Modelling of rectangular RC columns strengthened with FRP

Abstract

Existing analytical models for predicting the stress–strain or load–displacement response of fibre-reinforced polymer (FRP)-confined concrete are mostly derived for cylindrical plain concrete columns. In practice, however, typical concrete columns come in various shapes including circular, square, or rectangular and incorporate longitudinal and transverse steel reinforcements. Furthermore, strengthening or repairing is typically done while the column is under service loading. In this paper, an analytical model is proposed to predict the load–displacement response of wall-like (i.e. high aspect ratio) reinforced concrete columns strengthened with FRP wraps with and without sustained loading. The model assumes that the general load–displacement response of the strengthened column consists of two distinct branches: a parabolic ascending branch and a linear descending branch. The ascending branch is influenced by the lateral confining pressure from the transverse reinforcement as well as the FRP wraps, while the descending branch is influenced by the buckling of the longitudinal reinforcement and the failure of the core concrete. Comparisons between model results and experimental results indicate close agreement between the two.