Authored by Abdulrahman Abdulaziz Helmi*
Abstract
Structural columns that are made up of two or more different materials are known as composite columns. Studying composite structures is beneficial since it is a new and modern way to build structures and benefit from materials in a different way. Concrete- filled steel tubular structures makes the composite column a very stiff, more ductile, cost effective (as compared to reinforced concrete structures) and consequently a structurally efficient member in building and bridge constructions. In this study a numerical simulation of a circular composite column was conducted. In order to achieve the study objectives, Finite Element Method (FEM) based software (ABAQUS) was used due to many advantages including saving time of the calculation and providing a simulation of the behavior of the member. A load-deflection curve of a circular composite column was plotted by considering the stress-strain curve of normal concrete and compared with the experimental results. It was found that the load capacity was less than that of experimental results. The reason of this underestimation was the confinement effect. A correction factor for lateral confining pressure of 1.5 was found for circular sections since the equation used for confining pressure obtain from literature was applicable to square composite columns.
Introduction
Concrete-filled steel tubular columns (CFT) are effective in earthquake- resistance, structures subjected to impact, and highrise buildings columns. Due to the increasing use of composite columns, various researches have been carried out in recent years. In 1998, Schneider SPE [1] conducted an experimental and analytical study on the behavior of short, concrete-filled steel tube columns concentrically loaded in compression to failure. In 2003 Shosuke Morino & Keigo Tsuda [2] introduced the structural system and discuss advantages, research findings, and recent construction trends of the CFT column systems in Japan. The paper also described design recommendations for the design of compression members, beam-columns, and beam-to-column connections in the CFT column system. In 2014, Hsuan-Teh Hu et al. [3] proposed and verified proper material constitutive models for (CFT) columns. In 2014 Ananya John et al. [4] presented analytical study on stress-strain behavior of reinforced concrete column by modelling concrete and steel part separately. In this paper an analytical study on stress- strain behavior of CFT column was conducted. The finite element-based software used to conduct the analytical study was ABAQUS. The results were validated using the available experimental data.
Material Properties and Constitutive Models
The cross section of the CFT column in this study is modeled the same way it was used in the experimental study. The geometry and material properties are shown in Table 1. To predict the load– deformation relationships of CFT columns, an accurate constitutive model for steel and confined concrete is needed.
Constitutive model for Steel tube
The steel properties are shown in Table 1. The stress-strain curve used for the steel tube is assumed to be elastic-perfectly plastic.
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