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International Journal of Advanced Research in Engineering and Technology (IJARET) Volume 9, Issue 5, September - October 2018, pp. 170–179, Article ID: IJARET_09_05_016
Available online at http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=9&IType=5
ISSN Print: 0976-6480 and ISSN Online: 0976-6499
© IAEME Publication
RELIABILITY STUDY OF CFST COLUMNS
FILLED WITH FRC BY USING MIDAS CIVIL &
SPHERICAL SAMPLING SIMULATION
Mohammed Zia Sultan
Department of Civil Engineering,
Final Year Student, Ghousia college of Engineering, Ramanagaram,
VTU, Belgaum, Karnataka, India
Khalid Nayaz Khan
Department of Civil Engineering,
Assistant Professor, Ghousia college of Engineering, Ramanagaram,
VTU, Belgaum, Karnataka, India
N S Kumar
Department of Civil Engineering,
Professor and Director (R&D-Civil Engineering),
Ghousia college of Engineering, Ramanagaram
VTU, Belgaum, Karnataka, India
ABSTRACT
In this study, the CFST columns are analyzed with the help of MIDAS CIVIL
software. The models are prepared and analyzed in MIDAS CIVIL software to
determine the failure loads for different lengths, slenderness ratio and thickness of
CFST columns. The obtained analytical Pu values are compared with codal formulae
such as AISC LFRD Code, EURO code and CCES code. Corresponding graphs are
plotted to get the difference between analytical Pu and codal Pu values. For these
CFST columns, reliability analysis is carried out to know the design goal to achieve
the nominal load carrying capacity with less deflection.
The reliability analysis is carried out with the help of Comrel 9.5 software and the
results such as reliability index (β) and probability of failure (pf) are tabulated for
each CFST model. The reliability analysis is performed by two methods namely
FORM and spherical sampling method.
To identify and pick the combination of parameters that yield the best reliability
index, Taguchi’s approach is used.
Key words: AutoCAD, ETABS, High-Rise building, Post Tensioned slab, Prestressed
Concrete, Seismic zones, Wind zones.
Mohammed Zia Sultan, Khalid Nayaz Khan and N S Kumar
http://www.iaeme.com/IJARET/index.asp 171 [email protected]
Cite this Article: Mohammed Zia Sultan, Khalid Nayaz Khan and N S Kumar,
Reliability Study of CFST Columns Filled with FRC by Using Midas Civil &
Spherical Sampling Simulation. International Journal of Advanced Research in
Engineering and Technology, 9(5), 2018, pp 170–179.
http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=9&IType=5
1. INTRODUCTION
Steel and cement are the two most essential construction materials in structures. Steel
possesses high tensile strength, greater ductility and excellent elastic modulus. While
concrete has high compressive strength, low elasticity and lower thermal conductivity when
compared to steel, which usually causes the members to become bulky in which brittle tensile
cracking, creep and shrinkage properties may influence their long term structural
performance. Steel concrete composite structures combine the benefits of steel and concrete
materials to provide general improvement in quality and stiffness. CFST section, containing
an empty steel tube infilled with concrete has been broadly utilized as a part of tall structures.
The local buckling of the external steel tube is delayed or even avoided by the concrete infill
while the inward concrete in centre is restricted by the steel tube-giving improvement in
quality and flexibility under high compressive load. The steel tube can serve as formwork for
concrete and thus it eliminates the need for formwork and promotes quick construction
process. CFST made by the blend of at least two materials having distinctive basic properties.
The two materials work in tandem to give the composite enhanced features with excellent
structural characteristics. CFST are picking up in popularity and are widely used in present
day construction industry because of large structural and economic advantage and in addition
better aesthetic appearance.
Ultimate load carrying capacity is determined by using MIDAS CIVIL software.
Moreover, Reliability study of these CFST columns is performed for members with varied
diameters and lengths.
1.2. Introduction to Reliability
In the normal day to day life the word Reliability (Reliable / unreliable) is commonly used.
The words reliable and un-reliable are used synonymously with the words
“Dependable” and “Undependable”, respectively. When we say that an electric motor
manufactured by a particular firm is reliable, it is that its performance is trouble-free, but we
do not completely rule out the possibility of failure. However, based on the quality of the
component used in the manufacture of electric motor and our experience with other units of
same make, we conclude that the chances of its failure are few.
. The degree of certainty or uncertainty is related to the amount of information available
about that particular equipment, in general, about its design characteristics the quality of
components is used in it its performance, so on. The combined knowledge of these factors
gives us a descriptive picture, which is purely qualitative, of the word reliability.
In the previous statement, a specific level of vulnerability about the execution of
equipment is included. The level of certainty or vulnerability is identified with the measure of
data accessible about that specific equipment, in general, about its design attributes the nature
of parts is utilized as a part of it its execution, so on. The combined knowledge of these
factors gives us an elucidating picture, which is simply subjective, of the word reliability
(unwavering quality).
Such a qualitative descriptive is unsatisfactory for following reason.
1. It does not help us to calculate reliability.
Reliability Study of CFST Columns Filled with FRC by Using Midas Civil & Spherical Sampling
Simulation
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2. It does not permit comparison of reliability of different components and systems.
3. It does not indicate the means of improving the reliability of a components or systems.
4. It does not help us to stipulate the reliability requirement for an equipment at design state.
For these reasons, it is necessary to have certain criteria of reliability. However, reliability
depends on numerous factors, most of which are random. It is difficult to measure reliability,
since there is no instrument by means of which this may be done for particular equipment.
The respective reliabilities of various component of a complex equipment depend on
technology of their production, the quality of materials used in there manufacture, the
conditions or environment in which they operate and so on. In view of these consideration,
the reliability of equipment is closely related to several uncertainty, therefore, forms the
starting point for a quantitative analysis of reliability. The theory, which deals with study of
uncertainty, is the probability theory.
1.2. Objectives
The various objectives of my project work are discussed below
To determine load carrying capacity of CFST columns with varying lengths, thickness and
diameter using MIDAS CIVIL software.
To determine the maximum load carrying capacity of CFST by using FEM software’s
such as MIDAS CIVIL for different percentage of fiber mixed concrete (0%, 0.2%, 0.3%
& 0.4%)
To study the critical load carrying ability of CFST columns with varying fck (22.5, 27.05,
28.06, 30.05, 31.95, 34.06, 35.5 & 37.28).
To compare the ultimate loads obtained by MIDAS software with those of loads obtained
from different codal provisions.
To perform Reliability analysis of CFST columns using FORM and SSM (Spherical
Sampling Method).
To determine Reliability index β and Probability of failure pf using FORM and SSM
simulations.
To calculate strength to weight ratio of various combinations using Taguchi’s method.
Materials and Methodology
Constituent materials used
The following are the materials used for making concrete mix for testing.
Cement
In this study 53 grades ordinary Portland cement (OPC) was used for all concrete mixes.
Fine aggregates
The fine aggregates used is manufactured sand, which is free from deleterious materials.
Coarse aggregates
The coarse aggregates used for this study is 12mm size which is free from deleterious
materials.
Water
Clean portable tap water with required standard, available from library is used for the
experiments.
Mohammed Zia Sultan, Khalid Nayaz Khan and N S Kumar
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Recron3s polypropylene fiber
Recron 3s fiber was used as an auxiliary reinforcement material. It reduces shrinkage splits
and increases protection from water entrance, and impact. The utilization of fiber makes
concrete homogenous. Both flexibility and flexural strength is expanded makes the concrete
to accomplish the higher capacity to absorb more energy. Utilization of uniformly spread
Recron 3s strands diminishes segregation and bleeding, resulting in a more analogous mix. It
increases compressive strength and durability and lessened permeability.
The fibers used were fine polypropylene monofilaments. Reliance Industry supplied the
fibers by name RECRON 3s. It is available in three different sizes i.e. 6mm, 12mm and 24
mm.In the present study, 12mm fiber length is used.
2. INTRODUCTION TO MIDAS SOFTWARE
MIDAS is software used in FEM (finite element analysis) and in CAD; engineering software
was released in the year 2006. In mechanical components and assemblies, this software is
used for modelling, analysis of finite element analysis results. This software involves both
pre-post processing module can be used independently.
MIDAS Civil is innovative building programming that set another standard for the outline
or connects common structures. It includes a particularly easy to understand interface and
ideal outline arrangement works that can represent development stages and time subordinate
properties. It has exceptionally created demonstrating and investigation capacities, which
empower designers to overcome normal difficulties and wasteful aspects of limited
component examination. With MIDAS Civil, we can have the capacity to make sound &
aesthetic plans with uncommon levels of productivity and precision.
This software is more useful in academic and research institutions for modelling
Software contains extensive range of material model can be used for modelling of
elements.
Post processing generates images, animation from output file.
Table 1 Total models to be prepared
SL
NO Diameter (mm) Thickness (mm) Length(mm)
1 33.7 3.2 337
2 33.7 3.2 405
3 33.7 3.2 472
4 42.4 3.2 424
5 42.4 3.2 509
6 42.4 3.2 594
7 48.3 3.2 337
8 48.3 3.2 405
9 48.3 3.2 424
10 33.7 3.2 337
11 33.7 3.2 337
12 33.7 3.2 337
13 33.7 3.2 337
14 33.7 3.2 405
15 33.7 3.2 405
16 33.7 3.2 405
17 33.7 3.2 405
18 33.7 3.2 472
19 33.7 3.2 472
20 33.7 3.2 472
Reliability Study of CFST Columns Filled with FRC by Using Midas Civil & Spherical Sampling
Simulation
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21 33.7 3.2 472
22 42.4 3.2 424
23 42.4 3.2 424
24 42.4 3.2 424
25 42.4 3.2 424
26 42.4 3.2 509
27 42.4 3.2 509
28 42.4 3.2 509
29 42.4 3.2 509
30 42.4 3.2 594
31 42.4 3.2 594
32 42.4 3.2 594
33 42.4 3.2 594
2.1. Modelling
The modelling procedure is as shown by below flowchart.
Figure 1 Modelling Procedure.
Modelling and Analysis using MIDAS CIVIL Software
Step 1: Change the dimensions to kN Step 2: Go to the structure option
and select and mm in bottom tool bar BASE STRUCTURE and check 2-d
phase option
Figure 2 Setting units Figure 3 Selection of Structure type
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Step 3: Defining the dimensions of the column, Step 4: Setting the boundary
While defining the length of the column make sure conditions by checking
that the given length is divided into DALL and R-AL option.
required number of small elements,
which acts as meshing.
Figure 4 defining the dimension of column Figure 5:Segregation of Elements.
Step 5: Defining the material properties. Step 6: Providing the outer and
inner diameter of the CFST tube.
Figure 6 Material property Figure 7 providing the diameter
Step 7: Applying load on the CFST Step 8: Obtaining results, Mode
column by selecting (user define) option and Analyze. shapes and Load calculation
Figure 8 Applying the load Figure 9 Buckling column.
Reliability Study of CFST Columns Filled with FRC by Using Midas Civil & Spherical Sampling
Simulation
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3. ANALYSIS RESULTS
Exp
no
Diameter
(mm)
Thickness
(mm)
% of
fiber
Area
(mm2)
Length
(mm)
Fck from
cube
testing
(Pu)
analytical
(MIDAS)
kN
1 33.7 3.2
306.62 337 0 173.42
2 33.7 3.2
306.62 405 0 133.6
3 33.7 3.2
306.62 472 0 105
4 42.4 3.2
394.08 424 0 241.3
5 42.4 3.2
394.08 509 0 185.7
6 42.4 3.2
394.08 594 0 145.8
7 48.3 3.2
1832.2 337 0 346
8 48.3 3.2
1832.2 405 0 361.4
9 48.3 3.2
1832.2 424 0 300
10 33.7 3.2 0 891.96 337 22.5 173.42
11 33.7 3.2 0.2 891.96 337 27.05 177.33
12 33.7 3.2 0.3 891.96 337 28.06 179.22
13 33.7 3.2 0.4 891.96 337 30.05 180.65
14 33.7 3.2 0 891.96 405 22.5 133.6
15 33.7 3.2 0.2 891.96 405 27.05 138.4
16 33.7 3.2 0.3 891.96 405 28.06 143.58
17 33.7 3.2 0.4 891.96 405 30.05 151.16
18 33.7 3.2 0 891.96 472 22.5 105
19 33.7 3.2 0.2 891.96 472 27.05 120.54
20 33.7 3.2 0.3 891.96 472 28.06 134.69
21 33.7 3.2 0.4 891.96 472 30.05 141.18
22 42.4 3.2 0 1412 424 22.5 241.3
23 42.4 3.2 0.2 1412 424 27.05 265.2
24 42.4 3.2 0.3 1412 424 28.06 276.31
25 42.4 3.2 0.4 1412 424 30.05 281.19
26 42.4 3.2 0 1412 509 22.5 185.7
27 42.4 3.2 0.2 1412 509 27.05 188.38
28 42.4 3.2 0.3 1412 509 28.06 194.62
29 42.4 3.2 0.4 1412 509 30.05 197
30 42.4 3.2 0 1412 594 22.5 145.8
Graph 1 Analytical Pu
0
50
100
150
200
250
300
350
400
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31
(Pu) analytical (MIDAS) kN
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4. RELIABILITY ANALYSIS
In the consequences of getting aftereffects of CFST column by MIDAS CIVIL software the
reliability ponder must be made for acquired outcomes i.e. Monotonic load and axial loads.
To get reliability results, for example, reliability index there are numerous strategies, for this
situation, we will recognize reliability index an incentive by FOSM and spherical simulation
technique. From FOSM strategy we will get reliability index esteem and from spherical
simulation technique we obtain the probability of failure. To get this reliability comes about
we utilized COMREL 9.5 software, from this software we can without much of a stretch get
the reliability after effects of the considerable number of strategies, for example, FOSM,
spherical simulation technique. The brief strategy is as given in below figure.
Figure 4.1 About the COMREL 9.5 software Figure 4.2 Tools and working window
Figure 4.3 coding a limit state function equation. Figure 4.4: Feeding the Distribution
Mean Value & Standard Deviation
Figure 4.5: Reliability Analysis technique to be carried out Figure 4.6: Reliability analysis
. Obtained from SSM.
Reliability Study of CFST Columns Filled with FRC by Using Midas Civil & Spherical Sampling
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4.1. Reliability & Percentage Reliability Obtained by SSM
Ex
no
Diameter
(mm)
Thickness
(mm)
Length
(mm)
fck from
cube
testing
fy
(Mpa)
Reliability
index β Reliability % Reliability
1 33.7 3.2 337 0 310 -0.026 0.51 51
2 33.7 3.2 405 0 310 -1.389 0.98 98
3 33.7 3.2 472 0 310 -0.056 0.98 98
4 42.4 3.2 424 0 310 -2.753 0.997 99.7
5 42.4 3.2 509 0 310 -1.737 0.98 98
6 42.4 3.2 594 0 310 -0.515 0.99 99
7 48.3 3.2 337 0 310 -3.82 1 100
8 48.3 3.2 405 0 310 -4.06 1 100
9 48.3 3.2 424 0 310 -3.07 0.99 99
10 33.7 3.2 337 22.5 310 -2.438 0.99 99
11 33.7 3.2 337 27.05 310 -2.491 0.98 98
12 33.7 3.2 337 28.06 310 -2.535 0.97 97
13 33.7 3.2 337 30.05 310 -2.548 0.98 98
14 33.7 3.2 405 22.5 310 -1.054 0.86 86
15 33.7 3.2 405 27.05 310 -1.161 0.89 89
16 33.7 3.2 405 28.06 310 -1.33 0.92 92
17 33.7 3.2 405 30.05 310 -1.568 0.95 95
18 33.7 3.2 472 22.5 310 0.55 0.29 29
19 33.7 3.2 472 27.05 310 -0.45 0.71 71
20 33.7 3.2 472 28.06 310 -1.015 0.87 87
21 33.7 3.2 472 30.05 310 -1.217 0.908 90.8
22 42.4 3.2 424 22.5 310 -2.702 0.997 99.7
23 42.4 3.2 424 27.05 310 -3.13 0.98 98
24 42.4 3.2 424 28.06 310 -3.331 1 100
25 42.4 3.2 424 30.05 310 -3.387 1 100
26 42.4 3.2 509 22.5 310 -1.269 0.89 89
27 42.4 3.2 509 27.05 310 -1.254 0.89 89
28 42.4 3.2 509 28.06 310 -1.404 0.92 92
29 42.4 3.2 509 30.05 310 -1.429 0.92 92
30 42.4 3.2 5 22.5 310 0.081 0.46 46
Graph 2 Percentage Reliability by Spherical Sampling Method
0
20
40
60
80
100
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31
% Reliability
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5. CONCLUSIONS
[1] As the length of the steel tube decreases for a given diameter and thickness, load carrying
capacity (Pu) increases.
[2] As percentage of polypropylene fiber is increased, load carrying capacity (Pu) also increases
up to 0.3% fiber and thereafter there is a slight decrease in Pu value for 0.4% fiber.
[3] Load carrying capacity (Pu) increases with increase in diameter for addition of fiber up to
0.3%. A slight decrease in Pu is observed for 0.4% of fiber.
[4] The Pu values obtained from MIDAS software are higher than those obtained from
Theoretical calculations.
[5] It is observed that the Pu value for 0.4% of fiber the value in MIDAS constantly increases
whereas the value obtained by experiment show slight decrease in Pu value for 0.4% fiber.
[6] The strength of CFST columns increases as D/t ratio decreases.
[7] Calculations such as FOSM, FORM and SORM can be done manually, but the simulations
such as SSM, MCS and ASM cannot be done manually and they require suitable software.
[8] Tubes, which are filled with (22.5, 27.05, 28.06, 30.05, 31.95, 34.06, 35.5 &37.28) grade
concrete infill, takes higher loads than that of hollow steel tubes.
[9] With increase in thickness of steel tubes the Reliability index value decreases.
[10] Increase in length of CFST column having constant diameter and thickness, increases the
Reliability index (β).
[11] Usually the short columns failure is accompanied either by concrete crushing or by diagonal
shear failure in concrete. (Fig- 5.9).
[12] Whereas the long CFST columns fails due to buckling when the axial load reaches its critical
load carrying capacity.
AUTHOR PROFILE
Graduated in the year 2015 from VTU, Belgaum. Presently perusing Master
of Technology in Structural Engineering at Ghousia College of Engineering,
Ramanagaram Also working on this topic for the dissertation under the
guidance of Khalid Nayaz khan and Dr. N S Kumar.
Associate Professor Dept. of Civil Engineering GCE, Ramanagaram
562159. He has a teaching experience of 32 years. Has published about 13
papers in various journals.
Dr. N.S. Kumar, Prof and Director (R & D) is involved in the Research field
related to composite steel columns. He received BE, in Civil Engineering
from Mysore University (1985), ME & Ph.D degrees from Bangalore
University during 1988 & 2006 respectively. He has guided 1 ph.D, 1 M.sc
Engineering (By Research) under VTU, Belgaum. Presently he is guiding 6
Ph.D, scholars and has guided more than 30 M.tech projects. He has more
than 30 years of teaching experience & has published over 130 papers in
National & International journals including conferences.