Closed-Form Solution of the Ductility of Short FRP-Wrapped Rectangular Concrete Prisms under Eccentric Loads

Abstract

Confinement reinforcement, such as tubes, stirrups, and wraps, can significantly improve the strength and, more importantly, ductility of eccentrically loaded concrete prisms. However, the confinement effect in flexural analyses is sometimes not considered in design codes because there is no simple approach for quantifying it. Although the finite-element method has been proposed to analyze laterally confined concrete prisms under eccentric loads, the complicated computational program may hinder its wide applications. In this paper, based on fundamental partial-interaction shear-friction and bond–slip material properties, a passive stress–strain model of concrete with the confinement effect is introduced and reduced to a rectangular stress block. A closed-form solution is then derived for the ductility of fiber-reinforced polymer (FRP)-wrapped concrete prisms under eccentric loads. The main advantage of the solution is that the size effect is considered and no structural tests are required. After the validity of the solution is verified with experimental results, a parametric study is conducted to quantify the effects of various key factors on the ductility of FRP-wrapped concrete prisms under eccentric loads.