Analysis-oriented stress-strain models for FRP-confined concrete

Many stress-strain models have been developed for fibre-reinforced polymer (FRP)-confined concrete. These models fall into two categories: (a) design-oriented models in simple closed-form expressions for direct use in design; and (b) analysis-oriented models in which the stress-strain curve is generated via an incremental process. This paper is concerned with analysis-oriented models, and in particular, those models based on the commonly accepted approach in which a model for actively-confined concrete is used as the base model. The paper first provides a critical review and assessment of existing analysis-oriented models for FRP-confined concrete. For this assessment, a database of 48 recent tests conducted by the authors' group is presented; this database includes 23 new tests which have not previously been published. This assessment clarifies how each of the key elements forming such a model affects its accuracy and identifies a recent model proposed by the authors' group as being the most accurate. The paper then presents a refined version of this model, which provides more accurate predictions of the stress-strain behaviour, particularly for weakly-confined concrete.