NUMERICAL MODELING OF CONCRETE COMPOSITE STEEL TUBES

Rahel H. Khizer, B.R.Narayana, N.S.Kumar

Abstract: In modern days, building design emphasizes on enhancing flexibility of the floor space by reducing the cross section of column size. Enhancing compressive strength of concrete on a smaller column gives more strength and more usable floor space. The use of high strength concrete in smaller column, endeavor to brittle failure. This would be prevented by reducing space of stirrup for higher ductility. However, this causes the stirrup to form a natural plane of separation between the confined concrete core and the unconfined concrete cover, the risk of a premature spalling of the concrete cover increases. This is one important reason why it is advantageous to use Composite Columns consisting of Concrete-Filled Steel Tubes (CFST) instead of traditional Reinforced Concrete Columns. This study aims at developing a suitable constitutive model addressing the behavior of Concrete Filled Steel Tubular column on the compressive response under axial loads. Ultimate load carrying capacities obtained by the Authors using experiments have been compared with the Numerical model values. Three-dimensional nonlinear finite element models developed to study the force transfer between steel tube and concrete core. The nonlinear finite element program ABAQUS 6.12-1 is used. The interaction between steel tube and concrete core is the discussing issue for understanding the behavior of Concrete-Filled Steel Tube Columns (CFST). The numerical results validated with experimental data extracted from previous researchers (International & National) in the field including few experiments by the Authors in terms of Ultimate loads and deformation modes. Modeling related problems such as the definition of boundary conditions, imperfections, concrete-steel interaction, material representation and others are investigated using a comprehensive parametric study. The numerical results are validated through comparison with experimental data in terms of ultimate loading and deformation modes. A comparison of ultimate failure loads from nonlinear finite element program ABAQUS 6.12-1 with the predicted failure load from Eurocode Part-4 (EC4) (British Standards Institutions), ACI-318 (2005) (American Concrete Institute), for axially loaded columns will be carried out in this research study From the study it is concluded that, developed Numerical model fits nearer to perfection and depicts the behavior well with 5-10% error. Also, behavior when only Steel tube is loaded has been depicted with loading only Concrete-infill and loading on both infill and Steel tube simultaneously and the combination gave higher ultimate loads. The numerical results validated well with the previous researchers too

Keywords: Composite, Confinement, Capacity, Stiffness, Ductility

DOI: https://doi.org/10.15623/ijret.2014.0318030