TVB Model for Estimating the Long-Term Effects of Deck Replacement on Concrete Bridge Behavior

The effects of deck replacement on the long-term behavior of concrete girder bridges are investigated in this study. This study is needed because, as bridges age and decks degrade, bridge owners are increasingly faced with either replacing the structure or replacing only the deck. The latter is a viable option because the lifespan of girders typically exceeds that of concrete decks. Early in the study, a survey of engineers at state departments of transportation showed that, although most states have a need to replace bridge decks, few have plans for assessing the long-term effects of deck replacement on girder behavior. To address this need, the time-varying behavior (TVB) model is developed to estimate concrete bridge behavior over time using a time-step analysis approach to calculate incremental changes in girder behavior through several lifespan stages delineated by changes in loading or boundary conditions. The B4 model, which is based on a large data set of shrinkage and creep tests, is used to estimate concrete creep and shrinkage strains. This paper describes the modeling approach and assumptions, validation of TVB model components, and illustrates the utility of the model with an example bridge. The modeling results suggest that deck replacement can have long-term effects on bridge behavior, particularly on midspan deflection and longitudinal concrete stresses. Nevertheless, further investigation is needed to identify conditions when these effects tend to be substantial enough to warrant consideration by engineers.