FLEXURAL BEHAVIOR OF PERMANENT PRECAST...
Transcript of FLEXURAL BEHAVIOR OF PERMANENT PRECAST...
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FLEXURAL BEHAVIOR OF PERMANENT PRECAST FORMWORK BEAMS
NURULSIQQIN AISHAH BT MD YUSUF
A project report submitted in partial fulfillment of the
requirements for the award of the degree of Master of Civil Engineering (Civil – Structure)
Faculty of Civil Engineering
Universiti Teknologi Malaysia
JANUARY 2014
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Specially dedicated to my beloved
Family and friends
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ACKNOWLEDGEMENT
Foremost, I would like to express my sincere gratitude to my supervisor, Dr
Roslli Noor Mohamed for the continuous support of my master project research, for
his patience, motivation, enthusiasm, and immense knowledge. His guidance helped
me in all the time of research and writing of this thesis. I could not have imagined
having a better supervisor and mentor for my master study.
My sincere thanks also go to all technicians at Material and Structure
Laboratory, Faculty of Civil Engineering who have provided assistance at various
occasions. Their views and guidance are useful indeed.
I thank my fellow lab mate, Shariwati Mansor, for the stimulating discussions, for
the sleepless nights we were working together before deadlines, and for all the fun
we have had in the last one and half years.
Last but not the least; I would like to thank my family supporting me
spiritually throughout my life.
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ABSTRACT
This study is to explore the flexural behaviour of permanent precast formwork beam.
The total three beams that have dimensions 150 mm x 300 mm x 3000 mm have
been casted and tested. Two beams are permanent precast formwork beam and one
beam as a control beam. The beam have been tested using America Society Testing
and Material (ASTM) C78 for testing flexural strength of concrete beams using a
four point bend test by the third-point method. The results show that the permanent
precast formwork beams exhibit increased flexural strength and higher bending
capacity compared to normal concrete beam.
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ABSTRAK
Kajian ini adalah untuk mengkaji kelakuan lenturan rasuk acuan kekal
pratuang. Tiga rasuk sebagai spesimen yang mempunyai dimensi 150 mm x 300 mm
x 3000 mm telah diuji. Dua rasuk pratuang adalah rasuk acuan kekal dan satu rasuk
sebagai rasuk kawalan. Rasuk telah diuji menggunakan America Society Testing and
Material (ASTM) C78 untuk menguji kekuatan lenturan rasuk konkrit menggunakan
kaedah ujian empat titik dengan kaedah tiga titik. Keputusan menunjukkan bahawa
rasuk pratuang acuan tetap menunjukkan peningkatan kekuatan lenturan dan
keupayaan lenturan yang lebih tinggi berbanding dengan rasuk konkrit biasa.
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TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLE x
LIST OF FIGURE xi
LIST OF SYMBOL xiii
1 INTRODUCTION
1.1 Introduction
1
1
1.2 Background of study 2
1.3 Problem Statement 8
1.4 Objectives of The Study 10
1.5 Scope of The Study 10
2 LITERATURE REVIEW 11
2.1 Introduction
2.2 Concrete Formwork
2.3 Mortar Mix
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2.4 Concrete Mix
2.5 Concrete Material
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2.5.1 Cement 17
2.5.2 Aggregate 18
2.5.3 Water 20
2.6 Concrete Quality 20
2.7 Fiber-Reinforced Mortar 21
2.6 Flexural Behavior Of Concrete Beam
2.7 Glass Fibre
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2.7.1Type of Glass Fibre 27
2.7.2 Properties of Glass Fibre 28
2.6 Glass Fibre Reinforced mortar 29
2.7 Stress and Strain Distribution in Concrete Beams 32
3 METHODOLOGY 34
3.1 Introduction 34
3.2 Types of Mix Design
3.3 The Material for the Mix Design
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3.4 Beam Specimen 40
3.3 Experimental Work 41
3.3 Beam design 46
3.3 preparation of steel reinforcement 48
3.3 Preparations of Formwork 49
3.3 Method for mixing the concrete 51
3.3 Curing method 53
3.3Compression Strength Test 55
3.3 Flexural Strength Test on Mortar Prism 56
4 RESULTS AND DISCUSSIONS 57
4.1 Introduction 57
4.2 Optimum Content of Glass Fibre In Mortar Mix 58
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4.3 Cube Test for Concrete
4.4 Flexural Strength Test of Beam
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4.4.1 Load deflection analysis 65
4.4.2 Strain Distribution Across The Depth 69
4.4.3 Reinforcement Strain Analysis
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5 CONCLUSION
5.1 Introduction
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5.2 Conclusion 72
5.3 Recommendation
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REFERENCES 75
APPENDICES
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LIST OF TABLES
TABLE
NO
TITLE PAGE
1.1 Properties of glass fibre reinforced concrete. 8
3.1 Weight required for mortar mix design 33
3.2 Steel reinforcement arrangement 44
4.1 Average Compression strength of glass fibre mortar cube 59
4.2 Compressive strength of concrete for design mix 61
4.3 Comparison in term of ultimate load and deflection 65
4.4
4.5
The value of x beam Result of splitting tensile test
Comparison between experimental and theoretical on ultimate
load and ultimate moment
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LIST OF FIGURES
FIGURE
NO
TITLE PAGE
1.1 Sample of permanent precast formwork 2
1.2 The view of site construction that uses traditional timber
formwork.
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2.1 Permanent concrete formwork beam 12
2.2 Flexural behaviour of concrete beam 23
2.3 The reaction of the beam under un-cracked zone 24
2.4 The reaction of the beam under service load zone 25
2.5
3.1
The reaction of the beam under ultimate strength zone.
Ordinary Portland Cement
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34
3.2 Sand 35
3.3 Various size of aggregate. 36
3.4 Glass Fibre Polymers 37
3.5 Strain gauge. 39
3.6 Linear Variable Differential Transformers (LVDT). 40
3.7 Hydraulic jack 41
3.8 Load cell. 41
3.9 Beam testing frame 42
3.10 The Third-Point Loading Flexural Strength Test (ASTM C78). 43
3.11 The location of the loading for ASTM C78. 43
3.12 The arrangement of reinforcement and link for the beam 45
3.13 Bar bend machine used to bend steel bars into desire shape 46
3.14 Beam ready for concreting 46
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3.15 Formwork for normal concrete beam 47
3.16 (a),
(b)
The casting process of preparing permanent formwork 48
3.17 Permanent precast formworks 49
3.18 Compaction processes of cubes 50
3.19 The beam while been casted 50
3.20 The concrete was vibrated by vibrator poker 51
3.21 Curing of beam using wet gunny sacks 52
3.22 Curing process inside water tank for concrete cubes 52
3.23 The preparation of mortar cube 53
3.24 The compression test on mortar cube 53
3.25 The flexural test on mortar prism 54
3.26 The condition of the mortar prism after flexural test 54
4.1 (a),
(b)
Graph of Average Compressive Strength (Mpa) Versus
Percentage of Glass Fibre in Mortar Mix (%)
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4.2 (a),
(b)
Graph of tensile stress (Mpa) versus deflection (mm) of mortar
prism
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4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10 (a)
4.10 (b)
4.10 (c)
4.11 (a)
Optimum content of glass fibre in mortar mix design
Graph of load (kN) versus deflection (mm) for mortar
Graph of Compressive strength (MPa) versus age (day
Failure mode of concrete cube after compression test
The arrangement of flexural strength test on beam
Damage at glass fibre permanent precast formwork beam
Graph of load (kN) versus deflection (mm) for beam
The condition of the beam after flexural test done for Normal
concrete beam
The condition of the beam after flexural test done for glass
fibre permanent precast formwork beam
The condition of the beam after flexural test done for wire mesh
permanent precast formwork beam
Concrete strain distributions for normal concrete beam
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4.11(b)
4.12
Concrete strain distributions for glass fibre permanent precast
formwork beam
Graph of load (kN) versus reinforcement strain
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LIST OF SYMBOLS
As - Area of tension reinforcement
av - Shear span
b - Width of beam
bv - Width of beam, to be taken as b for a rectangular beam
d - Effective depth
E - Elastic modulus
Es - Modulus of elasticity of steel
εo - Concrete strain when peak stress is reached
εcu - Ultimate concrete strain at compression = 0.0035
εy - Design yield strain
Fcc - The resultant compressive force in the concrete
Fst - The resultant tensile force in the reinforcing steel
fcu - Characteristic strength of concrete
fy - Characteristic strength of reinforcement
h - Overall depth of beam
M - Bending moment
sv - Longitudinal spacing of link reinforcement
V - Shear force
v - Design shear stress
vc - Design shear stress for concrete
x - Neutral axis depth
γs - surface energy
Φ - Curvature
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LIST OF EQUATIONS
EQUATION NO. PAGE
Equation 2.1 15
Equation 2.2 15
Equation 4.1 73
Equation 4.2 73
Equation 4.3 73
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CHAPTER 1
INTRODUCTION
1.1 Introduction
Formworks as temporary structures are an important elements of the overall
construction plan. A temporary structure in construction affects the safety of the
workers on the job and the general public and there is also the relationship of the
temporary structure to the finished structure.
Temporary structures are sometimes incorporated into the finished work or
are removed at the end of the conclusion of their usefulness. In either case, the
contractor will have to deal with supervision work, code requirements, contract and
legal requirements, and perhaps disputes with others over the work being performed.
As far as design, drawings and specifications are concerned, they depend on the
temporary structure under consideration.
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In the new era of construction, a more efficient and advantageous type of
formwork is widely used by growing numbers of contractors, which is the permanent
precast formwork. Permanent precast formworks have been widely used in nowadays
construction because it can develop innovative, it is more economical, and more
efficient method in construction compared to the usage of temporary formwork. By
using a permanent precast formwork, the construction of building can be more
efficient; the speed of the construction can be increased as well as the cost of the
construction, and can also reduce the manpower needed at the construction site.
Figure 1.1 Sample of permanent precast formwork
1.2 Background of Study
Formwork development has paralleled the growth of concrete construction
throughout the 20th century. The increasing acceptance of concrete as a major
construction material presents the form builder a new range of problems in the
development of appropriate sheathing materials and maintenance of rigid tolerances.
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Formwork is a mould including all supporting structures, used to shape and
support the concrete until it attains sufficient strength to carry its own weight. It
should be capable of carrying all imposed dead and live loads apart from its own
weight.
There are some requirements of a good formwork system, which are:
i. The way the formwork can be erected and de-shuttered fast
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ii. The good concrete quality and surface finish can be achieved.
iii. The optimum stock of formwork required for the size of work force, the
specified time schedule and flow of materials.
iv. The overall cost savings that can be achieved using the right type of
formwork.
v. The safety that can be improved for the site personnel.
In order to successfully carry out its function, formwork must achieve a
balance of following requirements such as containment, strength, resistance to
leakage, accuracy, ease of handling, access for concerted and economy.
Containment of formwork mean formwork must be capable of shaping and
supporting the fluid concrete until it cures. Strength of formwork must be capable of
safely withstanding without distortion or danger the dead weight of the fluid concrete
is placed on it, labour weight, equipment weight and any environmental loadings.
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Resistance to leakage for formwork can be defined with all joints in
formwork must be either close fitting of covered with form tape to make them grout
tight. If grout leakage occurs the concrete will leak at that point. Leakages cause
honeycombing of the surface. Formwork must be accurately set out so that the
resulting concrete product is in a right place and is of correct shape and dimensions.
The formwork must be easy to handle which form panels and units should be
designed so that their maximum size does not exceed that which can be easily
handled by hand or mechanical means. In addition all formwork must also be
designed and constructed to include facilities for adjustments, levelling, easing and
striking without damage to the form work or concrete.
Any formwork arrangement should provide access for placing of the
concrete. The extent of this provision will be depending on the ease of carrying out
the concrete operations.
The cost of formwork is very expensive. On average about 35% of the total
cost of any finished concrete unit or element can be attributed to its formwork, out of
this just over 40% can be taken for material for formwork and 60% for labour. The
formwork designer must therefore not only consider the maximum number of times
that any form can be reused, but also produce a design that will minimize the time
taken for erection and striking.
Traditionally, formwork requirements have been left to the construction stage
and the main contractor's temporary works designer, but this can lead to significant
loss of benefit unless the permanent works designer provides appropriate guidance.
Permanent formwork in construction defines the terminology relating to permanent
formwork, identifies where the responsibilities lie for its design and safe use and
outlines the regulations governing its use.
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This study is all about of the application of permanent precast formwork
beam that can develop innovative, economical and efficient methods of construction
in reducing the application of temporary formwork. There are many advantages of
using permanent precast formwork beam such as:
i. The construction of building more efficient.
ii. It can increase the speed of construction time and reduce money.
iii. The construction site is cleaner.
iv. It also can reduce the manpower at construction site improved safety
and economy of construction,
v. Long-term durability, appearance and reduced maintenance costs in
civil engineering applications.
According to Kamran (2007), formwork can be defined as a structure, usually
temporary, but in some cases wholly or partly permanent used to contain poured
concrete to mould it to the required dimensions and support it until it is able to
support itself. It consists primarily of the face contact material and the bearers that
directly support the face contact material.
Permanent formwork can be classified into two groups which participating
and non-participating (Design Manual for Roads and Bridges, 1991).
i. Participating formwork
Precast concrete units incorporating a welded lattice projecting into and
providing shear connection with the overlying insitu concrete deck to form a
composite deck slab. This is the only type of participating permanent
formwork which has been used in bridges in recent years.
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ii. Non-participating formwork
a. Glass fibre reinforced cement (GRC) consisting of hydraulic mortars
reinforced with alkali resistant glass is manufactured to give a range of
sections designed to support various deck slab thicknesses and spans. Single
skin panels, either flat sheet or corrugated, where the in-situ concrete is in
contact with the GRC over the full surface area of the panel, are acceptable
for use. The use of polystyrene formers in the corrugations is not permitted.
b. Profiled steel sheeting (PSS) is usually of the order of 1mm thick and is
protected by galvanising with an additional polyester coating. This material
has not been widely used, but in a few instances corrosion to untreated cut
edges and site damage to the coatings has been observed, although this has
not seriously impaired the structural performance. PSS should not contain
indentations which may form a shear connection with the in situ concrete,
since there is a risk of fatigue cracking initiating from this detail.
c. Glass reinforced plastic (GRP) is a flat laminated panel consisting of a resin
mortar filling between two thin sheets of glass reinforced plastic. One surface
of the panel has projecting steel reinforcing ribs on edge encased within the
GRP. Generally these have performed satisfactorily although there have been
isolated cases of corrosion of the steel ribs. This was due to incomplete
covering by GRP material and was exacerbated by poor storage conditions of
the steel prior to manufacturing the panels. Properly manufactured panels
should not suffer from this problem. GRP formwork should only be used
with the ribs projecting into the in-situ concrete deck slab. There should be
no filler materials such as expanded polystyrene placed between the ribs,
which would prevent full contact between the deck concrete and the surface
of the ribbed panels.
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In this study, there are two types of permanent precast formwork beam that
were used which are glass fibre reinforced concrete and glass fibre reinforced
concrete with wire mesh. Besides that, normal beam is used to be a control beam.
The study is carried out to investigate the differences of flexural behaviour precast
permanent formwork beam with normal beam.
Glass fibre Reinforced Concrete (GRC) has been extensively used as
permanent formwork for the past twenty years, corrugated or flat to suit all
supporting beam design.
GRC formwork has excellent performance characteristics and its inherent
material properties provide the specified and contractor with a permanent surface
skin to the bridge deck concrete which:
i. Has a thin cross section, yet provides durability and steel protection
equal to much thicker concrete cover.
ii. has a high resistance to fire and will not emit toxic fumes
iii. Eliminates spalling of exposed faces.
iv. Provides flexibility for pouring sequences and concreting schedules,
which can reduce construction time.
v. Enables the final appearance of the deck structure to be assessed on-site
before concrete is poured.
The GRC shall be the following properties on completion of cure. The dry
density of the GRC should not be less than 1700 kg/m³
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Table 1.1 Properties of glass fibre reinforced concrete.
Compressive Strength (tested to ASTM : C 109/C 109M : 2002)
Maximum Load 53269.7 N
Compressive Strength 21.31 N/mm²
Flexural Strength (tested to ASTM : C 580 – 98)
Flexural Strength 33.8 N/mm²
Modulus of Elasticity 6172.8 MPa
Charpy Impact Strength (tested to ASTM 10.5 µm/mºC
Coefficient of Thermal Expansion (tested
to ASTM E831 : 2000)
10.5 µm/mºC
Thermal Conductivity (tested to ASTM
C518 : 1991)
0.12258 w/mºK
1.3 Problem Statement
Generally, conventional formwork is widely used in the construction in
Malaysia because of its flexibility and easy to produce. The most common
material for conventional formwork is timber and plywood. Traditional Timber
formwork is widely used in the construction in Malaysia because of its flexibility
and easy to produce. Traditional timber formwork is built on site out of timber and
plywood or moisture-resistant particleboard. Although it is easy to produce, the
time-consuming for larger structures to be built is longer, and the plywood facing
has a relatively short lifespan. The formwork which is made of wood or timber
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may have to be replaced after a few uses.
Figure 1.2 The view of site construction that uses traditional timber
formwork.
As compared to traditional timber formwork, permanent precast formwork is
manufactured at factory. The main advantages of this permanent precast formwork is
reducing the traditional site based trades like traditional timber formwork, brickwork,
and plastering and thus enabling the contractors to reduce the overall labour content
in the building construction. By using permanent precast formwork, the use of wood
formwork can be reduced. It is also can develop the economical method of
construction. However, it is still used extensively where the labour costs are lower
than the costs for procuring reusable formwork. Moreover, the unskilled labourer can
be easily trained to construct building using the permanent precast formwork and
provide faster construction and cost saving.
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1.4 Objectives of Study
The objectives of this case study are:
i. To obtain an optimum content of glass fibre in glass fibre mortar mix
design.
ii. To investigate the flexural behaviour and bending capacity of
permanent precast formwork beams.
1.5 Scope of Study
This study is mainly focused on the testing of concrete beams with different
types of permanent precast formwork under the four point bend test. Design
calculation and laboratory work were carried out accordingly to achieve the
objectives of this study.
This study was conducted in the Material and Structure Laboratory. In the
laboratory work, three beams were casted and tested using the same grade of
concrete, steel bars reinforcement, and testing method. The results of this study are
used to determine the flexural behaviour of the beam and which types of formwork
have higher bending capacity under the four point bend test.
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