Bond Stress-Slip Model for Concrete-Embedded Smooth Bars in Salt-Frozen Environment

Abstract

Experimental and numerical studies were used to establish a bond stress-slip constitutive model for smooth bars embedded in concrete exposed to freeze-thaw cycles in a chloride-rich environment. Pull-out tests were conducted on reinforced concrete specimens using a self-made bidirectional compression-reinforced concrete pull-out device. The RC (reinforced concrete) specimens which pasted strain gauges on the inner milling slots of steel bars were subjected to freeze-thaw cycles. The test results indicate that an increase in the freeze-thaw cycles results in a linear decrease in the ultimate bond strength and shifts the section corresponding to the maximum bond stress towards the unloaded-end more and more severely. The relative slip value and bond stress between the smooth bars and concrete were evaluated through numerical simulation and test results. After the curve of bond stress and the position coordinate along steel bars of the RC (reinforced concrete) specimens were fitted, which is expressed by position function, the bond stress-slip constitutive relationship between concrete and smooth bars was consequently established under frost-salt conditions. This constitutive bond model that considered the position function may provide parameters for the finite element analysis, which contributes to the durability assessment of the RC (reinforced concrete) structures in a cold chloride-rich environment.