Computational & Technology Resources
an online resource for computational,
engineering & technology publications
PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY
Edited by: B.H.V. Topping, G. Montero and R. Montenegro
A Three-Dimensional Numerical Model of Circular Concrete Filled Columns
C. Lacuesta1, M.L. Romero1, S. Ivorra2 and J.M. Portoles3
1Department of Continuous Medium Mechanics and Theory of Structures,
C. Lacuesta, M.L. Romero, S. Ivorra, J.M. Portoles, "A Three-Dimensional Numerical Model of Circular Concrete Filled Columns", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Eighth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 22, 2006. doi:10.4203/ccp.83.22
Keywords: concrete filled tubular, high strength concrete, non-linear finite element analysis, buckling.
The use of concrete filled tubular (CFT) columns is becoming popular due to its high stiffness and ductility, but also because they present other advantages: higher speed construction, the possibility to regularize the joints and what it is more important, a higher fire resistance.
The utilization of hollow steel sections filled with concrete is well-known in multi-story buildings because a substantial reduction of the cross section is obtained. Moreover, the high strength concrete is used more and more for precast concrete structures, but the influence of the high strength on this type of columns (CFTs) requires further research.
For the particular case of high strength concrete, Gourley  affirms that as the concrete has a low dilatation, an important confinement effect is not produced. However other authors do not agree with this statement. Johansson and Gylltoft [2,3], and Zeghiche and Zahoui , have demonstrated by using numerical and experimental studies that it is possible to use high-strength concretes and still achieve a structural ductile behaviour. However a thicker steel tube is needed for HSC compared with normal strength concrete if the aim is the same ductility.
Romero et al.  reviewed the numerical models of CFT focussing the interest in the high strength concrete.
Most of the numerical models in the literature take into account separately the contact between the steel and concrete and the slippage. For the contact, a gap model is used and on the other hand the bond-slip is included with elastic-plastic springs in the longitudinal direction. Any of the models have taken into account interaction between both effects. A bond-slip relationship for high strength concrete dependent on the lateral confinement should be provided.
There is uncertainty about the effect of bond between the steel and concrete of slender columns for slender columns of HSC. The effect of slenderness ratio on improving the bond between concrete and steel needs to be studied.
The authors are performing a research project to study the effect of high strength concrete in the buckling. It has three parts: an experimental study, a one-dimensional numerical model and a three-dimensional model. In this paper the initial results of the three-dimensional model are presented. The model is adjusted using experimental data from the literature and from the experiments performed by the research group.
The experimental tests selected to adjust the numerical model corresponds to circular tubular columns filled with concrete (CFT) with pinned supports at both ends subject to axial load and uniaxial bending. In these tests the eccentricity of the load at the ends is fixed and the maximum axial load of the column is evaluated.
The numerical model implemented has presented a suitable degree of accuracy in comparison with thirty experimental tests from the literature.
The numerical model is more rigid and needs to be improved both for the cases of smaller and higher eccentricities, where the displacement corresponding to the maximum load is not well predicted.
purchase the full-text of this paper (price £20)