Response prediction of concrete beams reinforced with FRP bars

The use of FRP bars to reinforce concrete structures has received a great deal of attention in recent years. It is considered as one of the most prominent solutions that may overcome the corrosion deficiency of reinforcing steel bars under long-term service load conditions. A number of researchers have attempted to propose modifications to the ACI 318 empirical equation for estimating the effective moment of inertia of reinforced concrete beams. Others used numerical methods to calculate the deflection. The purpose of this paper is to present an analytical solution for calculating the load–deflection response of simple beams at any load stage. A bilinear moment–curvature function is assumed, defined by section flexural crack initiation, and ultimate capacity. The curvature distribution, along the span, is determined for uncracked and cracked regions based on the moment variation. Closed form equations are developed for the case of four-point bending, three-point bending and uniform loading. Comparisons with experiments indicate the effectiveness of the procedure in accurately predicting the load–deflection and the moment–curvature response relative to other analytical equations. Parametric studies are conducted to explore the agreement of the various empirical equations with that of the present procedure for a wide range of geometric and material properties as well as different loading conditions.