Effect of dynamic impact at modular bridge expansion joints on bridge design

To analyze the dynamic impact induced by a heavy vehicle crossing a modular type expansion joint and its effect on the bridge response, a numerical method based on a distributed spring-damper element is presented, in which the contact patch between the tire and the road is considered. The dynamic response of the vehicle and bridge can be obtained by dynamic finite element analysis of the vehicle-bridge system taking into account the bumpy ride of vehicle at the expansion joint. The reduced support to the parts of tire structure over the cavities of the modular expansion joint is considered, and the vertical tire load can be obtained by an iteration procedure. To assess the dynamic impact at the expansion joint on bridge design, the impact factors associated with the vehicle tire loads, and the bearing reactions, shear forces and bending moments of the bridge are evaluated. The multi-gap modular expansion joints leads to lower impact factors than single-gap expansion joints. The effects of dynamic impact at expansion joint on the bearing reactions and shear forces are greater than that on the bending moments of the bridge. Numerical results also show that the impact effects of vehicle axle load and internal forces of the bridge may be higher than those recommended by bridge codes, and they may affect the durability of components in the vicinity.