United States Department of Transportation
i
Post-Tensioned Concrete Box-Girder Bridge Deck Replacement Analysis
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2019-06-01
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[PDF-109.69 MB]
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Edition:Final Report, 6/1/2016-9/30/2018
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Abstract:Issues related to the replacement of damaged bridge decks were examined in this study. Finite element analyses of four post-tensioned box-girder bridges were conducted to investigate various strategies for safe and effective deck replacement without the use of falsework for any of the superstructure spans. Parameters of the study included straight, curved and skewed bridges, and simple versus multi-span bridges. Deck replacement in post-tensioned box-girder bridges needs special attention as the deck forms an integral part of the load-resisting mechanism and the large prestressing stresses are being locked in by the post-tensioning in the superstructure. Considerations must therefore be made to include an assessment of the potential for unfavorable stress redistribution during the deck replacement. In the analysis of the four bridges, implementable strategies for lane closure and traffic re-routing for deck replacement were included. Options in terms of temporal longitudinal and transverse replacement sequences were accounted for in the analyses. Time-dependent properties of concrete and steel were incorporated in the finite element model. Transient as well as long-term service stresses and deflections up to 50 years were extracted for comparison among different replacement options. Results indicated that full-depth deck replacement may be difficult as the current AASHTO stress and deflection limits were violated in all four of the bridges selected for the study. Results indicated that the “all-span replacement strategy” and the “negative-moment-region-first replacement strategy” were the two best options for deck replacement if stress and deflection violations can be mitigated. As a general trend, the top of the web stress and the girder downward deflection were found to accumulate when the deteriorated deck was removed and a new deck was cast. Tensile stresses in the top fiber of the deck were found to be critical at mid-span and over the bent for these four bridges. Mitigating measures such as the use of precast, prestressed deck panels or other means of providing pre-compression to the new deck are suggested to counteract the potentially large tensile stresses.
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