Concrete Curved Box Girders Interacted with Vehicles in Braking or Acceleration

In this study, an experimentally validated spatial analysis method for the vehicle-bridge interaction system was modified to include the features of vehicle braking and accelerating. The effect of braking or accelerating was considered as external force acting on the vehicular center of gravity and was quasi-statically distributed to every tandem, for which the formulae of load redistribution were derived. The effect of centrifugal force was also incorporated in the model. Based on the modified spatial analysis method, the dynamic responses of a three-span continuous concrete box girder bridge due to vehicle braking and accelerating were studied. Impact factors, including deflection, bending moment, torsional moment and shear force, were examined. The results show that vehicle braking has considerable effect on dynamic responses and the impact factors are related to braking rise time and braking position, but cases of vehicle braking do not always cause larger effects. While the increase in initial speed can produce higher maximum dynamic responses and corresponding impact factors, the dynamic responses in the first span of a multi-span bridge are smaller than those in other spans due to vehicle accelerating.