CCEER 01-7: Removal and Replacement of Cast-in-Place, Post-tensioned, Box Girder Bridge

Abstract

This report descrihes the analytical investigation of the removal and replacement of cast-in-place, post-tensioned, box-girder bridge decks. In order to extend the life of the overall bridge, the deck typically must be replaced. This is problematic in a post� tensioned bridge where the deck is part of the structural system that resists the prestress force. This analytical investigation examines the impact of deck removal and replacement. As bridges deteriorate due to environmental effects, this deterioration is more severe in the decks. Four specific bridges were chosen for analysis. These bridges were two simple span bridges (non-skewed and skewed), a two-span continuous bridge, and a three-span continuous bridge. The investigation was perfonned on bridges that might be considered for deck replacement in the future. A 3D finite element analysis was performed on all bridges and compared with a 2D analysis. Processes and recommendations for deck removal were given for simple and continuous span bridges. The impact in the amount of skew was also investigated in this topic. Recommendations were also given for traffic analysis and future design considerations for simple and continuous span bridges. It was found that deck removal and replacement must be considered on a case-by� case basis. If the bridge is a simple span bridge, then additional prestressing can be used to support the bridge while the deck is being replaced. The additional prestressing tendons placed on the bottom of the bridge were found to be ineffective at reducing the stress levels for the continuous structures. If the bridge is a continuous span bridge, then

a 2D analysis must be performed to evaluate if shoring is necessary. Additional prestressing keeps the concrete stresses within allowable levels.