A Novel Finite Element Method for Analysing the Confinement Effect in Concrete-Filled Steel Tubes

Most theoretical models of non-uniform concrete confinement use empirical equations and thus are applicable only to limited ranges of geometric and material parameters. In light of such shortcomings, a novel finite element (FE) method is proposed to explicitly compute the non-uniform lateral confining stresses in the concrete section. To determine the lateral stresses, the lateral strains are divided into two components: an elastic component and an inelastic component, and a 2-dimensional FE analysis of the concrete section with the inelastic laterals strains taken as initial strains is carried out. Since the lateral stresses and inelastic lateral strains are inter-related, an iterative process of evaluating the lateral stresses from the inelastic lateral strains by FE analysis and then evaluating the inelastic lateral strains from the lateral stresses by a lateral strain model is employed until convergent results are obtained. This FE method is herein applied to square concrete-filled steel tube columns.