Development of a numerical model for bridge–vehicle interaction and human response to traffic-induced vibration

The perceptible vibration of composite steel girder bridges under live loads is an important design consideration in today’s bridges, which have longer spans and lighter decks than older bridges, and have with limited damping. Although, in accordance with the bridge design codes, the strength design and the deflection control of these bridges are covered fairly well, vehicle movement on the bridge may still cause vibrations that are too strong from the viewpoint of pedestrians. This investigation presents a comprehensive numerical model for studying bridge–vehicle interaction and the resultant perceptible vibration. 3D finite element models are developed for trucks, road surface and the composite girder bridge itself. Truck parameters include the body, the suspension and the tires. The bridge is treated as a 3D composite steel girder bridge on a simply-supported span. A parametric study is performed to identify the effect of various parameters on the vibration of the bridge, such as vehicle speed, neoprene stiffness, the effect of the aspect ratio (ratio of height to length) of steel girders, vehicle type, continuity of the deck slab on top of the pier and the initial bounce of the vehicle due to road surface roughness. The results have been expressed in the form of human perceptibility curves (graphs of perceptible vibration acceleration versus vibration frequency). This study finds that the bridge response is significantly influenced by the vehicle speed, stiffness of the elastomeric pad, continuity of the RC deck slab at pier and the ratio of vehicle weight to total weight of the superstructure, especially for values greater than 10%. In order to validate the proposed interaction model, dynamic field tests were performed on a simple span composite steel girder bridge, located downstream of Karkheh River Dam in Iran, which has significant vibrations under moving truckloads. The results show that the inclusion of features such as increasing the aspect ratio of steel girders and decreasing the number of expansion joints of the RC slab in the design has major effects on the reduction of perceptible vibration.