BOND-SLIP BASIC CONSTITUTIVE RELATION MODEL BETWEEN REBAR AND CONCRETE UNDER REPEATED LOADING

The bond-slip basic constitutive relation model is one of basic relations for structural fatigue computation and finite element analysis. Thusly the thorough study on the rebar slip, bond-slip fundamental relation and bond stress shape function and bond safe fatigue criterion is presented by 23 pull-out experiments. The formulas for slip and residual slip are derived from the present test data. According to the bond-slip development rules, the bond stress-slip relation after repeated loading was put forward as a function of residual slip, stress level, and the number of load cycles. Shape functions of bond stress are fitted by the rebar stress data. Finally, based on a safe fatigue criterion (i.e., the condition of bond fatigue damage is that slippage under repeated loading reach the maximum slippage under monotonic loading), the fatigue life equation is deduced theoretically. The research shows that the bond strength and the slip at peak bond stress are not influenced much by repeated loadings if bond fatigue does not occur. The results of the present study are expected to be useful for theoretical analysis of a crack width, anchorage length, stiffness, and plastic hinge rotation problems.