history analysis method have been comparative analyzed.Finally,time-history analysis was selected in this paper.According to the time-history analysis method and the vibration equation of the track structure,the time equation of track seismic response was derived,and the seismic transmissibility function of the track structure is also obtained.2.Beijing-Tianjin inter-city was selected as the main research object,and the seismic wave in Tianjin was selected as an earthquake excitation according to the site type.From spectrum analysis we found,this seismic wave is low-frequency vibration,and the peak frequency of vibration mainly concentrated in 0?40Hz.The peak frequencies of horizontal seismic waves are mainly around 1.093Hz,1.77Hz and 3.489Hz.The peak frequencies of the vertical seismic waves are mainly around 3.49Hz,9.13Hz,20.38Hz and 31.51Hz.3.In order to analyze mode of slab,a finite element model of CRTS ? ballastless track slab on bridge foundations was established.According to the results we found,that the first ten natural frequencies of CRTS ? track structure on bridge foundations agree with the peak frequencies of the seismic waves,and the mode shapes were mainly transverse deformation.4.The time-history response as well as the stress and deformation under earthquake of track structure are calculated.From the result,we found that lateral vibration and transverse bending deformation was mainly happened under the excitation of Tianjin seismic wave,and the tensile stress of slab exceeds the tensile strength of the concrete material,which will damage the track slab.In addition,the seismic transmissibility of slab is greater than 1,which indicating that CRTS ? ballastless track on bridge foundations has no capability of earthquake isolation.5.The seismic response of track structure with different track parameters(the elastic modulus of CA mortar and the abutment stiffness of bridge)was calculated.According to the analysis,when the elastic modulus of CA mortar is increased,the lateral vibration acceleration of rail decreased obviously,but the vertical vibration acceleration and longitudinal vibration acceleration increased obviously.When the bridge abutment stiffness is increased,the acceleration of rail and slab are showing an increasing trend.6.According to the isolation design of building structure,and the design of rubber floating slab track structure,the isolation of track slab is carried out.According to time-domain analysis and frequency-domain analysis,it can be concluded that the isolation slab can avoid the peak frequency of Tianjin seismic wave and avoid the excitation of track resonance.7.A vehicle-track-bridge analysis model was established to analyze the response of the vehicle and track under earthquake.The results show that under the action of earthquake,the indicators were significantly improved,such as vertical and horizontal vibration of vehicle,rail and slab vibration,wheel and rail contact force,derailment coefficient and rate of wheel load reduction(approaching the limit of 0.6).And the high-frequency vibration of the track structure was influenced more significantly.In addition,with the increase of vehicle speed,the indicators above shown an increasing trend under the earthquake.When the speed exceeds 200km/h,the increasing trend of each indicator is more obvious.