Study On Dynamic Response Of CRTS Ⅱ Slab Ballastless Track Structure On Bridge Under Earthquake

China is located in the most active area of the global continent,and is a country with a wide distribution of seismic belts.With the continuous extension of the high-speed railway network,high-speed railway will inevitably cross the earthquake-prone area.CRTS II slab ballastless track is a kind of longitudinally integrated track type and commonly used in high-speed railways.Under strong earthquake load,the track structure is easily damaged,which poses a serious threat to the safe operation of trains.Therefore,this paper will study the dynamic response of the CRTS Ⅱ slab ballastless track structure on the bridge and the dynamic response of the train running on the bridge under seismic action,so as to provide reference for establishing and improving earthquake early warning system of the high-speed railway and ensuring the safe operation of the trains.The main research work of this paper is as follows:(1)Review and summarize the development of three structural seismic response analysis theories:static analysis theory,response spectrum theory and direct dynamic analysis theory;Four kinds of input methods of seismic excitation,such as direct acceleration method,large mass method,displacement input method and large stiffness method,and their respective applicable situation and characteristics were compared and analyzed.Finally,this paper was determined to adopt the direct dynamic analysis theory and the direct acceleration method seismic input mode.(2)Three kinds of theories of ballastless track structure calculation models,such as elastic foundation composite beam model,elastic foundation beam-plate model and beam-solid finite element model,were analyzed.And established three corresponding finite element models,compared and analyzed the differences of each model in the design and calculation of ballastless track structure.Finally,this paper decided to adopt the beam-solid finite element model.(3)The CRTSⅡ slab ballastless track and bridge coupling analysis model was established,and its modal analysis was carried out to obtain its dynamic characteristics.Then the result differences between the time history analysis method and the response spectrum method for the seismic calculation of CRTS Ⅱ slab ballastless track structure on the bridge and its application were analyzed.Finally,the seismic response of the CRTSⅡ slab ballastless track structure on the bridge under the excitation of six actual seismic waves were calculated by time history analysis method.It is concluded that under the lateral design earthquake under the 7 degree fortification,the normal stress and shear stress of the interface between the track plate and the CA mortar layer will exceed the limit,resulting in cracking between the track plate and the C A mortar layer.On this basis,the influences of seismic wave spectral characteristics,pier height,seismic intensity and site type on the seismic response of CRTS II slab ballastless track structure on the bridge were analyzed and some meaningful conclusions were obtained.(4)The vehicle-track-bridge coupling system analysis model was established,and the dynamic response of the train running on the bridge in the absence of earthquakes and earthquakes were calculated and compared.It is concluded that under the lateral earthquake action,the wheel-rail lateral force,derailment coefficient and wheel load reduction rate is significantly increased.Then influence of vehicle speed and earthquake intensity on the dynamic response of the train running on the bridge were calculated and analyzed,and the safety and stability of the train running on the bridge under earthquake action were evaluated.Finally,the safety threshold of the train running on the high-speed railway bridge under earthquake action was given.It was recommended that deceleration or parking measures should be taken when the earthquake intensity reaches 0.07g during earthquake warning.