Dr. Shih-Ho Chao and Dr. Nur Yazdani received a three-year research grant of $413,142 from the Texas Department of Transportation. The objective of this project is to determine if adequate horizontal shear capacity is provided by the 5-inch concrete deck on slab and box beams, despite lack of reinforcement development. Horizontal cracks between the precast beams and the cast-in-place decks were noticed in several TxDOT bridges. Those cracks could be due to stresses induced by shrinkage or shear forces. In any case, this shows that that current TxDOT details might not provide sufficient horizontal shear resistance in those members.

First phase of this project involves small scale tests to investigate the three major components of horizontal shear resistance: (1) cohesion and/or aggregate interlock, (2) friction between the crack faces, and (3) dowel action of the reinforcement. A simple bar pullout test will also be used to evaluate the influence of the bend curvature on the bond and slip characteristics of the horizontal shear reinforcement. Alternative details for surface roughness and bar geometries will be investigated. In the second phase of this project, the research team will be testing several full-scale composite box and slab beams with current and proposed alternative details to investigate the overall composite behavior.