Calibrating an Improved I-Effective Method for Prestressed Concrete Beams Strengthened with FRP

Abstract

Abstract

The deflection of prestressed (pretensioned) concrete members strengthened with FRP requires a comprehensive evaluation. An extensive parametric study is performed using a rigorous analysis procedure based on a trilinear moment-curvature approach. There are 8100 pretensioned concrete beams analyzed by varying the cross-section dimensions, span length-to-depth ratio, shear span-to-span ratio, concrete compressive strength, prestressing reinforcement ratio, FRP strengthening ratio and FRP material properties. It was determined that the normalized effective moment of inertia at first yielding is statistically correlated with the normalized cracked moment of inertia, with an almost-perfect regression (R2 = 0.9886). It was further found that when postulating the inverse of the effective moment of inertia in terms of a parabolic function of the beam maximum moment, the deflections of the cracked beam agree closely with experimental deflections. Boundary conditions for that equation are applied at the cracking and prestress-yielding points. Ultimately, it was realized that the immediate deflection predictions based on the modified beam effective moment of inertia expression proposed yield reliable deflection estimates for cracked prestressed members externally strengthened with FRP, compared with experimental results and other analytical predictions.