Analysis of the bond behavior difference in steel and steel fiber reinforced concrete (SSFRC) composite member with circular section

Abstract

In order to solve the difficulties in the construction of Concrete Encased Steel (CES) structure, Steel and Steel Fiber Reinforced Concrete (SSFRC) was proposed by replacing the traditional rebar cages with discrete steel fibers. It is a basic principle for the bond behavior between steel and steel fibers reinforced concrete (SFRC) to ensure the co-working of two materials. The standard push-out test of 16 circular specimens which were designed with different steel fiber ratio (ρsf), different embedded length of reinforcing steel (Le) and different concrete thickness (Css) have been carried out. That is for the study of bond behavior and interface damage between steel and SFRC without rebar cages. The load–displacement curves, coefficient of displacement difference, interface energy dissipation and other important performance indices are obtained. The results show that the displacement of the free end doesn’t keep level with the loading end, and the relative slip occurs at the free end before the loading end. The displacement difference between two ends reaches the maximum under the ultimate load. The longer Le, the more significant the displacement difference and interface energy dissipation difference, and with bigger Css, the opposite is true. The damage difference between two ends of specimens is all found after a certain relative slip. The damage variable of the free end is always ahead of the loading end, and with the increase of ρsf, Le or Css, the development of relative slip and interface damage are slower. Increasing the Css is beneficial for plastic redistribution of bond stress along with the interface and reduce the damage difference between two ends. When the Css or ρsf grow, the influence of other design parameters on the maximum damage difference becomes more and more obvious.