Effect of Bonding Type on the Failure of Reinforced Concrete Beam Strengthened with In-Situ High Performance Fibre Reinforced Concrete Layer

High performance fibre reinforced concrete (HPFRC) materials with tensile hardening behaviour can effectively be used for strengthening reinforced concrete beams. A perfect bond between the original and the reinforcing layer cannot be formed, the load-bearing capacity and ductility of the strengthened beam can significantly be affected by the interfacial bond strength between the contacting surfaces. In this paper, beam retrofitting with cast in-situ strengthening type is examined. The purpose of this experimental study is to investigate the impact of the different bond types on the load-bearing capacity, ductility, and failure mode of the strengthened beams in the case of cast in-situ strengthening. Twenty-four beam tests were performed with untreated and rough surfaced beams, with or without connecting elements. The effect of the bond type proved to be significant regarding the failure mode in the case of compression side strengthening, stronger bond resulted in higher load bearing capacity and ductility, too. When tensile side reinforcement was investigated no average increment was experienced in the maximal force and ductility due to the stronger bond. Based on the results, it can be concluded that the generally applied analytical models that assume perfect connection may lead to exaggerated results in the case of a compressed side HPC-strengthened beam. Therefore, it is necessary to develop a model that considers the effect of the imperfect bond.