Early-Age Behavior of an Adjacent Prestressed Concrete Box-Beam Bridge Containing UHPC Shear Keys with Transverse Dowels

Adjacent precast prestressed concrete box-beam bridges have been used in the United States for many years and have performed well. However, the shear keys between adjacent box beams are susceptible to cracking, which can cause reflective cracks in an overlay or composite deck. The shear-key cracks have been observed shortly after casting and have developed as a result of thermal load, shrinkage, live load, or a combination of these factors. Little research has been done to investigate the early-age field behavior of these bridges. In this study, the early-age behavior of a bridge containing partial-depth shear keys grouted with ultra-high-performance concrete (UHPC) and equally spaced dowel bars was investigated. The bridge, which is the first adjacent box-beam bridge in the United States utilizing reinforced UHPC shear keys, was instrumented and monitored. This paper presents the early-age field results of the bridge during the first week after construction. The bridge performed well, with no cracking in the shear keys based on field observations and data analysis. Furthermore, it is shown that the transverse dowels play a role in helping to carry the transverse stresses in the key at the early age, before the UHPC has gained sufficient strength. (C) 2017 American Society of Civil Engineers.