A Comparative and Parametric Investigation of Circular and Square CFST Columns Using Finite Element Analysis

Abstract

This thesis presents a comparative and parametric investigation into the structural behavior of circular and square Concrete-Filled Steel Tube (CFST) columns using finite element analysis. CFST columns, a composite system where a hollow steel tube is filled with concrete, offer significant advantages over traditional reinforced concrete, including enhanced strength, stiffness, and ductility due to the synergistic interaction between the steel and concrete. The primary objectives of this research were to develop and validate nonlinear finite element models using ANSYS software, evaluate the axial compression and deformation properties of circular and square CFST columns, determine their ultimate load-bearing capacities, and analysis the influence of key design parameters such as steel tube thickness, cross-section depth, and concrete grade.

The methodology involved creating detailed three-dimensional models in ANSYS, simulating axial loading conditions, and comparing the results with design calculations based on Eurocode 4. The study's findings demonstrate that circular CFST columns exhibit superior performance, experiencing up to 70% less deformation compared to their square counterparts due to more effective concrete confinement. Results consistently show that CFST columns are more robust than plain concrete columns of identical dimensions. Furthermore, the ultimate load-carrying capacity is inversely proportional to the diameter/breadth-to-thickness (D/t or B/t) ratio and directly proportional to the compressive strength of the concrete core. The conclusions affirm that a lower D/t or B/t ratio, combined with higher-grade concrete, substantially enhances column strength and efficiency.