A numerical model with varying passive confinement for circular and elliptical concrete-filled steel tubular columns

Abstract

[EN] In this work, a non-linear 3D numerical model to study concrete-filled tubular (CFST) columns is presented. The numerical model is capable to consider the passive confinement that occurs in the concrete core of CFST columns, under which an increase in the strength and ductility of the element is expected. Passive confinement is governed by the volumetric deformation of the concrete core and by the increment of concrete strength, so it was necessary to define both aspects in the constitutive model. In the volumetric deformation, the elastic and plastic components were included, the latter by using the Drucker-Prager model. Different values for the angle of dilatancy were defined for normal and high strength concrete. The model was validated by using experimental tests performed on stub columns and eccentrically loaded columns. In addition, different section geometries were tested. According to the results, the model was able to describe the non-uniform confinement that appears in the concrete core of CFST columns.