Refinement of a Design-Oriented Stress–Strain Model for FRP-Confined Concrete

TLDR

This study refines Lam and Teng’s design‑oriented stress–strain model for FRP‑confined concrete under axial compression by introducing two modified versions based on newly derived expressions. The new expressions are derived from recent tests and a parametric study using an accurate analysis‑oriented stress–strain model, and the authors present two modified versions: one updating the ultimate axial strain and compressive strength equations, the other accommodating stress–strain curves with a descending branch. The refined model offers more accurate expressions for ultimate axial strain and compressive strength that explicitly account for confinement stiffness and jacket strain capacity, and can be readily incorporated into Lam and Teng’s model for improved predictions.

Abstract

This paper presents the results of a recent study conducted to refine the design-oriented stress–strain model originally proposed by Lam and Teng for fiber-reinforced polymer (FRP)-confined concrete under axial compression. More accurate expressions for the ultimate axial strain and the compressive strength are proposed for use in this model. These new expressions are based on results from recent tests conducted by the writers' group under well-defined conditions and on results from a parametric study using an accurate analysis-oriented stress–strain model for FRP-confined concrete. They allow the effects of confinement stiffness and the jacket strain capacity to be separately reflected and accounts for the effect of confinement stiffness explicitly instead of having it reflected only through the confinement ratio. The new expressions can be easily incorporated into Lam and Teng's model for more accurate predictions. Based on these new expressions, two modified versions of Lam and Teng's model are presented. The first version involves only the updating of the ultimate axial strain and compressive strength equations. The second version caters to stress–strain curves with a descending branch, which is not covered by the original model.