A simplified method to obtain time-dependent curvatures and deflections of concrete members reinforced with FRP bars

The design of concrete beams reinforced with fibre reinforced polymer (FRP) bars is often governed by the serviceability limit state, in which deflections play an important role. One of the most straightforward and easiest methods for calculating time-dependent deflections is based on applying multiplicative coefficients to instantaneous deflections. These methods have been adopted by ACI.440.1R-06 and CSA-S806-02 for FRP reinforced concrete structures (RCS), introducing slight modifications with respect to steel reinforced concrete members. However, the influence of different material mechanical properties and environmental conditions are not accounted for properly. In this paper, a new method based on a simplified coefficient for the prediction of time-dependent deflections is presented. The influence of variations in environmental conditions and the mechanical properties of the materials are taken into account. The numerical predictions obtained are compared to other models available in the literature and experimental results to validate the accuracy and suitability of the methodology presented.