High-Strength Reinforcing Bars (HSRB) and TMS 402: A First Study on Grade 80 (550 MPa) Bars

In 2019, ACI 318 introduced a major code change by incorporating the usage and applications of high strength steel reinforcing bars (HSRBs). The adoption of HSRBs was motivated by several factors, including the reduction in steel congestion and construction cost, gain in member strength, and reduction in the carbon footprint of reinforced concrete buildings. However, code adoption of HSRBs has lagged in masonry design, which is attributed to the absence of relevant analytical and experimental data. Currently, TMS 402/602 defines the maximum allowable design stress for reinforcing bars at 60,000 psi. This research presents the first study on using Grade 80 (550 MPa) bars in the context of TMS 402/602. An analytical investigation was performed to examine the feasibility of using these bars with consideration to the ASD/SD provisions and the potential for reduction in material weight and cost in comparison with Grade 60 bars. The analytical investigation was followed by an experimental study of lap-splice tests for Grade 80 ASTM A615 and ASTM A706 reinforcing deformed bars. The experimental program included twenty-two contact lap-splice experiments in concrete and clay brick masonry, with test variables being the bar size, the lap-splice length, and the ASTM designation of the bars. Experimental and analytical results corroborated the technical feasibility of embedding Grade 80 bars in structural masonry with reasonable lap-splice lengths, following revisions to the design formulas of TMS 402/602. The need for future research is emphasized toward testing of large-scale masonry members reinforced with Grade 80 bars in flexure and shear.