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Download this complete Project material titled; Structural Grade Properties Of Some’ Selected Nigerian Timber Species: Chlorophoral Excelsa (Iroko); Khaya Senegalensis (Mahogany); Ceiba Pentandra (Araba); And Daniellia Oliveri (Maje) with abstract, chapters 1-5, references, and questionnaire. Preview Abstract or chapter one below

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ABSTRACT

 

In this research work, structural grade properties of some selected Nigerian timber species
namely: Chlorophoral excelsa (Iroko), Khaya senegalensis (Mahogany), Daniellia
oliveri (Maje) and Ceiba pentandra (Araba) were carried out after classifying the species
to international strength classification system using EN338 (2008) with the aid of
statistical package Easyfit (2010). This was done after establishing the physical and
mechanical properties of the species in the laboratory using ASTM D193 (2000) and
EN408 (2003). Chlorophoral excelsa was assigned to strength Class D70 with
characteristic density of 474.95 kg/ , bending strength of 74.76 N/ and modulus of
elasticity of 9,899.32 . Khaya senegalensis was assigned to strength Class D70
with characteristic density of 800.21 kg/ , bending strength of 80.64 N/ and
modulus of elasticity of 8,944.0 . Daniellia oliveri was assigned to strength Class
D50 with characteristic density of 509.01 kg/ , bending strength of 57.6 N/ and
modulus of elasticity of 6,865.87 N/ and Ceiba pentandra was assigned to strength
Class C40 with characteristic density of 300.78 kg/ bending strength of 41.16 N/
and modulus of elasticity of 4,423.64 N/ . Also, the distribution models were
established for Chlorophoral exelsa, Khaya senegalensis, Daniellia oliveri and Ceiba
pentandra to be normal, lognormal ,gumbel and weibull respectively.

 

TABLE OF CONTENTS

 

Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of contents vi
List of tables ix
List of figures x
List of plates xxi
List of appendices xxii
Abstract xxiii
CHAPTER ONE: INTRODUCTION 1
1.1 General 1
1.2 Aim and Objectives of the Study 4
1.2.1 Aim 4
1.2.2 Objectives 4
1.3 Scope of Study 5
CHAPTER TWO: LITERATURE REVIEW 6
2.1 General 6
vii
2.2 Strength Properties of Timber 11
2.2.1 Three – point bending test 13
2.2.2 Four – point bending test 17
2.3 Statistical Works on Timber 18
CHAPTER THREE: MATERIALS AND METHODS 21
3.1 Materials 21
3.2 Methods 22
3.2.1 Moisture content and density 22
3.3 Modulus of Elasticity and Bending Strength 22
CHAPTER FOUR: RESULTS AND DISCUSSION 28
4.1 Results 28
4.1.1 Moisture content and density 28
4.1.1.1 Calculation of means , standard deviations and coefficients
of variation 28
4.1.2 Modulus of elasticity and bending strength 29
4.1.2.1 Moisture content adjustment 30
4.1.3 Grading for moisture content, density, modulus of elasticity and
bending strength 35
4.2 Discussion of Results 37
4. 2. 1 Test of goodness of fit 37
4. 2. 2 Distribution model for density 38
4. 2. 3 Distribution model for bending strength 55
viii
4. 2. 4 Distribution model for modulus of elasticity 71
4.3 Strength classification of the species 87
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION 90
5.1 Conclusion 90
5.2 Recommendation 90
References 91
Appendix A 95

Project Topics

 

 

 

CHAPTER ONE

INTRODUCTION
1.1 GENERAL
From the earliest years of recorded history, trees have provided mankind with food
and materials for shelter, fuel and tools. Timber is one of the earliest building materials
used by our predecessors and most of us experience a strong affinity with the beauty and
intrinsic characteristics of this natural material when it is used in the places we work and
live.
Timber is the oldest known building material capable of transferring both the
tension and compression forces making it naturally suited as a beam element. It has a very
high strength to weight ratio, it is relatively easy to fabricate and to join and it often out
performs alternative materials in hazardous environments and extremes of temperature
(including fire). Timber does not corrode and many species if detailed correctly can be
very durable . The unique properties of timber have made it a cornerstone contributor to the
advance of civilization and development of society as we know it today.
Timber has been used in the construction of buildings, bridges, machinery, war
engines, civil engineering works and boats since mankind first learnt to fashion tools.
Timber is a truly remarkable materials whilst most of the structural materials we
use are processed from finite resources, requiring large amounts of energy and producing
significant green house emissions, timber is grown using solar energy in natural soil which
is fertilized by its own compost, fuelled by carbon dioxide and water by rain. Because it
literally grows on trees, timber is the only structural engineering material which can be
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totally renewed provided that trees are replanted (plantation) or natural regenerated (natural
forests) after felling.
At the same time forest provide a number of unique and varied benefits that include
protection of our climate, water and soil and a great range of recreational functions enjoyed
by the general public.
In the hands of skilled professionals who have an appreciation and understanding of
its natural characteristics, timber has significant advantages over alternative structural
materials, enhancing the best designs with a sense of appropriateness, unity, serenity and
warmth in achieving the marriage of form and function which is simply not possible with
concrete and steel.
Before the emergence of modern structural materials such as steel and concrete, timber
was the dominating structural material in the construction industry. The many species of
timber used in timber engineering can be divided into two categories: soft wood and hard
woods. Soft wood is a timber of a conifer where as hardwood is that of a deciduous tree .
One of the oldest existing timber bridges is the 222 meters long chapel bridge in Luzern
Switzerland which was built in 1333 (Stadelmann, 1990). This bridge is a well known
tourist attraction. As with many other bridges in Switzerland, it is covered by a roof, which
effectively protect the wood from biological deterioration. One aspect of long-term
durability of timber structures is that they are often designed in such a way that damaged
element can easily be replaced. Timber is naturally occurring organic material. There are
more than 300,000 species of trees throughout the world, producing timber with a wide
range of properties. Specific details of the properties of common species used in Nigeria
3
Appearance and physical properties of timber include its colour, texture, grain and density.
Others include its thermal properties, acoustic properties, chemical resistance, termite
resistance, electrical resistance and mechanical damping.
Strength properties are the key to structural design although other attributes may well
come into consideration when assessing the overall performance of a component on
structures.
Strength grading may be described as a set of procedures for assessing the strength
properties of a particular piece of timber. The strength grade is arrived at by either visual
grading or machine grading.
The starting point for the determination of many engineering timber properties is the
standard short duration test where failures is expected within a few minutes. In the last
decade much attention is given to study the behavior of timber and timber joints with
respect to damaging effect of sustained loads (Duration of load effect). There are a number
of load cases such as earthquakes and single blast where timber is exposed to substantially
higher loading rates than in the standard short duration test. Example of single blast loads
explosions but also vehicles that crash against a guard – rails. Both are associated with
loading times of a few thousand of a seconds.
In a number of countries like the Netherlands and the United states of America timber
guard –rail system are being considered as alternative for the traditional steel guard- rails.
Often impact tests showed the ability of wood to withstand impact loads better than
standard short duration test.
Mechanical properties most commonly measured and represented as strength properties
for design include modulus of rupture in bending, maximum stress in compression parallel
4
to grain, compressive stress perpendicular to grain and shear strength parallel to grain,
impact bending strength, tensile strength perpendicular to grain and hardness.
1.2 AIM AND OBJECTIVES OF THE STUDY
1.2.1 Aim
The aim of this research is to determine the structural grade properties of some
selected Nigerian timber species used in buildings in Nigeria in accordance with EN338
(2008) and EN384 (2004).
1.2.2 Objectives
The objectives of this research work are:
i) Determine the moisture content, density, modulus of elasticity and bending strength
of some Nigerian timber species: These are Chlorophoral excelsa (Iroko),
Khaya senegalensis (Mahogany), Ceiba pentandra (Araba) and Daniellia
oliveri (Maje) and classify these species based on EN384 (2004)
ii) Generate data on the derived material properties (tension and compression
strengths parallel and perpendicular to grain, shear strength and shear modulus
of the species based on EN 384 (2004) and JCSS (2006) requirements.)
iii) Determine the characteristic values of both the reference and the derived material of
each species in accordance with EN 384 (2004) with the aid of a specialised
statistical analysis distribution fitting packages (Easy fit 2010).
iv) Perform strength grading in order to assign appropriate strength class to each
species based on EN 338 (2008) recommendations.
5
1.3 SCOPE OF STUDY
1.3.1 The scope of the research work is limited to carrying out
(i) A three – point bending test in accordance with EN408 (2003) and
(ii) A four – point bending test
Tests on four Nigerian Timber species, namely Clorophoral excelsa (Iroko), Khaya
senegalensis (Mahogany), Ceiba pentandra (Araba) and Daniellia oliveri (Maje). The
timber species were tested using three point bending test and four point bending test, to
determine the bending strength, the modulus of elasticity and the strength class of the
timber.
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