Simplified Nonlinear Analysis of Strengthened Concrete Beams Based on a Rigorous Approach

Abstract

The external fiber reinforced polymer (FRP) flexural and shear strengthening of reinforced concrete beams is a well-established technique for structural rehabilitation and upgrade. In the present work, an analytical solution is developed for the load–deflection calculation of FRP strengthened simple beams at any load stage. The solution assumes a trilinear moment–curvature response characterized by the flexural crack initiation, steel yielding, and ultimate capacity. Closed form expressions are presented for the case of simple beams subjected to three-point bending, four-point bending, and uniform load. These expressions are derived for beams with any extent of uncracked, postcracked, and postyielded regions along their span. An extensive parametric study is conducted yielding unique linear relationships between basic sectional moments of inertia and their corresponding effective beam values for a wide range of geometric and material variables considered. Accordingly, a simplified analysis procedure is developed by adopting a trilinear load–deflection response. The effectiveness of the simplified procedure is demonstrated by comparing its results to those of the analytical solution and the experimental values.