Experimental Investigation of Shear Behavior in High-Strength Concrete Beams Reinforced with Hooked-End Steel Fibers and High-Strength Steel Rebars

Shear failure is an unfavorable phenomenon as it is a brittle type of failure; however, adding rebars and fibers to a concrete beam can minimize its detrimental effects. The objective of this study was to experimentally investigate the shear behavior of high-strength concrete (HC) beams reinforced with hooked-end (H) steel fibers and high-strength steel (HS) rebars under three-point bending tests. For this purpose, nine HC beams (300 x 250 x 1150 mm in dimension) were cast with 0%, 1%, and 2% H fibers by volume in three longitudinal rebar ratios (i.e., 1.5%, 2.0%, and 3.1%) and compared with beams without fibers. Furthermore, numerical analyses were performed to validate the experimental results and compare them with design codes. The results showed that, irrespective of the fiber content or longitudinal rebar ratio, the beams failed in shear. Increasing the rebar ratio and fiber content increased the shear capacity to as high as 100% (for the specimen with 3% rebar and 2% fiber compared to its counterpart with 1% rebar and 2% fiber). In addition, the research-based equations proposed in the literature either overestimated or underestimated the shear capacity of fibrous HC beams significantly. The level of overestimation or underestimation was closely related to the sensitivity of the proposed model to the shear span ratio and the fiber content. Rebars proved to be more beneficial in contributing to the shear capacity, but the rate of this positive contribution decreased as the fiber ratio increased. Finally, the inverse analysis approach adopted herein proved to be an efficient tool in estimating the shear response of fiber-reinforced beams failing in shear (margin of error: less than 10%).