Shear behavior of large-scale concrete beams reinforced with CFRP bars and handmade strip stirrups

To obviate the premature failure of pultruded FRP stirrups due to low bent portion strength and slippage at overlapping region, this study fabricated handmade strip stirrups with a rectangular cross-section and investigated the shear behavior of concrete beams reinforced with handmade CFRP strip stirrups and CFRP longitudinal bars. Five large-scale concrete beams with the cross-section of 200 mm × 500 mm and the shear span ratio of 2.26 were tested under three-point loading. The effects of stirrups inclination and stirrups spacing were studied. Test results showed that inclined stirrups improved both the shear capacity and the serviceability performance. The beams reinforced with inclined stirrups exhibited 1.19–1.26 times higher shear capacities than the beam reinforced with vertical stirrups. Inclined stirrups not only increased the load corresponding to the maximum allowable crack width to 1.10–1.89 times higher, but also improved the ratio of the load corresponding to allowable crack width to the peak load. Moreover, inclined stirrups are more effective in improving the serviceability performance even compared with vertical stirrups with a halved spacing. The shear provisions in CSA S806-12 produced the most accurate predictions of the experimental shear capacities, while the predictions of ACI440.1R-15 and CSA S6-14 were relatively conservative.