Research and mechanism analysis on dynamic compressive behavior of steel fiber reinforced concrete

Abstract

This paper describes an investigation of the influence of steel fiber on the dynamic compressive behavior of steel fiber reinforced concrete (SFRC) at different strain rates, and reveals the mechanism of its change from the macro and meso levels. Meanwhile, a suitable dynamic constitutive model for SFRC is proposed. Four kinds of steel fiber contents (0 %, 1 %, 2 %, 3 %) and four kinds of high strain rates (40 s−1–220 s−1) were considered in the Split Hopkinson pressure bar (SHPB) test. Based on the designed tests, the failure pattern, the stress–strain curve, and the mechanical characteristic parameters of the SFRC under different loading conditions were obtained. The effects of steel fiber content and strain rate on the dynamic mechanical properties of concretes were analyzed. It is indicated that there are great differences in the failure pattern of the SFRC under different loading conditions. On the one hand, with the increase in the strain rate, the specimen is broken more completely. On the other hand, the reinforcing effect of steel fibers is obvious and as the steel fiber content increases, the crushing degree of the sample decreases significantly. The dynamic compressive strength of the SFRC is most sensitive to the strain rate and reaches its maximum value when the fiber content is 1 %. However, the variation of the peak strain showed no obvious regularity. The reinforcement mechanism of steel fibers was analyzed via the CT scanning technology. The results show that the main factors affecting the mechanical properties of SFRC are fiber content and porosity, but the fiber distribution is almost unaffected. The SFRC dynamic constitutive model was proposed by improving the HJC dynamic constitutive model. In the proposed model, the influence of steel fiber on strength was introduced and the influence term of strain rate was adjusted. The proposed model was verified by applying it to the numerical simulation of the dynamic compression performance of SFRCs and it shows good applicability. The presented research provides a theoretical basis for calculation and analysis of SFRC structures under extreme dynamic loads.