Evaluating Lap-Splice Length Requirements for Grade 80 Deformed Bars in Structural Masonry

Abstract

In 2019, a major code change made by the American Concrete Institute incorporated the extensive 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 due to the absence of relevant analytical and experimental data. Currently, masonry design standards define the maximum allowable design stress for reinforcing bars at 420 MPa (60,000 psi). This paper presents the first research study on HSRBs for structural masonry with a focus on the lap-splice demand for Grade 80 (550 MPa) deformed bars. The research study included 22 contact lap-splice experiments in concrete and clay brick masonry, with test variables being the bar size, the lap-splice length, and the standard specification of the bars. A high-fidelity finite-element model was developed to simulate the bond-slip behavior of HSRBs in structural masonry and complement the experimental findings. Experimental and numerical results corroborated the technical feasibility of embedding Grade 80 bars in structural masonry with reasonable lap-splice lengths, following revisions to the code design formulas. Furthermore, it was found that different standard specifications of bars present different lap-splice length requirements, a distinction that is not currently made by existing code provisions.