Experimental research on the shear behaviors of hybrid fiber reinforced RPC beams

12 specimens were prepared to investigate the shear performance of Hybrid Fiber Reinforced Reactive Powder Concrete (HFRPC) beams. Variation parameters include: the shear span ratio, reinforcement ratio, stirrup strength, stirrup placement angle and fiber volume. The test results show that: hybrid fibers can significantly improve the RPC beam's shear deformation capacity, turning beam shear failure mode from brittle shear failure to ductile failure. Macro polyolefin fibers can effectively inhibit extension of critical diagonal cracks, slow down the decrease rate of post-peak bearing capacity, increase the number of diagonal cracks, and reduce crack width. When the shear span to effective section height ratio was 3.5, the beams mainly exhibited diagonal tension shear failure. When shear span ratio increased, the bearing capacity decreased, and the high-strength stirrups yielded. When stirrup ratio was increased from 0.42% to 0.64%, and the shear span ratio was 1.5, 2.5 and 3.5, the shear capacity increased by 22.1%, 7.1% and 8.1% respectively. Further increasing stirrup ratio for beams with shear compression failure had little effect on the bearing capacity. When steel fiber volume fraction was increased from 1% to 2%, the shear capacity was augmented by about 17%. Existing codes for the calculation of shear capacity of beams give too conservative values. Calculated value obtained using the French specifications for RPC shear formula is not safe for diagonal tension failure beams, and coefficient of variation is large. This paper puts forward the concept of shear toughness index to characterize HFRPC beam shear deformation capacity and toughness. The classical plasticity theory is for the first time modified by introducing plastic shear coefficient into the bearing capacity formula, taking into account the influence of fiber crack resistance, bridging effect and shear span ratio on the shear capacity and diagonal cracks propagation. The theoretical calculation results agree well with the test results. ©, 2015, Editorial Office of China Civil Engineering Journal. All right reserved.