The Theory And Application Of Vehicle-track-bridge Spatial Interaction Analysis

In the present to analyze and study the train-track-bridge dynamic interaction, in addition to the accurate vehicle models, the dynamic FEM models which can describe the actual operational condition of the bridges/track is more significant and necessary. Vertical and transverse vibration, as well as the longitudinal vibration should all be analyzed, but not just the unilateral vertical or transverse vibration in an accurate and effective model of train-track-bridge coupling vibration. Based on it various components of the whole dynamic system should be analyzed comprehensively; the interaction of the vehicle-bridges should be considered systematically; the wheel-rail contact force and the wheel-rail relationship are taken into account reasonably.With Wuhan Tianxinzhou Bridge (a highway and railway bi-purposed bridge) and its field test as background, An accurate model of train-track-bridge dynamic interaction was study systematically in the present study. The finite element model and the modal method equations of the train-track-bridge coupling vibration with the wheel track closure in vertical direction and in normal direction were established respectively. The traditional basic assumption of nominal moving in traverse was abandoned. The effects of the original configuration and the elastic deformation of the bridge were considered. By analyzing the longitudinal vibration of the vehicle, the novel thought of vehicle-line-bridge coupling vibration based on the of finite element model was proposed. And then the field test data of the Wuhan Tianxinzhou highway and railway bi-purposed Bridge was used for verification. The main contents and achievements of the thesis include:1. The train, bridge and track are considered as an entire system, and two degrees of freedom of the wheel set, roll and bouncing, are determined by the displacement of the rail. Respectively, based on the modal coordinate and physical coordinates, motion equations for both of the train-bridge system and the train-track-bridge system are established according to the principle of total potential energy with a stationary value in elastic system dynamics and the rule of "set-in-right-position" Then disengaged assumption of right-and-left symmetry, the vehicle model can involve more actual factors, such as the eccentricity of vehicles, the high-speed spin angular momentum of wheel set and so on.2. As the profiles of rail and wheel tread are special curve, their interaction should be tight constraints on the direction of common normal at contact points. In this thesis, application of the vertical tight constraint is studied, and coupling motion equations of the train-track-bridge system based on normal tight constraints are established, compared with those based on vertical tight constraints.3. In fact, the train is moving on oblique deck of bridges, especially on that of long-span flexible ones, because of the deformation under vehicle load as well as pre-camber. The motion of vehicle is divided into two components, oblique movement along the track and micro-amplitude vibration relative to itself. Then vertical and special models of the train-track-bridge system are developed respectively based on the original and deformed decks, and verified by experimentations.4. In tradition analysis of train-track-bridge interaction, longitudinal nominal motion of vehicle was defined first, and the longitudinal vibration was not considered, involving no driving or braking force of train. In this thesis, a model of train-track-bridge spatial dynamic interaction considering longitudinal vibration is established without the presumption of vehicle longitudinal nominal motion. Not only the spatial vibration of train-track-bridge interaction, but also the longitudinal vibration of train and the special dynamic problem such as braking or driving on the bridge, can be analyzed more comprehensively.5. In previous study of train-track-bridge interaction, the vibration finite element model of bridge established mainly in term of design drawings is usually different from practical states of bridge. A baseline FEM model reflecting the actual dynamic characteristics of bridge structure can be obtained by updating the initial model based on the field measured data. According to this baseline model, the bridge dynamic characteristics can be researched more reasonably. Taking Wuhan Tianxinzhou Bridge and its field test as background, the baseline FEM model reflecting the actual bridge dynamic characteristics is obtained by model updating on the base of the field measured data. Then the numerical results obtained by the train-track-bridge model proposed in this thesis are validated by comparing with field experimental results.6. Adopting conventional elements to model track structures often leads to considerable degrees of freedom and large amount of calculation. In this study, the vehicle, rail and bridge are taken as a whole system. The rail and bridge are discredited by B-spline wavelet element, while the rails bed between the rail and bridge is simulated by uniform distribution springs and dampers, thus a model of train-track-bridge spatial dynamic interaction is established, and the corresponding dynamic response calculation is carried out.