In this dissertation, a study on the development of the finite analysis models, which improve the accuracy of the 2-dimensional analysis model and the efficiency of the full 3-dimensional analysis model of high-speed train-bridge interactions, is performed. For the purposes, the simplified 3-dimensional bridge-vehicle interaction analysis model (S-MODEL), substructuring technique-applied model (SS-MODEL), and full 3-dimensional bridge-vehicle interaction analysis model (F-MODEL) are proposed. Through investigating the characteristics of dynamic behaviors of high-speed railway bridges under train passing, using these models, the applicability and validity of these models are verified.
A simplified 3-dimensional bridge-vehicle interaction analysis model (S-MODEL) considers the eccentricity of the vehicle axle loads and the neutral axis of cross section of a railway bridge. By considering this eccentricity, the influence of the torsional forces and torsional rotations on the dynamic behavior of a bridge can be reflected in analysis results. Therefore, this analysis model can improve the accuracy of the 2-dimensional analysis model nearly to the level of full 3-dimensional analysis model and reduce modeling efforts, analysis preparing time, and computing time as well. The 2-dimensional vehicle model devised to model a high-speed train is used, which has an articulated bogie system. The equations of kinetic energy, potential energy and damping energy are expressed by the degrees of freedom of the vehicle and bridge. And then by applying Lagrange's equations of motion, the equations of motion of the vehicles are obtained. By deriving the equations of the forces acting on the bridge considering the bridge-vehicle vertical interactions and also by identifying the position of vehicle as time goes by, the mass matrix, stiffness matrix, damping matrix and load vector of total bridge-vehicle system are constructed in accordance with the position of bogies. By solving these equations of motion, the dynamic behavior of total bridge-vehicle system can be analyzed.
Substructuring technique-applied model (SS-MODEL) is firstly based on the simplified 3-dimensional analysis model (S-MODEL) and apply substructuring technique to bridge-vehicle interaction analysis. By using this analysis model, which models respectively the super-structure and sub-structure of a railway bridge, it is possible to perform bridge-vehicle interaction analysis efficiently. In dynamic analyses, in which we ask for the solutions, problems with only 1000 D.O.F. can be difficult. However, condensation method can be employed to reduce the number of D.O.F., which reduces the expense of computing eigenvalues and eigenvectors and the expense of subsequent calculations. Condensation method is detrimental to accuracy, but negligibly so if properly used. Guyan reduction method is employed as a substructuring technique in this study. Combining the simplified 3-dimensional bridge-vehicle interaction analysis with Guyan reduction method, the efficient and accurate analysis of bridge-vehicle interaction can be performed.
A full 3-dimensional bridge-vehicle interaction analysis model (F-MODEL) using various improved finite elements, models the specific structural members of a railway bridge, which are not considered in the existing 2-dimensional analysis models. Main bridge decks are modeled by NFS(Nonconforming Flat Shell) element, which are the defect-free flat shell element with 6 degrees of freedom per a node. To model the box-girder structure which is a sort of folded plate structures, NFS elements are versatile. NFS elements have shown the high performance in the numerical examples of the previous researches. Rails are modeled by beam finite elements and sleepers are modeled by beam elements on Winkler foundations with two-parameter. These beam elements are also used to model I-girder with the concept of rigid link. The 3-dimensional vehicle model devised for a high-speed train is used, which has an articulated bogie system.
In this dissertation, the finite element analysis programs for the bridge-vehicle interaction analysis using these improved analysis models are developed and the validity of these analysis models is verified through the analyses of the application examples. Finally, these analysis models are applied to investigate the structural behavior of high-speed railway bridges under train passing.
