Study on dynamic splitting tensile mechanical properties and microscopic mechanism analysis of steel fiber reinforced concrete

With high compressive strength and high fracture toughness, steel fiber reinforced concrete is widely used in large-span bridges and high-rise buildings. Since concrete structures are subjected to strong dynamic loads such as impact blast during service, it is essential to clarify the dynamic mechanical behavior of steel fiber reinforced concrete and to propose an adapted dynamic constitutive model for structural dynamic response calculation. Therefore, in this paper, a static and dynamic splitting tensile test study was conducted on steel fiber reinforced concrete with four fiber contents (0%, 1%, 2%, and 3%), and a separated Hopkinson compression bar (SHPB) was used to conduct dynamic splitting tensile tests on steel fiber reinforced concrete to obtain the failure pattern, stress–strain curves, and basic mechanical parameters of steel fiber reinforced concrete. The results showed that the static and dynamic splitting tensile strength of steel fiber reinforced concrete increased with increased steel fiber content. The dynamic splitting tensile strength and peak deformation of steel fiber reinforced concrete increased significantly with increasing strain rate, and the dynamic splitting tensile strength of steel fiber reinforced concrete increased in the range of 1.1 to 3.3 compared with static splitting tensile strength. The enhancement of dynamic splitting tensile strength with increasing strain rate at different fiber contents showed a significant and then flattening trend. In addition, the dynamic splitting tensile strength and strain-rate sensitivity of non-steel fibered concrete are higher than that of steel fiber reinforced concrete. Meanwhile, the X-CT scanning technique was applied to reveal the strain rate reinforcement and steel fiber reinforcement mechanism from the microscopic perspective. Finally, the K&C model was modified based on the experimental results and applied to the dynamic splitting tensile simulation of SHPB to verify the accuracy and adaptability of the proposed constitutive model. The research results finally provide a theoretical basis for the mechanical response of steel fiber reinforced concrete structures under impact blast.