Experimental Study On Mechinal Behavior Of Steel Fiber Reinforced Concrete Beams With High-Strength Reinforcement

Many researchers have performed experimental and theoretical studies on the flexural and shear behavior of steel fiber reinforced concrete beams with conventional reinforcement,few studies involve the flexural and shear behavior of SFRC beams with high-strength reinforcement.When the high-strength reinforcement with is used to replace the conventional reinforcement in steel fiber concrete beams,whether the flexural capacity,bending stiffness and shear capacity of the beams can still be calculated by Chinese and American codes needs to be verified by experimental research.This paper focuses on the flexural and shear behavior of steel fiber reinforced beams with high-strength reinforcement,and the test results are mainly concerned with the applicability of Chinese and American codes to calculate flexural capacity,bending stiffness and shear capacity of steel fiber reinforced beam with high-strength reinforcement.The main research contents include:(1)Under the condition of 1.02% and 2.99% longitudinal reinforcement ratio,the beams with steel fiber volume fraction of 0%,1% and 2% were tested,respectively.The effect of steel fiber volume fraction and longitudinal reinforcement ratio on on the flexural behavior were investigated,including the load-deflection curve,cracking load,flexural capacity,depth of compression zone,maximum crack width,bending stiffness,ductility and failure mode.(2)The flexural capacity of steel fiber reinforced concrete beams with high-strength reinforcement was studied by using calculated method of CECS38:2004.Based on the experimental results,a formula for calculating the flexural capacity of steel fiber reinforced concrete beams with high-strength reinforcement was established.(2)Comparing the measured load-deflection curves with the load-deflection curves calculated by the CECS 38:2004,the reasons for the difference were analyzed,and the CECS 38:2004 stiffness equation was modified.The test values for the initial moment of inertia and the yield moment of inertia were compared with the calculated values by ACI 318-14,and the effective moment of inertia equation for steel fiber reinforced concrete beams with high-strength reinforcement was proposed based on the experimental results.(3)The shear tests were carried out on five beams without stirrups and six beams with stirrups.The effects of steel fiber volume fraction and stirrup ratio on the shear behavior of the beams were investigated,inculding the load-deflection curve,cracking load of diagonal section,shear capacity,concrete strain of diagonal section,stirrup strain,diagonal crack width,failure mode and.(4)Comparing the measured shear capacities with the values calculated by CECS38:2004 and ACI544.4R,the reason for the difference between the experimental values and the calculated values of the codes was analyzed,and the equations of the codes were modified.(5)By referring to the design principle of the mix proportion of GJT472-2015,the steel fiber at the crack was equivalent to concrete aggregate across the crack section,and two calculation models of steel fiber at the crack with shear stress and without shear stress are proposed based on the modified compression-field theory.At last,the data of 106 experimental beams proved that the shear stress of steel fiber in cracks can be neglected when calculating the shear capacity of steel fiber reinforced concrete beams.