Long-term Implications of Redecking Bridges with Prestressed Concrete Girders

Abstract

Precast/prestressed concrete girders with cast-in-place decks are commonly used for bridge construction throughout the United States. There is a need to replace concrete decks on many of these bridges because girders last much longer than concrete decks. This study surveyed United States Department of Transportation (DOT) engineers to determine common deck removal practices. Survey results showed that, although most states have a need to replace bridge decks, few states have comprehensive plans for assessing the long-term effects of deck replacement on girder behavior. This study developed a Python model to estimate girder behavior over its lifespan that accounts for the effects of deck replacement, changes in loading conditions, changes in restraint conditions, and concrete deformations. Time-step analysis was used to calculate incremental changes in girder behavior throughout time, considering several lifespan stages delineated by changes in loading or boundary conditions. The B4 model (Wendner et al., 2013) was used to estimate the creep and shrinkage strain in the concrete. The model was validated against examples in the literature and applied to an example bridge to illustrate function. Modelling results suggest that deck replacement had minimal effect on long-term girder behavior for the bridge considered. A parametric study was also conducted to evaluate the influence of input parameter variations on long-term prestress loss, deflections, and stresses and strains for the example bridge. Parametric study results showed that girder behavior varies widely based on input parameters, suggesting that more research is needed to determine whether other bridge configurations would also be insensitive to deck replacement.