No abstract

When a train passes over bridges, the magnitude of forces and accelerations is altered due to sudden changes in the track stiffness. These forces can change with the variation in operational parameters and are effective particularly in high-speed passenger trains, when studying ride index parameter. In addition, by increasing the speed, old bridge structures could fall into resonance, which has harmful consequences for both bridge and ride comfort index. Moreover, to harmonize the old bridges with the new operational conditions dynamic behavior of the vehicle and ride comfort need to be taken into account. In this paper, coupled vertical and roll vibration of a horizontally curved bridge are considered. During pass over the bridge, acceleration and ride comfort of a passenger vehicle are studied. The eccentric vertical and lateral forces are the major excitation sources in the analysis, an issue that is rarely noticed in the literature. A multi-body model of a normal wagon is built in three dimensions, passing over a horizontally curved bridge. The governing equations of the vehicle-bridge system are written, taking into account the wheel-rail interactions. The major variables are the cant, train speed, track quality, and radius of curvature. The paper studies the effects of the prescribed variables on ride comfort. The results show that track quality and cant have considerable influences on ride comfort index. The ride comfort is improved when the speed is approached to a so-called equivalent speed.

Abstract. Annoying vibration waves generated by passing trains highlight the necessity for the assessment of the e ects of railways on their environment. Dynamics of structures close to railway tracks is amongst such important issues. Contrary to the past studies, this article proposes a modeling method that is totally based on the idea of discrete masses. It considers three major parts as the accomplices causing undesirable oscillations including the track, the ground bed, and the structure in the vicinity of the track. The ground bed is considered as an elastic half space subdivided into discrete masses. It facilitates modeling for the track systems that may include any deliberate discontinuity, such as voids and trenches, in the ground bed that supports the railway track. Such discontinuities arise from engineering perception and are useful in controlling the spread of noise and vibrations. A \MATLAB" based computer program is written to solve the motion equations in the time domain. The proposed method provides exibility in modeling. Variety of track loading and wave propagation scenarios can be simulated without the need to rebuild the model. This method can be practically used when seeking remedies for controlling the levels of unwanted vibrations in the structures.