Bond and flexural behavior of concrete elements strengthened with NSM CFRP laminate strips under fatigue loading

This paper presents the results of an experimental research on bond and flexural behavior of concrete elements strengthened with carbon fiber reinforced polymer (CFRP) laminate strips under fatigue loading conditions, applied according to the near-surface mounted (NSM) strengthening technique. Long-term performance of the NSM system could be compromised by fatigue loading, which may result in deterioration and weakening of individual components (steel, FRP, concrete), or loss of bond performance and composite action. Hence, an experimental program composed of direct pullout tests and slab specimens was carried out to evaluate the influence of the stress level and amplitude of cycles imposed to the specimens. In bond fatigue tests, debonding failure occurred for a maximum stress level corresponding to 60% of the ultimate bond load obtained from monotonic loading. The fatigue loading imposed on the slabs did not yield to its failure. Consequently, the load carrying capacity obtained from post-fatigue tests of strengthened slabs was not significantly affected by this action.