Unified stress–strain model of concrete for FRP-confined columns

This paper presents a unified stress–strain model of concrete for circular, square, and rectangular columns confined by fiber-reinforced polymer (FRP) jackets. Through the unification, the variation of parameters is continuous and consistent, which overcomes the inconsistency or discontinuity in the results predicted by all existing models. The unification also improves the performance of the stress–strain model by greatly extending the range of the parameter space, thus allowing a clearer picture of the trends and variations in the results. The new model is developed based on a large and up-to-date database that includes data from both the authors’ own tests and that collected from the literature, involving circular, square, and rectangular short columns and carbon FRP, glass FRP, and aramid FRP jackets with a wide range of parameter values. The proposed stress–strain model is compared with existing models, showing good agreement with the experimental results and improved performance.

► A new stress–strain model for FRP-confined concrete columns is proposed.
► The model has a unified form for circular, square and rectangular columns.
► Unification is made by introducing 2 factors: corner radius ratio and aspect ratio.
► The model shows improved performance particularly for curves with strain softening.