AN EXPERIMENTAL STUDY ON CFDST COLUMN UNDER AXIAL LOADING

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 10 | Oct 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 116
AN EXPERIMENTAL STUDY ON CFDST COLUMN UNDER AXIAL LOADING
Ranjith Gowda G1, Abdul Rehaman2
1Post Graduate Student, Dept. of Civil Engineering, Ghousia college of Engineering, Ramanagara-562159
2Assistant Professor, Dept. of Civil Engineering, Ghousia college of Engineering, Ramanagara-562159
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Abstract -
The research focuses on analysing the characteristics of
these columns under axial compression circumstances. The
behaviour and properties of CFDST columns with CHS
(circular hollow section) inner and exterior tubes are
investigated through experimental research.
This research study centers on a meticulous evaluation
of Circular-Filled Double-Skin Tubular (CFDST) columns
when compression in the axial direction conditions. By
employing a systematic approach of experimental analysis,
we aim to investigate into the intrinsic properties of these
columns. Specifically, our focus lies on CFDST columns that
exhibit a unique composition, with both interior and
exterior tubes constructed using Circular Hollow Sections
(CHS).
Understanding the behaviour and characteristics
column CFDST data is at the core of our work. Through
rigorous experimental analysis, we subject these columns to
the axial compression – a simulation of real-world loading
conditions. This approach provides a direct window into
their load-carrying capacity, deformation patterns, and
underlying response mechanisms. By shedding light on the
behavior of the CFDST columns featuring CHS outer and
interior tubes, we aim to contribute vital insights that can
potentially transform the way the columns in these
incorporated into structural designs.
Key Words: CFDST, CHS, capacity.
1.Introduction
In the modern age, the uses of space, which is includes
the spaces needed by a vertical member (smaller are always
better), is given the utmost priority in the current period.
The most crucial component of a structure for transferring
compressive and tensile loads is the vertical elements. A
column's lateral dimensions are surprisingly tiny when
contrasted to its height. A Column can be horizontal or
vertical elements. Struts are members that experience
compression in the vertical, diagonal, or horizontal
directions.
1.1 Concrete Filled Double Skin Steel Tubes
(CFDST)
A concrete filled double skin steel tube (CFDST) is a type
of composite structure that is commonly used in modern
construction. It is made up of an inner and outer steel tube,
which are separated by a space or void that is filled with
concrete. The inner and outer steel tubes provide the
primary load-bearing structure of the CFDST, while the
concrete filling provides additional strength and stiffness.
The concrete filling also helps to protect the steel tubes from
fire and corrosion. CFDST structures are often used in tall
buildings and bridges because they are able to withstand
high levels of compression, tension, and bending. They are
also relatively lightweight compared to traditional
reinforced concrete structures, which will help to reduce the
overall weight of the building or bridge. CFDST structures
can be designed in a variety of shapes and sizes, depending
on the specific needs of the project. They can also be
prefabricated off-site and assembled on-site, which can help
to reduce construction time and costs. Overall, CFDST
structures are a durable and efficient construction option
that can provide a range of benefits for building and bridge
projects.
Fig 1.1: A concrete-filled double-skin steel tubular
(CFDST) member with CHS exterior and interior steel
tubes is shown schematically, and the geometric notations
used here are described.
2. Literature Review
The Ultimate Axial Load Carrying Capacity of a Column
can be accurately estimated, according to the Time Series
Plot. From this research, parametric optimisation and
factors impacting the reaction, such as concrete thickness,
length, and grade, may be accurately anticipated. When
results from ANSYS software were compared to
experimental data, they ranged from 5% to 10%. When
outcomes from the EC4 code of practise were compared to

experimental data, they ranged from 2% to 15%. When
results from the ACI code of practise were compared to
experimental data, the differences ranged from 6% to 25%.
When results from the BS400 code of practise were
compared to experimental results, they ranged from 5% to
15%. When compared to experimental results, the results
from the AISC 360-10 code of practise ranged from 5% to
15%. For M30 grade of concrete (constant diameter,
constant thickness), load carrying capacity decreased by 4%
to 8%. For M40 grade of concrete (constant diameter,
constant thickness), load carrying capacity decreased by 5%
to 10%. For Hollow CFST (constant diameter, constant
thickness), the load capacity decreased by 5% to 10%.
2.1 Scope of the Work
1. Examine the mechanical characteristics of the steel
with the concrete utilised to construct the CFDST columns.
2. A mix design is carried out for concrete of grade M50.
3. Examine the CFDST columns' deformation properties,
load-deflection behaviour, and failure mechanisms.
4. A practical examination was done to ascertain the
CFDST columns' ability to support an axial load.
5. To estimate the load-carrying capability of CFDST
columns under axial for validation, static structural analysis
is performed.
2.2 Objective of the Research Work
1.Testing experimentally CFDST column specimens with
axial loads in a UTM machine.
2.Recognising Concrete and Tube Behaviour in CFDST
Columns.
3.Determining CFDST Column Deformation
Characteristics under Axial Load.
4.Use the models to examine stress distribution, load-
carrying capability, and deformation behaviour, and
validate the simulation findings against the data.
3. Methodology
The method employed for casting the specimens and
subsequently conducting tests. The casting process involves
carefully assembling interior and exterior steel tubes with
precise spacing, followed by controlled pouring of concrete.
The evaluation stage encompasses subjecting these
specimens to various loading conditions using a Universal
Testing Machine (UTM), evaluating their mechanical
properties and performance. This comprehensive approach
underscores the integration of fabrication and evaluation
methodologies, offering a holistic understanding of
Concrete-Filled Double-Skinned Steel Tube (CFDST)
behaviour.
3.1 About UTM:
An essential piece of machinery used in engineering,
manufacturing, and research to assess the mechanical
properties and behaviours of various materials and
components is a universal testing machine (UTM), also
known as a material testing machine or a mechanical testing
machine. By applying controlled mechanical forces to
specimens, the UTM is able to measure tensile strength,
compressive strength, bending characteristics, shear
resistance, and other parameters. It is essential to
comprehend how materials behave under various loading
scenarios in order to inform the development of innovative
materials and products as well as quality control practises
and design decisions.
4. Validation
There are various ways to analyse the columns,
including limit state analysis and elastic analysis.
Approximate or accurate procedures were employed in
limit or elastic state methods. Using a FEM software
(ANSYS), I have examined the axial loads placed on the
columns and compared the results to the Practical analysis
(experimental conduction) in the current thesis.
4.1 Finite Element Method
Finite Element Analysis (FEA) is a powerful
computational technique used in engineering and physics to
simulate the behavior of complex structures and systems.
It's based on the concept of dividing a complex geometry
into smaller, simpler elements, each represented by a set of
equations that describe its behavior. By solving these
equations collectively, FEA enables engineers and
researchers to analyze the response of a structure or system
to various loading and boundary conditions.
4.2 About ANSYS
ANSYS (version 21) is a popular software suite used for
engineering simulation and analysis. It provides a
comprehensive set of tools for simulating a wide range of
physical phenomena, including structural, thermal,
electromagnetic, and fluid dynamics problems. ANSYS is
widely used in industries such as aerospace, automotive,
energy, electronics, and biomedical engineering.
The software package comes with a number of modules,
including ANSYS Mechanical, ANSYS Fluent, ANSYS
Electronics, ANSYS Maxwell, ANSYS CFX, and ANSYS HFSS,
among others. Each module is designed to address a
particular set of simulation needs, and they are employable
together for multi-physics simulations.

5. Materials Used
5.1 Steel
Steel is an alloy, which means the material composed of
two or more chemical elements, with iron being the main
component. Other elements commonly found in steel
include carbon, manganese, silicon, and sulfur, among
others. The specific composition of steel can vary depending
on its intended use, with different alloys being used for
different applications.
Due to its strength, longevity, and versatility, steel is one
of the most frequently used materials in the world. It can be
used for a wide range of things, including building and
infrastructure, transportation, and industrial. Consumer
products including electronics, furniture, and appliances are
frequently made from steel.
5.2 Concrete
Concrete is a versatile and frequently utilised building
supplies produced by mixing cement, water, and aggregates
(such as sand, gravel, or crushed stone). The resulting
mixture can be poured into moulds or forms to create
structures, such as buildings, bridges, roads, and dams.
Concrete is known for its strength, durability, and
versatility, making it a popular choice for a variety of
construction applications.
Table 5.1. Properties of CFDST
Particular Interior tube
Exterior
tube
Outer diameter 62.50mm 175mm
Thickness 3.60mm 2.60mm
Inner diameter 55.30mm 169.80mm
Grade of
Concrete
M50
Youngs modulus
of concrete
41833.00 MPa
Youngs modulus
of Steel
200000 MPa
6. Results
Chart 1: Max. stress allowed in models and specimen
without stiffener.
In the assessment of maximum stress within
configurations lacking stiffeners, a notable discrepancy
emerged between the analytical and experimental
approaches. Specifically, the analytical method projected a
greater maximum stress value than that gleaned from
experimental results. This divergence indicated a significant
variation of 22% between two methodologies. This
disparity underscores the challenges inherent in precisely
modeling the intricate behaviors of Concrete-Filled Double-
Skinned Steel Tube (CFDST) structures through theoretical
computations alone. The observed discrepancy highlights
the necessity of harmonizing theoretical predictions with
empirical findings to achieve a more comprehensive and
accurate understanding of CFDST behavior.
Chart 2: Max. stress allowed in models and specimen with
stiffener.
Upon scrutiny of maximum stress levels within
configurations featuring stiffeners, a distinct contrast
surfaced between the analytical and experimental
methodologies. Specifically, the analytical predictions
yielded a greater maximum stress when value compared to
the empirical results. This divergence signaled a significant
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ANALYTICAL EXPERIMENTAL
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ANALYTICAL EXPERIMENTAL

discrepancy of 23% between experimental and the
analytical approaches. This observation underscores the
intricate nature of replicating Concrete-Filled Double-
Skinned Steel Tube (CFDST) behaviors through analytical
calculations alone. The discernible variance accentuates the
significance of integrating theoretical understanding with
empirical validation, culminating is more holistic
comprehension of CFDST structural responses.
7. CONCLUSIONS
1. ANSYS software analysis resulted in a reasonable
variation of 20% to 25% compared to experimental
outcomes.
2. This variation indicates alignment between
computational predictions and real-world data.
3. It provides a solid foundation for refining computational
models and their application in engineering scenarios.
4. Evaluation of CFDST column performance revealed an
improvement in elastic energy absorption capacity with
higher concrete strength.
5. Choosing the right concrete strength strategically can lead
to superior energy-absorbing properties.
6. This has promising implications for structural resilience
and durability.
8. Future Scope
The domain of research within the realm of Concrete-Filled
Double-Skin Tubular (CFDST) columns presents an array of
promising prospects for future investigation and
advancement. The following directions provide a robust
framework for expanding the existing comprehension of
these intricate structural elements:
1. Investigating various column shapes under different
loading conditions offers valuable insights.
2. It deepens our understanding of how geometries affect
the structural behavior of CFDST columns.
3. Diverse loading scenarios reveal relationships between
design parameters and performance characteristics.
4. This research enriches the knowledge base in structural
engineering.
5. Studying different concrete and steel grades provides in-
depth material analysis.
6. Systematically varying these parameters uncovers how
combinations affect strength, durability, and behavior of
CFDST columns.
7. Optimized material selections for specific applications
may result from this exploration.
8. Contributes to the development of more efficient and
resilient structures.
9. Evaluating different column dimensions provides data on
their influence on critical parameters.
10. Factors like buckling behavior, load distribution, and
overall stability are considered.
11. Helps refine design guidelines for optimal column sizing
in practical applications.
REFERENCES
1. In 2018, Fa-Cheng Wang, Lin-Hai Han, and Wei Li
conducted a study investigating the analytical behavior
of concrete-filled double skin tubular (CFDST) stub
columns featuring external stainless-steel tubes under
axial compression. Their research findings were
documented in "Thin-Walled Structures," Volume 127,
Pages 756-768.
2. Research conducted by Hong Huang, Lin-Hai Han, Zhong
Tao, and Xiao-Ling Zhao in 2010 explored the analytical
behavior of CFDST stub columns. Published in the
"Journal of Constructional Steel Research," Volume 66,
Pages 542-555, their work delved into the structural
characteristics of concrete-filled double skin steel
tubular (CFDST) stub columns.
3. A theoretical study in 2000 by LiangQ.Q. and B. Uy delved
into the post-local buckling behavior of steel plates
within concrete-filled box columns. This investigation,
published in "Computers and Structures," Volume 75,
Pages 479-490, examined the response of steel plates
within such columns subsequent to experiencing local
buckling.
4. In 2014, M. Pagoulatou, T. Sheehan, X.H. Dai, and D. Lam
conducted finite element calculations on the strength of
circular double-skin steel tubes filled with concrete
(CFDST) stub columns. Their work was published in
"Engineering Structures," Volume 72, Pages 102-112.
5. M. Elchalakani, V.I. Patel, A. Karrech, M.F. Hassanein, S.
Fawzia, and B. Yang carried out finite element
simulations in 2019 to investigate the behavior of
circular short concrete-filled double-skin steel tubular
(CFDST) columns under axial compression. Their
research findings were published in "Structures,"
Volume 20, Pages 607-619.
6. Xi-Feng Yan and Yan-Gang Zhao conducted research in
2020 on the compressive strength of axially loaded
circular concrete-filled double-skin steel tubular short
columns. Their findings were published in the "Journal of
Constructional Steel Research," Volume 170, Pages 106-
114.
7. You-Fu Yang, Lin-Hai Han, and Ben-Hao Sun's 2012
research focused on the experimental behavior of
partially loaded concrete-filled double-skin steel tube
(CFDST) sections. Their study was published in the
"Journal of Constructional Steel Research," Volume 71,
Pages 63-73.
8. Yanze Wang and Baishou Li conducted a finite element
analysis in 2013 for concrete-filled double-skin steel
tubular stub columns. Their work was published in

"Advanced Material Research," Volume 690-693, Pages
696-699.
9. Kojiro Uenaka and Hiroaki Kitoh explored the mechanical
behavior of concrete-filled double skin tubular circular
deep beams in 2011. Their study, featured in "Thin-
Walled Structures," Volume 49 (2011), Pages 256–263,
focuses on understanding the structural performance of
circular deep beams filled with concrete within a double
skin tubular configuration.
10.In 2016, Kojiro Uenaka conducted research on CFDST
stub columns with outer circular and inner square
sections under compression. The study was featured in
the "Journal of Constructional Steel Research," Volume
120 (2016), Pages 1–7, and focuses on the behavior of
these columns under compressive loads.
BIOGRAPHIES
Ranjith Gowda G
Post Graduate Student, Dept. of
Civil Engineering, Ghousia college
of Engineering, Ramanagara-
562159
Abdul Rehaman
Assistant Professor, Dept. of Civil
Engineering, Ghousia college of
Engineering, Ramanagara-
562159

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