Bond failure of steel beams strengthened with FRP laminates – Part 1: Model development

To strengthen deteriorated steel structures, bonding fiber reinforced polymer (FRP) laminate applied externally to the steel surface is a promising method. For FRP strengthened steel structures, the bond performance between the FRP laminate and the steel structure is a crucial consideration which will directly influence strengthening effect and determine the final capacity of the strengthened structures. To investigate the bond failure mechanism of FRP bonded steel structures, experiments on three types of FRP-steel joints were conducted. The bond strengths of different configuration joints were found out. Besides the experimental investigation, finite element analyses were also carried out to study in detail the stress and strain distributions along the bondline. It was found that the most important factors that influence the final bond failure is the stress concentration at the end of the bondline. After analyzing the mechanism of bond failure, a bond failure model based on the failure criterion of equivalent strain energy density was proposed.