Experimental and numerical study on the shear behavior of hybrid BFRP/steel RC beams without shear reinforcement

Abstract

Hybrid reinforcement of steel and fiber-reinforced polymer (FRP) bars can provide a balanced performance between strength, ductility, and durability for the concrete structures. Thus, this study evaluates the shear performance of hybrid Basalt-FRP/steel-RC beams without shear reinforcement. A total of twelve RC beams were cast and tested under four-point loading to study the influence of reinforcement type, reinforcement ratio of longitudinal bars and axial stiffness between FRP and steel ratio, [Formula: see text] on the shear performance of the concrete beams. The test results were analyzed in terms of crack patterns, load-midspan deflection, load-crack width relationships, and shear strength of the tested beams. In addition, the experimental results were compared with the theoretical results obtained from various design codes and guidelines. Moreover, a finite element (FE) model was created, and the experimental results were used for validation of the FE model. The test results revealed that the beam specimens designed with similar effective reinforcement ratio exhibits comparable shear strength nevertheless the tensile reinforcement used. Experimental test results demonstrated that using hybrid bars increased the shear capacity of the beams by 11% compared to steel bars. Furthermore, the energy absorption of the hybrid-RC beams was enhanced by 16% compared to FRP-RC beams. By elevating the [Formula: see text] ratio from 1.25 to 2.44, both the shear strength and energy absorption improved by approximately 10%. Notably, there was a significant decrease in the deflection and crack width of the hybrid-RC beams in comparison to the FRP-RC beams. The design codes ACI440.11-22 and CSA S806-12 displayed accurate enough estimates of the shear strength, while JSCE-1997 showed a conservative result.