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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


Assistant Professor, Ghousia college of Engineering, Ramanagaram,


N S Kumar


Professor and Director (R&D-Civil Engineering),

Ghousia college of Engineering, Ramanagaram


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


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


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.



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


Simulation


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



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.


Simulation


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



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.


Simulation


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



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.

reliability study of cfst columns filled with frc by … · reliability study of cfst columns...

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