Effects of design parameters on deck cracking from restrained concrete shrinkage in jointless bridges

Bridges have traditionally relied on a system of expansion joints, roller supports, and other structural releases to accommodate expansion and contraction movements due to temperature, creep, and shrinkage loading. Joints and elements in their vicinity experience a high amount of damage and degradation; thus modern design approaches are advocating their removal, with movement accommodated through flexible piles and abutment walls. While jointless bridges have been performing well, many of them suffer from widespread early-age transverse deck cracking. A literature review and field investigation was conducted to identify the primary causes for early-age deck cracking in jointless bridges. The most dominant source of early-age transverse deck cracking is due to restrained concrete shrinkage. Experimentally-calibrated finite-element models were used to predict cracking behavior in various full bridge systems with different bridge design parameters undergoing shrinkage loading. Simulation results confirmed that the more restraint present in the system, the more cracking that will occur. Models showed that steel and concrete beam bridges are equally susceptible to restrained shrinkage cracking. The lowest amount of cracking was predicted for bridges with non-integral abutments, higher shear connector spacing, and a low-shrinkage concrete mix. Changing the deck reinforcement configuration had little effect on the bridge performance. Of the parameters considered, a low-shrinkage mix had the greatest impact on minimizing deck cracking. Overall, the simulations indicated that restrained shrinkage cracking in jointless bridge decks is unavoidable, but that modifying design details and improving concrete mixture designs can help reduce its extent.