Track-Bridge Interaction Between Continuous Welded Rail And Long-span Steel-truss Arch Bridge Of High-speed Railway

Abstract:For long-span bridges on high-speed railway (HSR), the expansion length and the deck-end rotation are relatively large. Carrying multiple railway lines, the bridge and the track constitute a mechanical equilibrium system due to the nonlinear constraint between them. In general, the track-bridge interaction is a quite significant dominant factor for the design and safe operation of the long-span bridges and continuous welded rails (CWR).In this dissertation, the long-span steel-truss arch bridge in HSR was discussed and researched. Integrative coupling spatial models, considering the nonlinear characteristics of resistance between the bridge and the track, were established on the basis of nonlinear analytical theory of long-span bridge. By developing specialized calculating modules, taking the effect of loading history into account, the numerical research was focused on the mechanical characteristics of the CWR and long-span steel-truss arch bridge system subjected to the multi-field coupling actions of temperature, traffic loads and seismic load. In addition, the stability of CWR on arch bridge as well as the transient fracture process of rails were investigated. The main contents of this dissertation are given as follows:1. Based on the time-varying characteristic of longitudinal resistance between track and bridge, the iterative formulas were derived, and the simulating method has been improved. Furthermore, the Resistance-difference Method was proposed to transfer the resistance from unloaded condition to loaded condition freely, and vice versa. Adopting this new method considering the influence of previous load history on nonconservative mechanical system of track and bridge, the full-process analysis could be executed on those static or dynamic behaviors such as temperature hysteresis, trains passing over bridge, trains braking on bridge, etc.2. The new integrative spatial model of rails-deck system-stringers-cross beams-main trusses-pier-foundation was established, adopting improved overlapping nonlinear link element to simulate the longitudinal resistance between track and bridge. In this new model, ideal elastic-plastic resistance model capable of unloading to include the influence of load history was selected, and the longitudinal resistance, transverse resistance as well as vertical stiffness were simulated. This model could represent the correlative relations among tracks, deck, transverse and horizontal girders, main trusses, supports, piers as well piles more accurately. Moreover, it could also calculate different operation conditions including single line load case and multi-line load case, and analyze the additional longitudinal forces of CWR and the track’s stability on bridges. The validity of the model in this thesis has been verified through a series of comparative analyses with those in relative codes or papers.3. The characteristics and distribution law of various longitudinal forces in the track-beam system of steel-truss arch bridge were described. The nonlinear calculations considering multi-load history and the results calculated by linear superposition method were comparatively analyzed. The influence of several sensitive factors on the longitudinal force was discussed, such as temperature combination cases, trains’ moving direction, live load model, train formation, braking force ratio, ballast resistance, stiffness of pier and abutment, layout scheme of adjacent spans, friction of movable supports and other factors. Besides, the curtailment mechanism of locating the Rail Expansion Joints (REJ), selecting the track type and the deck form, as well as setting up the Shock Transmission Unit (STU) on piers were illustrated and the optimal schemes were expounded.4. Taking the coupling of initial level irregularity and vertical profile irregularity into consideration, the track stability of CWR on the long-span steel-truss arch bridge and the transmission law of track fracture force were researched. Comparative study on the track’s instability status with track-bridge interaction or not was carried out, and sensitive research was conducted to investigate the effect of rail type, transverse resistance, vertical stiffness of railway line, and initial irregularity vector. Meanwhile, the whole transient process of track’s fracture was traced and surveyed, and the static and dynamic rail-breaking forces were compared.5. Utilizing improved Penzien model to simulate pile-soil effect, developing self-programming software to generate artificial seismic waves, the natural vibration characteristics of long-span steel-truss arch bridge considering track constraint or not were described, the seismic responses under different input modes of earthquake motion (including seismic wave’s spectral characteristics, site phase difference and so on) were studied for the track-bridge system of long-span steel-truss arch bridge. Besides, the influence law of sensitive factors such as ballast resistance, frictional effect of movable supports, layout of adjacent span, stiffness of pier and abutment were summarized, and the coupling effect of temperature, bending-braking force as well as earthquake acceleration was investigated. Additionally, some seismic applicability measures were proposed and analyzed, such as REJ, nonlinear viscous damper and track types.