A new impact dynamic constitutive relation of steel fiber reinforced concrete and the determination of material parameters

In the present study we carried out the dynamic compression experiments of steel fiber reinforced concrete with the fiber volume ratios of 0%, 0.75% and 1.5% using the ∅75 mm large-diameter split Hopkinson pressure bar experimental system to obtain the stress-strain curves at different strain rates. The experimental results show that with the increase of the fiber content and the strain rate, both the peak strain and the peak stress of the steel reinforced concrete rise higher, and the strain softening is observed after the peak stress. Based on the assumption that there are two independent factors controlling the dynamic behavior of the steel fiber reinforced concrete, one related to the strain to indicate the nonlinear stress-strain behavior and the other related to the strain rate to express the strain rate effect, a new type of the dynamic nonlinear visco-plastic constitutive equation was proposed. The details concerning how to get the equation and the material parameters were discussed thoroughly. The experiment curves were fitted using the least squares optimization numerical simulations. Good agreement between the numerical simulations and the experiment curves was achieved, thereby concluding that the new constitutive relation proposed is perfect for steel fiber reinforced concrete.