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Abstract: Hybrid cable-stayed bridges consist of steel and concrete bridge segments, of which steel–concrete joints are of great importance and raise strong research interest. Due to the limitation of the traditional methods, i.e., the member finite element (FE) method and Mixed Dimensional Coupling (MDC) method, the present study proposes a substructure method to model long span bridges. The current application of the substructure method is to extract some specific parts of the whole structure to refine and analyze them. Different from the routine substructure approach, here the entire structure is modeled in detail and divided into many substructures. All the substructures are then condensed into super-elements except the concerned part. The application of the method is then illustrated through numerical studies of the vehicle–bridge coupling vibration of the Jingyue Yangtze River Bridge with a main span of 816m. The entire bridge is first divided into many substructures with a reasonable length. Among them, the concerned substructure with 23.8m in length including the steel–concrete joint is modeled in detail but not formed into super-element, while all the other components are modeled in detail and formed into super-elements using the component mode synthesis (CMS) method. All the components including both the super-elements and non-super-elements are then assembled into a complete and fine full bridge model. Finally, the model is used for the vehicle-induced dynamic analysis under deterministic traffic flows. The results show that the joint works well, and the transition between the steel girders and concrete beams is very smooth. [Copyright &y& Elsevier]

Abstract: The problem of identification of parameters of a beam-moving oscillator system based on measurement of time histories of beam strains and displacements is considered. The governing equations of motion here have time varying coefficients. The parameters to be identified are however time invariant and consist of mass, stiffness and damping characteristics of the beam and oscillator subsystems. A strategy based on dynamic state estimation method, that employs particle filtering algorithms, is proposed to tackle the identification problem. The method can take into account measurement noise, guideway unevenness, spatially incomplete measurements, finite element models for supporting structure and moving vehicle, and imperfections in the formulation of the mathematical models. Numerical illustrations based on synthetic data on beam-oscillator system are presented to demonstrate the satisfactory performance of the proposed procedure. [Copyright &y& Elsevier]

Abstract: A numerical model for dynamic vehicle–track interaction at rail welds with longitudinal surface irregularity is presented. In the model, the vehicle and track, except for the rails, are treated as rigid multi-body systems. A Timoshenko beam is used to model the rails which are discretely supported by sleepers. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. The model is applied to calculate the dynamic wheel–rail contact forces and the sizes and locations of the contact areas. A three-dimensional finite element model of rail at welds is then built up to investigate the plastic deformation of rail. The contact forces, the sizes and locations of contact areas obtained by the vehicle–track dynamics simulation are utilized as the inputs to finite element model. The influence of different geometries of rail welds on the dynamic wheel–rail contact forces, stresses and deformations of rail is investigated. The analysis reveals that the train speed and the wavelength and wave depth of the irregularities at rail welds have great effects on the wheel–rail contact forces. The dynamic forces due to the welded rail surface irregularity cause increased plastic deformation not only at the rail weld but also at the base metal near the rail weld. The numerical results obtained are very useful in the tolerance design of welded rail surface irregularity. [Copyright &y& Elsevier]