steel fiber;  high-strength concrete;  Cracking moment

Through the test of 12 reinforced steel fiber high-strength concrete beams, the influence of steel fibers on the crack bending moment of the positive section of reinforced high-strength concrete beams was analyzed. The experimental results show that the addition of steel fiber improves the cracking bending moment of the positive section of the steel high-strength concrete beam, and the increase trend is increasing with the increase of the volume rate of steel fiber, and the increase range is between 40%~100%. The reinforcement ratio of longitudinal rebar, the height of the beam and the strength grade of the rebar also have an impact on the cracking and bending moment of the rebar high-strength concrete beam. The cracking moment increases with the increase of the reinforcement ratio of the longitudinal rib and the decrease of the cross-sectional height. Combined with the current relevant specifications, the calculation formula of the cross-section resistance to the influence of plasticity of reinforced steel fiber high-strength concrete beam and the calculation formula of the cracking bending moment of reinforced steel fiber high-strength concrete beam are proposed, and the correctness of the formula is verified by test data.