Critical Review of Deflection Formulas for FRP-RC Members

Abstract

The design of fiber-reinforced polymer reinforced concrete (FRP-RC) is typically governed by serviceability limit state requirements rather than ultimate limit state requirements as conventional reinforced concrete is. Thus, a method is needed that can predict the expected service load deflections of fiber-reinforced polymer (FRP) reinforced members with a reasonably high degree of accuracy. Nine methods of deflection calculation, including methods used in ACI 440.1R-03, and a proposed new formula in the next issue of this design guide, CSA S806-02 and ISIS M03-01, are compared to the experimental deflection of 197 beams and slabs tested by other investigators. These members are reinforced with aramid FRP, glass FRP, or carbon FRP bars, have different reinforcement ratios, geometric and material properties. All members were tested under monotonically applied load in four point bending configuration. The objective of the analysis in this paper is to determine a method of deflection calculation for FRP RC members, which is the most suitable for serviceability criteria. The analysis revealed that both the modulus of elasticity of FRP and the relative reinforcement ratio play an important role in the accuracy of the formulas.