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TERM PAPER ON TIMBER

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TERM PAPER ON TIMBER
COURSE: CVE411
GROUP: 5
LEVEL: 400L
DEPARTMENT: CIVIL ENGINEERING
UNIVERSIRTY OF BENIN, EDO STATE.
NIGERIA
2017/2018 SESSEION
02/04/2018
GROUP MEMBERS
S/N
NAMES
MAT. NO
DEPT
1
OKWESE GODSPOWER C.
ENG1403540
CVE
2
ONWUCHEKWA OBIALOR PHILIP
ENG1403543
CVE
3
ORHUE LANGFORD E.
ENG1403544
CVE
4
OSEMWOTA JEFFERY E.
ENG1403546
CVE
5
OSIFO O. EMMANUEL
ENG1403547
CVE
6
AGHEDO GREGORY
ENG1406909
CVE
7
GBOBODO OREZI DESMOND
ENG1406922
CVE
8
EBIMODEI M. TOHUR
ENG1406915
CVE
INTRODUCTION
Timber is the most useful and important material for construction in
building without which entire process is incomplete. Selecting timber is not an
easy task as it seems to be, because timber has different type and selecting the right
material is an important key. Timber is again an expensive material to be
incorporated in a building for different purpose for which it should be necessarily
be strong and tough. There are many useful needs of timber during the construction
of building such as in doors, windows, cupboards, cabinet and railings which
contribute a lot in the beautification and overall look of interiors. Timber has many
other uses but which type of timber should be used for right purpose is important to
know because if timber used in construction comes out to be of low quality then
one may need replacement again and again. Timber while selecting should be
considered for its quality aspect which must be free from any decay like rotten,
warp, knot, fungi and mold or termite so that it would not give problem afterward.
Before purchasing timber material for the construction, one must be well informed
regarding timber types and forms to select as a single knot can bring down the
show of whole wood work.
TYPES OF NIGERIA TIMBER
There are many types of timbers in Nigeria but to mention a few
S/N
1
2
3
4
5
Botanical Name / Scientific
Name
Mitragyna ciliata, stipulosa
Common Nigeria
NAME
Y – Abura
Terminalia superba
Ibibio-uburu
Benin Egboin-nofua,
Ibibio
Afara (White)
White afara, Limba
limbo Ofram.
Terminalia ivorensis
Edo-ocha Y=Afara
Benin. Egboin-nebi
Edoi-Oji
Afara (Black)
Black afara Idigbo
Gossweileinidendron
balsamiferum
Albizia spp
Y= Idigbo
Benin = Agba, Achi
Yor Loshi-orin
Benin- Ekpaghudo
Hau:- Nyie avu
Yor:- Ayinreta
Trade Name
Other Names
Elelom, Subuha
Agba
Albizia
Okuro, pampena
6
Alstonia boonei
Benin: Ukhu; Egbu
Alstonia
Otondo, Stoolwod
7
Antiaris Africana
Yor:- Ahun
Benin: Ogiovu
Antiaris
Ako
8
Afzelia spp
Yor: Oro
Benin: Arinyan
Hau: Kawo
Apa
Bilinga, Doussie
9
Distemonanthus
Yor:- Apa
Benin: Anyaran
Ibibio: Ochasi
Ayan
Ayanran, satinwood
Berlinia
Essoule
benthamianus
10
Berlinia spp
Yor: Anyan
Benin: Ekpogboi
Hau: Dokar rafi
Ibibio: Ububa
Yor: Apado
etc.
Properties of Timber
The properties of timbers are determined by the structure of the wood, i.e., the
types of cells and the chemical composition of the cell walls and cell contents, and
by the proportion of the various cell types present in the wood. The distribution
and arrangement of these wood elements vary considerably in different species of
trees.
Properties of Timbers Required for Joinery and Cabinet Work
The characteristics of timber suitable for furniture making and which are important
to the cabinet maker include:
The Physical Characteristics
1.



Colour
Depends on the substances and chemicals in the cells and cell walls.
Most timbers show variation in colour between species and within species.
Colour descriptions usually relate to the heartwood. Finishes, light and
weather all affect colour.
Tasmanian Oak
Radiata Pine
Blackwood
Jarrah
2. Grain
Grain is used to describe the cells and their direction in the timber.
The tree is made up of millions of tiny narrow cells. Their length generally follows
the same direction as the length of the tree. Deviations in direction often occur and
are therefore not always consistent grain direction within the tree. Knots or
irregular growth of a tree may also distort grain direction.
The grain will also be effected by the conversion method used.
 Quarter sawn: the edges of the growth rings are seen on the face.
 Back sawn: displays growth ring markings (known as cathedral grain)
Types of grain
Straight grain
Sloping grain
Interklocked grain
Wavy grain
3. Figure


A term applied to timbers which possess unusual or attractive designs resulting
from variations in colour, grain and texture due to the natural arrangement of the
elements, method of conversion or irregularities in the tree such as knots, burls
and crotches.
Major figures are: bird’s eye, fiddleback, ropey, ribbon, swirl, wavy and wild.
Bird’s eye
Fiddleback
Swirl
Wavy
4. Texture


Texture is dependent on the size and arrangement of the wood cells.
Timber can be coarse, fine, even or uneven and either rough, smooth or oily to
touch.
The Mechanical Properties
1. Density/Weight
Density is the mass of wood substance and moisture enclosed within a piece
expressed in kg per cubic metre. (Kg/m³)
Heavy timbers have thick cell walls and small cell cavities; this means that it is
made up of a lot of wood substance and little air. Whereas light timbers have thin
cell walls and large cavities, these have little wood and a lot of air. Balsa is an
excellent example of light timber as only 7% of its volume is solid wood, the
remaining is air cavities.
2. Strength
Strength refers to a timbers ability to resist and withstand the different types of
external forces.
This property is due to the (abundance) of interlocked fibres to provide strength.
The direction and structure of the cells also effects the strength of the timber,
straight grained timber is stronger than a cross grained or wavy timber. Defects
like cracks, decay or a knot will decrease the strength of the timber.
The strength of a timber is important when designing furniture where the member
will be placed under stress, such as bed rails, table rails and chair construction.
3. Durability of Timber
• Durability is being able to withstand disease or insect attack.
• Impregnated in the cell walls during growth are chemical substances, oils, resins
that cause the timber to be durable.
• Impregnating the wood with a suitable preservative can increase durability.
4. Hardness
The ability to resist indentation, bruising and abrasion
This can be gauged in different ways:
 The timbers resistance to nails, the difficulty in sawing and working, and the
resistance to wear. As a rule, hardwoods are more resistant to wear than
softwoods as they have small thick walled cells, and the softwoods generally
have thin walled cells. The thickness of the cell wall and the smallness of the
cell cavities make the wood hard. The moisture content of the wood and the
maturity of the timber also affect the hardness.
 The Janka hardness test measures the resistance of a sample of wood to
denting and wear. It measures the force required to embed an 11.28mm (.444
in) steel ball into wood to half the ball's diameter. This method leaves an
indentation. A common use of Janka hardness ratings is to determine
whether a species is suitable for use as flooring.
5. Weathering
The word 'weathering' is the general term used to define the slow change of
materials exposed to the weather.
For timber, the weathering is the breakdown of the exposed surfaces due to action
of sunlight, rain, wind, dew and frost and airborne pollution.
Weathering is a process distinct from decay (also called rot) which is caused by
fungi. Weathering initially means that dark colours become paler through leaching
and bleaching and pale colours darken because of oxidation. Eventually all
exposed timber surfaces become grey. The surface may appear dirty or blotchy in
situations favouring fungal organisms, but in dry or coastal climates an attractive
silvery grey usually results.
To prevent the weathering effects, timber requires coating with paint or oil stains.
6. Working Qualities
The working qualities of timber is the ease or difficulty of sawing, planning,
chiseling, carving, shaping, turning, gluing and nailing. Also the ability of the
timber to take finishes such as paints, stains, fillers, polishes etc.
These are influenced by the density, texture, grain, hardness and toughness of the
wood.
GRADING
Grading is simply sorting a production run into groups that have similar properties.
The grouping of the properties can be any mixture of appearance and structural
properties. In order to give some uniformity across the industry there are standards
for the sorting of timber products
TIMBER CLASSIFICATION
The terms timber and wood are often used synonymously, but they have distinct
meanings in the building industry. Wood is the hard, fibrous material that makes
up the tree under the bark, whereas timber may be defined as a wood which retains
its natural physical structure and chemical composition and is suitable for various
engineering works. Following is the classification of timber as per IS: 6534.
TIMBER CLASSIFICATION ON THE BASIS OF GRADING
All grading specifications are clearly distinguished between
structural or stress grading, and commercial or utility grading based on Indian
Standard classification.
STRUCTURAL GRADING
It is also known as stress grading. However, there is a small distinction between
the two. Structural grading refers to the principle by which the material is graded
on the basis of visible defects which have known effects on the strength properties
of the material.
Stress grading refers to the principle by which the material is graded by
consideration of maximum principle stresses to which it can be subjected.
Structural grading is further divided as:
1. Grading based on known effects of defects and estimating accumulative value.
2. Machine grading.
COMMERCIAL GRADING
It is also known as yard grading or utility grading refers to the principle by
which the material is graded by consideration of usefulness of the material
and price factors. Commercial grading is further divided in the following
classes:
Grade A: It is based purely, and sometimes arbitrarily, on dimensions and
general appearance. The dimensions of lengths and girths for logs, or
lengths, widths and thicknesses of converted material are measured
according to specified methods. This system is prevalent in Kerala and
Mysore. Under these classifications, teak is placed in four grades with two
sub-classes in each grade. In the case of other hardwoods, there are
similarly four grades in Mysore (Coorg) but the dimensions are fixed
separately for each of the species. In Kerala, there seem to be only two
grades of hardwoods
Grade B: It is based on the best ultimate use of logs or converted material.
Such a system is mostly prevalent in Andhra Pradesh and some parts of
Tamil Nadu, and seems to be one of the quickest systems of grading and
marking. The logs are classified into grades on the best use possible as for
beams, planks, scantlings, etc., and each grade is further divided into ‘A’,
‘B’ and ‘C’ classes to indicate occurrence of defects. Only two lengths are
recognized; ‘long (that is, 5 m and above) and ‘short’ (that is, under 5 m).
Each log is thus quickly stamped with the first letter of the grade
classification, the sub-class, and ‘L’ or ‘S’ for ‘long’ and ‘short’, for example,
BAL and PBS indicate, respectively, ‘ beam, A-class, long ’ and ‘planks, Bclass, short’. Sometimes another letter is also added to indicate the
species, for example, ‘T’ for teak.
Grade C: This classification is based on qualitative evaluation of defects
and rough estimate of out-turn of utilizable material. It is prevalent in
Madhya Pradesh.
Grade D: It is based purely on evaluation of ‘units of defects’ and fixing the
-number of units permissible for a standard volume in each grade. Such
practices are common in the Bombay region; sometimes an estimated outturn is also indicated in each grade. In general three grades are
distinguished for various categories of logs and sawn timber. Sizes and
other dimensions are also fixed in a few cases, separately for different
species and different depots in the same state. This system is being
increasingly adopted in the specifications of Indian Standards Institution,
and in international grading specifications. This system has a distinct
advantage of evaluating cumulative effect of defects in a particular grade.
REFERENCE
 IS – 6534 – 1971
 http://www.iiste.org/conference/upcoming-conferences-call-for-paper/
 www.aboutcivilblog.com
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