Study On Longitudinal Mechanical Characteristics Of Slab Track CWR On Bridge Under Pier Displacement

With the rapid development of China's high-speed railway,high pier and long-span continuous beam structure are widely used in crossing river valley,mountain area and bad geological area with many advantages.The displacement of pier caused by sunshine,post construction settlement,earthquake and other external disturbances will cause interaction between the upper bridge and track structure,and its mechanism is more complex.In this paper,according to the long-span continuous beam bridge and CRTS I slab track,CRTS II slab track widely used in China's high-speed railway,the longitudinal force and displacement characteristics of the slab track CWR on the bridge under the condition of displacement of each pier were studied,the longitudinal force transmission mechanism was revealed,the relevant influence parameters were analyzed,and reasonable suggestions were put forward for the design,construction and maintenance of the track and bridge structure,the research content includes the following aspects:1.According to the double track(70+130+70)m continuous box girder and 32 m simply supported box girder of high-speed railway,based on the interaction mechanism of pier-beam-slab-rail and the finite element method,the actual space size and mechanical properties of CWR,slab track,beam were fully considered.Taking CRTS I and CRTS II slab track as examples,the refined finite element models of slab track CWR on bridge were established considering the longitudinal-horizontal-vertical space coupling.2.In view of the deflection of the pier under the longitudinal temperature gradient load and the displacement of the pier top,the longitudinal force and displacement distribution of the slab track CWR on bridge under the condition of pier top longitudinal displacement were studied.The results show that under the condition of uniform longitudinal displacement at the top of each pier,the maximum longitudinal force of CRTS I slab track structure appears at the movable end of the first span simple supported beam and the right abutment;the maximum longitudinal force of CRTS II slab track rail appears near the abutment at both ends,the relative displacement of the base plate and bridge and the longitudinal shear force of the consolidation mechanism are large.Under the condition of uneven longitudinal displacement at the top of each pier,It is necessary to pay attention to the state of the simply supported beam continuous beam joint pier top of CRTS I slab track and the under rail fastener base plate at the adjacent pier top with large height difference.When the height of the continuous beam pier is higher than the adjacent simply supported beam pier of CRTS? slab track,it is necessary to fix the pier top of the continuous beam fixed support and the simply supported beam with a larger temperature span in the design process The shear capacity of the consolidation mechanism at the top of the fixed support pier is checked and calculated.The relative displacement of the base plate and bridge at the place where the height difference of the adjacent piers is large needs to be monitored in real time.The research conclusions provide support for the monitoring and maintenance of the two kinds of track structures in summer.3.In view of the post construction settlement and bad foundation of pier foundation,the longitudinal force and displacement distribution law of slab track CWR on bridge under the condition of pier foundation settlement were studied.The results show that the longitudinal(stress)peaks of two kinds of slab track structures appear near the abutments on both sides and adjacent pier tops under the condition of uniform settlement of each pier foundation,and the longitudinal force of each track and bridge structure is linearly positively correlated with the settlement at the pier bottom;under the condition of differential settlement of each pier foundation,the longitudinal displacement difference at the pier top and the cumulative value of longitudinal displacement at the pier top have a positive effect on the rail structure of the bridge.The longitudinal stress peak of CRTS I track plate,CA mortar layer and base plate only appears at the difference of foundation settlement of adjacent piers.The longitudinal stress peak of CRTS II slab track rail appears at the difference of foundation settlement of adjacent piers,and the longitudinal stress of track slab,CA mortar layer and base plate is continuous at the beam end of the first and last spans The peak value appears at the top of the pier where the beam is connected with the simply supported beam,and the research conclusion provides a reference for the monitoring and maintenance of the two kinds of tracks in the long bridge and the bad geological area.4.In view of the joint occurrence of longitudinal displacement of pier top and expansion deformation of beam under complex temperature load,the longitudinal mechanical characteristics of CRTS I slab and CRTS II slab track CWR on long-span continuous beam bridge under complex temperature load were studied.The results show that the two types of slab track should adopt the same longitudinal displacement direction of pier and beam.The difference of longitudinal displacement of each pier has a greater impact on the structure of CRTS? slab track and a smaller impact on the structure of CRTS? slab track.In the design process,the longitudinal displacement of each pier top and the temperature difference of the beam should be based on the local daily temperature difference and the spatial size of the pier,it is necessary to optimize the arrangement of bearings,make sure that the longitudinal displacement direction of pier-beam is opposite under complex temperature load.The research conclusion provides theoretical support for the design and laying of two kinds of tracks in hot areas.5.For the element(CRTS I)slab track and the longitudinal continuous(CRTS II)slab track,the longitudinal force characteristics of the two kinds of slab track on the bridge under the condition of pier top longitudinal displacement,pier foundation settlement and complex temperature load were compared and analyzed.The results show that the CRTS? slab track is better than the CRTS? slab track in resisting the displacement of pier top,which is especially beneficial to the stress of rail and the sliding out of the fastener base plate under the control rail.In high temperature season,the longitudinal stress of the CRTS? slab,CA mortar layer and the base plate are large,and the bonding mechanism and the "two cloth and one film" sliding layer are also weak links,which should be taken into account when selecting.The additional longitudinal force of CWR on the bridge caused by the pier foundation settlement can not be regarded as the controlling factor of track selection in the design process.Compared with CRTS I slab track,the stress and deformation of CRTS II slab track CWR under complex temperature load are smaller,but whether the shear strength of consolidation mechanism meets the design requirements is the key.The research results can provide reference for the selection and laying of two kinds of tracks in long and large bridges,hot areas and unfavorable geological areas.6.Based on El Centro seismic load,the seismic response law of CRTS ? slab track CWR on bridge was analyzed.The results show that pier,beam and track structure are forced to vibrate under the joint action of earthquake,gravity and structural interlayer constraints.The interaction of pier-beam-slab-track should be used for analysis.The response law of longitudinal displacement of track and bridge structure is basically consistent with the change of seismic load,but the peak value of longitudinal displacement of each structure decreases layer by layer from the bottom to the top,which shows that the friction between layers of each structure has a certain restraining effect on the transfer of displacement.The relative displacement of rail and slab,the peak value of longitudinal shear force on top of fixed bearing pier and consolidation mechanism are all large,and the relative displacement peak value of rail and slab has far exceeded the limit value of the longitudinal elastic deformation of the fastener.