A. Espinos

Fire resistance of axially loaded slender concrete filled steel tubular columns. Development of a Three-dimensional numerical model and comparison with eurocode 4

In recent 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 a fire, the degradation of the material properties will cause CFT columns to become highly nonlinear and inelastic, which makes it quite difficult to predict their failure. In fact, it is still not possible for analytical methods to predict with enough accuracy the behaviour of columns of this kind when exposed to fire. Numerical models are therefore widely sought. Many numerical simulations have been carried out worldwide, without obtaining satisfactory results. This work proposes a three-dimensional numerical model for studying the actual fire behaviour of columns of this kind. This model was validated by comparing the simulation results with fire resistance tests carried out by other researchers, as well as with the predictions of the Eurocode 4 simplified calculation model.

Comparison of a Three-Dimensional Numerical Model for Fire Resistance of Axially Loaded Concrete Filled Steel Tubular Columns with Eurocode 4

In this paper, the behaviour of slender axially loaded square and circular CFT columns exposed to fire is modelled using the finite element analysis package ABAQUS. A realistic sequentially coupled nonlinear thermal-stress analysis is conducted for a series of columns available in the literature. By means of this model, a comparison between fire resistance simulations results and experimental tests found in literature is made. Similarly, simulations results are compared to the Eurocode 4 simplified calculation model predictions. Comparisons show that whereas Eurocode 4 predictions are very conservative for both circular and square section CFT columns, the results obtained from the developed numerical model are much more realistic.