Long-term deflections of FRP reinforced concrete beams

ABSTRACT Concrete beams reinforced with fiber-reinforced polymer bars (FRP) are becoming widely used. The sustained deflections due to creep and shrinkage for these beams control the design due to the low modulus of elasticity of FRP bars. The current work presents a successful finite elements modeling for tests on FRP reinforced concrete beams along with study for some factors influencing the long-term deflection such as the reinforcement ratio and the type and the level of sustained load. Increasing the FRP reinforcement ratio results in reduction in the total sustained load deflection. Similarly, for the reduction in the sustained load level. Carbon FRP reinforced beams have the least total long-term deflections. FRP design codes such as ACI 440.1 R-06 and CSA-S806-02 provide simple equations for calculating the sustained deflection based on multiplicative factors. Also, the literature gives other equation for creep and shrinkage deflections based on multiplicative coefficients. The three original methods and the same methods with their amendments are verified against experimentally calibrated finite element models. The ACI440.1 R-06 method modified with Bischoff’s effective moment of inertia is found to yield the best results. The current paper further modifies this method. The currently modified ACI440.1 R-06 with the effective moment of inertia as proposed by Bischoff is found to produce better accuracy for the calculations of the total sustained load deflections.