Full-Range Deflection of Prestressed Concrete Bridge Girders with Harped Strands Externally Strengthened with FRPs

Abstract

Prestressed concrete (PC) highway bridges often experience deterioration over time, necessitating structural strengthening to restore or increase capacity and maintain serviceability. One common external strengthening technique is the application of fiber-reinforced polymers (FRPs). However, limited research has addressed the deflection analysis of FRP-strengthened PC girders incorporating harped prestressing strands. This study presents a nonlinear sectional analysis, simplified through a trilinear moment–curvature response, to develop closed-form analytical expressions for the deflection of simply supported PC girders under various loading conditions. Using the trilinear moment–curvature response and moment-area theorem, the procedure derives closed-form deflection equations for uncracked, postcracked, and postyielded regions. The developed equation is used to compare the present analytical results with available experimental results, as well as the predictions of other deflection equations proposed in the literature, such as Branson and Bischoff's effective moment of inertia equations. The variables influencing the deflection of FRP-strengthened PC girders with harped strands, the current procedures in the literature to determine instantaneous deflection, and a proposed method for the effective moment of inertia after cracking of PC girders with harped strands are presented.