Structural failures during recent earthquakes and terrorist attacks have demonstrated shortcomings in the design procedures for reinforced concrete structures. Earlier research has demonstrated that a major limitation of the Finite Element (FE) modeling of the response of reinforced concrete is the accurate modeling of the interaction of the concrete with the steel reinforcement. Presently, there are insufficient data on the dynamic nonlinear interaction between the concrete material and the steel reinforcement to develop a numerical model of this interaction.
The primary objective of this study was to experimentally investigate the dynamic interaction (bond slip) of reinforcement with concrete and gain a better understanding of the parameters that control this interaction. Specifically, the effects of concrete confinement, bar deformation and bar diameter on the bond slip, and the influence of loading rates - static to impact – on these effects were investigated. Additionally, the variation of the strain along the length of the steel bar and strain transfer to the concrete were investigated. Finite element analyses were performed using the experimental parameters to determine the value of the chemical adhesion and to compare the experimental results with the analytical values.
To accomplish the research objectives, thirty-three pullout tests were performed. The test specimens were subjected to quasi-static, dynamic and impact loadings, to investigate the influence of rebar size and shape, confinement and loading rate on pullout resistance and failure mode.
The results of the study have shown that, for the concrete and steel used in this investigation, the stress due to static friction and chemical adhesion is 960 psi for quasi-static loading, 2600 psi for dynamic loading and 3200 psi for impact loading. The steel bar deformations accounted for 70% to 77% of the total resistance to pullout regardless of loading rate. Impact loaded specimens had nearly twice the pullout resistance of the quasi-statically loaded specimens, and the development length decreased as the loading rate or confinement increased. Bond stresses obtained for both smooth and deformed bars were in good agreement with results obtained in earlier studies involving quasi-static tests.