Hillsborough River Bascule Bridge Vibration and Rehabilitation

Hillsborough River Bascule Bridge, located in Tampa, Florida, vibrates significantly under traffic loading, and discomforting noises have been reported, especially in recent years. The cause of such a significant vibration was investigated. The bridge is briefly described. Analytical theory is then presented, including the vehicle model, bridge model, road surface model, and numerical methods. A vehicle is simulated as a three-dimensional nonlinear model. The bridge is treated as a space structure consisting of three-dimensional frame elements. The road profile is modeled as a stationary Gaussian random process that is described by a power spectral density function. The free and forced vibration characteristics of the bridge were investigated with trucks traveling over a rough deck. The stiffness effects of the main girders, bracings, and floor beams were studied. Analytical results indicate that insufficient stiffness of lateral bracings and floor beams is a main factor causing the severe vibration. Some rehabilitation schemes for mitigating the severe vibration were investigated. The actual behaviors of the rehabilitated bridge indicate that research results were correct and applicable to bascule bridge design and rehabilitation.