Experimental Study On Shear Resistance Properties Of Steel Fiber High-strength Reinforced Concrete Beam

The failure characteristics of high-strength reinforced concrete beams under shearshow great brittleness and poor ductility. It is feasible to add steel fibers into concreteto improve the brittleness of concrete. By the addiction of steel fibers, shear resistanceand deformation capacity of reinforced concrete beams are improved and diagonalcracks are restrained effectively. This paper presents the experimental study on shearresistance properties of steel fibers high-strength reinforced concrete beams, the maincontents include:According to the experimental study of6steel fibers high-strength reinforcedconcrete beams and2control beams under shear, the characteristics of diagonal cracks,failure mechanism, longitudinal reinforcement strain and concrete strain ofshear-compression zone of beams are analyzed. The influence law of contents of steelfibers, concrete strength and other parameters on shear-cracking load, shear capacityand maximum diagonal crack widths of beams are studied.According to the experimental study, the calculating formulas of regressioncoefficients of shear cracking load and shear capacity concerning shear-span to effectivedepth ratio and longitudinal reinforcement ratio are put forward, and the empiricalformulas are given to predict the shear-cracking load and shear capacity of steel fiberhigh-strength reinforced concrete beams under shear, the calculated value agreed withthe measured value well.According to the experimental data and based on the calculating model ofmaximum diagonal crack widths, coefficient about horizontal projection length ofdiagonal cracks, oblique section shear adjustment coefficient, nonuniformity coefficientconsidering stirrup strain and diagonal crack widths are modified, the practical formulais given to calculate the maximum diagonal cracks width of steel fiber reinforcedconcrete beams under shear, the calculated value agreed with the measured value well.The characteristics of the load-deflection curves of the steel fiber high-strengthreinforced concrete beams under shear are analyzed. Referenced the expression methodof the bend toughness, the modified multi-feature points theory is proposed to calculate the shear toughness indexes, and then the shear toughness of beams is analyzedquantitatively. The results show that the method could well reflect the energy dissipationcapacity and ductility of the whole processes of steel fiber reinforced concrete beamsunder shear.Based on finite element software ABAQUS, the finite element analysis model ofsteel fiber high-strength reinforced concrete beams is established, then the analysismodel is verified. The influence law of the shear-span to effective depth ratio,longitudinal reinforcement ratio and stirrup ratio on the load-deflection relationshipcurves of steel fiber high-strength reinforced concrete beams are analyzed.