Effects of Shape and Reinforcement Details of UHPC Shear Key on the Performance of Adjacent Prestressed Concrete Box Beam Bridges

Abstract

AbstractAdjacent precast prestressed concrete box beam bridges have often been preferred for medium to short span bridges in North America due to ease and speed of construction, and relatively low cost. However, longitudinal cracks in the shear keys have been identified as a recurring issue during their service life. In recent years, ultra-high-performance concrete (UHPC) has been used as filling material in the shear keys of adjacent box beam bridges due to its superior mechanical and bond properties. UHPC has outstanding bond with reinforcement, which allows shorter reinforcement embedment length. In the United States, fourteen adjacent box beam bridges with UHPC shear key connections have been completed between 2014 and 2018. In Canada, fifty-five adjacent box beam bridges with UHPC shear keys have been completed between 2007 and 2018. However, the UHPC shear key geometry and reinforcement details used in the United States (U-SK) are quite different from the once used in Canada (C-SK). No analytical, experimental or field studies have been conducted to compare the long-term performance of the two shear key types. This research investigates the two shear key types under traffic load and temperature effects. All the box beam bridges in the US used the same UHPC shear key details, while in Canada, there is no consensus which detail to use in bridges built in different provinces. Therefore, the C-SK shear key details that were found in available literature were used in this study. A finite element (FE) model was developed, then calibrated and validated based on the field test results from the first adjacent box beam girder bridge in the United States utilizing UHPC shear key connections. After validation, the model was used to investigate the effects of the shear key shape and reinforcement details on the bridge performance. The results indicate that U-SK generally experienced better performance in terms of stresses and interface bond degradation compared to the C-SK.