| As the lower driving foundation of high-speed railway,ballastless track will inevitably lead to the destruction of interlayer bonding by the joint action of weak bonding between new and old concrete layers and long-term operation environment in the later stage,and then affect the normal operation of the track.In this paper,with the help of practical engineering case of laying single layer rheda ballastless track on concrete deck of a large span steel bridge abroad,according to the structural characteristics of the bridge and ballastless track,the finite element method is used to establish the bridge-track solid model,combined with indoor full-scale model test,the mechanical characteristics of ballastless track interlayer connection are studied,and the design scheme of interlayer connection is optimized.The main contents and conclusions are as follows:(1)According to the literature,this paper briefly introduces the research background and significance of this paper,summarizes the research status of track type,composite surface,steel-concrete composite structure and track interlayer connection of long-span steel bridge in detail,and puts forward the research content and technical route of this paper;At the same time,combined with the bonding mechanism between the new and old concrete layers,the whole process of track interlayer stress and the design principle of track interlayer connector are described,and the calculation formula of shear bearing capacity between the new and old concrete layers is summarized.(2)A full-scale model test on the comprehensive mechanical properties of ballastless track is designed and carried out,and the mechanical properties of track interlayer connection under static and dynamic loads are tested.The analysis of the test results shows that the track structure has no interlayer cracking under the action of load,and the stress value of each measuring point does not exceed the design strength of concrete.Under the repeated dynamic load,the track slab and the bridge deck maintain a stable compression and tension state,and the connection of the door reinforcement plays a clear role.The collaborative stress of the track slab and the bridge deck is between the laminate beam and the composite beam.(3)With the help of finite element software,the mechanical characteristics of the interlayer door reinforcement and its surrounding concrete of the composite structure under the action of train load,temperature load and combined load are calculated and analyzed.Combined with theoretical calculation and indoor full-scale test,this paper explores the influence of the interlayer door reinforcement on the combination state of the slab and the bridge deck,evaluates the strengthening effect of the interlayer door reinforcement on the synergistic effect,and further optimizes the layout scheme of the door reinforcement.The results show that increasing the diameter of the door reinforcement or increasing the density of arrangement of the door reinforcement can improve the bonding degree of the track slab and the bridge deck,but it is difficult to achieve the degree of forming a complete bonding plate.It is suggested that 15 groups of Φ16 door type reinforcement should be selected at the junction of track slab and bridge deck slab for reasonable layout,so as to ensure that the door type reinforcement can work normally within the service life of track. |
