Fatigue Loading and Temperature Distribution in Single Cell Segmental Box Bridges

Precast segmental construction offers many advantages, such as construction economy, simplicity of construction, and reduced maintenance cost. Repeated loading due to moving vehicular loads on the bridges may soften the concrete in due course of time and cause early cracks and larger deflections. This loading in segmental bridges may also cause openings of the joints between the segments. This paper presents the results of an experimental study of a single cell precast posttensioned segmental box bridge system subjected to cyclic loading and temperature changes. The test bridge system is a 1:3.5 scale model of the Long Key Bridge in the Florida Keys. The behavior of the bridge model was examined under fatigue loading, with emphasis on joint performance and flexural stiffness. The temperature distribution of the bridge system was also measured, and compared with analytical predictions. The performance of the bridge model was evaluated in terms of deflections, strains in the concrete and strains across the joints, and cracking behavior of joints between the segments with an increasing number of cycles of fatigue loading. The studies indicated that the behavior of joints between the segments under static and fatigue loadings was satisfactory up to two million cycles. No joint openings or cracks were observed at the joints under the loading. The temperature distribution of the bridge model was also studied using finite-element analysis and the predicted temperatures across the cross section were compared with the observed values.