Experimental Study On Shear Capacity Of Steel Fiber Reinforced Concrete Members

Steel fiber can effectively improve the basic mechanical properties such as tensile strength and toughness of concrete materials,as a kind of high-performance construction material,steel fiber reinforced concrete has been applied to many branches of engineering construction.The shield tunnel segement is the main load-bearing structure of tunnel,thus excellent performance is highly desired,steel fiber reinforced concrete can be used to effectively improve its performance.In this paper,experiments and theoretical analysis are carried out based on the actual engineering application of steel fiber reinforced concrete segments.The mechanical properties of steel fiber reinforced concrete and the shear properties of symmetric inclation beams are studied.The main research contents and conclusions of this paper are as follows:(1)Accroding to test methods,the strength,slump and fiber distribution uniformity of steel fiber reinforced concrete materials were tested,and the three-point bending test was executed according to RELEM TC 162-TED experimental standard.The three-point bending test curves show hardened state after peak load,and the flexural tensile strength index and residual flexural tensile strength index reflect that the steel fiber concrete has good toughness.(2)Based on the shear test of 12 steel fiber reinforced concrete symmetric inclation beams without any longtitudinal reinforcement or stirrup and 16 steel fiber reinforced concrete symmetric inclation beams with longtitudinal reinforcement and stirrups,the influence of steel fiber on diagonal cracking strength was quantitatively investigated.The test results show that the steel fiber is effective in improving the cracking load,but under the condition of small shear span ratio,the steel fiber can not change the brittle damage of the beam.(3)The shear transfer mechanism considered in the calculation method in the Technical Specifications for Fiber Reinforced Concrete Structures(CECS38:2004)and RILEM TC 162-TDF is roughly the same,but the emphases of formulas are different.Accroding to Technical Specifications for Fiber Reinforced Concrete Structures(CECS38:2004),the value of the coefficient of shear bearing capacity is too small,leading to a conservative calculation result.In this paper,the method of calculating the influence coefficient of the special-shaped steel fiber with hooks is determined by the three-point bending test,and the empirical formula for calculating the diagonal cracking strength of the oblique section of eccentric compression members of steel fiber reinforced concrete beams is proposed.(4)ABAQUS finite element analysis software was used to further analyze the influence of shear-span ratio and concrete strength on the shear behavior of steel-fiber reinforced concrete members.The results show that the shear-span ratio has a significant effect on the failure modes of the members,and the increase in the strength of the concrete matrix can delay the diagonal cracking of the members.In the case of a shear-to-span ratio of 2.67,steel fibers can partially replace the stirrups in the bending shear region.But if there is no stirrups in the bending shear region,it will cause excessive deflection of the components and damage.