Load effects and associated forces for bridges subjected to light rail transit

Abstract

This paper presents a numerical study concerning light rail (LR) bridges, with emphasis on the characterisation of load effects and the interaction between LR loadings and supporting structures. The predicted bridge responses were employed to appraise the provisions of the Association of State Highway and Transportation Officials (Aashto) load and resistance factor design (LRFD) bridge design specifications (BDS) and the American Railway Engineering and Maintenance-of-Way Association manual. Because existing methods to determine live load distributions and skew correction factors are inadequate for LR bridges, new design equations are proposed. A single multiple presence factor of 1·0 is recommended for LR bridges, regardless of loaded tracks. The centrifugal force of curved bridges decays as the radius of curvature increases due to a change in centrifugal acceleration. Regarding the longitudinal force resulting from train braking, multipliers are suggested for design provisions. Temperature-induced loading is distributed to the bridge girders. Rail break is expected up to 75 mm within the range of thermal loading specified in Aashto LRFD BDS, which leads to an increase in dynamic load allowance. The force transfer from superstructure to substructure is marginally influenced by bearing arrangement. A statistical test was conducted to comparatively assess the equivalency of the bridge responses related to the above-mentioned design parameters.