ACI says there is interest in using HSS reinforcing bars in many concrete design applications as it 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.
Performance of Shear Specimens Reinforced with High- Strength Reinforcing Bars includes results of five push-off test specimens constructed using reinforcing steel meeting ASTM A706 Grade 80 (550) specifications. It also features five push off test specimens using reinforcing steel meeting ASTM A706 Grade 60 (420) specifications.
All specimens were reinforced with No. 5 (No. 16M) reinforcing bars across the shear interface and designed according to current AASHTO design equations.
According to ACI: “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.”
Additionally, the results indicate that Grade 80 (550) HSS may be used at its full design yield stress in shear-friction applications as long as the reinforcing bars yield.
This paper was written by André R. Barbosa, David Trejo and Drew R. Nielson.