THE EFFECT OF LOCATION OF POST DRILLED WEB OPENING ON …eprints.utm.my/id/eprint/78553/1/ChowHanSengMFKA2017.pdf · pemasangan perkhidmatan ini di bawah lantai yang lebih rendah

THE EFFECT OF LOCATION OF POST DRILLED WEB OPENING ON THE

STRENGTH OF REINFORCED CONCRETE BEAM

CHOW HAN SENG

A project report submitted in partial fulfilment of the

requirements for the award of the degree of

Master of Engineering (Structure)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

MAY 2017

iii

DEDICATION

Specially dedicated to my father and mother

iv

ACKNOWLEDGEMENTS

I would like to thank everyone who had contributed to the successful completion of

this project. I would like to express my gratitude to my research supervisor, Prof. Dr.

Redzuan for his invaluable advice, guidance and his enormous patience throughout

the development of the research.

v

ABSTRACT

The construction of modern buildings requires many pipes and ducts in order

to accommodate essential services such as electricity, air conditioning, telephone,

and network cables. Web openings in Reinforced Concrete (RC) beams enable the

installation of these services under lower floor to floor height without compromising

any architectural headroom. However, the requirement of opening often reaches the

engineers and contractors after the beam has been constructed. As such, there is a

need to reassess the new strength of the beam with the newly added opening without

the placement of trimmer reinforcement bar. Methods to assess the reduced strength

of the RC beams due to post drilling these opening are often complicated. To

overcome this, a research has been carried out with the aim to provide simple

guidance to engineers to access the new strength of the RC beams due to small post

drilled transverse circular web openings at different location of the beam. RC beams

with a series of opening at different location were analysed using LUSAS, by

conducting nonlinear analysis to determine the new strength of the RC beam. A

graph of relative load bearing capacity of an RC beam with respect to location of

post drilled web opening is proposed to aid design engineers to assess the beam

capacity without a need for detail calculation.

vi

ABSTRAK

Pembinaan bangunan moden memerlukan banyak paip dan saluran untuk

menampung perkhidmatan asas seperti elektrik, penghawa dingin, telefon, dan kabel

rangkaian. Bukaan web dalam rasuk concrete bertetulang (RC) membolehkan

pemasangan perkhidmatan ini di bawah lantai yang lebih rendah ke lantai yang lebih

tinggi tanpa menjejaskan mana-mana ketinggian lantai bangunan. Walau

bagaimanapun, keperluan untuk menebuk lubang sering sampai kepada jurutera dan

kontraktor selepas rasuk telah dibina. Oleh itu, terdapat keperluan untuk menilai

semula kekuatan baru rasuk dengan lubang yang baru ditambah tanpa dipasang

tetulang trimmer tetulan. Kaedah untuk menilai kekuatan baru rasuk RC selepas

penggerudian lubang ini sering rumit. Untuk mengatasi masalah ini, satu kajian telah

dijalankan dengan tujuan untuk memberi panduan mudah untuk jurutera untuk

mengakses kekuatan baru rasuk RC selepas ia digerudi untuk membuat lubang kecil

pada web di lokasi yang berbeza. Rasuk RC dengan lubang yang ditebuka di lokasi

yang berbeza dianalisis menggunakan LUSAS, iaitu dengan menjalankan analisis

tidak lelurus untuk menentukan kekuatan baru rasuk tersebut. Graf pengurangan

keupayaan galas beban rasuk RC lawan lokasi lubang pada web telah dicadangkan

untuk membantu jurutera reka bentuk untuk menilai kapasiti rasuk tanpa perlu

membuat kengiraan yang baru yang sukar.

vii

CHAPTER

1

TABLE OF CONTENTS

TITLE PAGE

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

INTRODUCTION 1

1.1 Problem Statement

1.2 Aim

1.3 Objectives

1.4 Scope of Work

1.4.1 Reinforced Concrete Beam - Normal Beam

1.4.2 Dimension of Opening

1.4.3 Location of Opening

1.4.4 Loading

1.4.5 Steel Reinforcement Layout and Arrangement

1.5 Model verification

2 LITERATURE REVIEW

2.1 Behaviour of Concrete Beam with Opening

2.2 Common Model of RC Beam with Opening

6

6

7

2.3 Finite Element Method for Reinforced Concrete Beam 8

2.4 Experimental RC Beam with Opening 9

METHODOLOGY 11

3.1 Model Verification 12

3.2 Modelling Parameter 12

3.2.1 Analysis Software 12

3.2.2 Mesh Properties 13

3.2.3 Geometric Line Properties 14

3.2.4 Geometric Surface Properties 14

3.2.5 Material Properties 15

3.2.6 Boundary Condition 17

3.2.7 Loading Parameters 17

3.2.8 Nonlinear & Transient Parameters 18

3.3 Beam Model 19

3.3.1 Boundary Restrain 19

3.3.2 Two Point Loaded - Simply Supported Beam 22

3.3.3 Uniformly Loaded - Simply Supported Beam 24

3.3.4 Uniformly Loaded - Fixed End Beam 25

RESULTS AND DISCUSSION 26

4.1 Model Verification 26

4.2 Two Point Loaded - Simply Supported Beam (TPL) 29

4.2.1 Bending Moment and Beam Capacity 29

4.2.2 Shear Bending Interaction and Beam Capacity 29

4.2.3 Stress Diagram (Sx) 30

4.2.4 Crack Pattern 34

4.2.5 Localize Stress Diagram around Opening (Smax) 36

4.2.6 Localize Crack Pattern around Opening (LCP) 37

4.3 Uniformly Loaded - Simply Supported Beam (UDL) 38

4.3.1 Bending Moment and Beam Capacity 38

4.3.2 Shear and Beam Capacity 38

4.3.3 Shear Bending Interaction and Beam Capacity 39




4.3.7 Localize Crack Pattern around Opening 47

4.4 Uniformly Loaded - Fixed End Beam (FE) 48

4.4.1 Reinforcement, Shear and Bending Moment. 48




4.4.5 Localize Crack Pattern around Opening 57

4.5 Relative Beam Capacity 58

4.6 Simplified Relative Beam Capacity 61

5 CONCLUSION 63

ix

REFERENCES 64

x

LIST OF TABLES

TABLE TITLE PAGE

1. 1 Codes and Clauses 2

3.1 Mesh Properties 13

3.2 Mesh Properties Definition 13

3.3 Geometric Line Properties 14

3.4 Geometric Surface Properties 14

3.5 Reinforcement Bar 15

3.6 Concrete Properties 16

3.7 Structural Support 17

3.8 Load Parameters 17

3.9 Nonlinear & Transient Parameters 18

4.1 Relative Beam Capacity 58

xi

LIST OF FIGURES

FIGURE TITLE PAGE

1.1 Free Body Diagram of Beam with Opening underTorsion (Mansor 1998) 3

3.1 Beam Attribute 19

3.2 Beam Restrain-Pin 20

3.3 Beam Restrain - Fixed End 20

3.4 Beam Restrain - Roller 21

3.5 Two Point Loaded - Simply Supported Beam 22

3.6 Bending Moment & Shear Force Diagram 23

3.7 Uniformly Loaded - Simply Supported Beam 24


3.9 Uniformly Loaded - Simply Supported Beam 25


4.1 Flexural Crack - Beam with Opening 26

4.2 Bending Moment & Shear Force Diagram of TwoPoint Loaded Beam 27

4.3 Typical Shear Failure of a Beam without ShearReinforcement 28

4.4 Bending Moment & Shear Force Diagram (TwoPoint Loaded - Simply Supported) 29

4.5 Maximum Capacity of Beam against Location ofOpening 30

4.6

4.7

4.8

4.9

4.10

4.11

4.12

4.13

4.14

4.15

4.16

4.17

4.18

4.19

4.20

4.21

4.22

4.23

4.24

4.25

4.26

4.27

xii

T P L -S x-C on tro l 30

TPL - Sx - (2850mm, 2250mm, 2250mm) 31

TPL - Sx - (1950mm, 1650mm, 1350mm) 32

TPL - Sx - (1050mm, 750mm, 450mm, 750mm) 33

TPL - Crack Pattern - (Control, 2850mm,2550mm, 2250mm, 1950mm) 34

TPL - Crack Pattern - (1650mm, 1350mm,1050mm, 750mm, 450mm) 35

Localize Stress Diagram around Opening (Smax) 36

Localize Crack Pattern around Opening 37

Bending Moment & Shear Force Diagram (UDL - Simply Supported) 38

UDL - Sx - Control 40

UDL - Sx - (2850mm, 2550mm, 2250mm) 41

UDL - Sx - (1950mm, 1650mm, 1350mm) 42

U D L -Sx-(1050m m , 750mm, 450mm) 43

UDL - Crack Pattern - (Control, 2850mm,2550mm, 2250mm 1950mm) 44

UDL - Crack Pattern - (1650mm, 1350mm,1050mm, 750mm, 450mm) 45

Localize Stress Diagram around Opening (Smax) 46

Localize Crack Pattern around Opening 47

Bending Moment & Shear Force Diagram FixedEnd 48

Maximum Capacity of Beam against Location of Opening 49

FE - Sx - Control 50

F E -S x-(2850m m , 2550mm, 2250mm) 51

F E -S x-(1950m m , 1650mm, 1350mm) 52

4.28 F E -S x-(1050m m , 750mm, 450mm) 53

4.29 FE - Crack Pattern - (Control, 2850mm, 2550mm,2250mm, 1950mm) 54

4.30 FE - Crack Pattern - (1650mm, 1350mm,1050mm, 750mm, 450mm) 55

4.31 Localize Stress Diagram around Opening (Smax) 56

4.32 Localize Crack Pattern around Opening 57

4.33 Relative Load Capacity of Beam 59

4.34 Chart of Relative Beam Capacity against Locationof Opening 61

xiii

CHAPTER 1

INTRODUCTION

In modern building construction, transverse openings in reinforced concrete

beams are often required for the passage of utility ducts and pipes due to high

requirement of Mechanical, Electrical and Plumbing (MEP) services. These ducts

and pipes are usually placed undemeaft the soffit of the beam and are often covered

by a suspended ceiling for aesthetic purposes, thus creating an unused space (waste

of space). This results in additional overall height or reduced headroom of a building

as these unused space accumulate in each floor respectively. The significant of extra

overall height depends on the depth of space required for MEP services.

Alternatively by providing web openings will enable engineers to reduce the overall

height of the structure. The reduced overall floor to floor height becomes significant

especially in tall building construction, which will result in a more economical

design. Thus, installation of mechanical and electrical services prompt structural

engineers to provide solutions by providing opening at primary and secondary beam

of a building.

1.1 Problem Statement

As mentioned above, installation of mechanical and electrical services prompt

structural engineers to provide solutions by providing opening at primary and

secondary beam of a building. In a building refurbishment project, installation of

new mechanical and electrical services are often required, which leads to requirement

of transverse opening on a constructed beam. These beams were usually constructed

2

without the provision of these openings, with no pipe sleeve or trimmer bar installed.

As such, structural engineers are required to assess the effect of the opening on these

beams, including the reduction of beam capacity, requirement of beam strengthening,

and beam strengthening method. Dealing with a project on a fast track basis,

engineers need a simple method of assessment to provide fast and accurate decision

andjudgement.

A simple formulated assessment method, or guidance to carry out preliminary

assessment on the effect of opening on beams is often absent in design standard

available locally, such as British Standard, Eurocode, Australian Standard or

American Standard. Description given in these codes are brief, as show in Table 1.1.

Table 1.1 : Codes and Clauses

Code and Standard Description in code

AS 3600-2009(+A2) Concrete Structure <Clause 8.6.4>

ACI318R-08 <Clause 11.1.1.1>

BS 8110-1-1997

BSEN 1992-11:2004

Crack control at openings and discontinuities Reinforcement shall be provided for crack control at openings and discontinuities in a beam.

Openings in the web of a member can reduce its shear strength. The effects of openings are discussed in Section 4.7 of Reference 11.1 and in References 11.4 and 11.5. In determining Vn, the effect of any openings in members shall be considered.

No detail information

No detail information

To assess the above stated problem, engineers are required to seek from

another source of information such as reference books, research journals of similar

works or advice from experience engineers. Without a simple formulated assessment

method, engineers are required to carry out advance analysis involving complicated

analysis method such as nonlinear finite element analysis or tedious hand

calculations.

For example, the presence of transverse openings will transform a simple

beam behaviour into a more complex behaviour such as a strut tie behaviour which

3

assessment involve complicated formulas and mathematical equations, provided in a

book by Mansur (1999). These methods of analysis are often too complicated and

only to be carry out by experience engineer or a specialist. Even so, the process is

often time consuming and prompt to human error, which eventually jeopardise the

progress of a project.

Figure 1.1 Free Body Diagram of Beam with Opening under Torsion (Mansor

1998)

Thus, a research to investigate the effect of post drilled circular small web

opening at different location on a beams on the load bearing capacity of beams is

carried out, using numerical modelling with Finite Element Method (LUSAS).

1.2 Aim

The aim of this study is to provide a simple guidance to design engineers to evaluate

the effect of post drilled circular small web opening at different location on a

reinforced concrete beam on the load bearing capacity of the beam.

4

1.3 Objectives

The objective of this research is to produce a chart for engineers to evaluate the

effect of post drilled opening at different location on a reinforced concrete beam on

the load bearing capacity of the beam

1.4 Scope of Work

The scope of work includes specification of reinforced concrete beam,

dimension of opening, location of opening, loading, steel reinforcement layout and

arrangement, and model verifications. Detail is as follows.

1.4.1 Reinforced Concrete Beam - Normal Beam

Beam investigated is a normal beam with dimension of beam to be

investigated shall be 6m (length) x 600mm (depth) x 300mm (width). The dimension

investigated comply with EUROCODE (BS EN 1992-1-1:2004+A1:2014, 2014)

clause 5.3.1 (3). The beam is modelled with concrete grade of 40MPa and reinforced

with steel rebar of grade 500MPa.

1.4.2 Dimension of Opening

Opening studied in this research is a small transverse circular opening with

dimension of 150mm diameter. The dimension comply with the definition of small

opening according to recommendation by Mansur and Tan (1999).

5

1.4.3 Location of Opening

Location of opening studied is at the centroid of the beam cross section, along

the length of the beam at a 300mm interval, 450mm, 750mm, 1050mm, 1350mm,

1650mm, 1950mm, 2250mm, 2550mm and 2850mm

1.4.4 Loading

Type of loading studied are uniformly distributed load and two point load at

1/3 of span of beam respectively, loaded to failure of the beam.

1.4.5 Steel Reinforcement Layout and Arrangement

The steel reinforcement consist normal beam reinforcement with no trimmer

bar around the opening, details as follows.

Bottom Reinforcement : 2% Reinforcement

Top Reinforcement : 2H12

Shear Reinforcement : 2H12 at 300mm centre to centre spacing

1.5 Model verification

The accuracy of the model is verified by comparing crack pattern of the beam

the model with existing research.

REFERENCES

ACI 318R-08. (2008). Building Code Requirements for Structural Concrete and

Commentary.

Ahmed, M. F. (2012). Reinforced concrete beams with web openings: A state of the

art review. Materials and Design, 90-102.

AS 3600-2009(+A2). (2009). Concrete Structures. Standards Australia.

Aykac B., I. K. (2013). Flexural behavior of RC beams with regular square or

circular web openings. Engineering Structure, 56, 2165-2174.

BS 8110-1-1997. (1997). Structural use o f concrete. Code o f practice for design and

construction. BSI.

BS EN 1992-1-1:2004+A1:2014. (2014). Eurocode 2: Design o f concrete structures.

General rules and rules for buildings. BSI.

Campione G., G. M. (2012). Behaviour of concrete deep beams with openings and

low shear span-to-depth ratio. Engineering Structures(41), 294-306.

Carpinteri A., G. F. (1999). Scale Effects and Transitional Failure Phenomena of

Reinforced Concrete Beams in Flexure. European Structural Integrity Society,

Volume 24, 1-30.

Du J., K. A. (1990). Direct FEM Analysis of Concrete Fracture Specimens. J. Eng.

Mech., 10.1061/(ASCE)0733-9399(1990)116:3(605), 605-619.

Fafitis A., a. W. (1994). Nonlinear Finite Element Analysis of Concrete Deep Beams.

J. Struct. Eng., 10.1061/(ASCE)0733-9445(1994)120:4(1202)„ 1202-1220.

Hardjasaputra, H. (2014). Using evolutionary structural optimization and load paths

method in finding strut-and-tie-models for designing reinforced concrete

member. Proceeding o f 6th International Conference o f Asian Concrete

Federation.

Hardjasaputra, H. (2015). Evolutionary structural optimization as tool in finding

strut-and-tie-models for designing reinforced concrete deep beam. Procedia

Engineering(125), 995 - 1000.

65

Liao, Z. H. (2015). An extended finite element model for modelling localised

fracture of reinforced concrete beams in fire. Computers and Structures(152),

11-26.

Mahmoud, A. (2012). Strengthening of concrete beams having shear zone openings

using orthotropic CFRP modeling. Ain Shams Engineering Journal(3), 177

190.

Makoto Kawakami, T. I. (2003). Nonlinear finite element analysis of prestressed

concrete members using ADINA. Computers and Structures(81), 727-734.

Mansur M.A. (1998). Effect of Openings on the Behaviour and Strength of R/C

Beams in Shear. Cement and Concrete Composites(20), 477-486.

Mansur M.A., T. K. (1999). Concrete beams with openings: analysis and design.

Boca Raton, Florida, USA: CRC Press LLC.

Potapov, S. M. (2016). Mixed DEM/FEM Modeling of Advanced Damage in

Reinforced Concrete Structures. J. Eng. Mech., 10.1061/(ASCE)EM.1943-

7889.0001173, 04016110.

Rami A. Hawileh, T. A.-M. (2012). Nonlinear finite element modeling of concrete

deep beams with openings strengthened with externally-bonded composites.

Materials and Design, 42, 378-387.

Salam, S. a. (1977, August 25-26). Beams with openings under different stress

conditions. Proceedings o f 3rd Conference on Our World in COncrete and

Structures, 259-267.

Schlaich, J. S. (1987). Special Report: Toward a Consistent Design of Structural

Concrete. Prestressed Concrete Institute Journal, 32(3), 74 - 150.

Tan, K. a. (1996, July-August). Design procedure for reinforced concrete beams with

large web openings. ACI Structural Journal, 93, 404-411.

Yang K.H., H. E. (2006). The influence of web openings on the structural behavior

of reinforced high-strength concrete deep beams. Engineering Structures, 28,

1825—1834.

THE EFFECT OF LOCATION OF POST DRILLED WEB OPENING ON …eprints.utm.my/id/eprint/78553/1/ChowHanSengMFKA2017.pdf · pemasangan perkhidmatan ini di bawah lantai yang lebih rendah

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