PERPUSTARAAN UMP

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A CASE STUDY ON COMPARISON BETWEEN WOOD TRUSS AND

STEEL TRUSS FOR ROOF STRUCTURE

It•J :i uvv u h1IISJi

A thesis submitted in fulfillment of the

requirements for the award of the degree of

Bachelor of Civil Engineering

Faculty of Civil Engineering & Earth Resources

University Malaysia Pahang

JUNE 2013

ABSTRACT

Roof is an important structure found in all types of buildings regardless of

size and shape. The using of wood trusses is widely used for generations before. With

the growing construction on this time, there are other alternatives to replace wood

truss that is widely use before with steel roof truss. Both have advantages and

disadvantages respectively. Features such as workability, durability or strength, and

suitability of the building will determine the type of truss to be used. Therefore, this

study was undertaken to determine the truss suitable for use at this time. This

approach is through questionnaires, observations, and the costs associated with the

use of the two trusses. From this study, we can conclude that both have advantages

and disadvantages truss, because they both have a lot different in terms of

workability and the durability or strength. The results of research shows that the

advantages mostly on using the steel truss. This difference makes them both special

and acting as principle and the contractor or developer choice to build such a

building.

Vi

ABSTRAK

Bumbung adalah merupakan satu struktur penting yang terdapat dalam semua jenis

bangunan tanpa mengira saiz dan bentuk. Penggunaan kekuda kayu adalah

digunakan secara meluas oleh generasi sebelum ini. Dengan pembangunan yang

semakin pesat membangun pada hari i, terdapat alternatif lain untuk

menggantikan kayu yang digunakan secara meluas sebelum mi dengan

menggunakan kekuda keluli untuk struktur bumbung. Kedua-duanya mempunyai

kelebihandan kekurangan masing-masing. Ciri-ciri seperti cara pemasangan,

ketahanan atau kekuatan, dan kesesuaian bangunan itu akan menentukan jenis yang

akan digunakan. Oleh itu, kajian mi dijalankan untuk menentukan kekuda yang

sesuai untuk digunakan pada masa mi. Pendekatan mi adalah melalui soal selidik dan

pemerhatian yang berkaitan dengan penggunaan kedua-dua kekuda. Daripada

kajian mi, kita boleh membuat kesimpulan bahawa kedua-duanya mempunyai

kebaikan dan keburukan kekuda, kerana kedua-duanya mempunyai banyak

perbezaan dari segi ,ketahanan atau kekuatan dan kos. Hasil kajian menunjukkan

bahawa kelebihan kebanyakannya adalah dengan menggunakan kekuda keluli

terutamanya untuk kekuda bumbung. Perbezaan mi menjaclikan mereka kedua-dua

khas dan bertindak sebagai prinsipal dan pemithan kontraktor atau pemaju untuk

membina apa-apa bangunan.

VII

TABLE OF CONTENTS

CHAPTER TITLE PAGE

TITLE PAGE i

SUPERVISOR'S DECLARATION

STUDENT'S DECLARATION

DEDICATION iv

ACKNOWLEDGEMENT v

ABSTRACT vi

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF APPENDICE xiv

INTRODUCTION I

1.1 Background of Study 1

1.2 Problem Statement 3

1.3 Objective of Study 3

1.4 Scope of Work 4

VIII

ix

2 LITERATURE REVIEW 5

2.1 Introduction 5

2.2 Wood Classification 6

2.2.1 Types of Wood 6

2.2.2 Main properties of wood 8

2.2.3 Safety Factor 9

2.3 Wood as material for roof truss structure 10

2.3.1 Truss Connection 13

2.4 Introduction of Steel Roof Truss 17

2.4.1 Type of Connection 18

2.4.2 Joint Design 18

2.4.3 Gusset Plate 19

2.5 Latest Application: Light Truss System 19

2.6 Cold Formed Steel Truss System 21

3 METHODOLOGY 23

3.1 Introduction 23

3.1.1 Literature Method 24

3.1.2 Survey Methods 24

3.1.3 Observation Method 24

3.2 Methodology Flowchart 27

x

4 RESULT AND DISCUSSION 28

4.1 Introduction 28

4.2 Compare the installation of steel and wood trusses 29

4.2.1 Installation Work 32

4.2.2 Connection work 33

4.2.3 Cutting Work 36

4.3 Comparison of Durability Wood and Steel Truss 36

4.3.1 Steel Truss 36

4.3.2 Termite attack problems 38

4.3.3 Wood easy to shrink and bend by weather 39

4.3.4 Durability and Strength of wood less 5 years 41

4.3.5 The use of immature wood 42

4.3.6 Resist to fire resistance 43

4.3.7 Weather Factor are considered 44

4.3.8 Does the Steel can sustain from corrode 46

5 CONCLUSION AND RECOMMENDATION 48

5.1 Introduction 48

5.2 Conclusion 49

5.3 Recommendation 50

REFERENCES 51

APPENDICES 53

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Type of nails and its use in wood working 15

4.1 Data indicate the need of skilled labor at the construction

site of woodand steel trusses 30

4.2 Data comparing needed of labor at the construction site of the

project using wood trusses and steel trusses. 31

4.3 The faster installation between wood and steel trusses. 32

4.4 Data use bolts and nuts used for the two trusses. 33

4.5 Use of equipment and machinery for both trusses 35

4.6 The number of respondents who agreed that the strength of steel

more than wood 37

4.7 Respondents who agreed the wood are exposed to termite

problems. 38

4.8 Weather factor of wood shrinkage and bending terms 40

4.9 Respondents agree that the durability of wood less than 5 years. 41

4.10 Data on the use of immature wood causes wood truss failed. 42

4.11 The number of respondents agreed steel can resist the fire

resistance. 43

4.12 Weather is considered due to the shrinkage and bends 45

4.13 Steel can resist corrosive 46

A

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Timber finish with defect 11

2.2 Arch Truss 12

2.3 Steep Truss 12

2.4 Flat Truss 12

2.5 Toothed Plate 14

2.7 Type of nail 16

2.8 Bolts 16

2.9 Screw 17

3.1 Building using wood truss 26

3.2 Building use steel truss 26

4.1 Pie chart percentages that needed skilled labor at

construction sites between the two trusses. 30

4.2 The pie chart showed the percentage of labor force

needed 31

4.3 Pie chart shows percentage of the faster installation time

between wood trusses and steel trusses. 33

4.4 Pie chart showing percentage use of bolts and nuts used for

the two trusses. 34

4.5 Pie chart showing the use of equipment and machinery for both

trusses 35

XII

4.6 Pie chart show the percentage of respondents who agreed that

the strength of steel is higher than wood.

4.7 Percentage of respondents agrees wood is exposed to termite

problems

4.8 Data on the percentage of weather factors in terms of wood

shrinkage and bend.

4.9 Pie Chart percentage of respondents agrees that the durability

of wood less than 5 years.

4.10 Pie chart of immature use of wood causes wood truss failed.

4.11 The pie chart on the number of respondents agreed steel

resist fire resistance

4.12 Data on the percentage of weather factors of shrinking and bend.

4.13 Data percentage of the steel can sustain from corrode.

37

39

40

41

42

44

45

47

XIII

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Questionnaire 47

xiv

CHAPTER 1

INTRODUCTION

1.1 Background of Study

Malaysia is rapidly developing in line with the government's vision of working

towards a developed nation by the year 2020, and government have implemented

various types of development such as schools, government offices, hospitals, factories,

housing, and so on. Accordingly, the use of roof trusses is one important foundation for

every building, regardless of whether the roof trusses are constructed of wood or steel.

Wood is a material that has long been used in the construction of the structure.

Interesting and rewarding design often produced from wood material. Apart from its use

in building structures of various shapes, wood is also used as a temporary structure for

structural concrete, brick and stone. Nowadays the wood is still an important material in

the construction, although there have been a lot of new materials created and used for

construction.

1

2

Wood also has many uses and advantages that are not may be available on other

materials, and it is more easily done by just using common hand tools. High

understanding of natural events, the advantages and disadvantages of wood is very

important in building design of timber structures. Only higher level of maturity wood is

suitable for the construction of the structure.

In general, this study was conducted to gather information on the use of roof

trusses (steel trusses). Because at present, has many housing projects using steel roof

truss structure replaces a wood truss structure is widely used before. Construction of

steel roof trusses had long been introduced in the country. Mostly, it is used in buildings

such as halls and warehouses, and also includes the housing project. The technology is

still not popular among the developers may be due to the system is still new and ourS

society still, hesitate to use it. Another possibility is steel roof truss system is considered

unsafe and may easily cause problems causing our society to consume less system.

Accordingly, a study involving the cooperation of government and private

agencies such as the Department of Public Works and construction and contractor is

intended to, provide a procedure on the difference between building structures using steel

trusses and wood trusses. Among the benefits derived from this study is to identify the

use of roof trusses and timber trusses which in terms of advantages and disadvantages as

well as the privilege of using the structure, and thus can be used as a more effective

framework in terms of building on the present and gives the developer more alternatives

in terms of construction costs, building facilities and truss structure durability.

3

1.2 Problem Statement

Roof is an important part in the construction of a building. No buildings

constructed without a roof. Thus, the components used to make the structure of the roof

trusses must be high quality and durable. As noted, the wood has a lot of problems such

as problem of termite attack, flammable, endurance less than 5 years and many more.

Previously, wood widely used as roof trusses in terms of durability it is easy to decline

compared with the use of steel. In terms of installation, the use of wood trusses is very

complicated and requires high expertise compared with steel trusses easier and save

time.

1.3 Objective of Study

i. Comparing the method of the installation of steel trusses and wood trusses.

ii. Determine the durability and strength of steel and wood.

4

1.4 Scope of Work

The buildings were selected for the study such as school buildings and

bungalows using wood and steel as the material for the roof trusses.

a) Do research on the advantages, privileges and the use of wood and steel

trusses. Analysis of the connection system is based on the size and type

current applied.

b) Visit the site and meet with the parties involved to obtain more detailed

information.

C) Collect data and display information from various aspects.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

Wood is a material that has long been used in the construction of the structure.

Interesting and satisfied design usually produced from wood material. In addition to

build the structure of uses in variety of shapes, wood is also used as materials for

temporary structures for structural concrete, brick and stone. Today wood remains as an

important ingredient in the construction although there were many new materials are

created and used for construction. This may be because the wood suitable as thermal

insulation and estimated 15 times more heat-resistant than concrete including the

suitability for the building that is always exposed to chemical gases (Mahyuddin Ramli,

1992). Wood is useful material that cannot be replace with other material because it is

easily handle by using common hand tools. Understanding and knowledge of weakness

of wood in the design of timber wood structure is important.

6

There are many type of wood available in Malaysia. Generally wood is divided

into two:

i. Hard wood

ii. Soft wood

Majorities' in Malaysia hard wood available because hard wood are mostly

found in tropical region like our country.

2.2 Wood Classification.

2.2.1 Types of Wood.

Forestry Department of Malaysia classified hardwood into three sub-groups

based on the density and durability of natural wood. Based on the classification of wood

Malaysian Grading Rules, (1984) classified the Malaysian timber as below:

Hardwood Weight (group A) has a density of 800kg/rn 3 to 1200kg/rn3 at 15%

moisture content (Tan Boon Tong, 1994). This type of strong wood and do not require

any preservation treatment to be used. The type of wood are Balau Merah, Cengal,

Giam, Belian, Merbau, Tembusu, Resak, Keranji, and Bitis.

7

ii. Medium Hardwood (group B) has a density of 720kg/rn 3 to 880kg/rn3 at 15%

moisture content (Tan Boon Tong, 1994). This type of natural wood less durability

when exposed to weather and soil. Therefore this kind of wood requires preservation

treatment. This is the type of timber Kempas, Kapur, Kasai, Kelat, Keruing, Kulirn,

Merawan, Petaling, Simpoh, Tualang, Mengkuas, Rengas, Resak, Tembusu and Jati.

Light Hardwood (group C) has a density of 400kg/rn 3 to 720kg/rn3 at 5%

moisture content (Tan Boon Tong, 1994). This type of wood do not have natural

durability. This is the type of wood Medang, Mersawa, Nyatoh, Petai, Pulai, Ramin,

rubber wood, Sentang, sesendok, bintangor, durian and kedondong.

iv. Soft wood (group D) has a density less than 400kg/rn 3 . Wood in this category are

dammar minyak, jelutung, Pulai, sempilor and podo.

Otherwise, wood also classified based on the strength of the wood. This new

classification of wood classify into groups A, B, C and D, from wood that has a high

strength to low strength depend on the basis and stress grade wood species. The

strength of timber in Malaysia is divided into the following groups:

i. Group A: Balau, bitis, cengal, Giarn, Keranji, Kempas and tualang with

strength of 4.9 N/mm2 to 9979 N/mm2 (Tan Boon Tong, 1994).

ii. Group B: merbau, balau merah, Resak, Tembusu, kapur, kelat, keruing,

Merawan, rengas and simpoh with strength from 4:34 N/mm 2 to 8.0 N/mm2

(Tan Boon Tong, 1994).

8

iii. Group C: for example durian, kasai, medang, dark red meranti, light red

meranti, mersawa, nyatoh, ramin, rubber and sentang with strength of 2.65

N/mm2 to 6.0 N/mm2 (Tan Boon Tong, 1994).

iv. Group D: damar minyak, jelutong, petal, Pulai and sesenduk. With strength

of less than 2.0 N/mm2.

2.2.2 Main properties of wood

For the purpose of structure and design, the main properties of wood used as a

reference are:

i. Strength

ii. Moisture content

iii. Finishing.

9

2.2.3 Safety factor

Strength of wood depends on the factors of density, moisture content, wood

grain structure, defects found in timber and wood modulus of elasticity. Typically wood

has a high strength stronger than the wood has low strength. Although of the same type,

there are also differences in terms of the strength of the wood. Strength variability is

caused by growth factors, age, breed and resources.

Moisture content is the quantity of water content in the wood. Decline in wood

moisture content will cause wood to shrink and may reduce the durability of the wood,

so perfect drying should be done to prevent the wood from deformed or damaged. Wood

used for interior work, it shall be 8% moisture content, while for external work, it must

have a 15% moisture content. Below fiber saturation point, wood strength increased

with decreasing moisture content of wood, while the fiber saturation point was no

change in the strength of the wood.

Wood that had cut usually are not free from defects, this defect may occur from

the growth process, splitting and drying. These defects destroy the look of wood

finishes. Excessive drying, exposure to wind and rain, restructuring and imperfect wood

distance will cause defect and influence of the wood finishing. Figure 2.1 shows the

condition of the wood finish may occur.

There are several factors that should be considered in the design to determine the

safety factor. These factors include the load, size, shape and other factors beyond

engineering research.

10

2.3 Wood as material for roof truss structure

The roof is a structure built to protect steep or flat buildings constructed of

wood, steel or concrete. It also acts as a self burden, the burden of roof coverings and

wind load (Jahiman Badrom, 1988). Roof should meet the following requirements and

characteristics

i. Stability

ii. Strength

iii. Durability

iv. Weather resistance

v. Resistance to fire

vi. Thermal insulation properties

vii. design of the building

Truss can be defined as a structural framework composed of members connected

to each other. In principle, it is charged at the points of connection and internal stresses

to its members. This is dependent on the tension compression (Jahiman Badrom, 1988).

The wood used for the trusses should be the least of the group B. There are three basic

types of trusses:

i. Arch truss (Figure 2.2)

ii. Steep truss (Figure 2.3)

iii. Flat truss (Figure 2.4)

(9)

Face knot

e)

Edge knot

11

Surface thk

Erd lit API. (h)

(a) k9s (b) sbake,3, (c) oanes (d) dicks and splits, () bowing (0 croQkIng g) cupping, arili r) twsrirg

Shake

Figure 2.1 Timber finish with defect.

12

14 L FAA ;1 JIL BOWSTRING

GAMBREL

Figure 2.2: Arch Truss

ATTIC

Figure 2.3: Steep Truss

FLAT

Figure 2.4: Flat Truss

FAN

13

The procedure to design the truss as shown below:

i. Select the layout and types of trusses appropriate.

ii. Allocates load on the roof.

iii. Analysis truss to obtain the forces in the members

iv. Moment analysis on the rafter and the bottom hanger ceilings.

V. Member design.

vi. Design connection

vii. Prepare detailed drawings.

2.3.1 Truss connection.

Appropriate connection need for the load of a structure to transfer a member to

another member to be distributed safely and effectively. There are various types of

connections in the market now among them are toothed plate (Figure 2.5), gusset plate

(Figure 2.6), nail (Table 2.1,and Figure 2.7), bolts (Figure 2.8) , screws (figure 2.9),

shear plates, and other patented connection type.

I,-...../

c ;;_:

IstT$

oijsr

L

14

Figure 2.5: Toothed Plate

Figure 2.6: Gusset Plate