Three-dimensional model of axially loaded slender concrete filled steel tubular columns under fire

In the last years, concrete filled tubular (CFT) columns have become popular among designers and structural engineers, due to a series of highly appreciated advantages: high load-bearing capacity, high seismic resistance, attractive appearance, reduced column footing, fast construction technology and high fire resistance without external protection. In fire, the degradation of the material properties will cause CFT columns to become highly nonlinear and inelastic, which makes quite difficult to predict their failure. In fact, it has not been possible for analytical methods to predict with enough accuracy the behaviour of this kind of columns when exposed to fire, that is why it is frequent to resort to numerical models. Up to now, a big amount of numerical simulations have been carried out worldwide, without obtaining satisfactory results. In this work, a three-dimensional numerical model will be proposed, in order to study the actual fire behaviour of this kind of columns. This model will be validated by comparing the simulation results with fire resistance tests carried Out by other researchers, as well as with the predictions of Eurocode 4 simplified calculation model.