BOND-SLIP RELATIONSHIP OF REINFORCING STEEL BARS WITH SHORT EMBEDMENT IN CONCRETE

The behavior of the reinforced concrete structures is influenced by the bond-slip mechanism between concrete and rebar. The performance and strength of the structure are strongly affected by this mechanism. Therefore, it is indispensable to take bond-slip effects into account when analyzing reinforced concrete structures. In the current study, bond-slip behavior between concrete and reinforcement is investigated and a new bond-slip model for deformed bar is proposed. The main distinction between the proposed model and the current models is that in this model, slip starts when bond stress reaches a threshold value. Constant parameters of the proposed model are maximum bond stress and maximum slip. Calibration of the constant parameters of the model is done based on trial and error method with the aim of achieving the best coincidence with the experimental results. For each of constant parameters of the model, three different values were selected. So in total, nine models were used in modeling the interaction between rebar and concrete. To calibrate the model, some pull-out tests are simulated by finite element software of ABAQUS. In this simulation in order to take bond-slip effects into consideration, steel nodes are connected to that of adjacent concrete through non-linear springs. The behavior of these springs is defined based on a variety of bond-slip models for deformed bar. Considering the error of models with respect to experimental values, the best model with the minimum error was chosen. Moreover the best proposed model was compared with current models. The results showed that the proposed model has much better predictions than the current methods regarding both the maximum load and post-peak behavior of load deformation curve. Furthermore, the proposed model can be expanded for long bonded length and splitting failure mode by adding a reduction function for take into account post-yield strain effects.