THE STRUCTURAL PERFORMANCE OF PRECAST LIGHTWEIGHT FOAMED CONCRETE PANEL (PLFP)
WITH DOUBLE SHEAR CONNECTORS
SURYANI BINTI SAMSUDDIN
A thesis submitted in
fulfilment of the requirements for the award Degree of Master in Civil Engineering
Faculty of Civil and Environmental Engineering UniversitiTunHusseinOnnMalaysia
THESIS TITLE iii
LIST OF TABLES xviii
LIST OF FIGURES xxii
LIST OF ABBREVIATION xxvii
CHAPTER 1 INTRODUCTION 1
1.1 Introduction 1
1.2 Problem Statement 3
1.3 Objectives of Research 4
1.4 Scope of Research 4
1.5 Important and Contribution of Research 5
CHAPTER 2 LITERATURE REVIEW 8
2.1 Precast Concrete Sandwich Panel (PCSP) 8 2.2 Material Properties on Sandwich Panel 10
2.2.1 Core Layer 10
2.2.2 Shear Connector and Reinforcement 13 2.3 Structural Behaviour of Sandwich Panel 15
2.3.1 Insulation Type 16
2.3.2 Slenderness Ratio 16
2.3.3 Effect of Shear Connector 18 2.4 Precast Lightweight Foamed Concrete 20
2.5 Advantage of Sandwich Panels 23 2.6 Foamed Concrete Fabrication 24 2.7 Process of Manufacturing Foamed Concrete 26 2.8 Properties of Foamed Concrete 26 2.9 Application of Foamed Concrete 28
2.10 Type of Sandwich Panel 29
2.10.1 Non-Composite Panel 30 2.10.2 Fully-Composite Panel 30 2.10.3 Partially-Composite Panel 30 2.11 Precast Concrete Sandwich Panel as 31
Structural Wall Elements
2.11.1 Plain Concrete Wall 31 2.11.2 Reinforced Concrete Wall 32 2.11.3 Response of Precast Concrete 33
Sandwich Panel Subjected to Axial Load
2.11.4 Precast Lightweight Foamed 34 Concrete Sandwich Panel (PLFP) with Single Shear Connector Subjected to Axial Loading
2.11.5 Solid Reinforced Concrete Wall 34 under Pure Axial Loads
2.12.1 Introduction 35
2.12.2 Connections between Precast 36 Concrete Sandwich Panels
2.13 Wall to Wall Connection 38
2.14 Finite Element Analysis 40
2.14.1 Introduction 40
2.14.2 Type of Finite Element Analysis 41 220.127.116.11 One-Dimensional Element 41 18.104.22.168 Two-Dimensional Element 42 22.214.171.124 Three-Dimensional Element 42 2.14.3 Material Non-Linearity 43 2.15 Previous Research of Finite Element 43
2.16 Summary 47
CHAPTER 3 METHODOLOGY 49
3.1 Introduction 49
3.2 Experimental Investigation on PLFP Panel 51 3.2.1 Designation and Dimension of 51
Single PLFP Panel under Axial Load Test
3.2.2 Designation and Dimension of 52 Connected PLFP Panel under
Flexural Load Test
126.96.36.199 Wall to Wall Connection 53 3.3 Materials Preparation and Fabrication 56
of PLFP Specimens
3.3.1 Material Preparation of Foamed 56 Concrete
i) Cement 56
ii) Fine Aggregates 57
iii) Foam Agent 57
i) Wythe 58
ii) Core Layer 59
iii) Normal Concrete Capping 59 iv) Reinforcement 60
v) Shear Connectors 60
3.3.3 Procedure of Casting the Panels 61
3.4 Testing of Material 66
(Cubes and Cylinder of Foamed Concrete)
3.4.1 Cube Test 66
3.4.2 Split Tensile Test 67
3.4.3 Young’s Modulus 68
3.5 Test of PLFP Panel under Axial Load 70 3.6 Four Point Load Test on Two Connected 74 3.7 Validation using Finite Element Method 75 3.8 Material Model for Finite Element Analysis 76 3.8.1 Constitutive Models 76 188.8.131.52 Concrete Model 77 184.108.40.206 Von Mises Model 78
3.9 Analysis of Results 78
CHAPTER 4 EXPERIMENTAL RESULTS 80
4.1 Introduction 80
4.2 Objectives of Experimental Work 82 4.3 Experimental Results and Analysis 82 4.3.1 Material Properties of 82
4.3.2 Tested PLFP Panel under 84 Axial Load
220.127.116.11 Ultimate Load 84 18.104.22.168 Crack Pattern and 85
22.214.171.124 Strain Distribution on the 91 Concrete Surface
4.3.3 Two PLFP Panels with L-Bar 93 Vertical Connection Tested under Flexure Load
126.96.36.199 Ultimate Load 93 188.8.131.52 Crack Pattern and Mode 94
184.108.40.206 Load-Horizontal Deflection 97 Profiles
220.127.116.11 Load-Strain Relationship 98 4.3.4 Effect of Slenderness Ratio on 101
Panel’s Structural Behaviour
18.104.22.168 Ultimate Load 101 22.214.171.124 Crack Pattern and 102
126.96.36.199 Load-Deflection Profile 103 188.8.131.52 Load-Strain Distribution 104 4.4 Comparison of the Load Bearing Capacity, 105
Pu, from Experiment withThe Pu values from Classical Formulae and Previous Research
4.5 Comparison Between Structural 107 Performances of Single PLFP Panel with
Two Panel PLFP Panels Connected using Vertical Connection
4.5.1 Ultimate Load 108
4.5.2 Crack Pattern and Mode of Failure 109 4.5.3 Load-Deflection Profile 110 4.5.4 Load-Strain Profile 111
CHAPTER 5 FINITE ELEMENT METHOD 113
5.1 Introduction 113
5.2 Objective 114
5.3 Modelling of PLFP Panel 114
5.3.1 Physical Model 114
5.3.2 Material Model 116
184.108.40.206 Concrete Wythe 117 220.127.116.11 Steel Reinforcement and 119
18.104.22.168 Concrete Capping 120 22.214.171.124 Loading & Analysis Control 121 5.4 PLFP Panel Subjected to Axial Load 123 5.4.1 Ultimate Load of PLFP Panel 123
Under Axial Load
5.4.2 Validation of Experimental Results 125 5.4.3 Comparison Result of Ultimate 125
Load from FEM and Experiment
5.4.4 Comparison Result of Load 126 Deflection From FEM and
Experimental for PLFP PA-5
5.4.5 Effect of Slenderness Ratio on 127 Ultimate Load
5.5 Connected PLFP Panel Subjected to 128 Flexural Load
5.6 Summary 129
CHAPTER 6 CONCLUSION 130
6.1 Conclusion 130
6.1.1 To Determine the Structural 130 Behavior of Single PLFP Panel
with Various Slenderness Ratios Subjected to Axial Load.
Behaviour of Two PLFP Panels with L-Bar Vertical Connection Subjected to Flexural Load.
6.1.3 To Compare the Ultimate Load 132
Obtained from Experiment with the
Values Obtained from Classical
Formulae and Previous Research.
6.2 Recommendations 132
Appendix A : Foamed Concrete
Table A1 : Result of Dry Density for PLFP 139 after 7, 14 and 28 Days
Table A2 : Compressive Strength at 7, 14 139 and 28 Days for PLFP Panel
Table A3 :Tensile Strength of Foamed 140 Concrete for PLFP Panel at 28-Days
Table A4 : Modulus Young, E for PLFP Panel 141
A5 : Data for Panel PA 1 (S1) 142
A6 : Data for Panel PA 2 (S2) 144
Appendix B : Strain Distribution 146 Table B : Maximum Surface Strain values from 146 Experiment
Table C :Tensile Strength of Reinforcement Bar 147 Figure C1 : Tension Testing Result for 3 mm 148 Diameter Reinforcement
Figure C2 : Tension Testing Result for 4 mm 148 Diameter Reinforcement
Figure C3 : Tension Testing Result for 6 mm 149 Diameter Reinforcement
Figure C4 : Tension Testing Result for 9 mm 149 Diameter Reinforcement
Appendix D : Load Strain Graph for PLFP 150 Panel
Appendix E : 154
Table E : Data for Deflection of PLFP Panel 154
Appendix F 162
Table F : Data for Surface Strain Readings 162 of PLFP Panel
Appendix G 170
Table G : Data for Surface Strain of PLFP Panel 170
Appendix H 171
Table H :Comparison of Load Bearing Capacity 171 by using Previous Formulae and Classical Formulae
Appendix I 175
LIST OF TABLES
TABLE TITLE PAGE
1.1 Density Classification of Concrete Aggregates 2 (Mindess and Young, 1981)
2.1 Typical Mixture Details for Foamed Concrete 11 (BCA, 1994)
2.2 Typical Properties for Foamed Concrete (BCA, 1994) 11 2.3 Experimental Results for Horizontal Bending Test 12
2.4 Ultimate Load and Deflection at Mid-High in 14 Panels Specimens (Mohammed & Nasim, 2009)
2.5 Crack and Failure Loads for Panel Specimens 17 (Benayouneet al., 2006)
2.6 Typical Foamed Concrete Mixes 25
(Newman & Choo, 2003)
2.7 Typical Properties of Foamed Concrete 27
(Cement Concrete Institute 2010)
2.8 Comparison of Load Capacity for Imperfect Walls 45 with Different Wall Height (Bagaber, 2007)
3.1 Dimension and Details of Specimens for Axial 52 Load Test
3.2 Dimension and Details of Specimens for Four 53 Point Load Test
3.3 Foam Concrete Ratio 58
4.2 Dimension and Properties of PLFP Connected using 81 L-Bar Vertical Connection
4.3 Compressive Strength at 7, 14 and 28 days for Panel 83 PA-1 to PA-8
4.4 Tensile Strength of Panel PA-1 to PA-8 at 28-Days 83 4.5 Young’s Modulus, E, for Panel PA 1 to PA 8 84
4.6 Ultimate Failure Load for PLFP Panels 85
4.7 Crack Pattern and Mode of Failure for PLFP Panels 86
4.8 Maximum Surface Strain 93
4.9 Ultimate Failure Loads of PLFP Panels 94
4.10 Crack pattern for panels PC-1, PC-2 and PC-3 94
4.11 Deflection Value of PLFP Panels 103
4.12 Ultimate Loads of PLFP Panels from Experiment, 105 Empirical Formulae and Previous Researchers.
4.13 The Difference Percentage of Load bearing Capacity 107 for PLFP PA-5
4.14 First Crack and Ultimate Load For Single and 108 Two Connected PA-1
4.15 Crack Pattern and Failure Mode for Panels PA-1 109 and PC-3
5.1 Dimension and Properties of PLFP Panels for FEM 115 Modelling
5.2 Properties of Foamed Concrete used in the PLFP FEM 117 Model
5.3 Plastic Properties of Foamed Concrete Wythes 118 5.4 Properties of Steel used as Reinforcement and 120
5.5 Properties of Normal Concrete used in the PLFP 121 FEM Model
5.6 Load Bearing Capacity for PLFP Panel 125
5.7 Ultimate Load of PLFP from Experiment and FEM 126 5.8 Ultimate Load of Connected PLFP from Experiment 128
A1 Result of Dry Density for PLFP after 7, 14 and 28 Days 141 After Exposed to Air
A2 Compressive Strength at 7, 14 and 28 Days for Panel 141 PA 1 to PA 8
A3 Tensile Strength of Foamed Concrete for Panel PA 1 to 142 PA 8 at 28 Days
A4 Modulus Young, E, for Panel PA 1 to PA 8 143 A5 Sample Calculation for Modulus Young for Panel PA 1 144 A6 Sample Calculation for Modulus Young for Panel PA 2 146 B1 Maximum Surface Strain Values from Experiment 148
D1 Data for Deflection of PLFP Panel PA 1 153
D2 Data for Deflection of PLFP Panel PA 2 154
D3 Data for Deflection of PLFP Panel PA 3 155
D4 Data for Deflection of PLFP Panel PA 4 156
D5 Data for Deflection of PLFP Panel PA 5 157
D6 Data for Deflection of PLFP Panel PA 6 158
D7 Data for Deflection of PLFP Panel PA 7 159
D8 Data for Deflection of PLFP Panel PA 8 160
E1 Data for Surface Strain Readings of PLFP Panel PA 1 161 E2 Data for Surface Strain Readings of PLFP Panel PA 2 162 E3 Data for Surface Strain Readings of PLFP Panel PA 3 163 E4 Data for Surface Strain Readings of PLFP Panel PA 4 164 E5 Data for Surface Strain Readings of PLFP Panel PA 5 165 E6 Data for Surface Strain Readings of PLFP Panel PA 6 166 E7 Data for Surface Strain Readings of PLFP Panel PA 7 167 E8 Data for Surface Strain Readings of PLFP Panel PA 8 168 F Surface Strain Distribution of PLFP Panel 169 G1 Comparison of Load Bearing Capacity by using Previous 170
Formulae and Classical Formulae for PA 1
G2 Comparison of Load Bearing Capacity by using Previous 170 Formulae and Classical Formulae for PA 2
G3 Comparison of Load Bearing Capacity by using Previous 171 Formulae and Classical Formulae for PA 3
Formulae and Classical Formulae for PA 4
G5 Comparison of Load Bearing Capacity by using Previous 172 Formulae and Classical Formulae for PA 5
G6 Comparison of Load Bearing Capacity by using Previous 172 Formulae and Classical Formulae for PA 6
G7 Comparison of Load Bearing Capacity by using Previous 173 Formulae and Classical Formulae for PA 7
LIST OF FIGURES
FIGURE TITLE PAGE
2.1 Types of Sandwich Construction (An, 2004) 9 2.2 Shotcrete Lightweight Sandwich Panel (Kabir, 2005) 13 2.3 Schematic for the Test Setup for Four-Point Bend Test 14
with Strain Gauge Location (Mohammed &Nasim, 2009) 2.4 Schematic Diagrams for the Panels used in the 15
Experimental Work (Mohammed &Nasim, 2009)
2.5 Comparison between AAC and FRP/AAC Shear ` 15 Strengths (Mohammed &Nasim, 2009)
2.6 Typical Precast Concrete with Truss Shaped 21 Shear Connector(Benayouneet al., 2006)
2.7 Precast Concrete Sandwich Panel 22
(Mohamad and Muhammad, 2011)
2.8 Manufacturing Process of Foamed Concrete (Ying, 2007) 27
2.9 Precast Concrete Sandwich Panel 28
2.10 Twenty-Storey Mutual Benefit Life, Philadelphia, 29 Pennsylvania (PCI Commitee, 1997)
2.11 Window Wall Panels Serve as Elements of Vierendeel 29 Truss on One Hundred Washington Square Office
Building, Minneapolis, Minnesota (PCI Commitee, 1997) 2.12 Types of Precast Concrete Sandwich Panels 30
2.13 Typical Reinforcement Details (Jackson, 1995) 37
2.14 Mechanical Connection 38
2.15 Top View of Wall to Wall Connection 39 (Rossley et al., 2014)
2.16 Front View of Wall to Wall Connection 40 (Rossley et al., 2014)
2.17 1-Dimensional Elements (Guntor, 2011) 41 2.18 Applied of 1-Dimensional Element (Guntor, 2011) 42 2.19 2-Dimensional Elements (Guntor, 2011). 42 2.20 3-Dimensional Elements (Guntor, 2011). 43 2.21 Loading and Boundary Condition (Vaghei et al., 2006) 46
3.1 Flow Chart of the Methodology 50
3.2 Schematic Diagram for Single PLFP Panel 54 3.3 Details of Reinforcement in 2 PLFP Panels and Its 55
3.4 Plan View of Reinforcement Orientation in L-Bar 55 Connections
3.5 Ordinary Portland Cement 56
3.6 Foam Generator 57
3.7 Sample of Foam 57
3.8 Foamed Concrete Wythe in PLFP 58
3.9 Polystyrene Core Layer 59
3.10 Reinforcement and Shear Connectors 60 3.11 Arrangement of Double Shear Truss Connectors in PLFP 61 3.12 Double Shear Truss Connectors for 90mm Thick PLFP 61
3.13 (a) The First Step is to Place the First Layer of Foamed 62 Concrete Wythe
3.13 (b) The Second Step is to Place the Insulation Layer 62 (Polystyrene)
3.13 (c) The Third Step is to Place the Second Layer of 63 Foamed Concrete Wythe
3.14 (b) The BRC, Shear Connectors Truss and Polystyrene were 63 Placed Horizontally on the Top of the Lower Wythe
3.14 (c) Foamed Concrete Poured on the Top of Polystyrene 64 Layeras the Upper Wythe
3.14 (d) Finish of the PLFP Panel Specimen 64 3.15 The First Step is to put the Panel Side by Side and 65
Tight Tight Together with 30 mm Gap
3.16 The Second Step is to Place the Foamed Concrete 65 into the Connection
3.17 Cube Specimens 66
3.18 Compressive Strength Testing Machine 67 3.19 Specimen Positioned in a Testing Machine for 68
Determination of Splitting Tensile Strength
3.20 Test specimens placing at Universal Testing 70 Machine with attachment of Compressmeter
3.21 Experimental Set-Up of Wall Panel Clamped to 71 Reaction Frame.
3.22 Experimental Set-Up using Magnus Frame 72 3.23 Arrangement of Strain Gauges and LVDT 73 3.24 Testing Setup under Four Point Bending Test 74 3.25 The Arrangement of LVDT in Connected Wall for 75
3.26 Simplified Failure Envelope for Biaxial Concrete 77 Model(LUSAS, 2000)
3.27 Von Mises Failure Theory 78
4.1 Ultimate Strength versus Compressive Strength for 85 PLFP Panels
4.2 Crack and Crush at the Bottom Half of Panel PA-1 87 4.3 Crack and Crush at the Top half of Panel PA-2 87 4.4 Crack and Crush at the Bottom Part of the Panel PA-3 88 4.5 Crack and Crush at the Middle Part of Panel PA-4 88 4.6 Crack and Crush at the Top Half of the Panel PA-7 88 4.7 Load-Horizontal Deflection Profiles at Mid-Height 90
4.8 Load Strain Curves for Panel PA-2, PA-5 and PA- 6 92 under Axial Load
4.9 Crack and Crush on the Diagonal Angle Approximately 95
45o at the Top of Panel PC-2 and PC-3
4.10 Crack Occurred in PC-2 and PC-3 96
4.11 LVDT Position 96
4.12 (a) Load-Deflection Profile for Panel PC-3 97 4.12 (b) Load-Deflection Profile for Panel PA-3 across the Width 98
4.13 Strain Gauge Position 99
4.14 Load- Strain Profile at the Top and Bottom of the 99 Connection for PC-3
4.15 Load-Strain Profile at the Connection for PC-3 100 4.16 Load-Strain Profile at the Centre of the PLFP Panel 100
4.17 Ultimate Strength, Pu, versus Slenderness Ratio, h/t 102 PA-1 to PA-8
4.18 Slenderness Ratio versus Maximum Deflection of 104 PLFP Panels
4.19 Comparison of Ultimate Load vs Slenderness Ratio 106 as obtained from Experiment, Codes and Previous
4.20 (a) Crack and crush at Bottom Part of Panel PA-1 109 4.20 (b) Crack and Crush on the Diagonal Angle Approximately 109
45oat the Top of Panel PC-3
4.21 Load Deflection Profile Profile for PA-1 and PC-3 110 4.22 Load-Strain Profile at the Top, Middle and Bottom 111
Part of PA-1
5.1 2-D Plane-Stress Element Model of PLFP 116
5.2 Attributes of foamed concrete plastic properties as in 119 FEM
5.3 PLFP Support and Loading Condition 122
5.4 Deflection of Wythes in PA-5 124
5.6 Comparison of Load-Deflection between Experimental 127 and FEM value for PA-5
5.7 Model of Connected PLFP Panel under Flexural 128 Load Test
LIST OF ABBREVIATION
2D – Two Dimensional
3D – Three Dimensional
AAC – Autoclaved Aerated Concrete ACI – American Concrete Institute Code ASTM – American Standard Testing Method BRC – Bar Reinforcement
BS – British Standard
CFRP – Carbon Fibre-Reinforced Polymer
CIDB – Construction Industry Development Board of Malaysia
E – Modulus Young
EPS – Expanded Polystyrene Insulation
FE – Finite Element
FEA – Finite Element Anaysis FEM – Finite element method FRP – Fiber Reinforced Polymer GFRP – Glass Fibre-Reinforced Polymer IBS – Industrialised Building System
LUSAS – London University Structural Analysis Software LVDT – Linear Voltage Displacement Transducer
PCSP – Pre-Cast Concrete Sandwich Panel
PLFP – Precast Lightweight Foamed Concrete Sandwich Panel
SG – Strain Gauge
Construction material such as brick, timber, concrete and steels are increasing in demand due to rapid expansion of construction activities for housing and other buildings. For structure which is constructed by using conventional concrete, its self weight represents a very large proportion of the total load on the structure. Furthermore, it uses aggregate which is one of earth’s natural resources. With these two reasons, there is a need for alternative system to fulfill the construction demand in term of its strength, affordability and environmental friendly. For structure which is constructed by using conventional concrete, its self weight represents a very large proportion of the total load on the structure. The strength and other properties of concrete are dependent on how its ingredients are proportioned and mixed. It depends on the usage of a good quality concrete, which can be defined as having a workable fresh concrete and unlikely to segregate.
It is lighter than the conventional concrete with a dry density of 300 kg/m3 up to 1840 kg/m3 which is 23% to 87%lighter. It was first introduced by the Romans in the second century (Sarmidi, 1997).
One of the main properties that are associated with the lightweight concrete is its low density. Lower in density leads to reduction in weight and this means reduction in the total load. Foamed concrete is one of the lightweight concrete and is classified as cellular concrete. It has a uniform distribution of air voids throughout the paste or mortar. Scanlon (1998) stated that lightweight concrete is a concrete that have a low density concrete compared to the normal concrete. Table 1.1 shows the density classification of the concrete aggregates.
Table 1.1: Density Classification of Concrete (Mindess and Young, 1981)
Unit Weight of Concrete
Unit Weight of Dry-Rodded
Typical Concrete Strengths (Mpa) Typical Application Ultra
Lightweight 300 – 1100 < 500 < 7
Lightweight 1100 – 1600 500 – 800 7 – 14 Masonry Units
Lightweight 1450 – 1900 650 – 1100 17 – 35 Structural
Normal Weight 2100 – 2550 1100 – 1750 20 – 40 Structural
Heavy Weight 2900 – 6100 >2100 20 – 40 Radiation
Lightweight foamed concrete is suitable for both precast and cast-in-place applications. Good strength characteristics with reduced weight make lightweight foamed concrete suitable for structural and semi-structural applications such as lightweight partitions, wall and floor panels and lightweight block concrete. This structure has become more popular in recent years because it offers more advantages compared to the conventional concrete (Mindess and Young, 1981).
connection. Horizontal connections are the wall-floor and wall-roof connection while vertical connection is the connection between wall panels that are side by side in the same floor. Jointing system between these walls constitutes an essential link in the lateral load-resisting systems, and their performance influence the pattern and distribution of lateral forces among the vertical elements of a structure. The connections between panels are extremely important since it influences both the speed of erection and the overall integrity of the structure.
1.2 Problem Statement
The development of lightweight, industrialized and sustainable housing system in Malaysia as per modular coordination system is a need of the day. In Malaysia, brickwall is a common wall for use as load bearing wall. However, brickwall is time consuming, require large number of workers, difficult to control the quality and produce high wastage percentage at the construction site. Therefore an alternative precast system is required to replace this traditional system. To encounter demands from the growing population and migration of people to urban areas, new alternative technology is required in the construction industries which can meet demands for higher performance, affordable quality housing and environmental efficient. Current research on precast wall panel only focuses on the performance of solid panel from conventional concrete. These panels are strong but have a weakness such as heavy and not environmental friendly.
Dolan and Foschi (1989) stated that connections are an important part of every structure not only from the point of view of structural behavior, but also related to the cost of production. Connections play a key role in dissipation of energy and redistribution of loads. With a strong connection between wall panels, a structure will have strength of stability to prevent structure failure.
1.3 Objectives of Research
The objectives of the study are:
i. To determine the structural behavior of single PLFP panel with various slenderness ratios subjected to axial load.
ii. To determine the structural behaviour of two PLFP panels with L-bar vertical connection subjected to flexural load.
iii. To compare the ultimate load obtained from experiment with the values obtained from classical formulae and previous research.
The aforementioned structural behaviour refers to ultimate load, failure mode and crack pattern, load-deflection profile and strain distribution on the concrete’s surface.
1.4 Scope of Research
Various height and thickness of PLFP panels were used to study the influence of slenderness ratio on the structural behavior of single PLFP panels. The results for axial load test on single PLFP panel were validated using finite element method. Two single PLFP panels were connected using vertical connection with L-bar reinforcement. The material used as the infill for the connection is foamed concrete with density of 1700 kg/m2 to 1800 kg/m2.
The results for single PLFP panels tested under axial load and two PLFP panels connected and tested under flexural load were studied in terms of its load carrying capacity, crack pattern and mode of failure, load-deflection profiles, and strain distribution on foamed concrete surface. The results of this experiment were validated using the Finite Element Method and formula from previous researcher.
1.5 Importance and Contribution of Research
The main aim of this research is to investigate the structural behaviour of PLFP as a load bearing wall. Lightweight sandwich panel is of interest in this study since it has higher strength to weight ratio compared to solid precast made of conventional concrete. At the same time it will contribute to green building by producing a cleaner and neater environment at project site, controlled quality, and a lower total construction time and costs.
Single PLFP panel with various slenderness ratio and two PLFP connected panels vertically were tested under axial and flexure load, respectively. Findings from this research will encourage the use of the new approach to produce lightweight composite wall elements for industrialized building system and hence promoting better quality construction and innovative system in our construction industry.
1.6 Organisation of Thesis
This thesis consists of six (6) chapters. The summary of each chapter is described below:
This chapter presents the introduction of lightweight foamed concrete material and its properties to be used as precast wall panel as a substitute for conservative in-situ construction. It also presents the objectives and scope of research as well as the importance and contribution of research.
Chapter 2 presents the literature review from previous research on the structural performance of precast panel from various materials and design. Review on the connection between panels is also discussed. This chapter also covers the discussion on classical equations for panel’s ultimate load from the codes and previous research.
This chapter presents the results form material test, axial load test and four point bending load test. The result of validation using previous researcher and empirical formulae also presented in this chapter. The observed panel’s structural behavior is discussed in terms of its ultimate strength, crack pattern and mode of failure, load-deflection profiles, and load-strain profiles for both single and two connected PLFP panels.
This chapter presents the Finite Element Method, FEM, of PLFP panel which include the modeling and simulation process on single PLFP panel subjected to axial load and two PLFP connected panels tested under flexural load. The results obtained from FEM will be used as the validation of experimental results.
2.1 Precast Concrete Sandwich Panel (PCSP)
Precast concrete can be defined as a concrete member that is cast in a plant. The precast wall panel is one of the precast concrete structure that purposely constructed to speed up the wall making construction and to reduce the dependencies of the skilled worker as well as to reduce the construction waste and cost. Precast concrete sandwich panels are a layered structural system composed of a low-density core
material bonded to, and acting integrally with relatively thin, high strength facing
Recent development of precast concrete has encouraged studies on various lightweight materials such as structural wall panel systems. This system comply with the IBS concepts, which enable cost saving, energy efficient and quality improvement. A typical building element in a precast building system is precast wall panel. The difference between precast concrete wall and precast concrete sandwich panel is the presence of insulation layer (Aziz, 2002).
The development of a usage of sandwich panel is increasing within the past
used as exterior and interior walls for many types of structures. The main benefit of using the sandwich structure concept in structural components is its high bending stiffness and high strength to weight ratios (Belouttar et al., 2008). The sandwich structure may readily be attached to any type of structural frame, for instance, structural steel, reinforced concrete, pre-engineered metal and precast or prestressed concrete.
Precast concrete sandwich panel normally consists of two layers of high strength skins or wythe and are separated by a lower strength core layer. The wythes are relatively thin while the core is relatively thick but lighter in weight. The common materials used for wythes are steel, aluminium, timber, fiber reinforced plastic or concrete while the materials used for the cores are balsa wood, rubber, solid plastic material or polyethylene, rigid foam material (polyurethane, polystyrene, phenolic foam), or from honeycombs of metal or paper (Benayoune et al., 2006). Figure 2.1 presents a few types of sandwich panel elements (An, 2004). Such sandwich structures have gained widespread acceptance within the aerospace, naval/marine, automotive and general transportation industries as an excellent way to obtain extremely lightweight components and structures with very high bending stiffness, high strength and high buckling resistance (Mahfuz et al., 2004; Liang and Chen, 2006).
(a) Foam Core Sandwich
(b) Honeycomb Core Sandwich
(c) Web Core Sandwich
(d) Truss Core Sandwich
Sandwich panel have gained much attention by the researcher because of its effectiveness as a structural element in engineering field. In the building and construction industries, most of the researches published on sandwich panel are related to the study of load bearing non-composite type of PCSP (Jokela et al., 1981, Olin et al., 1984, Hopp et al., 1986 and Bush, 1994). Section 2.2 will discuss about the previous research related to the sandwich panel studies.
2.2 Material Properties on Sandwich Panel
The chosen of material for the core and wythe in the sandwich panel is really important. The material of core and wythe is one of the factor that determine the strength of the sandwich panel. The wythes of sandwich panels are generally made of thin, high strength sheets material. The structural requirements for wythe materials are their abilities to resist local loads and resistance to corrosion and fire. The core materials are generally thicker and made of lower dense materials. The core is low in density because the core usually does not take any load and function as an insulation material. Various types of materials therefore provide various structural behaviours of the sandwich panels.
2.2.1. Core Layer
According to British Cement Association (BCA, 1994), compressive strength of foamed concrete depends on the density, initial water / cement ratio and cement content. Density of foamed concrete has an influence on its ultimate strength. Foamed concrete with density below 600 kg/m3 usually consists of cement, foam and water. Higher densities foamed concrete are produced by adding fine sand. Ordinary Portland cement is used as the binder in foamed concrete. Cement contents for the most commonly used mixtures are between 300 kg/m3 and 375 kg/m3. Typical mixture details and properties of foamed concrete are given in Table 2.1 and Table 2.2 below:
Table 2.1: Typical mixture details for foamed concrete (BCA, 1994)
Table 2.2: Typical Properties of Foamed Concrete (BCA, 1994)
Dry Density (kg/m3)
Modulus of Elasticity
Drying Shrinkage (%)
400 0.5-1.0 0.10 0.8-1.0 0.30-0.35
600 1.0-1.5 0.11 1.0-1.5 0.22-0.25
800 1.5-2.0 0.17-0.23 2.0-2.5 0.20-0.22
1000 2.5-3.0 0.23-0.30 2.5-3.0 0.18-0.15
1200 4.5-5.5 0.38-0.42 3.5-4.0 0.11-0.09
1400 6.0-8.0 0.50-0.55 5.0-6.0 0.09-0.07
1600 7.5-10.0 0.62-0.66 10.0-12.0 0.07-0.06
Wet Density (kg/m3) 500 900 1300 1700
Dry Density (kg/m3) 360 760 1180 1550
Cement (kg/m3) 300 320 360 400
Sand (kg/m3) 420 780 1130
Base Mix W/C ratio Between 0.5 and 0.6
Ramli (2008) studied the use of ferrocement sandwich panel for industrialised building system. Experimental investigation was conducted to evaluate the structural performance of the ferrocement sandwich panel. This included the load-deflection characteristics, crack resistance, and moment curvature of the ferrocement elements when exposed to air and salt water curing. The results showed that continuous salt water curing made significant improvement on the flexural behaviour of panel by increasing its ultimate load carrying capacity, and reducing its crack width and deflection.
Kabir (2005) investigated the structural performance of shotcrete lightweight sandwich panel with compressive strength of 12 MPa and tensile strength of 1.2 MPa under shear and bearing loads. The sandwich panel consisted of shotcrete wythes which enclose the polystyrene core. Three specimens are provided for horizontal bending tests, each sandwich panel is 300 cm long and 100 cm wide, the upper and lower concrete wythes are 6 and 4 cm thick, respectively. It was reinforced by the diagonal 3.5 mm cross steel wires welded to the 2.5 mm steel fabric embedded in each wythe as shown in Figure 2.2. Tests for flexural and direct shear loading were carried out based on ASTM E-72 and ASTM 564, respectively. From the experiment result, it was found that the crack propagates to the upper layer, at 1200 kg load. The bottom mesh was yielded and the crushing of concrete causes the instability of the panel. The maximum load was recorded at 2200 kg. Table 2.3 shows the ultimate loads and their corresponding displacement of slabs for the horizontal flexural load test.
Table 2.3: Experimental Results for Horizontal Bending Test. (Kabir, 2005) Specimen No Thickness (cm) Type of Shotcrete Cement
Figure 2.2: Shotcrete Lightweight Sandwich Panel
2.2.2 Shear Connector and Reinforcement
Pantelides et al., (2003), tested nine precast concrete wall assemblies with CFRP connectors. Variations in shear area and surface preparation were investigated. Test results showed that failure of the CFRP composite connection was nonductile, similar to that of the steel connection but at three times the lateral load resisted by the steel connection.
be highly dependent on the geometry and stiffness of the connection. Mohammed and Nasim (2009) st
sandwich panel which composed of Fiber Reinforced Polymer (FRP) as the wythe and Autoclaved Aerated Concrete (AAC) as the core.
shown in Figure 2.3
different AAC wrapping systems
bidirectional FRP lamina. Figure 2.4 shows the on both strength and ductility of panels.
ultimate load and maximum deflection at mid
2.5 shows the comparison between AAC and FRP/AAC shear strength.
bidirectional FRP wrapping is shown to provide more ductility and toughness compared to the panels with unidirectional FRP wrapping
: Shotcrete Lightweight Sandwich Panel (Kabir, 2005)
Shear Connector and Reinforcement
Pantelides et al., (2003), tested nine precast concrete wall assemblies with CFRP Variations in shear area and surface preparation were investigated. Test results showed that failure of the CFRP composite connection was nonductile, that of the steel connection but at three times the lateral load resisted by the steel connection. The development length of the CFRP composite was found to be highly dependent on the geometry and stiffness of the connection.
Mohammed and Nasim (2009) studied the structural behavior of lightweight sandwich panel which composed of Fiber Reinforced Polymer (FRP) as the wythe and Autoclaved Aerated Concrete (AAC) as the core. Four-point bending tests as 3 were carried out on half scaled panel specimens with two different AAC wrapping systems, namely unidirectional FRP lamina and rectional FRP lamina. Figure 2.4 shows the significant influence of FRP lamina on both strength and ductility of panels. Table 2.4 shows the results
ultimate load and maximum deflection at mid-height of the panel specimens. Figure shows the comparison between AAC and FRP/AAC shear strength.
bidirectional FRP wrapping is shown to provide more ductility and toughness o the panels with unidirectional FRP wrapping (Plain AAC)
Pantelides et al., (2003), tested nine precast concrete wall assemblies with CFRP Variations in shear area and surface preparation were investigated. Test results showed that failure of the CFRP composite connection was nonductile, that of the steel connection but at three times the lateral load resisted by The development length of the CFRP composite was found to be highly dependent on the geometry and stiffness of the connection.
udied the structural behavior of lightweight sandwich panel which composed of Fiber Reinforced Polymer (FRP) as the wythe point bending tests as nel specimens with two namely unidirectional FRP lamina and significant influence of FRP lamina 4 shows the results which give the the panel specimens. Figure shows the comparison between AAC and FRP/AAC shear strength. Panels with bidirectional FRP wrapping is shown to provide more ductility and toughness
Table 2.4: Ultimate Loa
Panel No Dimension
UFFS BFFS1 BFFS2 BFFS3 1200×175×100 1200×175×100 1200×175×100 1200×175×100
Figure 2.3: Schematic
Strain Gauge Location
Figure 2.4: Schematic D
: Ultimate Load and Deflection at Mid-High in Panels (Mohammed and Nasim, 2009)
Dimension (mm) Reinforcement Type Ultimate Load (KN) 1200×175×100 1200×175×100 1200×175×100 1200×175×100 Unidirectional Bidirectional Bidirectional Bidirectional 15.54 13.56 14.14 16.24
: Schematic diagram for the Test Setup for Four-Point Bending Test with Strain Gauge Location (Mohammed and Nasim, 2009)
4: Schematic Diagrams for the Panels used in the Experimental (Mohammed and Nasim, 2009)
14 anels Specimens Load (KN) Final Mid-Deflection (mm) 11.97 33 25.40 28.24
Point Bending Test with (Mohammed and Nasim, 2009)
Figure 2.5: Comparison between AAC and FRP/AAC Shear S
As discussed above, the choice of materials used in sandwich panels have significant influence on its mechanical properties.
2.3 Structural Behaviour of Sandwich Panel
The complex behaviour of
uncertain role of the shear connectors and the interaction between its various components has led researchers to rely on experimental investigations backed by simple analytical studies.
important type of construction is due to the high cost of full scale testing and the extreme difficulty of fabricating small
factors that affected the structural behaviour of the panels slenderness ratio of the panel and the effect of connector.
5: Comparison between AAC and FRP/AAC Shear S (Mohammed and Nasim, 2009)
As discussed above, the choice of materials used in sandwich panels have significant influence on its mechanical properties.
Structural Behaviour of Sandwich Panel
The complex behaviour of sandwich panel is due to its material non
uncertain role of the shear connectors and the interaction between its various components has led researchers to rely on experimental investigations backed by simple analytical studies. The scarcity of information on the behaviour of this important type of construction is due to the high cost of full scale testing and the extreme difficulty of fabricating small-scale specimens. This part were discussed the factors that affected the structural behaviour of the panels such as insulation type, slenderness ratio of the panel and the effect of connector.
5: Comparison between AAC and FRP/AAC Shear Strengths
As discussed above, the choice of materials used in sandwich panels have
2.3.1 Insulation Type
Frankl et al. (2011) investigated six precast, prestressed concrete sandwich wall panels which were designed and tested to evaluate their flexural response under combined vertical and lateral loads. The study included panels fabricated with two different insulation types: expanded polystyrene (EPS) insulation and extruded polystyrene (XPS) insulation. According to the manufacturer, the selected EPS insulation had a nominal density of 16 kg/m3 and a nominal compressive strength of 90 kPa. The selected XPS insulation had a nominal density of 29 kg/m3 and a nominal compressive strength of 170 kPa. The panels were 6.1 m x 3.7 m, 200 mm thick and consisted of three layers. The flexural behaviors of six full-scale insulated precast, prestressed concrete sandwich wall panels were investigated. The panels were subjected to monotonic axial and reverse-cyclic lateral loading to simulate gravity and wind pressure loads, respectively. Based on the findings of this study, two conclusions were made as listed below:
i. Panel’s stiffness and deflections are significantly affected by the type and configuration of the shear transfer mechanism. Panel’s stiffness is also affected by the type of foam used.
ii. For a given shear transfer mechanism, a higher percent composite action can be achieved using EPS insulation rather than XPS insulation.
2.3.2 Slenderness Ratio
Benayoune et al. (2006) studied the behaviour of pre-cast reinforced sandwich wall panels under the influence of axial load. Six full-scaled specimens with various slenderness ratios, H/t, were tested. All specimens were made of square welded mild steel BRC mesh of 6 mm diameter with 200 x 200 mm and diagonal truss connectors bent at 45 degrees used to tie the inner and outer concrete wythe.
loads of 44 to 79 percent of the ultimate loads as shown in Table 2.
the strength of panels decreased nonlinearly with the increase in the slenderness ratio.
From the results
The linear strain distribution across the panel’s thickness reflected certain degree of composite behaviour.
in a fully composite manner.
the behaviour of wall panels with various types and sizes of shear connectors. Lian (1999) carried out a test
concrete sandwich panel under axial and eccentric loads. and tested. The panels were 1.5m long, 0.75m wide and 40 i.e. 40 mm thick concrete wythes with a 50 mm
load capacity for pure axial loaded panels was computed using expressions applicable to solid walls could not be directly applied to sandwich panel.
it may also be noted that the slenderness ratio, the load bearing capacity of axial loaded panels
varying from 8 to 28, aspect ratios (H/L) from 1 to 3.5 and thicknesses equal to 75 mm with hinged top and
loads of 44 to 79 percent of the ultimate loads as shown in Table 2.
the strength of panels decreased nonlinearly with the increase in the slenderness
Table 2.5: Crack and Failure Loads for Panel Specimens (Benayoune et al., 2006)
results, it shows that both concrete wythes were
linear strain distribution across the panel’s thickness reflected certain degree of composite behaviour. However, the study could not be concluded that the panels act in a fully composite manner. Further experimental works are required to understand the behaviour of wall panels with various types and sizes of shear connectors.
Lian (1999) carried out a test program to study the behaviour of reinforced concrete sandwich panel under axial and eccentric loads. Four specimens were cast The panels were 1.5m long, 0.75m wide and 40-50-40 mm construction, i.e. 40 mm thick concrete wythes with a 50 mm thick insulating layer.
for pure axial loaded panels was computed using expressions applicable to solid walls could not be directly applied to sandwich panel.
ted that the slenderness ratio, H/t is an important factor influencing the load bearing capacity of axial loaded panels.
Oberlender (1977) tested 54 wall panels with slenderness ratios (H/t varying from 8 to 28, aspect ratios (H/L) from 1 to 3.5 and thicknesses equal to 75 mm with hinged top and bottom edges under uniformly distributed axial and 17
loads of 44 to 79 percent of the ultimate loads as shown in Table 2.5. It shows that the strength of panels decreased nonlinearly with the increase in the slenderness
: Crack and Failure Loads for Panel Specimens
were deflected together. linear strain distribution across the panel’s thickness reflected certain degree of
However, the study could not be concluded that the panels act Further experimental works are required to understand the behaviour of wall panels with various types and sizes of shear connectors.
program to study the behaviour of reinforced Four specimens were cast 40 mm construction, thick insulating layer. The ultimate for pure axial loaded panels was computed using expressions applicable to solid walls could not be directly applied to sandwich panel. However, important factor influencing
eccentric loadings. The eccentricity was applied at 1/6 of the wall thickness. The reinforcement was disposed in double layers symmetrically and separately placed within the wall thickness. Vertical reinforcement ratios (ρv) were more than the minimum requirements and varied between 0.0033 and 0.0047. The compressive cylinder strength of the concrete was between 28 and 42 Mpa and yield strength of steel ranged from 512.8 to 604.2 MPa. The following conclusions were reached:
i. Under axial and eccentric loading, panels with H/tw values less than 20 failed by crushing while those with larger values of H/tw failed due to buckling. The lateral deflections at the instant of failure did not increase dramatically for H/tw values less than 20, while a dramatic increase was observed for values more than 20.
ii. The reduction in strength due to an eccentricity of tw/6 of the wall thickness varied from 18 percent to 50 percent for variation in slenderness ratios from 8 to 28 respectively.
Pillai and Parthasarathy (1977) tested eighteen large scale wall models with various H/t ratios from 5 to 30. The walls were grouped into three groups; namely group A, B and C. The walls in group A were provided with the minimum reinforcement. The group B walls had twice as much steel area as the walls in group A. The walls in group C were not reinforced. The walls were tested under pinned-end condition at both pinned-ends with applied axial loading until failure. The lateral deflection at critical points, the axial shortening, and the axial and lateral surface strain on both faces at critical points were measured at each stage of loading. The test results showed that steel ratio have small significance on the ultimate strength of these walls. It was found that the walls with low slenderness ratio, H/t ≤ 20, generally failed by crushing whereas wall with higher slenderness ratio, H/t > 20, failed by buckling.
2.3.3 Effect of Shear Connector
optimum structural performance. This system using the connector that was made by fiber reinforced plastic bars with prestressed steel strand chords. The experimental program included testing of small scale specimens by pure shear and flexural loading and full scale panels by flexural loading. The analytical investigation included finite element modeling of the tested small scale specimens and comparisons with theory of elasticity. It was found that the experimental and analytical results from software and from theory of elasticity equations correlated well and showed that the developed panel system meet the objectives of the research.
Further experimental investigation by Mohamad (2010) also studied the structural behavior of precast lightweight foamed concrete sandwich panel as a load-bearing wall. Fourteen (14) PLFP panels were involved in this experiment. The panel consists of two lightweight foamed concrete wythes with 40 mm thickness and a polystyrene insulation layer in between the wythes. The foamed concrete wythes in the panels were reinforced with 9 mm high tensile rebar which were tied up to 6 mm steel shear connectors for panels PA-1 to PA-8 and 9 mm steel shear connectors for panels PA-9 to PA-10 bent to an angle of 45º. The panel’s height is between 1800 mm to 2800 mm and its width is 750 mm. The height of the panel and the thickness of the polystyrene layer were varied to get various slenderness ratios.
2.4 Precast Lightweight Foamed Concrete Sandwich Panel
The sandwich panel is unique in its own way because the materials it uses are different from any other sandwich panel. Sandwich panel development had started with normal weight material as both core and faces. However, the use of lightweight material as core layer has become more familiar in recent years. Review of the previous studies below will explain the advantage of using the sandwich panel in the construction field. British Standard, BS 8110: Part 2 (1985) classifies the lightweight concrete as concrete with density of 2000 kg/m3 or less. Among the advantages in using the lightweight materials in the precast concrete sandwich panel are it helps to reduce the self-weight of the panel and overall cost of the construction.
One of the earliest studies on precast concrete sandwich panel was conducted by Pfeifer and Hanson (1964). The study included 50 reinforced sandwich panels with a variety of wythe connectors. The panels were tested in flexure under uniform loading. The test results showed that welded truss-shaped steel connectors are the most effective connection in transferring the shear force. The study also demonstrated the beneficial effect of using concrete ribs to connect the wythes.
According to Pessiki et al. (2003), four full scale of PCSP were tested. The first panel was a typical precast, prestressed concrete sandwich panel that had shear connector provided by regions of solid concrete in the insulation wythe, metal wythe connector (M-ties), and bond between the concrete wythes and the insulation wythe. It was found that the solid concrete region provide most of the strength and stiffness that contribute to composite behaviour. Steel M-ties connectors and bonded between the insulation and concrete contribute relatively little to composite behaviour. Therefore, it is recommended that solid concrete region be proportioned to provide all of the required composite action in precast sandwich panel wall.
Steel Wire Mesh Insulation
Concrete Wythe the insulation layer governs the insulation value of the panel. Precast sandwich panel functions as efficiently as precast solid wall panel but differ in their build-up.
Steel Shear Connector
Figure 2.6: Typical Precast Concrete with Truss Shaped Shear Connector (Benayoune et al., 2006)
Pillai and Parthasarathy (1977) conducted an investigation on solid reinforced concrete about the influence of H/t ratio and steel ratio of the ultimate strength of sandwich wall panels. It was found that the steel ratio has very little influence on the ultimate strength of the walls. The result showed that the models with low H/t ratios generally failed by cracking and splitting near one or both ends of the plates. However, models with H/t ratio > 20 (higher slenderness wall) fail at the mid depth.
panel PA-2 (with symmetrical truss) had a higher strength at 355 kN than panel PE-1 (single diagonal truss) which was at 188 kN. Therefore, the targeted strength for panel PE-2 is achieved. For the load-deflection profiles, panel PE-2 showed smaller deflection measurement than panel PE-1. This indicates that a stronger panel will deflect lesser. Based on the results, the panels failed at the top and bottom of the panel but did not crack at the middle part. This is due to premature material failure which caused local buckling. Despite the failure of the materials which will cause an early crushing, it is believed that by using the double symmetrical truss, it manages to help holding the two concrete wythe together.
Figure 2.7: Precast Concrete Sandwich Panel (Source: Mohamad and Muhammad, 2011)
Insulated sandwich panels are widely used to provide a structural shell for buildings. These panels typically consist of two layers (wythes) surrounding an insulating layer. The outer layers are usually constructed of precast or prestressed concrete and are connected through the insulation layer to form a structurally composite panel. This composite action causes the panel to deflect when the structural wythe experience differences in temperature or humidity due to the presence of the insulation wythe (Einea et al., 1994).
behaviour of reinforced concrete sandwich panels under axial and eccentric loads. However, the numbers of the tested panels were so small which were only four (4) specimens. No generalised inferences could be drawn out of testing on these four specimens. Therefore, in this research eight (8) specimens will be cast and tested. The capacity of panel and its behavior could be accurately studied and concluded. The ultimate load capacity for pure axial loaded panels was proposed based on expressions for design of solid reinforced walls from the codes and for design of sandwiched panels from previous research.
From the previous research, it is noticed that most of the panels developed were made of conventional concrete. Any structural element made from conventional concrete are normally strong but has lower strength over weight ratio. Therefore, further research on this type of panel with lightweight materials is very much in need. The research investigates the structural behavior of Precast Lightweight Foamed Concrete Sandwich Panel, PLFP, with double shear truss connectors under axial Load and two Connected PLFP panels under four point bending load. The aim of this research is to achieve the intended strength for use in low to medium rise building. Considering its lightweight and precast construction method, it is feasible to be developed further as a competitive IBS building system. The result from this research could be used as a guideline for future research to develop PLFP panel as a walling unit in the industry and the future development of PLFP as a structural material.
2.5 Advantage of Sandwich Panels
In concrete construction, self-weight of structure represents a very large proportion of the total load on the structures (Mouli and Khelafi, 2006). Thus reduction in the self-weight of the structures by adopting an appropriate approach results in the reduction of element cross-section, size of foundation and supporting elements thereby reduced overall cost of the project. The lightweight structural elements can be applied for construction of the buildings on soils with lower load-bearing capacity (Carmichael, 1986).
Reduced self-weight of the structures using lightweight concrete reduces the risk of earthquake damages to the structures because the earth quake forces that will influence the civil engineering structures and buildings are proportional to the mass of the structures and building. Thus reducing the mass of the structure or building is of utmost importance to reduce their risk due to earthquake acceleration (Ergul et al., 2003). Among all the advantages, its good thermal insulation due to the cellular thick core makes it an ideal external construction component (Bottcher and Lange, 2006). Some recent investigations suggest their excellent energy-absorbing characteristics under high-velocity impact loading conditions (Villanueva and Cantwell, 2004). Sandwich structures have also been considered as potential candidate to mitigate impulsive (short duration) loads (Nemat-Nasser et al., 2007).
2.6 Foamed Concrete Fabrication
Foamed concrete is a mixture of cement, fine sand, water and special foam which once hardened results in a strong, foamed concrete containing millions of evenly distributed, consistently sized air bubbles and cells. It uses a stable foaming agent and a foaming generator to create a lightweight concrete. In lightweight foam concrete, the density is determined by the amount of foam added to the basic cement. The strength of the concrete is determined by controlled the amount of foam added into cement mixer.
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