Direct shear strength of rebar-coupler anchor systems for steel-plate composite (SC) walls

This paper focuses on the direct shear behavior of rebar-coupler anchor systems, and their use for anchorage of steel-plate composite (SC) walls to the concrete basemat of safety-related nuclear facilities. Large-scale rebar-coupler anchor specimens were tested under direct shear loading until failure. The results included the applied load-slip displacement responses of the specimens, the direct shear strength, and the observed failure mode. The American Concrete Institute (ACI) 349 code equation for calculating the direct shear strength of embedded anchors was compared with the direct shear strengths from the tests. The code equation underestimated the direct shear strength of the anchor system, because shear failure was assumed to occur in the rebars, whereas experimental observations indicated that shear fracture failure occurred in the couplers rather than the rebars. The design equation was updated to utilize the net shear area of the couplers instead of the rebars, after which the direct shear strengths from the tests could be calculated with reasonable accuracy. The experimental results were also used to propose an empirical model for the shear force vs. slip displacement response of rebar-coupler anchor systems.