PERPUSTARAAN UMP

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FINITE ELEMENT ANALYSIS OF RC DEEP ) BY CARBON

FIBER REINFORCED POLYMER (CFRP)

SEOW CHUN MUN

Report submitted in partial fulfilment of the requirements

for the award of the degree of

Bachelor of Eng (Hons.) Civil Engineering

Faculty of Civil Engineering and Earth Resources

UNIVERSITI MALAYSIA PAHANG

JUNE 2015

ABSTRACT

The research was to deal with overall behaviour of reinforced concrete deep beams with openings strengthened and un-strengthened by carbon fiber reinforced polymer at the shear span near support. The major objectives of the research are to determine the load-deflection curve, crack pattern and effects of opening shape for each beam with and without CFRP strengthening as well as identifying the most effective strengthening method. Due to limited research in numerical approach, this research was conducted by validating the finite element modelling results with experimental results. A total of eleven (11) beams with dimension of 120 x 600 x 2400 mm were modelled as simply supported beams in three-dimensional (31)) analysis by using finite element program, Ansys 12.0. In the research, two (2) types of opening shapes, rectangular (270 x 600 mm) and circularised rectangular (270 x 330 mm, 0 270 mm) openings were placed at the mid shear span of the beams. In addition, reinforcement used was 2T16 for bottom bar, 2T10 for top bar, R6-300c/c for shear link and R6-150c/c for riser bar. Based on the analytical results, all the beams were failed in shear mode with cracking diagonally from the support to the sharp edge of the rectangular opening and around the circular edge of circularised rectangular opening. By comparing with solid beam, rectangular and circularised rectangular openings have resulted into a reduction in the beam bearing capacity by 70.6% and 68.2% respectively. As for CFRP strengthening beams with vertical surface wrap, horizontal surface wrap, vertical U-wrap and horizontal U-wrap, respectively, an increment of 10.4%, 13.6%, 28.0% and 36.0% for rectangular opening beams and 11.1%, 22.2%, 40.7% and 51.9% for circularised rectangular opening beams in terms of strength regain. Generally, there is good agreement on the crack patterns between FEA and experimental results.

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ABSTRAK

Kajian mi dijalankan bertujuan untuk mengkaji sifat dan kelakuan rasuk konkrit bertetulang dalam yang mempunyai pembukaan web diperkukuhkan dan tidak diperkukuhkan dengan gentian karbon polimer bertetulang (CFRP) di rentang ricih terdekat sokongan. Objektif utama kajian mi adalah untuk menentukan graf beban-pesongan, corak retakan dan kesan rasuk bagi setiap pembukaan bentuk dengan atau tanpa pengukuhan CFRP serta mendapatkan kaedah pengukuhan yang paling berkesan. Oleh kerana penyelidikan yang terhad dalam simulasi berangka, kajian mi dijalankan bagi mengesah keputusan FEM dengan keputusan eksperimen. Sebanyak sebelas (11) rasuk dengan dimensi 120 x 600 x 2400 mm telah dimodelkan sebagai rasuk disokong mudah dalarn analisis tiga-dimensi (3D), menggunakan program FEM, ANSYS 12.0. Dalam kajian mi, dua (2) jenis bentuk pembukaan, iaitu segi empat tepat (270 x 600 mm) dan segi empat tepat edaran (270 x 330 mm, 270 mm 0) diletakkan di pertengahan rentang ricih. Di samping itu, tetulang yang digunakan adalah 2T16 bagi bar bawah, 2T10 bagi bar atas, R6-300c / c bagi pautan ricih dan R6-150c/c bagi bar lintang. Berdasarkan keputusan analisis, semua rasuk adalah gagal dalam mod ricih dengan retakan yang menyerong dari sokongan ke pinggir tajam pembukaan segi empat tepat dan sekitar pinggir bulat pembukaan segi empat tepat edaran. Berdasarkan perbandingan dengan rasuk pepejal, segi empat tepat dan segi empat tepat edaran telah menyebabkan pengurangan kapasiti rasuk sebanyak 70.6% dan 68.2% masing-masing. Bagi rasuk diperkukuhkan oleh CFRP dengan pembalutan permukaan (menegak), pembalutan permukaan (mendatar), pembalutan-U (menegak) clan pembalutan-U (mendatar), peningkatan sebanyak 10.4%, 13.6%, 28.0% dan 36.0% bagi rasuk pembukaan segi empat tepat serta 11.1%, 22.2%, 40.7% dan 51.9% bagi rasuk pembukaan segi empat tepat edaran dari segi kapasiti kekuatan masing-masing. Secara umumnya, persamaan yang baik telah diperolehi bagi corak retakan hasil FEA dan keputusan eksperimen.

TABLE OF CONTENTS

Page

SUPERVISOR'S DECLARATION

STUDENT'S DECLARATION

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK

TABLE OF CONTENTS vii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xv

LIST OF ABBREVIATIONS xvi

CHAPTER 1 INTRODUCTION

1.1 Background 1

1.1.1 Finite Element Analysis 2 1.1.2 Deep Beam 2 1.1.3 Openings 2 1.1.4 Carbon Fiber Reinforced Polymer 3

1.2 Problem Statement 3

1.3 Research Objectives 4

1.4 Scopes of Research 4

1.5 Significances of Research 5

1.6 Overview of Research 6

CHAPTER 2 LITERATURE REVIEWS

2.1 Introduction of Reinforced Concrete Deep Beams 7

2.2 Reinforced Concrete Deep Beams with Large Openings 8

2.2.1 Function of RC Deep Beams with Large Openings 8

2.2.2 Advantages of RC Deep Beams with Large Openings 9 2.3 Behaviour of Reinforced Concrete Deep Beams with Large Openings 9

VII

VIII

2.3.1 Effects of Opening Shapes 10 2.3.2 Effects of Opening Sizes 11 2.3.3 Effects of Opening Locations 11

2.4 Material Modeling of RC Deep Beams with Large Openings 12

2.4.1 Concrete 12 2.4.2 Steel Reinforcement 12 2.4.3 Carbon Fiber Reinforced Polymer (CFRP) 13

2.5 Finite Element Analysis 14

2.5.1 Linear Analysis 14 2.5.2 Nonlinear Analysis 14

2.6 Strengthening of RC Deep Beam with Large Openings 15

2.6.1 Experimental Approach 15 2.6.1.1 Internally Strengthening 15 2.6.1.2 Externally Strengthening 16

2.6.2 Finite Element Modeling 17 2.6.2.1 Internally Strengthening 18 2.6.2.2 Externally Strengthening 18

2.7 Results of Finite Element Analysis (FEA) 19

2.7.1 Ultimate Loads 19 2.7.2 Crack Patterns 21 2.7.3 Load Deflection Behaviours 22

2.8 Verification on Finite Element Analysis 23

2.9 Summary 25

CHAPTER 3 RESEARCH METHODOLOGY

3.1 Introduction 28

3.2 Details of the Research 29

3.2.1 Beam Model Configurations 30 3.2.2 Control Beam 31 3.2.3 Deep Beams with Openings 32

3.2.3.1 Deep Beam with Rectangular Openings 32 3.2.3.2 Deep Beam with Circularised Rectangular Openings 33

3.2.4 Deep Beam with Opening Strengthened by CFRP 34 3.2.4.1 Deep Beam with Rectangular Opening Strengthened 35

by CFRP (Surface) 3.2.4.2 Deep Beam with Rectangular Opening Strengthened 36

by CFRP (U-wrap) 3.2.4.3 Deep Beam with Circularised Rectangular Opening 36

Strengthened by CFRP (Surface)

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3.2.4.4 Deep Beam with Circularised Rectangular Opening 36 Strengthened by CFRP (U-wrap)

3.3 Data Pre-Processing 37

3.3.1 Material Parameters 37 3.3.2 Geometrical Joints 43 3.3.3 Geometrical Lines 45 3.3.4 Elements Modeling 45 3.3.5 Openings 46 3.3.6 Bar Reinforcement 47 3.3.7 Nodes Merging 48 3.3.8 Supports and Loads 49 3.3.9 Carbon Fiber Reinforced Polymer (CFRP) Modeling 50 3.3.10 Mesh Generation 51 3.3.11 Numbering Control 51

3.4 Finite Element Nonlinear Analysis 53

3.4.1 Solution and Controls 53 3.4.2 Solve Analysis Solution 54

3.5 General Post-Processing 54

3.5.1 Crack Patterns 55 3.5.2 Load-Deflection Curves 55 3.5.3 Stress and Strain Contours 55

3.6 Validation of Results 56

3.7 Methodology Chart 57

CHAPTER 4 RESULTS AND DISCUSSIONS

4.1 Introduction 58

4.2 Load-Deflection Behaviour 58

4.2.1 Unstrengthen RC Deep Beams with Openings 59 4.2.2 Strengthened RC Deep Beams with Openings 60

4.2.2.1 Rectangular Opening 60 4.2.2.2 Circularized Rectangular Opening 61

4.3 Crack Pattern 64

4.3.1 Control Beam 65 4.3.2 Unstrengthen RC Deep Beams with Openings 65 4.3.3 Strengthened RC Deep Beams with Openings 66

4.4 Strain Distribution 68

4.4.1 Control Beam 68 4.4.2 Unstrengthen RC Deep Beams with Openings 69

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4.4.3 Strengthened RC Deep Beams with Openings 69

4.5 Stress Contour 71

4.5.1 Control Beam 71 4.5.2 Unstrengthen RC Deep Beams with Openings 72 4.5.3 Strengthened RC Deep Beams with Openings 73

4.6 Validation between FEA Results and Experimental Results 74

4.6.1 Load-Deflection Curve 74 4.6.2 Crack Pattern 76

4.7 Summary 78

CHAPTER 5 CONCLUSION AND RECOMMENDATIONS

5.1 Conclusion 80

5.2 Recommendation for the Future Research 81

REFERENCES 83

APPENDICES

A Final Year Project Gantt Chart (Semester 1) 86

B Final Year Project Gantt Chart (Semester 2) 87

C Crushing Patterns at Ultimate Load 88

Xi

LIST OF TABLES

Table No. Title Page

2.1 Comparisons ultimate loads between experimental and ANSYS 20

2.2 Findings of literature review for unstrengthen beam 25

2.3 Findings of literature review for strengthened beam 26

3.1 Details of research parameters 30

3.2 Specific data of listed objects 37

3.3 Details of material models 39

3.4 Coordinates of the geometrical joints for control beam model 44

4.1 Comparison of ultimate load bearing capacity 63

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LIST OF FIGURES

Figure No. Title Page

2.1 Deep beam with openings 8

2.2 Elements of deep beams with openings in ANSYS 10

2.3 Deep beam with opening strengthened by steel reinforcement 16

2.4 Deep beams with openings strengthened by CFRP 19

2.5 Typical cracking signs occurring in finite element models 21

2.6 Load-deflection plots for the four beams in ANSYS FE models 22

2.7 Comparison between principal strain from FEA and crack pattern 23 from experimental for control beam

2.8 Comparison between principal strain from FEA and crack pattern 23 from experiments for beam with square openings

2.9 Crack pattern at failure for control beam 24

3.1 Beam reinforcement and CFRP details (unit: mm) 29

3.2 The flow of beam model configurations in the research 31

3.3 Beam model configurations with CFRP arrangement 31

3.4 Control beam detailing 32

3.5 Deep beam with rectangular openings 33

3.6 Deep beam with circularised rectangular openings 34

3.7 Deep beam with rectangular openings strengthened by CFRP 35

3.8 Deep beam with circularised rectangular openings strengthened 35 by CFRP

3.9 Selection of material element in ANSYS + CivilFEM 38

3.10 Real constant setting in ANSYS + CivilFEM 38

3.11 Definition of material model behaviour in ANSYS + Civi1FEM 39

XII I

3.12 Young's modulus and Poisson ratio for Material I (Concrete) 40

3.13 Material's coefficient for Material 1 (Concrete) 40

3.14 Young's modulus and Poisson ratio for Material 2 (main 41 reinforcement)

3.15 Yield stress for Material 2 (main reinforcement) 41

3.16 Young's modulus and Poisson ratio for Material 3 (shear 42 reinforcement)

3.17 Yield stress for Material 3 (shear reinforcement) 42

3.18 Young's modulus and Poisson ratio for Material 4 (CFRP fabric) 43

3.19 Yield stress for Material 4 (CFRP fabric) 43

3.20 Work Plane of constructed geometrical joints in ANSYS 44

3.21 Work Plane of constructed geometrical lines in ANSYS 45

3.22 'Concrete elements (Solid 65) for control beam 46

3.23 Beam models with openings 47

3.24 Steel bar reinforcement for control beam 48

3.25 Numbering control for nodes merging 49

3.26 Supports and loads for control beam in ANSYS 50

3.27 Real constant for CFRP element (Solid 46) 51

3.28 Numbering control of keypoints for CFRP fabric sheet (Solid 46) 52

3.29 RC deep beam model with rectangular opening strengthened by 52 CFRP

3.30 Solution control setting before running analysis 53

3.31 Solve the analysis solution in current load step 54

3.32 Setting for crack patterns 55

3.33 Methodology flow chart 57

4.1 Load-deflection curve for unstrengthen beam model 59

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4.2 Load-deflection curve for rectangular opening beam model 61

4.3 Load-deflection curve for circularized rectangular opening model 62

4.4 Stages of cracking opening 64

4.5 Crack pattern for control beam (CB) 65

4.6 Crack pattern for unstrengthen beam models with openings 66

4.7 Crack pattern for rectangular opening beam models 67

4.8 Crack pattern for circularized rectangular opening beam models 67

4.9 Strain distribution for control beam (CB) 68

4.10 Strain distribution for unstrengthen beams with openings 69

4.11 Strain distribution for rectangular opening beams 70

4.12 Strain distribution for circularized rectangular opening beams 71

4.13 Stress contour for control beam (CB) 72

4.14 Stress contour for unstrengthen beams with openings 72

4.15 Stress contour for rectangular opening beams 73

4.16 Stress contour for circularized rectangular opening beams 74

4.17 Load-deflection curve for experimental versus FEM of CB 75

4.18 Load-deflection curve for experimental versus FEM of RB 75

4.19 Load-deflection curve for experimental versus FEM of RBS4 76

4.20 Crack pattern for experimental versus FEM of CB 77

4.21 Crack pattern for experimental versus FEM of RB 77

4.22 Crack pattern for experimental versus FEM of RBS4 78

LIST OF SYMBOLS

m Metre

mm Millimetre

kN Kilo Newton

N/mm2 Newton per millimetre square

MPa Mega Pascal

G35 Garde 35

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LIST OF ABBREVIATIONS

RC Reinforced Concrete

CFRP Carbon Fiber Reinforced Polymer

FEM Finite Element Modeling

FEA Finite Element Analysis

3D Three Dimensional

FRP Fiber Reinforced Polymer

GFRP Glass Fiber Reinforced Polymer

EC2 Eurocode 2

EC3 Eurocode 3

ACI American Concrete Institute Code

BS British Code

L Length of Beam

A Shear Span of Beam

H Depth of Beam

NL Number of Layer

LS Load Step

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CHAPTER 1

INTRODUCTION

1.1 Background

With the rapid growth of construction work in many developing countries

nowadays especially in Malaysia, deep beam with opening design and its behavior

prediction is a subject of considerable relevance. Deep beam with opening may be of

different shapes, sizes and are usually located near to supports where shear is dominant.

In construction, deep beam with openings are frequently required for mechanical and

electrical conduits or even for means of passageways, such as openings for doors and

hallways in building. By allowing openings in deep beams for utilities to pass, there can

be reduction in building storey height as well as cost effective. However, realizing the

effect of opening towards the strength of deep beam itself in term of shear force and

bending moment, today, a relatively large number of studies have investigated the

different main factors included in the problem: shear span-to depth ratio, cross sectional

properties, amount, type and location of web reinforcement, concrete strength, size,

shape and location of opening (Campione & Minafo, 2012). Anyhow, these studies gave

more emphasis on the behavior of deep beam with opening and no comprehensive study

has investigated the effects of carbon fiber reinforced polymer (CFRP) in reinforced

concrete deep beam with openings. Also, study to identify the most effective wrapping

method by using carbon fiber reinforced polymer seems to be lacking.

2

1.1.1 Finite Element Analysis

Finite element analysis is a type of numerical method which provides solutions

to problems that would otherwise be difficult to obtain. It is originally developed for

solving solid mechanics problems. However, it is a commonly used method for

multiphysics problems nowadays. In term of fracture, it is most often involved the

determination of stress intensity factors. In the field of civil engineering, finite element

analysis is usually used for structure analysis such as cantilever, bridge, oil platform and

reinforced concrete frame.

1.1.2 Deep Beam

Deep beam are defined as members loaded on one face and supported on the

opposite face so that compression struts can develop between the loads and the supports.

It is strong in resisting bending moment as well as shear force. Therefore, it has been

widely used in the constructing of transfer girders in offshore structures and foundations,

walls of bunkers, load bearing walls in buildings, plate elements in folded plates, pile

caps, floor diaphragm and shear walls.

1.1.3 Openings

Openings in deep beams are implemented in construction to provide passage for

a network of pipes and ducts. Thus, it can reduce the building storey height as well as

cost of construction. However, creating an opening in the deep beam will reduce the

stiffness which can leads to cracking and other complicated structural response.

Therefore, a good rehabilitation method must be applied to deep beams with openings

in order to regain the strength for better bearing capacity.

3

1.1.4 Carbon Fiber Reinforced Polymer

Carbon fiber reinforced plates are produced by pultrusion process with precise

material properties. It is mostly used for flexural strengthening of dynamic and static

loaded structures such as bridges, beams, ceilings or walls. While carbon fiber

reinforced polymer fabrics are bidirectional fabrics with carbon, glass and ararnid fibers.

It was commonly used for seismic retrofitting and shears strengthening.

Essentially, this chapter provides an overview of what motivates the researcher

to carry out the study. It begins with a brief background where this study would be

conducted, followed by the statement of the problem,, research objectives, research

questions and significance of the study.

1.2 Problem Statement

The use of deep beams at lower levels in tall buildings for both residential and

commercial purposes has increased rapidly because of their convenience and economic

efficiency. In order to allow utilities to pass through the beam and without increasing

the building floor height, an opening is required to construct at the deep beam. However,

the opening near the support of deep beam will reduce the strength in term of shear

force as well as bending moment resistance and different shape of opening will brings

different degree of strength reduction towards the deep beam structure. Besides that, the

stiffness of the deep beam will also be affected by creating a large opening with

different shapes. Furthermore, a large opening is also affects the cracking pattern on the

RC deep beam and causing immediately shear failure. Thus, the overall serviceability of

the RC deep beam will be lower after an opening is created on it. Traditionally,

engineers are solving this problem by strengthening the 'deep beam by installing steel

plate but it might having high possibilities to damage the concrete structure or the

reinforcement inside the concrete during bolting the steel plate in order to attach to the

deep beam. Hence, the implementation of latest technology, carbon fiber reinforced

Polymer which also have very high tensile strength about 3900 N/mm2. The efficient

roll-on installation process enables the CFRP to be applied in a very short time. This

4

can save considerable working time and also gives greater flexibility in construction

planning for strengthening work.

1.3 Objectives of the Research

The research is consisted several principal aims which are important to achieve

certain expected results:

i. To detennine the behavior of reinforced concrete deep beam with opening

strengthened and unstrengthen by carbon fiber reinforced polymer in term of

load-deflection curve, crack pattern as well as stress and strain contours

ii. To identify the effects of openings in the size and shape, i.e. rectangular and

circularized rectangular

iii. To identify the most effective strengthening method for deep beam with opening

by carbon fiber reinforced polymer

1.4 Scopes of the Research

In this particular research, commercial software, ANSYS, is adopted to run the

numerical analysis of finite element method to solve the approximate solutions of

stresses, strains and displacements at each node of elements in 3-dimension. Numerical.

analysis will be done to identify the behaviour of RC deep beams with large openings as

well as the behaviours of beams after strengthening using CFRP. A total of eleven deep

beams are considered in this research. A deep beam without any opening acts as a

control beam while the remaining modeled deep beams are with openings. One of the

modeled deep beams with opening will not be strengthened while the remaining two

deeps beams will be modeled with different strengthening methods to identify the most

effective strengthening method by applying CFRP around the openings. Two most

effective strengthening methods with CFRP will be selected through trial and error in

Ansys Finite Element Modeling. The simply supported deep beam with opening before

and after CFRP strengthening will be tested by applying four-point-loading to evaluate

the crack pattern, load deflection failure, stress and strain contours. The deep beams are

5

tested to failure by constantly increasing the force on the both point loads. The results

from the Finite Element Analysis will be compared with the experimental results to

determine the similarities and differences between the behaviours of deep beams.

The dimensions of the deep beam with opening that being studied are 120 x 600

mm for the cross section of width and height and length of 2400 mm. The size of

opening has been decided to be 45% of reduction from the depth of the RC deep beam

which is 270 mm in height for both models of rectangular and circularized rectangular

opening. Meanwhile, the diameter of steel reinforcement for the RC deep beams with

openings at tension region, which are bottom reinforcement, is 16 mm with a total of

two reinforced steel bars. The diameter of steel reinforcement for the compression

region, which is top region, is 10 mm with the number of two reinforcement steel bars.

The shear link being used for this study is decided to be mild steel with 6 mm in

diameter. The concrete grade used for the RC deep beam model in this research is set at

grade 35 (G35).

1.5 Significance of the Research

Installed deep beam without opening need to increase the building storey height

in order to ensure each floor have sufficient clear storey height, thus delaying

construction progress and additional cost required especially for high rise building

construction project. Since such problem is becoming more and more common in many

populated countries which having rapid development such as Malaysia, deep beams

with large openings strengthened by carbon fiber reinforced polymer needs to be

practiced. Indeed, it can improve the durability and life span of the structure besides

increasing the load bearing capacity. Moreover, the installation process of carbon fiber

reinforced polymer will not damage the concrete structure compare to steel plate

installation. The implementation of deep beam with opening strengthened by carbon

fiber reinforced polymer not only to find a solution for reduce building storey height, in

addition the use of deep beams with openings will save the construction cost since it has

minimize the overall building weight as well as improving the safety during

Construction

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1.6 Overview of the Research

Chapter one introduced the background of the RC deep beams with openings,

carbon fiber reinforced polymer strengthening and Finite Element Analysis. In this

chapter also presented the challenges that are occurred in the construction site nowadays.

There are also other subtopics in this chapter including research objectives, scope of the

research and significance of research.

Chapter two is the literature review that- listing all the findings of researches,

study of journals and articles that done by the other authors. In this chapter, the

functions and negative effects according to shapes, sizes as well as location are

discussed. Subsequently, the different types of material properties in Finite Element

Modeling and strengthening methods proposed by other authors are listed and further

discuss the suitability for the research. Lastly, the results from Finite Element Analysis

and verification with experimental results are also explained and discussed in this

chapter.

Chapter three will discuss the research methodology that will be implemented to

conduct the whole process of simulation research. From obtaining material properties,

modeling of beams and CFRP, analyzing the beam models, abstracting result data and

validating and justifying the results of the research is clearly stated in the chapter.

Chapter four will present and discuss on the data and results obtained from FE

Analysis including crack patterns, load-deflection behaviours and stress-strain contours.

Load-deflection curve will be plotted and the result will be compared with experimental

results for validation purpose.

Chapter five is the conclusion and recommendation, the recommendation to

improve the research after analyzing the results. The conclusion also considered as the

last chapter, which concluding the suitability and effectiveness of carbon fiber

reinfored polymer on strengthening RC deep beam with large openings.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction of Reinforced Concrete Deep Beams

Reinforced concrete (RC) deep beams are sfructural members commonly used as

load-distribution structural elements which load is transferred to the support by a

compression thrust joining the loading and reaction point. Alsaeq, (2014, as cited Yang

et al, 2006) clarified that deep beams should be loaded on loading points and supported

on reaction points so that compression struts can develop between the loads and

supports. RC deep beams are characterized by shear span and depth ratio falls between

1 and 2 as well as subjected with loads within support zones. Therefore, Campione

(2012) claimed that their strength is generally controlled by shear rather than flexural

strength. Besides that, they are also considered as host zones of static and geometric

discontinuities.

According to ACT 318-08 code, deep beams have clear span which is equal to or less

than four times the overall member depth. In addition, the concentrated loads in beam

region are twice the member depth from the face of the support.

S

2. 2 Reinforced Concrete Deep Beams with Large Openings

In contrast to solid deep beams, a good deal of work has been done with deep

beams with openings by engineers in the last few years. The web openings in deep

beams are conducted in different shapes, sizes and location due to the construction

requirement as well as the reduction of shear and flexural strength of the beam

structures. Sometimes, openings are made with a core boring technique, and it may be

necessary to determine the mechanical properties of the concrete in existing structures

as shown in Figure 2.1. Campione and Minafo (2012) justified that if openings intercept

the stress field joining the loading and the reaction point; it is obvious that the simple

load path changes and the shear capacity are reduced.

Figure 2.1: Deep beam with openings

Source: Kumar (2012)

2.2.1 Function of RC Deep Beams with Large Openings

Large openings are inevitably installed in the deep beam structure members are

frequently required in order to create electrical and mechanical conduits in civil plants

9

like electricity wiring, hydraulic piping and computer network or even for means of

passageways such as openings for doors and windows in buildings (Kumar, 2012).

2.2.2 Advantages of RC Deep Beams with Large Openings

In the practical life of construction, deep beams with large openings are widely

used to provide convenient passage of environmental services which reduce the storey

heights of buildings and the overall weight of the concrete beams as it improves the

demand on the supporting structural frame both under gravity loading and seismic

excitation, indirectly it saved construction cost (Hafiz, Ahmed, Barua & Chowdhury,

2014).

2.3 Behaviour of Reinforced Concrete Deep Beams with Large Openings

Large openings on reinforced concrete deep beams as shown in Figure 2.2 which

are also known as structural penetrations are effective in term of reducing building

storey height and construction cost, but it also issues problems toward the structural

behaviour based on different parameters such as size, shape and location of web

opening, shear span-to-depth ratio, cross sectional properties, amount, type and location

of web reinforcement as well as concrete strength.

Kaur, Singh and Shafiq (n.d.) also found that concrete and steel have different

behaviours in compression as well as tension mode. Concrete is affected by the

confinement due to the stirrups and the buckling of the steel bars in compression mode.

In tension mode, the tensile loads are carried by steel reinforcement even though there

are cracks in concrete in order to achieve its full load. Concrete and steel may lead to

longitudinal cracking which causing several durability problems, excessive deformation

and a decrease in load carrying capacity especially when the bonding between concrete

and steel is weaken.

10

Figure 2.2: Elements of deep beams with openings in ANSYS

Source: Alsaeq (2014)

2.3.1 Effects of Opening Shapes

Most of the researches and studies are focus on four types of opening shape

which are circular, square, rectangular and elliptical as these openings are mostly

constructed openings on reinforced concrete deep beams in the industry. For example,

reinforced deep beams with circular openings are used to accommodate service pipes

and electrical supply while reinforced concrete deep beams with rectangular openings

are used to accommodate rectangular air conditioning ducts.

Generally, square opening reduces the ultimate load more than the circular

opening with the same size due to stress concentration occurs at the existing orthogonal

corners in square opening (Hafiz, et al., 2014). In addition, Alsaeq (2014) concluded

that using a circular opening instead of a square one with the equivalent size can save a

19% of structural strength. Furthermore, Kaur, Singh and Shafiq (2011) found that

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reinforced concrete deep beams with elliptical and rectangular Opening have higher

ultimate load capacity compared to solid and square Opening beam.

2.3.2 Effects of Opening Sizes

Construction of an opening on a deep beam caused the loss of concrete area,

which directly results in the reduction of resistance in the term of strength and axial

stiffness. The way penetration area is configured, the flexural or shear stiffness and

deflection resistance of the beam is also affected (Kaur, Singh, & Shafiq, n.d.). On the

other hand, Hafiz and his colleagues (2014) have justified that there is no effect on the

ultimate load capacity towards a deep beam structure if the diameter of a circular

opening of a reinforced concrete deep beam is less than 44% of the overall depth of the

beam. However, the ultimate load capacity will experience at least 34.29% of reduction

if the diameter of a circular opening of a reinforced concrete deep beam is more than 44°A

of the overall beam depth. Besides that, Campione and Minafô (2012) found that the

concrete compressive strength on the load-carrying capacity significantly decreased in

deep beams with openings depended on span-to-depth ratio which equivalent to the size

of the openings.

2.3.3 Effects of Opening Locations

Campione and Minafo (2012) have proposed that the web opening position in

the beam is one of the main factors affecting the beam structural strength based on a

comparative analysis of the experimental, results. Moreover, the researchers found that

the failure mode mainly depended on the position of the opening and the highest load

capacity reduction occurred when the opening was placed within the interior shear span

(Campione, et al., 2012).