Dynamic Behavior of Continuous and Cantilever Thin-Walled Box Girder Bridges

The free vibration characteristics and the dynamic response to a multivehicle load moving across rough bridge deck of continuous and cantilever thin-walled box girder bridges are studied. The box girder bridge is divided into a number of thin-walled beam elements. Both warping torsion and distortion are considered in the study. The analytical vehicle is simulated as a nonlinear vehicle model with 11 independent degrees of freedom according to the HS20-44 truck design loading contained in the AASHTO specifications. Four different classes of road-surface roughness generated from power spectral density function for very good, good, and average roads are used in the analysis. One continuous and two cantilever three-span box girder bridges are designed based on the AASHTO specifications. The dynamic responses of the bridges are evaluated for single truck, three, and six trucks, with different speeds and road surface roughness. The analytical results show that the effects of different loading models, road surface profiles, and vehicle speeds on the dynamic response for different types of bridges are quite different. The most important factor which affects the impact of cantilever bridges is the vehicle speed.