Time-Dependent Flexural Deformations in Composite Prestressed Concrete and Steel Bridge Beams. I: Prediction Methodology

A methodology will be presented to predict the complete history of flexural deformations in composite prestressed concrete and steel beams from inception to the end of service life, which will include a prediction of beam rebound and subsequent deformations when the deck is replaced. The methodology will use distinct creep curves for each loading event and will provide an efficient framework to account for the effects of differential creep, differential shrinkage, shrinkage-induced creep, loading time, concrete aging, prestress losses, and temperature gradients on composite and noncomposite beam flexural deformation history. The method will be based on a time-dependent strain compatibility analysis, which will provide curvatures at various points along the span as a function of time to obtain the history of the deflected shape of the beam. Measured discrete and periodic flexural deformation data will be used to validate the methodology. The presented method will be used to quantify the influence of creep, shrinkage, modulus of elasticity models, temperature gradients, deck placement and replacement time, and time step generation method on the beam flexural deformation history. The results show that steel beams can rebound to their original position after the deck has been removed, the rebound in the prestressed concrete beams varied from 51% to 92%. In addition, the influence of the initial deck placement time had a marked effect on the short-term beam flexural deformations at service, and its influence diminished after 200 days for the cases that were considered in this study. In addition, the selection of models for creep, shrinkage, and modulus of elasticity at prestress release and 28 days had a marked effect on the beam deformation history, and the considered models for the variation in modulus with time resulted in similar predictions.