Effectiveness of Alternative Reinforcing Strategies for Non-Contact Hooked Bar Lap Splices

Closure joints are used in precast bridge construction to join two pieces of precast concrete. The pieces of concrete are joined by a lap splice which consists of longitudinal steel sticking out of each precast element and overlapped over the minimum required development length. State departments of transportation find it desirable to make the width of closure joints short. To achieve this, bridge engineers have been using hooked bars in the closure joints in lieu of straight bars, with the assumption that this would allow for shorter splice lengths. Though engineers in practice are doing this, design guidance does not exist. One research project by Coleman (2024) tested 58 beam-splice specimens to investigate the impacts of a variety of parameters on bond and anchorage and develop design guidance for hooked bar lap splices. This project did not investigate three parameters: the number of lap splices, the placement of transverse reinforcement, and the addition of steel fibers in the closure joint. For this thesis, 15 beam-splice specimens were tested in 4 point-bending to investigate the impact of these parameters on bond and validate the descriptive equation developed by Coleman (2024) to determine the bar stress of a hooked bar lap splice. The findings of this study suggest that the number of splices and the placement of transverse reinforcement has minimal impact on the bar stress developed, and the equation by Coleman (2024) adequately predicts the bar stress when these parameters were varied. The addition of steel fibers to the closure joint had a substantial impact on increasing the splice strength. In the beams where steel fibers were added in a 1% fiber volume fraction, the descriptive equation by Coleman (2024) underpredicted the bar stress for both unconfined and confined beams with the addition of fibers. Thus, this thesis proposes a factor to multiply the descriptive equation by determining the bar stress when steel fibers are added. With these findings, using steel fibers in closure joints for precast concrete can be used to reduce splice length in non-contact hooked bar lap splices.