DURABILITY-BASED TIME-DEPENDENT RELIABILITY DESIGN FOR FRP-STRENGTHENED CONCRETE BEAMS

Durability-based probabilistic design methodology for FRP-strengthened reinforced concrete beams was conceptually established by reliability theory and the considerations of time-dependent material properties. The limit state functions were developed both for unstrengthened and strengthened concrete beams. The Rackwitz-Fiessler method combined with the Monte Carlo procedure was applied to the analysis of an example. The analytical results have revealed that the instants to initiation of chloride-induced corrosion and corrosion-induced cracking are subjected to a large scatter due to significant variances exist in concrete cover, surface chloride concentration, critical chloride concentration, chloride diffusion coefficient and aging factor. If aging time is greater than the instant to initiation of corrosion-induced cracking, reliability indexes would decrease almost linearly as increasing time. By the results, it can be concluded that bonding FRP laminates externally to the surface of reinforced concrete beams can significantly increase not only their flexural resistances but also reliability levels, even under adverse chloride-ingress exposure conditions.