The transfer of forces from reinforcing bars to surrounding concrete in reinforced concrete is influenced by many factors, so the steel{concrete bond is a fundamental property in reinforced concrete structures. This thesis focuses on the problems of the bond{strength between concrete and reinforcement, and denes how local slip at the interface of reinforcement and matrix of cement{based composite, aects the durability of the bond. The study experimentally evaluates the bond between smooth and ribbed steel bars and concrete of 20 and 37 MPa compressive strength. The method used for testing the bond{strength was uniaxial pull{out test. The main contribution of this study, based on the results obtained and the methodology used, is to present dierences of the steel{concrete bond in case of using smooth or ribbed steel bars. Experimental study herein described includes 36 pull{out tests. The slip values have been measured, throughout the performed pull{out tests, allowing the force slip curves to be obtained. Test result showed better bond durability when ribbed bars are used. Numerical study was also performed to show how can appearance of local slip be implemented in three dierent numerical models. Numerical study was based on experimental investigation of a column from the PEER Structural Performance Database. The calibration was carried out using nonlinear models in OpenSees (PEER, Berkley).