An experimental study was conducted in which five identical, full-scale bulb-T bridge girders were constructed and tested to shear failure. Although the shear span was kept the same for all of the tests (a = 3d), the distance from the end of the specimen to the center of the support bearing (overhang length) was varied. Varying the overhang length controlled whether or not the critical section subject to shear fell within the transfer length, which affected whether the specimen failure was caused by a traditional shear mechanism (web crushing, flexure-shear, etc.) or a nontraditional shear mechanism (e.g., horizontal shear or shear failure induced by anchorage zone distress). The shear failure values were compared with each other to investigate whether nontraditional shear mechanisms result in a lower capacity than traditional mechanisms. These values were also compared with nominal design capacities related to each different failure mechanism.

The Florida Slab Beam (FSB) has been developed by the Florida Department of Transportation (FDOT) to be used for short-span bridges [less than about 19.8 m (65 ft) long]. The FSB system consists of shallow precast, prestressed concrete inverted-tee beams that are placed adjacent to each other and then involve reinforcement and concrete being placed in the inner joints and deck all in one single cast. Ultra-high-performance concrete (UHPC) is becoming more widely used in bridge construction applications as a result of its remarkable structural performance. Many departments of transportation have tested and deployed the use of UHPC in bridges around the United States. Most of these applications have been to connect precast members (e.g., slabs to beams and slabs, adjacent beams, caps to columns, etc.). A modified FSB design is desired to eliminate the cast-in-place (CIP) deck and allow for UHPC to be used in the joint region, which will allow for accelerated construction and decrease the impact of construction on traffic. Different joint details and cross-section geometries were analyzed and experimentally evaluated to determine feasible joint details with UHPC for slab beam bridges used in accelerated construction. Results from numerical modeling, strength, and fatigue experimental testing of the transverse joint performance of four different UHPC joints in two different depth slab beam bridges are presented. Straight-side and shear-key UHPC joint details were found to behave similar to or better than the current FSB joint detail.