Ultra high performance concrete, specifically Ductal® concrete, has begun to revolutionize the bridge design industry. This extremely high strength material has given smaller composite sections the ability to carry larger loads. As the forces being transferred through composite members are increasing in magnitude, it is vital that the equations being used for design are applicable for use with the new materials. Of particular importance is the design of the horizontal shear reinforcement connecting the bridge deck to the top flange of the beams. Without adequate shear transfer, the flexural and shearing capacities will be greatly diminished. The current design equations from ACI and AASHTO were not developed for use in designing sections composed of Ductal® and Lightweight concrete.

Twenty-four push-off tests were performed to determine if the current horizontal shear design equations could accurately predict the horizontal shear strength of composite Ductal® and Lightweight concrete sections. Effects from various surface treatments, reinforcement ratios, and aspect ratios, were determined. The results predicted by the current design equations were compared to the actual results found during testing. The current design equations were all found to be conservative. For its ability to incorporate various cohesion and friction factors, it is recommended that the equation from AASHTO LRFD Specification (2004) be used for design.