FRP-confined concrete in circular sections: Review and assessment of stress–strain models

An important application of FRP composites is as a confining material for concrete, in both the seismic retrofit of existing reinforced concrete columns and in the construction of concrete-filled FRP tubes as earthquake-resistant columns in new construction. Reliable design of these structural members necessitates clear understanding and accurate modeling of the stress–strain behavior of FRP-confined concrete. To that end, a great number of studies have been conducted in the past two decades, which has led to the development of a large number of models to predict the stress–strain behavior of FRP-confined concrete under axial compression. This paper presents a comprehensive review of 88 models developed to predict the axial stress–strain behavior of FRP-confined concrete in circular sections. Each of the reviewed models and their theoretical bases are summarized and the models are classified into two broad categories, namely design-oriented and analysis-oriented models. This review summarizes the current published literature until the end of 2011, and presents a unified framework for future reference. To provide a comprehensive assessment of the performances of the reviewed models, a large and reliable test database containing the test results of 730 FRP-confined concrete cylinders tested under monotonic axial compression is first established. The performance of each existing stress–strain model is then assessed using this database, and the results of this assessment are presented through selected statistical indicators. In the final part of the paper, a critical discussion is presented on the important factors that influenced the overall performances of the models. A close examination of results of the model assessment has led to a number of important conclusions on the strengths and weaknesses of the existing stress–strain models, which are clearly summarized. Based on these observations, a number of recommendations regarding future research directions are also outlined.

► A comprehensive review of FRP-confined concrete stress–strain models is reported.
► The review provides a detailed background and unified framework for future efforts.
► The models reviewed in the paper are assessed using a comprehensive test database.
► A discussion on the factors that influence the model performances is presented.
► Recommendations on future testing, modeling and research directions are given.