Behavior of longitudinal joints in staged concrete bridge decks subject to displacements during curing

Staged bridge deck construction is the practice whereby a portion of a bridge is left open to traffic while the closed portion is constructed, repaired, replaced, or widened. Traffic-induced deflections and vibrations during staged construction may affect the integrity of the longitudinal construction joint between the deck stages and the bond between reinforcing steel and concrete in this area. In this investigation, two test specimens were constructed using a simulated staged bridge deck construction process. To simulate traffic, the specimens were subjected to different magnitudes of differential deflections during curing of the second-stage concrete. Once the concrete achieved its specified compressive strength, the specimens were tested to failure to evaluate the integrity of the longitudinal construction joint and the bond between concrete and lap-spliced steel reinforcement in the construction joint region. Immediate damage caused by the induced differential displacements was minimal; only a single hairline crack was observed in each specimen at the location of maximum negative moment. When subjected to a flexural strength test, both specimens failed in flexure-compression at the end of the spliced reinforcement after substantial inelastic deformations had taken place. Additionally, strain data indicated that even when subjected to differential displacements during curing, the concrete-steel bond was capable of developing the actual yield strength of the reinforcing bars (558 MPa or 81 ksi).