Early-Age Bond Behavior of Deformed Bars in Concrete Subjected to Bilateral Pressures

Abstract

In RC structures during construction, the bond behavior of deformed bars in concrete is governed by the age-related concrete strength, the local confining pressure, the bar diameter, and the concrete cover thickness. In this paper, an experimental investigation was performed to quantify the influences of the curing age and the bilateral pressure on the bond behavior of deformed bars in early-age concrete with 204 pull-out specimens for different concrete strengths, bar diameters, and relative concrete cover thicknesses. It was shown that the failure mode was associated greatly with the age-related concrete strength, the concrete cover thickness, and the pressure level, and that the bond strength increased with the pressure level and curing age, whereas the corresponding slip decreased with the curing age. Based on the regression analysis, calculation models were developed to predict the ultimate bond stress and the corresponding slip. A bond–slip model is proposed to describe the bond stress–slip relationship of deformed bars in early-age concrete under bilateral pressures, and the model was verified with the test results. For RC structures, there is experimental evidence that the lateral pressure around the bond region has a great effect on the bond behavior of deformed bars in concrete. From an engineering practice perspective, the early-age bond behavior of deformed bars in concrete under bilateral pressures plays an important role in the structural analysis of RC structures during construction, and is very meaningful for the entire life-cycle modeling of RC structures. In this study, an experimental investigation was conducted to predict the failure mode and bond parameters, and to propose a universal bond–slip constitutive model of deformed bars in concrete under bilateral pressures. The good agreement between the model predictions and the experimental results shows that the proposed bond–slip model can be used effectively for the design and reliability assessment of RC structures during construction, and therefore demonstrates the potential of the proposed bond–slip model in the entire life-cycle analysis for practical applications.