Effective Moment of Inertia Expression for Concrete Beams Reinforced with Fiber-Reinforced Polymer (FRP)

This paper will discuss that due to concerns with corrosion, the use of fiber reinforced polymer (FRP) as a replacement to conventional steel reinforcement has greatly increased over the last decade. However, elastic modulus values of some commercially available FRP reinforcement hardly reach 20% of that for conventional steel. Existing code relationships for conventional steel have been modified to address this proprietary difference but the modifications are restricted by the empirical nature of the expressions. This paper provides an alternate approach to estimate the deflection of concrete beams by considering effects of tension stiffening that incorporate material properties of the reinforcement as well as the effects of concrete non-linearity in compression. A database containing experimental load-deflection records from 139 glass FRP (GFRP) and 48 carbon FRP (CFRP) reinforced concrete beams was used to calibrate a tension stiffening model for the proposed approach and establish its accuracy as well as precision through statistical analysis. Results were compared to those obtained from existing relationships and indicate that the revised approach provides higher accuracy at service conditions ranging from 25% to 80% of ultimate.