A new analysis method for polymer-confined concrete columns

The confining stresses in a concrete column confined with fibre-reinforced polymer (FRP) are uniform across the section and isotropic only when the column is under concentric loading and circular in shape. If the column is under eccentric loading or non-circular in shape, the confining stresses in the column become non-uniform and anisotropic. However, without knowing the confining stresses, it is impossible to predict the structural behaviour of confined concrete columns. To overcome this difficulty, a new finite-element (FE) method was developed based on the most up-to-date lateral strain-axial strain and axial stress-strain constitutive models of concrete. This paper reports on using the method to analyse circular concrete columns confined by FRP under eccentric loading. It was found that, under eccentric loading, the confining stresses are generally smaller at larger eccentricity. Overall, good agreement between the theoretical results and published experimental data was achieved. In theory, the FE method can be applied to concrete columns of any shape and even those provided with lateral reinforcement, as will be elaborated upon in subsequent papers.