Dynamic Response Analysis of Slab-Type Bridges

The response of a bridge under a moving vehicle is a complex phenomenon because of the interaction between the bridge and the vehicle. This complexity makes it difficult to identify the significant parameters that govern the response; yet a knowledge of such parameters is important for developing rational procedures for design. An earlier study by the writers used a beam model to identify the controlling parameters. In the present study, the bridge is idealized by a rectangular isotropic or orthotropic plate and the vehicle is represented by a single sprung mass moving along the deck. The plate is discretized by finite elements and the nonlinear equations of motion are solved in their incremental form by a process of numerical integration. The study shows that the governing parameters for an isotropic plate models are the aspect ratio, the speed parameter, the frequency ratio, and the mass ratio, while those for an orthotropic model are χ and θ, characteristics that depend on the geometry and the natural properties of the plate, as well as the speed parameter, the frequency ratio, and the mass ratio.