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College of Engineering and Science
NEF4101 Research Project 1
Extended Project Brief [20%]
Project title: Nonlinear Analysis of Double Square Steel Tubular Short Columns Filled with
Concrete
Student Name:
Student ID:
Supervisor:
Date submitted:
28/02/2020
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Abstract
Thin walled squarer concrete-filled double steel tubular (CFDST) columns is designed by
outer square steel column filled with concrete as well as the inner square steel tube. CFDST
increasingly being used in the performance-based design applications in construction projects
around the world. CFDST have become popular because they utilize the inherent
characteristics of two building materials; steel and concrete to improve compressive strength
and ductility. This research aims at performing a numerical model to investigate the
behaviour of short CFDST structural components under axial- compression in order to have a
predictive model for future design. This research is necessary and will add to the body of
existing knowledge due to a dearth of studies on the effects of local buckling, which have
gained scant attention during advanced methods of analyzing CFDST performance.

Introduction and background
A contemporary popular design principle being adopted globally in building is performance-
based design; it allows designers to tailor structural members to specific performance levels
based on need (Liang, 2009). Concrete-filled double skin tubular columns (CFDST) are
structural columns is an example of this principle (Ahmed et al. 2020). CFDST is a
composite structural component made up of two steel layers with a concrete layer in between
them. The inner hollow steel section is the reinforcement and formwork for the concrete and
both materials work in a complimentary manner where concrete delays buckling, improving
its ductility. The concrete core is important in adding compressive strength and stiffness to
the tubular column while at the same time reducing the potential for inward buckling. CFDTS
are popular because of their high strength, good fire and seismic performance, as well as high
stiffness to bending (Ahmed et al. 2018).
Aims and Objectives
The aim of this project is to undertake a numerical model to investigate the behaviour of short
CFDST structural components under different weight loads in order to have a predictive
model for using the components under different axial loads and their biaxial bending.
Objectives
 To perform nonlinear research on the long-term load bearing performance and
strength test of CFDST.
 To use the results to develop a predictive model on the CFDST axial load bearing and
biaxial bending to be used in future design.
Significance
This research is significant because of the effect of steel plates in CFDST buckling when
subjected to various loads and this results in the thin walled concrete filled box columns
having reduced performance when under axial compression. Local buckling effects have not