Reliability-based calibration of partial safety coefficients for fiber-reinforced plastic

The scope of this paper is to present a possible methodology for the calibration of partial safety factors for the design of strengthening measures of reinforced-concrete (RC) members using fiber-reinforced plastic (FRP). The methodology is general and can be used for any type of strengthening measure, e.g., in flexure, shear, ductility, or for the design of anchorage zones. The approach considers the problem of strengthening an RC member from a current unsafe situation, where all involved quantities are known from assessment, though only in probabilistic terms, to a target safe one, of which only the desired reliability is known. All relevant random variables are attributed a predefined probability distribution, based on a statistical survey separately conducted on geometrical and mechanical characteristics of old-style components. A first-order reliability method based optimization procedure is used to seek the solution of such a problem so that the target reliability is attained with the optimal FRP quantity, the appropriate collapse mechanism of the strengthened member, and the FRP design strength, with the associated partial safety factor. From Monte Carlo design simulations, the partial safety factor is probabilistically characterized, thus allowing one to select an appropriate fractile value for it.