Performance of Shear Specimens Reinforced with High-Strength Reinforcing Bars

There is interest in using high-strength steel (HSS) reinforcing bars in many concrete design applications. HSS reinforcement has the potential to decrease construction costs and reinforcement congestion. However, the design value of HSS reinforcing bars for concrete-concrete shear-friction interfaces is currently limited to a nominal yield strength of 60 ksi (420 MPa) in both bridge and building code provisions. In part, this is due to the limited information on the performance of HSS reinforcing bars in concrete shear interfaces. This paper presents new data on the performance of shear-friction interfaces containing Grade 80 (550) HSS reinforcing bars. The results of five push-off test specimens constructed using reinforcing steel meeting ASTM A706 Grade 80 (550) specifications and five push off test specimens using reinforcing steel meeting ASTM A706 Grade 60 (420) specifications are presented. All specimens were reinforced with No. 5 (No. 16M) reinforcing bars across the shear interface and designed according to current AASHTO design equations. Results indicate that the specimens containing the HSS reinforcing bars across the interface exhibited higher peak forces and higher post-peak sustained interface shear forces. Results indicate that as long as the reinforcing bars yield, Grade 80 (550) HSS may be used at its full design yield stress in shear-friction applications.