Reliability of RC Members Strengthened with CFRP Laminates

Strengthening of concrete structures in flexure with externally epoxy-bonded carbon-fiber-reinforced plastic (CFRP) laminates is becoming an increasingly popular retrofit technique among researchers and engineers worldwide. A reliability study of such structures is the topic of this paper. First, considering the statistical character of the design variables (geometry, material properties), the effect of changes in these variables on the flexural capacity of CFRP-strengthened members is established. Variabilities in concrete strength and CFRP failure strain and area fraction are most influencial on flexural strength. Next, strength reduction factors are derived, with the aim of achieving a uniform reliability index of about three over a broad spectrum of design conditions. A general strength reduction factor φ= 0.80 is proposed. Finally, the effect of each design variable on the reliability of the system is examined and quantified in terms of the reliability index.