STRUCTURAL STRESS GRADING OF SELECTED SARAWAK TIMBER USING

NON-DESTRUCTIVE TESTS

ALIK ANAK DUJU

DOCTOR OF PHILOSOPHY UNIVERSITI SAINS MALAYSIA

2009

STRUCTURAL STRESS GRADING OF SELECTED SARAWAK TIMBER USING NON-DESTRUCTIVE TESTS

by

ALIK ANAK DUJU

Thesis submitted in fulfilment of the requirements for the degree of

Doctor of Philosophy

May 2009

ii

ACKNOWLEDGEMENTS

I wish to express my sincere gratitude and appreciation to my supervisors

Associate Professor Dr. Badorul Hisham Abu Bakar and Senior Lecturer Dr. Megat

Azmi Megat Johari of School of Civil Engineering, Engineering Campus, Universiti

Sains Malaysia (USM), Pulau Pinang, Malaysia for their invaluable guidance,

suggestions and constructive criticisms that lead to the completion of the research

project for Doctor of Philosophy (PhD).

Sincere thanks are due to the Managing Director/Chief Executive Officer of

Sarawak Forestry Corporation Sdn. Bhd. (SFCSB), Datu Haji Len Talif Salleh, General

Manager of Applied Forest Science and Industry Development (AFSID), SFCSB, Mr.

Nigel Lim Poon Teck and Senior Assistant Director (Research and Development) of

Forest Department, Sarawak, Tuan Haji Abang Mohamad Moktar Abang Pawozan for

giving me the opportunity to use the research equipment and testing facilities.

Acknowledgements are due to Dr. Takashi Nakai, ex-JICA Team Leader, Dr.

Naohiro Kuroda, Dr. Toshinari Tanaka and Dr. Hirofumi Nagao of Forestry and Forest

Products Research Institute (FFPRI), Tsukuba, Japan, Professor Dr. Mohd. Hamami

Sahri and Associate Professor Dr. Paridah Md. Tahir of Faculty of Forestry, Universiti

Putra Malaysia (UPM), Serdang, Associate Professor Dr. Mohd. Ariff Jamaludin of

Faculty of Applied Science, Universiti Teknologi Mara (UiTM), Shah Alam, Associate

Professor Dr. Taksiah Abdul Majid and Lecturer Dr. J. Jayaprakash of School of Civil

Engineering, Engineering Campus, SM and Manager Mr. Kandau Jenang, of Testing and

iii

Consultancies, AFSID, SFCSB, for their comments and suggestions on the write-up of

this thesis.

Thank you very much goes to the staff of Basic Wood Study of Forest Products

of SFCSB particularly Development Executive Mr. Andrew Nyorik Nibu, Laboratory

Technicians namely, Mr. Nungah Liang, and Mrs. Yeo Hui Choo for assisting in the

preparation and testing of timber samples. Thanks also to Development Executive Mr.

Lai Jiew Kok on assisting in the analysis of data using SPSS and Laboratory Technician

Mr. Tan Jui Liah for his assistance in providing the data on drying of timber species. To

all the staff of Wood Anatomy Section especially to Development Executive Mr. Yang

Min Chin, Laboratory Technicians viz., Mr. Voon Shin Lee and Mr. Charles Diyom for

assisting in identification of timber species are very much appreciated. Once again, I

would like to express my profound thanks to all of them.

Finally, I like to convey my very special gratitude to my beloved wife, Dumang

Dullah, my son Lawrence Insol who is currently pursuing his Bachelor of Science

Degree in Timber Technology at UPM, daughters Delphanie Lonnie and Valarie Ching

for their patience, love and encouragement. To my beloved mother Noi Insol, brother

Ujoh Duju, sisters viz., Urie Duju, Gansau Duju, Tanai Duju, Choawan Duju and Runtie

Duju, brother in-laws, sister in-laws, friends and colleagues for their encouragement,

concern and moral support throughout the course of this study.

iv

TABLE OF CONTENTS

Page

Acknowledgments ii

Table of Contents iv

List of Tables x

List of Figures xi

List of Plates xix

List of Abbreviations xxi

Abstrak xxiii

Abstract xxiv

CHAPTER 1 - INTRODUCTION 1

1.1 Background 1

1.2 Problem Statement 5

1.3 Objectives of Study 6

1.4 Scope of Works 6

1.5 Outline of the Thesis 7

CHAPTER 2 - LITERATURE REVIEW 11

2.1 Forestry of Sarawak 11

2.2 Forest Industry Sector of Sarawak 15

2.3 Utilization of Timber in Construction 18

2.4 Properties of Selected Timber Species 21

2.4.1 Selangan batu bukit (Shorea foxworthyi) 22

v

2.4.2 Menggris (Koompassia malaccensis) 23

2.4.3 Penyau (Upuna borneensis)

24

2.4.4 Kapur paya (Dryobalanops rappa)

25

2.4.5 Alan batu (Shorea albida) 27

2.4.6 Jongkong (Dactyloclados stenostachys) 28

2.4.7 Geronggang (Cratoxylum arborescens) 29

2.5 Grading of Timber 31

2.5.1 Visual Grading of Timber 34

2.5.2 Mechanical Grading of Timber 36

2.5.3 Limitations of Timber Grading 37

2.5.4 Grade Stresses of Timber 39

2.6 Destructive Evaluation of Timber 40

2.7 Non-Destructive Evaluation of Timber 41

2.7.1 Frequency Vibration Method 43

2.7.2 Bending Deflection Method 44

2.7.3 Penetration Depth of Pin Method 45

2.8 Strength Properties 45

2.8.1 Timber Species 46

2.8.2 Density 48

2.8.3 Moisture Content 50

2.8.4 Wood Defects 51

2.8.4.1 Knots 51

2.8.4.2 Sloping Grain 53

vi

2.8.4.3 Other Factors 55

2.9 Summary 57

CHAPTER 3 - MATERIALS AND TEST METHODS 58

3.1 Introduction 58

3.2 Materials 58

3.2.1 Sampling of Timber Samples 59

3.2.2 Preparation of Timber Samples 63

3.2.3 Seasoning and Conditioning of Timber Samples 63

3.3 Test Methods 65

3.3.1 Non-Destructive Testing 65

3.3.1.1 Longitudinal Vibration Frequency Method

65

3.3.1.2 Dead Weights Loading Method

67

3.3.2 Destructive Testing 69

3.3.2.1 Static Bending Test for Full Size Structural Samples

69

3.3.2.2 Static Bending Test for Small Clear Specimens

71

3.3.2.3 Compression Parallel to Grain for Small Clear Specimens

72

3.3.2.4 Pilodyn Penetration Depth 73

3.3.3 Physical Properties 74

3.3.3.1 Moisture Content Determination 74

3.3.3.2 Density Determination 75

3.2.3.3 Grain Angle Determination 76

3.3.3.4 Knot Size Ratio Determination 77

vii

3.3.4 Statistical Analysis

77

3.4

Summary 78

CHAPTER 4 - RESULTS AND DISCUSSION 79

4.1 Introduction 79

4.2 Physical and Mechanical Properties of Structural Timber 80

4.2.1 Moduli of Elasticity of Structural Timber 82

4.2.2 Bending Strength of Structural Timber 85

4.2.3 Air-Dried Density of Structural Timber 87

4.2.4 Moisture Content of Structural Timber 88

4.2.5 Strength Properties of Small Clear Specimens 90

4.2.6 Compressive Strength Parallel to Grain for Small Clear Specimens

92

4.3 Results of Visual Parameters and Pilodyn Penetration of Structural Timber

93

4.4 Comparison of Grade Stresses of Strength Properties of Timber 95

4.4.1 Comparison of Grade Stresses of Moduli of Elasticity and Timber Species

96

4.4.2 Comparison of Grade Stresses of Bending Strength of Timber Species

99

4.5 Rupture Pattern of Static Bending Test of Structural Timber 102

4.6 Summary 105

CHAPTER 5 – RELATIONSHIP OF NDT WITH OTHER PARAMETERS

106

5.1 Introduction 106

5.2 Relationship between Strength Properties of Structural Timber 106

viii

5.2.1 Relationship between Moduli of Elasticity of Heavy Hardwood

107

5.2.2 Relationship between Moduli of Elasticity and Bending Strength of Heavy Hardwood

113

5.2.3 Relationship between Moduli of Elasticity of Medium Hardwood

117

5.2.4 Relationship between Moduli of Elasticity and Bending Strength of Medium Hardwood

123

5.2.5 Relationship between Moduli of Elasticity of Light Hardwood

127

5.2.6 Relationship between Moduli of Elasticity and Bending Strength of Light Hardwood

134

5.2.7 Relationship between Moduli of Elasticity of Timber Species

138

5.2.8 Relationship between Moduli of Elasticity and Bending Strength of Timber Species

145

5.2.9 Effect of Visual Parameter and Strength Properties of Timber Species

151

5.3 Effect of Density on Strength Properties of Structural Timber 154

5.3.1 Relationship between Density with Strength Properties of Heavy Hardwood

155

5.3.2 Relationship between Density with Strength Properties of Medium Hardwood

159

5.3.3 Relationship between Density with Strength Properties Light Hardwood

164

5.3.4 Relationship between Density with Strength Properties of Timber Species

168

5.4 Relationship between Pilodyn Penetration with Density and Strength Properties of Structural Timber

174

5.4.1 Relationship between Pilodyn Penetration with Density and Strength Properties of Heavy Hardwood

175

ix

5.4.2 Relationship between Pilodyn Penetration with Density and Strength Properties of Medium Hardwood

178

5.4.3 Relationship between Pilodyn Penetration with Density and Strength Properties of Light Hardwood

180

5.4.4 Relationship between Pilodyn Penetration with Density and Strength Properties of Timber Species

183

5.5 Relationship between Small Clear and Structural Size Samples 186

5.6 Effect of Length/Height and Modulus of Elasticity (Efrl/Etru) Ratio of Timber Species

189

5.7 Summary 191

CHAPTER 6 - CONCLUSIONS AND RECOMMENDATIONS 193

6.1 Conclusions 193

6.2 Recommendations 196

REFERENCES 200

APPENDICES 211

PUBLICATION LIST 266

x

LIST OF TABLES

Page

Table 2.1 Timber species found in different forest types

13

Table 2.2 Number and types of timber mills in Sarawak

17

Table 2.3 Non-destructive tests methodologies for wood products in North America

42

Table 2.4 Strength properties of non-dipterocarp timbers of Sarawak 47

Table 3.1 Local name and botanical name of timber species

59

Table 4.1 Main test results of strength properties of timber species

81

Table 4.2 Number of days to achieve air-dried condition of timber species

90

Table 4.3 Test results of visual parameters and pilodyn penetration

95

Table 4.4 Comparison of grade stresses in moduli of elasticity of structural and small clear specimens

98

Table 4.5 Comparison of grade stresses in static bending strength of structural and small clear specimens

100

Table 4.6 Strength ratio of almost defect free structural and small clear specimens

101

Table 5.1 Coefficient of correlation between moduli of elasticity of heavy hardwood

108

Table 5.2 Coefficient of correlation between moduli of elasticity of medium hardwood

118

Table 5.3 Coefficient of correlation between moduli of elasticity of light hardwood

129

Table 5.4 Coefficient of correlation between moduli of elasticity of timber species

140

Table 5.5 Correlation of coefficient between visual parameters and strength properties

153

Table 5.6 Number of samples with different timber span 190

xi

LIST OF FIGURES

Page

Figure 2.1 Derivation grade stresses from strength properties of small clear specimens

40

Figure 2.2 Relationship between air-dried density and modulus of rupture of Kapur species (Alik, 2002)

49

Figure 2.3 Normalized frequency of bending strength of Kapur species at green and air-dried conditions (Alik and Andrew, 2006)

50

Figure 3.1

Flow-chart on the samples preparation and testing

62

Figure 3.2 Test set-up for longitudinal vibration frequency method

67

Figure 3.3 Test set-up for dead weights loading deflection method

68

Figure 3.4 Test set-up of structural sample for static bending

70

Figure 3.5 Test set-up for small clear specimen for static bending

72

Figure 4.1

Mean of moduli of elasticity of structural timber 83

Figure 4.2

Mean bending strength of structural timber 86

Figure 4.3

Mean of air-dried density of structural timber 88

Figure 4.4

Mean of modulus of elasticity of small clear specimens 91

Figure 4.5

Mean of bending strength of small clear specimens 92

Figure 4.6 Mean of compressive strength parallel to grain of small clear specimen

93

Figure 4.7

Number of specimens tested for each timber grade 97

Figure 4.8

Distribution pattern of rupture bending test of structural timber

104

Figure 5.1 Relationship between Edwe and Efrl of structural timber of heavy hardwood

109

xii

Figure 5.2 Relationship between Edwf and Efrl of structural timber of

heavy hardwood

109

Figure 5.3 Relationship between Eapp and Efrl of structural timber of heavy hardwood

110

Figure 5.4 Relationship between Etru and Efrl of structural timber of heavy hardwood

110

Figure 5.5 Relationship between Edwf and Edwe of structural timber of heavy hardwood

111

Figure 5.6 Relationship between Eapp and Edwe of structural timber of heavy hardwood

111

Figure 5.7 Relationship between Etru and Edwe of structural timber of heavy hardwood

112

Figure 5.8 Relationship between Eapp and Edwf of structural timber of heavy hardwood

112

Figure 5.9 Relationship between Etru and Edwf of structural timber of heavy hardwood

113

Figure 5.10 Relationship between Eapp and MOR of structural timber of heavy hardwood

114

Figure 5.11 Relationship between Etru and MOR of structural timber of heavy hardwood

115

Figure 5.12 Relationship between Edwe and MOR of structural timber of heavy hardwood

115

Figure 5.13 Relationship between Edwf and MOR of structural timber of heavy hardwood

116

Figure 5.14 Relationship between Efrl and MOR of structural timber of heavy hardwood

116

Figure 5.15 Coefficient of correlation between MOE and MOR of heavy hardwood

117

Figure 5.16 Relationship between Edwe and Efrl of structural timber of medium hardwood

119

xiii

Figure 5.17 Relationship between Edwf and Efrl of structural timber of

medium hardwood

119

Figure 5.18 Relationship between Eapp and Efrl of structural timber of medium hardwood

120

Figure 5.19 Relationship between Etru and Efrl of structural timber of medium hardwood

120

Figure 5.20 Relationship between Edwf and Edwe of structural timber of medium hardwood

121

Figure 5.21 Relationship between Eapp and Edwe of structural timber of medium hardwood

121

Figure 5.22 Relationship between Etru and Edwe of structural timber of medium hardwood

122

Figure 5.23 Relationship between Eapp and Edwf of structural timber of medium hardwood

122

Figure 5.24 Relationship between Etru and Edwf of structural timber of medium hardwood

123

Figure 5.25 Relationship between Eapp and MOR of structural timber of medium hardwood

124

Figure 5.26 Relationship between Etru and MOR of structural timber of medium hardwood

125

Figure 5.27 Relationship between Edwe and MOR of structural timber of medium hardwood

125

Figure 5.28 Relationship between Edwf and MOR of structural timber of medium hardwood

126

Figure 5.29 Relationship between Efrl and MOR of structural timber of medium hardwood

126

Figure 5.30 Coefficient of correlation between MOE and MOR of medium hardwood

127

Figure 5.31 Relationship between Edwe and Efrl of structural timber of light hardwood

129

xiv

Figure 5.32 Relationship between Edwf and Efrl of structural timber of light

hardwood

130

Figure 5.33 Relationship between Eapp and Efrl of structural timber of light hardwood

130

Figure 5.34 Relationship between Etru and Efrl of structural timber of light hardwood

131

Figure 5.35 Relationship between Edwf and Edwe of structural timber of light hardwood

131

Figure 5.36 Relationship between Eapp and Edwe of structural timber of light hardwood

132

Figure 5.37 Relationship between Etru and Edwe of structural timber of light hardwood

132

Figure 5.38 Relationship between Eapp and Edwf of structural timber of light hardwood

133

Figure 5.39 Relationship between Etru and Edwf of structural timber of light hardwood

133

Figure 5.40 Relationship between Eapp and MOR of structural timber of light hardwood

135

Figure 5.41 Relationship between Etru and MOR of structural timber of light hardwood

135

Figure 5.42 Relationship between Edwe and MOR of structural timber of light hardwood

136

Figure 5.43 Relationship between Edwf and MOR of structural timber of light hardwood

136

Figure 5.44 Relationship between Efrl and MOR of structural timber of light hardwood

137

Figure 5.45 Coefficient of correlation between MOE and MOR of light hardwood

137

Figure 5.46 Relationship between Edwe and Efrl of structural timber

140

xv

Figure 5.47 Relationship between Edwf and Efrl of structural timber

141

Figure 5.48 Relationship between Eapp and Efrl of structural timber

141

Figure 5.49 Relationship between Etru and Efrl of structural timber

142

Figure 5.50 Relationship between Edwf and Edwe of structural timber

142

Figure 5.51 Relationship between Eapp and Edwe of structural timber

143

Figure 5.52 Relationship between Etru and Edwe of structural timber

143

Figure 5.53 Relationship between Eapp and Edwf of structural timber

144

Figure 5.54 Relationship between Etru and Edwf of structural timber

144

Figure 5.55 Relationship between Eapp and MOR of structural timber

147

Figure 5.56 Relationship between Etru and MOR of structural timber

148

Figure 5.57 Relationship between Edwe and MOR of structural timber

148

Figure 5.58 Relationship between Edwf and MOR of structural timber

149

Figure 5.59 Relationship between Efrl and MOR of structural timber

149

Figure 5.60 Coefficient of correlation between MOE and MOR of timber species

150

Figure 5.61 Relationship between density and Etru of structural timber of heavy hardwood

156

Figure 5.62 Relationship between density and Eapp of structural timber of heavy hardwood

156

Figure 5.63 Relationship between density and Edwe of structural timber of heavy hardwood

157

Figure 5.64 Relationship between density and Edwf of structural timber of heavy hardwood

157

Figure 5.65 Relationship between density and Ef rl of structural timber of heavy hardwood

158

xvi

Figure 5.66 Relationship between density and MOR of structural timber of

heavy hardwood

158

Figure 5.67 Coefficient of correlation between density and strength properties of heavy hardwood

159

Figure 5.68 Relationship between density and Eapp of structural timber of medium hardwood

160

Figure 5.69 Relationship between density and Etru of structural timber of medium hardwood

161

Figure 5.70 Relationship between density and Edwe of structural timber of medium hardwood

161

Figure 5.71 Relationship between density and Edwf of structural timber of medium hardwood

162

Figure 5.72 Relationship between density and Efrl of structural timber of medium hardwood

162

Figure 5.73 Relationship between density and MOR of structural timber of medium hardwood

163

Figure 5.74 Coefficient of correlation between density and strength properties of medium hardwood

163

Figure 5.75 Relationship between density and Eappof structural timber of light hardwood

165

Figure 5.76 Relationship between density and Etru of structural timber of light hardwood

165

Figure 5.77 Relationship between density and Edwe of structural timber of light hardwood

166

Figure 5.78 Relationship between density and Eawf of structural timber of light hardwood

166

Figure 5.79 Relationship between density and Efrl of structural timber of light hardwood

167

Figure 5.80 Relationship between density and MOR of structural timber of light hardwood

167

xvii

Figure 5.81 Coefficient of correlation between density and strength

properties of light hardwood

168

Figure 5.82 Relationship between density and Eapp of structural timber

170

Figure 5.83 Relationship between density and Etru of structural timber

171

Figure 5.84 Relationship between density and Edwe of structural timber

171

Figure 5.85 Relationship between density and Edwf of structural timber

172

Figure 5.86 Relationship between density and Efrl of structural timber

172

Figure 5.87 Relationship between density and MOR of structural timber

173

Figure 5.88 Coefficient of correlation between density and strength properties of timber species

173

Figure 5.89 Relationship between pilodyn penetration and density of heavy hardwood

176

Figure 5.90 Relationship between pilodyn penetration and Etru of heavy hardwood

176

Figure 5.91 Relationship between pilodyn penetration and Eapp of heavy hardwood

177

Figure 5.92 Relationship between pilodyn penetration and MOR of heavy hardwood

177

Figure 5.93 Relationship between pilodyn penetration and density of medium hardwood

178

Figure 5.94 Relationship between pilodyn penetration and Etru of medium hardwood

179

Figure 5.95 Relationship between pilodyn penetration and Eapp of medium hardwood

179

Figure 5.96 Relationship between pilodyn penetration and MOR of medium hardwood

180

Figure 5.97 Relationship between pilodyn penetration and density of light hardwood

181

xviii

Figure 5.98 Relationship between pilodyn penetration and Etru of light

hardwood

181

Figure 5.99 Relationship between pilodyn penetration and Eapp of light hardwood

182

Figure 5.100 Relationship between pilodyn penetration and MOR of light hardwood

182

Figure 5.101 Relationship between pilodyn penetration and density of structural timber

184

Figure 5.102 Relationship between pilodyn penetration and Etru of structural timber

184

Figure 5.103 Relationship between pilodyn penetration and Eapp of structural timber

185

Figure 5.104 Relationship between pilodyn penetration and MOR of structural timber

185

Figure 5.105 Relationship between Etru of structural and MOE of small clear specimens

187

Figure 5.106 Relationship between Eapp of structural and MOE of small clear specimens

188

Figure 5.107 Relationship between structural and small clear specimens in MOR

188

Figure 5.108 Relationship between ratio of L/H and ratio of Efrl/Etru

191

xix

LIST OF PLATES

Page

Plate 2.1 Forest types of Sarawak

12

Plate 2.2 Longitudinal surface of Selangan batu bukit

22

Plate 2.3 Longitudinal surface of Menggris

24

Plate 2.4 Longitudinal surface of Penyau

25

Plate 2.5 Longitudinal surface of Kapur paya

26

Plate 2.6 Longitudinal surface of Alan batu

28

Plate 2.7 Longitudinal surface of Jongkong

29

Plate 2.8 Longitudinal surface of Geronggang

30

Plate 2.9 Knot

53

Plate 2.10 Measurement of slope of grain

54

Plate 2.11 Split

55

Plate 2.12 Check

56

Plate 3.1 Mixed Dipterocarp Forest

60

Plate 3.2 Peat Swamp Forest

60

Plate 3.3 Identification of timber samples

61

Plate 3.4 Processing and machining of timber samples

63

Plate 3.5 Drying of timber samples

64

Plate 3.6 Compression parallel to grain

73

Plate 3.7 Pilodyn wood tester

74

Plate 3.8 Drying oven

75

xx

Plate 3.9 Swivel handled scriber

77

Plate 4.1 Brash tension

103

Plate 4.2 Cross grain

103

Plate 4.3 Compression and tension

103

Plate 4.4 Horizontal shear

103

Plate 4.5 Sloping grain

104

xxi

LIST OF ABBREVIATIONS

ALAN Alan batu

BS British standard

AD Air-dried density

Eapp Apparent modulus of elasticity, obtained at mid-span deformation under two-point loading

Edwe Dead weights loading modulus of elasticity at edgewise

Edwf Dead weights loading modulus of elasticity at flat-wise

Efrl Dynamic longitudinal fundamental vibration frequency modulus of elasticity

EMC Equilibrium moisture content

Etru True modulus of elasticity

FSP

Fibre saturation point

GERO Geronggang

JONG Jongkong

KAPA Kapur paya

KSR Knot size ratio

MC Moisture content

MGR Malaysian grading rules

MGRS Menggris

MOE Modulus of elasticity

MOR Modulus of rupture (Ultimate bending strength)

xxii

MS Malaysian standard

n Number of test specimens

PYAU Penyau

SG Strength group

SLGB Selangan batu bukit

xxiii

PENGGREDAN TEGASAN STRUKTUR BAGI KAYU TERPILIH SARAWAK MENGGUNAKAN UJIAN-UJIAN TANPA MUSNAH

ABSTRAK

Sebanyak tujuh spesies kayu terpilih iaitu, Selangan batu bukit, Menggris,

Penyau, Kapur paya, Alan batu, Jongkong dan Geronggang digunakan untuk mengkaji

hubung kait diantara ciri-ciri kekuatan bagi kayu yang bersaiz struktur. Lima ujian-ujian

tanpa musnah iaitu, Efrl, Edwe, Edwf, Eapp dan Etru telah dibandingkan bagi meramalkan

ciri-ciri fizikal dan kekuatan lenturan kayu pada tahap kering udara. Hasil daripada

kajian, didapati bahawa Selangan batu bukit merupakan spesies kayu yang paling kuat

berdasarkan Eapp dan Etru diikuti oleh Menggris, Kapur paya, Penyau, Alan batu,

Jongkong dan Geronggang. Berdasarkan nilai MOR, Selangan batu bukit juga adalah

paling kuat diikuti oleh Menggris, Penyau, Kapur paya, Alan batu, Jongkong dan

Geronggang. Didapati bahawa korelasi sederhana kuat hingga kuat diantara modulus

kenyalan tanpa musnah dan MOR bagi kumpulan kayu keras berat, sederhana dan

ringan. Dengan mengabungkan kesemua tujuh spesies kayu akan memberi keputusan

korelasi yang lebih baik. Daripada kesemua keadah tanpa musnah, Efrl merupakan

keadah yang paling baik sekali dibandingkan kaedah tanpa musnah yang lain bagi

meramalkan ciri-ciri kekuatan kayu. Hubung kait antara ketumpatan, kedalaman pilodyn

dan nilai kekuatan diperolehi daripada kayu bersiz kecil dengan ciri-ciri kekuatan

struktur bagi tujuh spesies juga menghasilkan hubung kait yang kuat. Didapati bahawa

dengan menggunakan nilai MOEmin dihasilkan dari kayu bersaiz kecil merupakan nilai

yang selamat untuk tujuan rekaan.

xxiv

STRUCTURAL STRESS GRADING OF SELECTED SARAWAK TIMBER USING NON-DESTRUCTIVE TESTS

ABSTRACT

A total of seven selected timber species namely, Selangan batu bukit, Menggris,

Penyau, Kapur paya, Alan batu, Jongkong and Geronggang were used to study the

relationship between the strength properties of full size structural timber. Five non-

destructive tests namely, Efrl, Edwe, Edwf, Eapp and Etru were used to predict the physical

and strength properties of air-dried full size structural timber. Results indicated that

structural timber of Selangan batu bukit exhibited the highest values of Eapp and Etru

followed by Menggris, Kapur paya, Penyau, Alan batu, Jongkong and Geronggang.

Selangan batu bukit also produced the strongest in term of MOR followed by Menggris,

Penyau, Kapur paya, Alan batu, Jongkong and Geronggang. Moderately strong to strong

coefficient of correlations was observed between non-destructive moduli of elasticity

and MOR on heavy, medium and light hardwood groups. Pooled results of the seven

timber species indicated better correlations. Efrl seemed to be the best method compared

to the other non-destructive tests in predicting the strength properties. Relationships

between density, pilodyn penetration and strength values from small clear specimens

with strength properties of structural timber of the seven timber species also indicated

strong correlations. It was found that MOEmin values and their grade stresses derived

from small clear specimens seemed to be safe values for use for design purposes.

1

CHAPTER 1

INTRODUCTION

1.1 Background

Malaysia is very fortunate to be blessed with abundant tropical rain forests

that contained the multi-species of fauna and flora. The forests provide a wide range

of goods and services for the benefit of mankind and also play significant roles in the

socio-economic development of our country. The tropical rain forests is

heterogeneous and complex in nature where it contains various species of trees that

produce timber and timber products that contributed significantly to the Growth of

National Products (GNP) and foreign exchange. The natural heritage is a relatively

cheap and renewable source of readily available foods and daily goods for the rural

populace. In addition, it is important for environmental protection, source of

invaluable genetic materials and to ensure a continuous supply of clean water to the

mankind.

The natural forests of Sarawak alone are estimated to contain about 2,500 to

3,000 timber species and floristically are among the richest in the world (Anderson,

1980). Out of the total number of these timber species, the properties and

characteristics of only a few hundred species have been properly described and are

known for their commercial values through the publication of the Malaysian grading

rules for sawn hardwood timber. The properties and characteristics of a large number

of the timber species are not known because they were yet to be evaluated,

documented and published. The large number of timber species available reflects the

high species diversity and variation between species, which will lead to difficulties

associated with species identification, classification and utilization. This has an

2

impact on the effective utilization of these timber species. Hence, it is necessary that

the stress grading system for tropical timbers be introduced for an economical and

efficient utilization if they are to be used as construction materials.

In Sarawak, sawn timber is widely used as construction materials especially

in the housing and construction industry sector. Since timbers in popular demand are

getting scarce and expensive, substitute for these timber species are made based on

the end-use classification rather than by species selection. Timbers species that are

well-known and readily available are always preferred for certain end-user.

According to Mamit (1987) a total of twelve indigenous timber species commonly

used in this industry in Sarawak. From the survey conducted, it was found that the

use of timber in construction revealed that there are considerable differences in the

specifications and sizes of timber used for specific building components. According

to Mamit (1987) specifications made were found to be inadequate with respect to

timber species, timber grades, moisture content and also preservative treatment.

Therefore, it is necessary to introduce the recommended timber specifications meant

for construction materials for the timbers to be utilized effectively and economically.

Generally, timbers intended for use as structural members are designed

through engineering calculations to be applied to timber construction. These types of

calculations, especially those adapted within engineering software are meant for

homogenous structural materials and may not be applicable to non-homogenous

material such as wood. This is very obvious especially in the housing and

construction sector. The contractors tend to have prejudices to timber materials thus

imposed high premium and insurance on timber buildings. The by-laws in the local

3

council normally inhibit the use of timber as permanent structures. Lately, metals and

concrete have been preferred over wood for the structural components due to

homogeneity in terms of their properties.

Generally, designers see timber as a novelty, suitable for domestic dwellings

but not for structural application. This attitude towards timber arises because of

timbers natural variation which tends to reduce designer’s confidence in the material

and also cause minor construction difficulties. To eradicate the prejudices on timber

such as, fire hazards, not durable and meant only for temporary structures, there must

be of good timber design, workmanship and proper timber specifications. For

example, it is well-known that although timber is combustible materials, it has low

ignitability and large cross-section do not buckles or crumbles like steel or concrete

which are non-combustible materials under intense heat. It is also known that most of

the designers, engineers and architects involved in the construction industry have

very little or no knowledge at all on timber design as a result of training background.

To have a proper utilization of timber as the materials, certain grading rules and

guidelines have to be properly understood and strictly adhered to and perceptions of

timber as a secondary construction material need to be changed.

Modern technology has made possible with the development of improved

grading practices and improved engineered timber products. A faster, more reliable

and cheaper way to determine the timber strength is inevitable as the demand of

timber with high strength values that has been graded in a controlled manner is on

the increase. After all, to use timber safely and reliably in construction, each member

has to be assessed for its load-bearing capacities. Non-destructive evaluation is one

4

of the methods that can be useful in grading of structural materials. Non-destructive

evaluation methods have been developed based on instrumented quantifiable

measurements and thus minimize human subjectivity (Bodig, 1994). This is the

potential method that can be tapped to replace the current visual grading which can

be considered obsolete and outdated. Limited work has been done to develop and

implement stress grading system for our tropical timber. In addition, so far there is

no unified international standard used to grade timber especially for the tropical

hardwood. The grading system for the tropical hardwoods based on the temperate

softwood would be not appropriate and not applicable as properties of hardwood and

softwood are very much different with each others.

The availability of renewable low-cost timber materials, coupled with

technical data on strength and durability properties and a strong commitment to

technology transfer and marketing to overcome the culture barrier can provide a

significant increase in the use of timber as construction materials. Culture

perceptions namely, the use of timber being reflective of a poor man’s material,

timber is non-durable material and being not able to acquire financing or insurance

would contribute to the restriction of timber as construction materials. At the

moment, there is no sawmill interested in producing mechanical stress graded timber

because they perceived that lack of market for such materials both domestically and

abroad. Unless there is a harmonized stress grading rule at least on a regional basis

meant for tropical hardwood timbers.

There are various techniques and equipment available in the market that can

be used for non-destructive evaluation of timbers, timber structures, wood products

5

and many others. The equipment available varies in term of the price, size, design,

function, efficiency and reliability. In the temperate countries, non-destructive testing

techniques have been widely used to grade and test full size timber structure. There is

a need to determine if this equipment is suitable or reliable to be used for non-

destructive testing equipment for tropical timbers.

1.2 Problem Statement

For the past years in Malaysia, strength properties of wood were determined

by testing of small clear specimens. The test results obtained are being used to

classify timber groups as stated in the Malaysian Grading Rules and also used to

derive the grade stresses such as select, standard and common grades, respectively

(Engku, 1971). However, it was found that the assumptions of stress ratio to derive

the permissible unit stress could not work effectively for every timber species.

According to the study conducted by Alik and Nakai (1997a) found that strength

results determined from full size structural timber was considered to be more reliable

to assign the design stress thus eliminates the risk of stress ratio assumptions.

Currently, visual stress grading rule is being used to grade timber however,

the grading rules are often unknown, the benefits are not understood and there is no

value-added pricing to the graded timber in the market place. It is used to grade

timber based on size and position of wood defects such as knot, slope of grain,

brittle-heart and wane (Anon, 1984). This type of grading on timber is more

appropriate for non-structural applications as it is not able to estimate the loading

capacity of timber in use. The highest grade with visual grading likely will not

achieved the highest possible grade technically. This could be due to wide variation

6

in the inherent characteristics and properties of timber. The control process on the

properties of timber through structural stress grading is an absolute necessity in order

to instill confidence and reliability in using such materials for structural applications.

1.3 Objectives of Study

The main objective of this study is to evaluate non-destructive and destructive

tests on the strength properties of full size structural timber in Sarawak. The

objectives are as follows:

(i) To determine and compare the physical and strength properties of full size

structural timber of selected species.

(ii) To determine the correlation between non-destructive testing and destructive

testing methods.

(iii) To study the relationship between visual parameters and strength properties

of full size structural timber.

(iv) To compare the grade stresses of timber for small clear specimens and full

size structural timber samples.

1.4 Scope of Works

Study on relationship of physical and strength properties of full size structural

timbers are limited to the timber species namely, Selangan batu bukit, Menggris,

Penyau, Kapur paya, Alan batu, Jongkong and Geronggang only. They are selected

for the reasons that the species are representative of each strength group as stated in

Malaysian Standard MS 544: Part 2 and Malaysian grading rules (MGR), being

7

commonly used as construction materials and also due to accessibility and

availability of the species.

Non-destructive tests are also limited to five methods viz., longitudinal

fundamental vibration frequency, dead weights loading deflection at flat-wise and

edgewise, load and deformation at mid-span and at moment constant area were used

for determination of modulus of elasticity values in full size structural timber. These

are considered as potential non-destructive testing methods that can be used for stress

grading of tropical timber. In addition, pilodyn penetration is also used as non-

destructive technique for prediction of physical and strength properties. Two-point

loading and centre-point loading methods are used as destructive tests to determine

the ultimate bending strength values of full size structural and small clear timber

samples, respectively.

1.5 Outline of the Thesis

Chapter 1 explained the background of the project that includes richness of

the timber species available in the country and only few hundred of these species are

known in the international market. Building contractors have prejudices on the use of

timber as construction materials hence, other materials such as metals and concrete

are given the priority for the structural components. The problem arises as those

involved in the construction industry have very little or no knowledge on the timber

properties and characteristics. Visual grading is used to grade timber is more towards

grading on its aesthetic rather than quantify the actual strength values. Permissible

unit stresses used for grading are derived from testing of small defect-free specimens.

Testing of full size structural timbers are very costly hence, the structural properties

8

most of timber species are not known yet. Therefore, testing the physical and

mechanical properties of full size structural timber and establish the reliable stress

grading method is a necessity as to develop the confidence of using timber as

construction materials.

Chapter 2 outlined the literature review on forestry and forest sector of

Sarawak. This sector contributed significantly towards socio-economic development

of the state that accounted 39% of total revenue and provide employment about

300,000 people. It also highlighted the use of timber in which building and

construction industry sectors are largest user of sawn timber. Properties and uses of

the seven selected species are also described in details. The current grading systems

of timber are also mentioned in details namely visual grading and mechanical

grading of timber. Various non-destructive evaluation techniques used to measure

and predict the property of timber and timber products used in the temperate

countries are also reviewed. Constraints related to timber grading in the state are

broadly divided into two aspects namely the availability of the raw materials and the

costing are also discussed. Factors such as timber species, density, moisture content

and wood defects on strength properties are also reviewed and highlighted.

Chapter 3 outlined the details on materials and methods in which seven

selected timber species were used in this study. Timber samples were collected from

the forests. The flitches obtained were subsequently machined and converted to the

sample size of 50 x 100 x 2000 mm in length. Tests were conducted on air-dried

samples. Dynamic and static non-destructive testing methods were used to determine

modulus of elasticity values of the timber samples. Static bending rupture tests of full

9

size structural and small clear samples were carried out after completed the non-

destructive tests. Rupture bending tests on timber samples were conducted in

accordance to the British standards. Measurement of penetration depth of pin of

Pilodyn wood tester and physical properties such as moisture content, density, grain

angle and knot size ratio were also carried out.

Chapter 4 highlighted the results and discussion on the physical and

mechanical properties of full size structural timber of seven timber species. Among

the mechanical properties of structural timber compared and discussed namely the

values of moduli of elasticity obtained by using the non-destructive and destructive

tests. In addition, ultimate bending strength of the timber species is also discussed.

Strength properties of small defect- free specimens are also included in the

discussion. Physical properties such as density and moisture content of the timber

species are also highlighted and discussed. Grades stresses of select, standard and

common building on moduli of elasticity and bending strength of the timber species

are compared and discussed. Various rupture patterns of static bending tests are

mentioned in this chapter.

Chapter 5 also highlighted the results and discussion on the relationships

among the moduli of elasticity for heavy hardwood, medium hardwood and light

hardwood and also for all the seven timber species. Prediction of modulus of rupture

using dynamic and static moduli of elasticity are also compared and discussed both

for three timber groups and also for all the selected seven timber species.

Relationships of density and strength properties are also discussed. In addition,

10

relationships between visual parameters with the strength properties are also

mentioned and discussed.

Chapter 6 highlighted the conclusions and recommendations derived from the

study. Among the conclusions that derived from the study namely the strongest and

the weakest timber species in term of modulus of elasticity and modulus of rupture

and also the heaviest and lightest timber species in term of their density. The best

non-destructive and destructive methods to predict bending strength of the timber

species are also concluded in the study. The minimum timber length recommended

for measurement by using vibration frequency method. To determine whether the

minimum values of modulus of elasticity derived from small defect-free specimens is

safe values for design purpose. Some recommendations such as timber species, small

diameter logs, height effect, creep deformation and mechanical grading of timber are

put forward for further studies in future.

11

CHAPTER 2

LITERATURE REVIEW

2.1 Forestry of Sarawak

Sarawak is one of the thirteen states in the federation of Malaysia. It is the

largest states in Malaysia and located at the longitude from 109º 40' to 115º 40' E and

latitude from 0º 50' to 5º N of the equator. The state has an area of 12.4 million

hectares and it made up 37.5% of the total land of Malaysia. Out of the total land

area, 8.46 million hectares or 68.7% of its land are covered with natural forest and

often regarded, as the world’s most complex in term of their ecosystem (Anon,

1990a). It is blessed with an abundance of natural resources and its natural forest

provides the world of tropical hardwood and produces about 9.0 to 10.0 million cubic

meters annually.

It is estimated that about 6.0 million hectares of the land are under the

Permanent Forest Estate, which meant for sustainable timber production, 1.0 million

hectares are designated as Totally Protected Area and the remaining is classified

under State Land Forest. The natural forests in Sarawak can be classified into five

main types viz., Mangrove Forest, Peat Swamp Forest, Hill Mixed Dipterocarp

Forest, Kerangas Forest and Montane Forest. In term of forest area, Hill Mixed

Dipterocarp Forest covers an area of 7,314 million hectares, Peat Swamp Forest

comprises 1,246 million hectares and Mangrove Forest takes up 168,000 hectares.

The other two namely Kerangas Forest and Montane Forest are minimal in size and

of less economic importance as far as production of timbers is concerned (Anon,

1996). The forest types of Sarawak are shown in Plate 2.1.

12

Plate 2.1 Forest types of Sarawak (Anon, 1996)

13

Hill Mixed Dipterocarp Forests are the most species-rich forest as far as

different types of forests is concerned. It is known to have approximately 8,000

species of flowering plants of which most are of economically important species and

over 20,000 species of animals of which the majority are insects. The dipterocarp

comprised about 65 to 80% of the total stem wood volume of commercial trees and

the rest belongs to non-dipterocarp (Anon, 1996). There are many valuable timber

species found with different forest types in Sarawak as listed in Table 2.1.

Table 2.1 Timber species found in different forest types

No. Forest Types Timber Species

1.

Mixed Dipterocarp Forest

Selangan batu & Meranti group (Shorea spp.), Kapur (Dryobalanops spp.), Keruing (Dipterocarpus spp.), Resak (Cotylelobium spp. and Vatica spp), Keranji (Dialium spp.), Menggris (Koompassia malaccensis), Asam (Mangifera spp.), Durian (Durio spp.), Simpoh (Dillenia spp.), Kembang semangkok (Scaphium spp.) and Sepetir (Copaifera palustris)

2.

Samp Forest

Ramin (Gonystylus bancanus), Alan batu (Shorea albida), Jongkong (Dactylocladus stenostachys), Entuyut (Tetramerista glabra), Geronggang (Cratoxylum spp.) and Terentang (Campnosperma spp.)

3.

Mangrove Forest

Bakau (Rhizophora spp.), Perepat (Sonneratia alba.), Api-api (Avicennia spp.) Baru laut (Hibiscus tiliaceus), Pedada (Sonneratia caseolaris), Putat laut (Barringtonia asiatica) and Seladah laut (Dacryodes incurvata)

14

The forests are managed for both their economic utilization and protection of

the environment, which takes into account the need to maintain a balanced eco-

system, conservation of species and genetic resources, protection of wildlife and soil,

safeguarding of water supplies as well as maintenance of sound climate conditions.

The natural forests of Sarawak form extremely important and valuable resources.

They provide essential life support systems for about 79% of the rural population

living in villages and longhouses. The forests have been important sources of food,

fuel, medicines and other produces for satisfying their basic needs since time

immemorial.

The forest resources of Sarawak have been systematically managed since the

beginning of the century by Forest Department, Sarawak. Over the years,

ecologically and environmentally sound forest conservation and management

practices have been developed to ensure that forest renewal and sustainable. Active

conservation strategies in Sarawak dated back as early as in the 1950's. There are

three legislative enactments in Sarawak pertaining to conservation viz., Forest

Ordinance (Sarawak Chapter 126), National Parks Ordinance (Sarawak Chapter 127)

and Wildlife Protection Ordinance (Sarawak Chapter 128). The forest management

and conservation programs implementation by the state in the past, present and future

are geared towards achieving the objectives of forest policy of the state (Anon,

1990a). As resources scarcity becomes more and more severe and the volume of

common timber species is depleting thus emphasis will be on the lesser-known and

under-utilized species as new raw materials. Land development and clearing of land

for agricultural purposes also contributed to the increasing volume of those species.

15

Besides managing the natural forest systematically under sustained yield

management and for the protection and conservation of soil and water, establishment

of trial plot was initiated since 1980’s. To date, the Forest Department of Sarawak

has planted about 24,741.1 hectares of fast growing exotics and indigenous timber

species (Anon, 2005). Amongst the species planted for establishments of forest

plantation are Acacia mangium, Albizzia falcataria, Eucalyptus spp., Gmelina

arborea, Binuang (Octomeles sumatrana), Engkabang jantong (Shorea

marcophylla), Kapur bukit (Dryobalanops beccarii), Kelampayan (Neolamarckia

cadamba) and Sentang (Azadirachta excelsa).

A total of 38 forest plantation licenses covering an area of 3.5 million

hectares have been issued and out the total hectares, about 1.0 million hectares are

targeted to be planted by the year 2020. In future, plantation species will become an

important source of raw materials for the industries. The focus of the plantation

forest is mainly due to the potentially high yield of plantation species, economics in

growing and harvesting arising from the concentration of the crop in one place,

uniformity of timber size and technical specifications. Hence, the development of

forest plantation sector is essential in order to supplement the timber supply from the

natural forests (Anon, 2005).

2.2 Forest Industry Sector of Sarawak

The forestry and forest industries sector has contributed significantly towards

the overall socio-economic development of the state of Sarawak. This sector also

contributes towards for increased in foreign exchange earnings, gross domestic

production growth, government revenue, employment opportunities for resource

16

based industries and improvement in the livelihood of the rural population. The

sector accounted for RM 0.824 billion in term of the state revenue that accounted

39% of the total revenue in 1999 and provides direct employment for more than

200,000 people and indirect employment for a further 100,000 people. There have

been rapid and wide-ranging developments in Sarawak’s timber processing industries

particularly since the early 1980’s. Sawmilling was the earliest processing industries

established followed by plywood, moulding and chipboard industries which had

expanded rapidly during 1980’s as a result of increasing demand for timber and

timber products in overseas markets. Now, the number of processing mills has

increased significantly with the number downstream processing plants exceeding the

primary processing mills.

Generally, processing industries can be categorized into primary, secondary

and tertiary processing. To date, a total of 1,104 mills are operated in the state. The

mills comprise 249 sawmill, 53 veneers and plywood mills, 21 dowels and moulding

mills, 7 laminated board mills, 4 fiberboard/particleboard mills and more than

hundred of furniture/carpentry shops and other timber mills engaged in the secondary

and tertiary processing. The number and types of timber mills for the year 2007 are

indicated in Table 2.2. The timber industry has maintained itself as an important

contributor to the economic development of the state. The industry emerged as one

the main foreign exchange earners in the commodity sector. Sarawak is the world’s

largest exporter of tropical logs mostly to Japan, Korea and Taiwan. The export level

has been declining over the years especially after Papua New Guinea increasing its

market shares to the importer countries.

17

Table 2.2 Number and types of timber mills in Sarawak*

No. Types of Mills

No. of Mills

1.

Sawmill

249

2. Veneer/Plywood 53 3. Dowels/Mouldings 21 4. Laminated Boards 7 5. Wood Chips 3 6. Wood Cement Board 1 7. Parquet/Flooring Products 1 8. Particleboard 1 9. Medium Density Fibreboard 3 10. Block Board 1 11. Briquettes 2 12. Furniture mills, Timber yards and Other Woodworking plants

Total

763

1,104

*Source: TR&TTC, Sarawak Forestry Corporation

Logs production has decreased considerably in past years consistent with the

efforts at forest conservation and also in line with the state policy to increase the

amount of logs processed domestically. Now, emphasis is given to the export of

processed timber products. The sawmilling industry is the largest timber processing

industry in the state followed by veneer/plywood industry. The state earned about

RM 5.0 billion from the export of timber and timber products in 2001. The biggest

earnings from the timber industry, which remains a major revenue earner came from

plywood which amounted to RM 2.2 billion. The government made every effort to

promote downstream processing, especially in the manufacture of furniture in order

to meet the demand from overseas as well as domestic market. Various policies and

measures have been designed to accelerate the development of the furniture industry.

In order to conserve timber resources as well as to encourage greater downstream

18

processing, the export of log from the state has tremendously decreased from year to

year. To provide the necessary infrastructure and other supporting services are

amongst the steps taken as to further facilitate the development of the industry.

There are numerous challenges faced by the industry either from the domestic

market or the international market. Among the challenges are raw materials supplies

for processing, skill manpower, low recovery rate and low productivity compared to

the main competitor countries like Japan, Germany and Italy. The industry is also

faced with competitions by low cost producing countries such as Indonesia, Vietnam

and China. In order for the timber and timber products to be competitive, there must

be proactive measures taken to enhance the quality, efficiency, expertise, skill as well

as productivity through technology enhancement in processing and enhancing

research and development activities in the state.

2.3 Utilization of Timber in Construction

Timber is one of the oldest building materials ever used and it has been

utilized throughout the history of mankind. Timber has provided humans with a

broad range of building products and construction materials. In line with the

modernization of the building and construction industry, efforts to minimize the costs

and new construction materials have to be produced. Non-wood products such as

concrete, metal and steel have redefined the construction industry. Timber is an

important building and construction materials in the state and the quality of its uses

related directly to how designers, architects and engineers understand the

characteristics and properties of the materials.

19

Timber has been known as a versatile material for building and construction

and it is readily available locally. Timber being a non-toxic, biodegradable,

environmental-friendly, renewable and relatively cheap source of raw material will

continue to be popular items for human livelihood. Timber can be planed, cut and

chiseled to the desired size and shape either by hand or by machine. Its high strength

to weight ratio and its ease of handling make it an ideal material for housing frame

for wall, floor and roof. For the same weight, timber possesses tremendously high

strength, which is more superior compared to other raw materials such as plastic,

steel and metal. On durability aspects, some species of timber are naturally highly

resistant to rot and decay and can be treated with preservatives to be resistant.

Timber is also more fire resistant compare to steel. Large solid timber member chars

at a predictable rate with the charcoal forming the insulating layer that protects an

inner core of materials.

The abundance timber species found in the state reflect that the forests are

very heterogeneous and complex in nature, which yielded a large number of timber

species for various purposes and applications. Traditionally, timber is classified into

two major groups namely hardwood and softwood but for structural application, this

form of classification is inadequate and requires grouping of timbers according to

their load carrying capabilities. Currently, in Malaysia about 700 timber species have

been identified and widely being used in building constructions. Out of the total

number, 468 species have been introduced to the domestic and international markets

under the Malaysian grading rules for sawn hardwood timber (Anon, 1984). The

properties have been properly described and are known in the international trade for

their commercial values. These species are aggregated into 100 timber groups that

20

mainly constitute of commercial timbers. Other species that are not included are due

to the small in volume or of less economic importance. The availability of such a

large number of timber species has often caused problems to the users for example in

predicting the actual supply of the species when required.

In Malaysia, sawn timber and plywood have been used extensively in

building construction. In general, the building and construction sectors are the largest

consumer of locally produced sawn timber that accounts about 60% of the total sawn

timber sold domestically (Anon, 1990b). Domestic demand for plywood used in the

construction sector, which absorb about 70% of the plywood while furniture industry

and packaging industry accounts for 17 and 4%, respectively. Timber has long been

and continues to be the predominant structural materials used in residential

construction in Sarawak especially in the rural areas. There are also many notable

examples of timber used especially in low cost houses, longhouses and kampong

houses.

The demand for construction materials has led to a better utilisation of wood,

which mainly comes from mixed species from different types of forests and of small

diameter trees. In addition, difficulties are also associated with the identification and

classification of our timber species. Freezaillah (1984) mentioned that most of the

timber species have been facing difficulties associated with identification and

marketing, particularly of lesser-known species. As for the users there is no simple

technique for species identification of sawn timber and also the standing trees. The

fact is that about 70% of our commercial timbers are sold under mixed species

(Anon, 1986). Hence, an efficient and effective utilisation of species is a challenge to

21

the construction and building industries in Malaysia. Technique and technology for

coping with multi-species forest will also be the greatest challenge in the use of

timbers for building and construction purposes.

There are changes in the specifications according to the classification of the

timber species when specifying sawn timber. Currently, classifications of our timber

are viz., heavy hardwood, medium hardwood and light hardwoods. Strength

groupings were used in specifying timber for the various applications in construction

both for non-structural and structural applications are shown in Appendices A, B and

C.

2.4 Properties of Selected Timber Species

A comprehensive knowledge on the characteristics and properties of any

timber is essential to determine utilization aspect of the species. The acquisition of

basic information on physical and mechanical properties is complicated due to the

fact that their properties are subjected to wide variations brought about by the

external factors affecting the tree growth. In addition, timber is a product on of not

one but of many species of trees therefore each kind of timber exhibits its own

anatomical, physical, mechanical and chemical characteristics and properties. The

properties of selected timber namely, Salangan batu bukit, Menggris, Penyau, Kapur

paya, Alan batu, Jongkong and Geronggang as follows:

22

2.4.1 Selangan batu bukit (Shorea foxworthyi)

Selangan batu bukit (Shorea foxworthyi) belongs to the family of

Dipterocapaceae. It is widely distributed throughout the State and commonly found

in lowland forest. The species occurring over a wide variety of habitats except peat

swamp forest. A total of 27 species of Selangan batu are recorded in the state

(Ashton, 1968). The species is considered one of the best heavy construction timbers

with the Strength group A (Anon, 1999b) Strength group SG 1 under MS 544 (Anon,

2001). The average density at air-dry condition is 906 kg/m3. The colour of

heartwood is yellow-brown to reddish brown whilst the sapwood is lighter in colour.

The longitudinal surface of the timber is shown in Plate 2.2.

Plate 2.2 Longitudinal surface of Selangan batu bukit

The timber is well-known for heavy construction, marine and wharf

construction, piling, boat building, parquet and heavy duty flooring, fence posts

23

telegraph and power transmission poles, columns, posts, joists, rafter, joinery, heavy

duty furniture, door and window frame.

2.4.2 Menggris (Koompassia malaccensis)

Menggris (Koompasia malaccensis) belongs to the family of Leguminosae.

The species is found very widespread throughout Sarawak and not concentrated in

any one locality. The species found in peat swamp forests and throughout the

lowland forests. The other names of the species are Kempas (Peninsula Malaysia)

and Impas (Sabah). The trees are tall and having large buttresses. The crown is

cylindrical and columnar and exhibits a wide variety of forms, ranging from closely

fissured, scaly, cracked and lenticellate to minutely dippled (Wong and Kochumen,

1973). The tree is capable of achieving 55 meters in height and 6.5 meters in girth,.

The timber is classified as a medium hardwood (Anon, 1984) strength group

(SG) 2 under MS 544 (Anon, 2001). The timber is relatively strong, hard and heavy

with an average density of 890 kg/m3 at 15% moisture content. The sapwood is pale

yellow in colour and easily distinguished from the heartwood. The heartwood is

brick red when freshly sawn and darkening to orange red or reddish brown. The

timber is very strong and dries readily but must be carefully handled to avoid checks

and honeycombing. It is considered difficult to work with and moderately durable

when exposed to our environment. The longitudinal surface of the timber is shown in

Plate 2.3.

24

Plate 2.3 Longitudinal surface of Menggris

The timber has gained a reputation for use in flooring and railway sleepers. The

timber is suitable for heavy construction works, posts, beam, joists, rafter, door and

window frames, vehicle bodies, tool handles, paneling and partitioning, furniture

making, parquet and strip flooring.

2.4.3 Penyau (Upuna borneensis)

Penyau (Upuna borneensis) belongs to the family of Dipterocarpaceae. The

mono species is widespread throughout the State and mostly found at sub-coastal

from Lundu to Lawas. The timber is classified under heavy hardwood and strength

group A (Anon, 1999b) strength group (SG) 3 under MS 544 (Anon, 2001). It has

mean density of 871 kg/m3. The colour of sapwood is light yellowish brown to light

brown while the heartwood is yellowish brown or brown and darkens to dark brown.

The longitudinal surface of the timber is shown in Plate 2.4. The grain is shallowly