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EXPERIMENTAL STUDY OF REINFORCED CONCRETE COLUMNS WITH

EMBEDDED PIPE

SAYED HOSSEIN MOUSAVIAN NAJAFABADI

A project report submitted in partial fulfillment of the

requirement for the award of the degree of

Master of Engineering (Civil – Structure)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

April 2010

v

ABSTRACT

An experimental study was carried out to investigate the effect of positioning rain water

down pipes inside reinforced concrete short braced columns in buildings. Thirty three

columns in eleven sets, having various sizes and reinforcements were constructed and

tested. The PVC or steel pipes were positioned at the centre of cross-section of each of

them. The installation of the strain gauges on the models was carried out before the

testing of the models. As an alternative solution, PVC drain pipes were replaced by steel

pipes in reinforced concrete columns. The ultimate strength of the columns obtained

from the present investigation is compared with the design strengths recommended by

the British code of practice (BS 8110) and the American code of practice (ACI). The

columns showed significant reduction in their load carrying capacities and the safety

factors obtained were much less than the nominal value usually recommended by

various codes of practice. Also the study showed that by using steel pipes instead of

PVC drain pipes, the load carrying capacity of the columns can be enhanced near 10

percent.

vi

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

TABLE OF CONTENTS vi

LIST OF TABLES ix

LIST OF FIGURES x

1 INTRODUCTION

1.1 Background 1

1.2 Problem Statement 4

1.3 Objectives 5

1.4 Scopes of Study 6

2 LITERATURE REVIEW

2.1 Reinforced Concrete Structure 7

2.1.1 General 7

2.1.2 Mechanics of Reinforced Concrete 8

2.1.3 Reinforced Concrete Members 9

2.1.4 Factors Affecting Choice of Reinforced 10

Concrete for a Structure

2.1.5 Objective of Design 13

vii

2.1.6 The Design Process 14

2.1.7 Mechanism of Failure in Concrete Loaded 15

in Compression

2.2 Previous Work Related To Reinforced Concrete 21

Columns Concealing Pipe

3 EXPERIMENTAL WORK AND TEST METHOD

3.1 Introduction 29

3.2 Test Models 30

3.3 The Test Models Classification 33

3.4 Models Preparation and Casting Procedure 34

3.4.1 Steel work 35

3.4.2 Concrete Work 37

3.4.3 Curing Technique 39

3.5 Instrumentation and Testing of the Models 39

3.5.1 Strain Gauge 39

3.5.1.1 Strain Gauge Principles 41

3.5.1.2 Strain Gauge Configuration 41

3.5.2 Loading Procedure 42

3.6 Flow Chart of the Research Methodology 44

4 RESULTS AND DISCUSSION

4.1 Introduction 45

4.2 Strength of Concrete Cube 45

4.3 Test Results of Loading Test 46

4.3.1 Vertical Stress- Strain relationship 48

Based On Composite Theory

4.3.2 Vertical Stress- Strain Curves of the 59

Models Based On Experimental Result

4.4 Reduction Load Carrying Capacity of Reinforced 73

Concrete Column Concealing Drain Pipes

4.5 Design Strength Requirement of the Columns 74

4.5.1 Design Strength of the Column Specimens 74

viii

Based On BS 8110 Code

4.5.2 Design Strength of the Column Specimens 75

Based On ACI Code

4.5.3 Load Carrying Capacity and Safety Factors 75

Assessment of the Models

5 CONCLUSION AND RECOMMENDATION

5.1 Conclusion 77

5.2 Recommendation 78

LIST OF REFERENCES 79

APPENDIX A – Strain Of The Columns From Data Logger 81

ix

LIST OF TABLE

TABLE NO TITLE PAGE

3.1 The Specification and Dimension of the Column Models 32

3.2 The Column Models Type 34

4.1 The Concrete Cubes Compressive Strength in First Batch 46

4.2 he Concrete Cubes Compressive Strength in Second Batch 46

4.3 Maximum Vertical Stress And Strain In The Columns 47

4.4 Reduction in Load Carrying Capacity of Column with

Embedded Pipes in Comparison with Control Model

73

4.5 Failure Loads, Design Loads Based On BS and ACI Codes of

Practice and the Corresponding Factors of Safety for the

Column Models

76

x

LIST OF FIGURE

FIGURE

NO.

TITLE PAGE

1.1 Rain Water Pipe Is Positioned Inside Columns 2

1.2 Typical Columns With Embedded Pipe 4

2.1 Plain and Reinforced Concrete Beams 8

2.2 Reinforced Concrete Building Elemen 10

2.3 Stress-Strain Curve For Concrete Loaded In Uniaxial

Compression

17

2.4 Effect Of Sustained Load On The Behavior Of Concrete In

Uniaxial Compression

20

2.5 Inappropriate Positioning of Rain Water Pipe in Column’s

Section

22

2.6 Formation Of Honeycombs Around The Drain Pipe 22

2.7 eakage in the Lapping Parts Of The PVC Drain Pipes 23

2.8 Congestion and Non-Uniformity in Beams Reinforcements at

Column’s Section Caused by the Presence Of Drain Pipe

23

2.9 Elbow Part Of The Drain Pipe At The Ground Level 24

2.10 Configurations of Lateral Reinforcement in Hollow Columns 27

3.1 Typical Column with Embedded Pipe 30

3.2 Steel Works Consist of Cutting, Bending and Tying Steel Bars 36

3.3 Positioning of the Pipes in Center of Column’s Cross-Section. 36

3.4 Column Form Work Was Positioned Horizontally and Ready

For Casting

38

3.5 The Fresh Reinforced Concrete Columns after Casting 38

3.6 A Typical Strain Gauge 42

3.7 The Test Setup 43

3.8 Figure 3.8: Flow Chart of Experimental Research 44

4.1 A Structural Member Consists Of a Rod Surrounded By a 48

xi

Tube

4.2 Strain-Stress Curves of All Test Models 59

4.3 Stress-Strain Curves of Column C-1 60

4.4 Column C-1 Collapse Mode 60









4.13 Stress-Strain Curves for Column C-6 67





4.18 Column C-8 Collapse Model 71


4.20 Column C-11 Collapse Model 72

CHAPTER 1

INTRODUCTION

1.1 Background

A column is the vertical structural member supporting axial compressive loads,

with or with-out moments. Columns support vertical loads from the floors and roof and

transmit these loads to the foundations. Failure of a column in a critical location can

cause the progressive collapse of the adjoining floors and the ultimate total collapse of

the entire structure.

In the construction of modern multistory buildings, pipes are positioned vertically

inside the reinforced concrete columns to accommodate the essential services such as

drainage of roof top rain water, electric wiring from floor to floor etc. The pipes are

placed inside the columns, based on pretext to maintain the aesthetic of the buildings.

The practice of embedding rain water down pipes inside reinforced concrete columns is

followed particularly in those multistory buildings which have flat roofs and glass front

views. The diameters of pipes vary, depending on the amount of drained water.

2

Tropical countries such as Malaysia is having rainfall throughout the year,

which require an effective and appropriate drainage system for rain water, and has to be

considered in the construction of all building projects having flat roofs. Therefore, the

practice of positioning Poly Vinyl Chloride (PVC) pipes inside reinforced concrete

(RC) columns has become quite common nowadays. The water from the roof tops of

multistory buildings is drained through these pipes and discharged at ground level

(Figure 1.1).

However, this method of drainage could cause serious damage to the safety of

the structure. And as a result, positioning drain pipe inside the columns may reduce the

effective cross-section area of it significantly and cause huge reduction in the load

carrying capacities of columns. A literature study on the problems shows that no

rational information and guidelines in codes of practice of ACI 318 (American), and

BS8110 (British Standard) on this problem are available.

Figure 1.1: Rain Water Pipe Is Positioned Inside Columns

3

A thorough literature survey on these types of columns indicates that, no significant

investigations have been carried out to study the actual reduction in load carrying

capacity of these types of columns. Most of the previous works in this regard have been

limited to the studies of the effect of constant axial load and eccentric load on the

behavior of rectangular and circular hollow reinforced concrete columns. [2-6]

From previous study is investigated that, column constructed with embedded PVC

drain pipes, not only have reduced load carrying capacities also could be very

dangerous to the safety of the entire building structure and could reduce its useful life as

well. Some of the problems caused by the practice of embedding drain pipes inside the

columns are:

i. Compressive strength of the column is reduced, because placing a pipe inside

the column, decreases it effective cross-sectional area.

ii. Reduction of cross-sectional area of the column will also affect its shear

capacity.

iii. There is a chance of formation of honeycombs around the drain pipe.

iv. Leakage from the joint lapping part of the pipe can cause corrosion of

reinforcement.

v. Load carrying capacity of the columns is further reduced, if the pipe is not

positioned vertically and centrally.

vi. Significant loss in the strength of the columns at ground level, where elbow part

is used to discharge rainwater.

In present study an experimental research has been carried out to investigate the

load carrying capacity of rectangular and square reinforced concrete short columns

(models) having PVC or steel drain pipes positioned inside them. The hysteric

performance of the columns is evaluated using various cross-sections with different

amount of reinforcement. Figure 1.2 shows a typical column with pipe positioned at the

4

center of column cross-section. The cross section dimensions of the column are

represented by h and b, where its height is l.

Figure 1.2: Typical Columns with Embedded Pipe

1.2 Problem Statement

The practice of positioning Poly Vinyl Chloride (PVC) pipes inside reinforced

concrete (RC) columns to drain the rain water common nowadays However, this

method of drainage could cause serious damage to the safety of the structure.

To the best of the knowledge of the authors, no significant investigations have been

carried out to study the load carrying capacity of these types of columns. Most of the

5

previous works in this regard have been limited to the studies of the effects of constant

axial load and eccentric load on the behavior of rectangular and circular hollow

reinforced concrete columns.

The major parameter will be focused in this study to investigate the load carrying

capacity of rectangular and square reinforced concrete short columns (models) having

PVC or steel pipes as a replacement for PVC pipe.

1.3 Objective of Study

The objective of this study is to investigate load carrying capacity of rectangular and

square reinforced concrete short braced column having pipe inside them. Objectives of

study are:

i. To investigate the load carrying capacity of rectangular and square

reinforced concrete short columns (models) having PVC or steel pipes with

different diameter inside them.

ii. To investigate load carrying capacity of column with various Steel pipe

diameters as the replacement of PVC pipe.

iii. To compare the experimental result with the recommended design strengths

of the codes of practice (BS8110-97 and ACI318-05).

6

1.4 Scope of the Study

It is impossible to study every parameter that will influence the behavior of columns

with embedded pipe in experimental study. Therefore, this study focuses on the

rectangular and square short braced axially loaded column with embedded pipe which

have 1.5 hour fire resistance. The scope of work includes:

i. Review of the design assessment and construction of braced short columns

based on the codes of practice of BS8110 (British) and ACI-318 (American).

ii. Casting of the half scale short columns as the control model with different cross-

section areas and steel contents.

iii. Casting the half scale short columns with embedded PVC pipes.

iv. Constructing of the half scale short columns with embedded steel pipes.

v. Models instrumentation and alignment.

vi. Testing of the models under axial compressive load and analyzing the results.

vii. Comparison of the load carrying capacity of the models with the design

strengths calculated based on the equations provided by the codes of practice.

79

List of Reference

[1] Bakhteri, J., W. Omar, and A. M. Makhtar. 2002. A Critical Review of the

Reinforced Concrete Columns Concealing Rain Water Pipes in Multistorey Buildings.

Journal of Civil Engineering. 14(2): 39-52.

[2] Jahangir Bakhteri and Sayd Ahmad Iskandar, 2005.“Experimental study of

reinforced concrete columns concealing rain water pipes”, Jurnal Teknologi,

[3] Yukawa, Y., T. Ogata, K. Suda, and H. Saito. 1999. Seismic Performance of

Reinforced Concrete High Pier with Hollow Section. Proc. of JSCE. 613/V(42):103-120.

[4] Yeh, Y. K., Y. L. Mo, and C. Y. Yang. 2000. Full Scale Tests on Ductility, Shear

Strength and Retrofit of Reinforced Concrete Hollow Columns (II). Report No.

NCREE-00-025, NCREE. Taipei, Taiwan.

[5] Iemura, H., K. Izuno, S. Fujisawa, and Y. Takahashi. 1994. Inelastic Earthquake

Response of Tall RC Bridge Piers with Hollow-Section. Proceedings of 9th Japan

Earthquake Engineering Symposium.1483-1488.

[6] Iemura, H., Y. Takahashi, K. Tanaka, and S. Maehori. 1998. Experimental Study on

Seismic Performance of RC High Piers with Hollow Section. Proceedings of 10th Japan

Earthquake Engineering Symposium. 2105-2110.

[7] Poston, R. W., T. E. Gilliam, Y. Yamamoto, and J. E. Breen. 1985. Hollow Concrete

Bridge Pier Behavior. ACI Journal. November-December: 779-787.

[8] Mander, J. B., M. J. N. Priestley, and R. Park. 1983. Behavior of Ductile Hollow

Reinforced Concrete Columns. Bulletin of the New Zealand National Society for

Earthquake Engineering. 97(7): 1969-1990.

[9] Inoue, S., and N. Egawa. 1996. Flexural and Shear Behavior of Reinforced Concrete

Hollow Beams under Reversed Cyclic Loads. Proceedings of 11th World Conference

on Earthquake Engineering. Paper No.1359.

[10] James G. MacGregor, James K. Wight 2009: Reinforced concrete mechanics and

design. Upper Saddle River, NJ : Prentice Hall.

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[11] Mansur.M.A,Kiang-Hwee.tan,1999: concrete beam with opening: analysis &

design, Florida:CRC press LLc.

[12] W.H.Mosley,J.H.Bungey,R.Hulse 1999: Reinforced concrete Design, New York:

Palgrave.

[13] BS 8110. 1997. Structural Use of Concrete, Part:1 Code of Practice for Design and

Construction , Part 2: Code of Practice for Special Circumstances. London,

U.K: ,British Standards Institution.

[14] BS 5328. 1997. Part 2: Method for Specifying Concrete Mix. London, U.K:

British Standard Institution.

[16] American Concrete Institute (ACI 318). 2008. Building Code Requirements for

Reinforced Concrete. USA

[17] M.Nadim Hassun, Akthem Al-Manaseer 2008: Structural Concrete /Theory And

Design, ,john Wiley & Sons INC. United States of America.

[18] Beer Ferdinand P., Johnston,E.Russell 1925: mechanics of material, 2th ed.Fakhr

Razi, Tehran.

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