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5.1 Timber Classification.

5.2 Timber Structure.

5.3 Moisture, Shrinkage and Strength.

5.4 Timber Defect

5.5 Treatment and Curing

5.6 Timber Products.

5.7 Wood in constructions

5.8 Timber Standard Testing

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Definition of wood, timber and lumber:

Wood vs Timber vs Lumber

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Wood : May be defined as

the material that forms the

trunks and branches of

trees

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Timber : Wood cut from

the trunk which can be

used for constructing

houses, furniture, bridges

and etc.

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I. HEAVY HARD WOOD (HHW) - over 880 kg/m3

- constructional timbers -some of them contain toxic material within their tissue such as alkaloids and other substances - can be used in most exposed conditions without undergoing preservative treatment - however, sapwood requires preservative treatment because less durable compare to heartwood - About 14 species under “Malaysian Grading Rules 1984 Edition 1”

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HARDWOOD classification

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II. MEDIUM HARDWOOD (MHW)

- 720 – 880 kg/m3 at 15% moisture content – MSS 544: 2001 (Consider Dry condition < 19%)

- Moderately heavy to heavy construction - Come of the timbers (kempas and tualang) are heavy

and strong, but insuffient for used in exposed condition and in ground contact.

- About 36 species under “Malaysian Grading Rules 1984 Edition 1”

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HARDWOOD classification

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II. LIGHT HARDWOOD (LHW)

- less than 720 kg/m3

- general utility timbers – joinery work, cabinet marking, furniture, decorative paneling and etc.

- require preservative treatment as a precaution against wood destroying agents such as fungi an insects.

- About 47 species under “Malaysian Grading Rules 1984 Edition 1”

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HARDWOOD classification

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SOFTWOOD (KAYU LAMPUNG)

No specific classification for softwood.

About 3 species under “Malaysian Grading Rules 1984

Edition 1”

Damar minyak is of commercial importance at the

moment.

Density range about 385 – 735 kg/m3

Timber mainly used as decorative plywood and paneling

Characteristics-not all soft, some softwoods are very hard.

-Eg; yew-strong and durable.

-derive from coniferous trees which are mainly evergreens.

-the leaves with needle shape and no dry outer covering of seeds.

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SOFTWOOD classification

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HARDWOODS (KAYU KERAS)

from broad-leaved trees

deciduous and majority of tropical trees are

evergreens.

densest, strongest and most durable timbers.

some hardwoods contain resins and/or oils which

interfere with the hardening of paints.

Eg; silica – make working difficult.

greater moisture movement than any softwoods.

examples of hardwoods;

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HARDWOOD characteristics

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Examples of hardwoods;

HEAVY MEDIUM LIGHT

Balau, balau merah, bitis,

cengalKapur, kasai, kempas

Durian, pulai,

bintangor,nyatoh

Giam, merbau, keranji, Keledang, keruing, kulimJelutong, macang,

merawan, ramin

Resak, tembusu, kekatongSimpoh, punah, mengkulang,

merpauh

Meranti, terap,

kedondong, gerutu

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HARDWOOD characteristics

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Wood Formation • Wood formed as a result of continuous secondary growth in cell.

When seed of a tree germinates, it forms a shoot consisting of thin medulla of spongy tissue commonly known as the pith. The pith is completely enclosed within thin meristematic tissue known as cambium, which is turn is protected on the outside tissue call bark.

• Growth of tree is a result of division of cambium cells, provides new cells to be added to the existing system. The accumulation of woody cells resulting from the cyclic activity of the cambium from year to year, accounts for the growth in height and diameter of a stem of a tree. The cambium produces bark tissue (phloem) on the outside and woody tissue (xylem) on the inside of the stem.

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TIMBER structure

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The wood functions are: a) Conduction of water and dissolved

mineral salt solution from the roots to leaves for manufacture of plant food materials

b) Storage and distribution of manufactured and reserved food materials

c) Provision of mechanical strength of the tree as a shole

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TIMBER structure

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SAPWOOD

food conduction and storage

less resistant to fungi and insect

can often be recognized, as it is usually lighter in colour

proportion decrease continuously with the age of tress

young tress being almost almost all sapwood

may be less than 20 % in mature three

HEARTWOOD

structural support

no longer store food

structural features is similar with sapwood except, the cell walls of the

latter are often permeated with resinous or gummy substances

more resistant to fungi and insect

it is usually darker in colour

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TIMBER structure

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BARK

the outer surface of the tree is protected by bark.

then followed by bast(basta)-the layer which transmits the nourishment from

leaves to the roots and to other parts.

then followed by cambium-thin layer. At certain age, the cambium will

change to sapwood and continue to heartwood with the growth of tree.

GRAIN

the comparative width of annual rings, the direction and the arrangement of

the cells and fibres are the causes of the wood grains.

the wood is said to be straight-grained when the cells are straight. And

cross-grained when the cells don’t run parallel to the axis.

cross-grain has a pronounced weakening effect on the strength of beams

when the slope of the grains is 1:15 or greater.

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By late autumn (after the fall of the leaves), growth for the year

end.

When the growth resumes in early spring, the cambium starts

putting on large and porous cells which contrast significantly in

texture with the cells of the immediate preceding layer of late

autumn wood. This contrast produces growth rings.

Tropical Species

Clear growth rings are exceptional because there are indistinct

seasonal changes in climate.

No notable differences between the textures of wood produced.

Therefore, in tropical woods, these rings even if distinct, are not

criterion of the age of the tree which calculated one year per

ring like temperate species.

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TIMBER structure

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Temperate Species

The rings of wood formed during each growing season may be

clear differentiated because the vigor of growth during a single

growing season is not uniform throughout.

Early spring, the tissue produced consists of large and porous cells.

This is followed by a gradual decline vigor (energy of growth)

which made the tissue become smaller and denser cells.

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Definition of rings

Usually one ring-gelang is added each year. The rings are widest at the

centre and narrower nearer the bark. The rings are widest at the bottom

in young, thrifty trees and near the top in old ones.

The rings consist of minute tabular or fibrous cells tightly cemented

together by lignin which gives the strength to wood and each ring has

two parts; the earlywood/springwood-kayu awal and the

latewood/summerwood-kayu akhir.

The types of ring:

Growth ring- gelang tumbesaran = one set of circumference added to

tree.

Annual ring- gelang tahunan = also known as growth ring.

These annual rings give valuable information about the age, the

rapidity and uniformity of its growth

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TIMBER rings

Shrinkage

All structures made from timber have the possible effect of shrinkage.

Strength

The factors affecting strength of timber are:

i) Density Normally, young trees often give low density and reduced stresses.

ii) Moisture content Mechanical properties if wood influenced by moisture content.

But the modulus of elasticity is less affected by changes in moisture.

iii) Temperature An increasing of temperature, the timber strength will decrease.

iv) Grains structure It determines the permissible stress and modulus of elasticity.

v) Condition of growth Environmental factors affecting tree growth such as temperature,

type of soil, spacing between trees.

vi) Defects

It can effects the strength of the wood and can

be classified natural defect, decay and insects

and parasites attacked. Common defect types

are shown in figure below:

• Buku (knots)

Occurs on the trunks and branches of a tree.

• Saku Kulit (bark pocket)

Occurs on the defect of cambium cell

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TIMBER defects

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TIMBER defects

Teras rapuh (brittle heart)

Due to decaying fungi attack in the

middle of the stem

Pepusar/ bonggol (burl)

due to abnormal plant growth

Kegagalan Mampatan (Compression

Failure)

-due to a series of woven fibers are

damaged

-by compression stress during plant

growth

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TIMBER defects

Dry root

Wet rot / Decay

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TIMBER diseases

Drywood termites

Beetle

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TIMBER diseases

Powderpost beetleOld house borer

1) Oil type preservatives

the moisture content in timber should not be more than 14%.

applied over outside of exposed timber.

unpleasant smell.

not suitable when timber is to be painted.

examples; creosote, carbolinium, solignum, with or without admixture with petroleum or suitable oils.

2) Water soluble preservatives

moisture content of 20 to 30% is permissible.

Odor less organic or inorganic salts and adopted for inside location only.

examples of leachable type of preservatives; zinc chloride, boric acid(borax), etc.

the types of zinc chloride, sodium fluoride and sodium-pentachloro-phenate are toxic to fungi. These types are expensive and odourless.

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TIMBER treatment and curing

benzene-hexa-chloride is used as spray against

borers.

Boric acid is used against Lyctus borers and to

protect plywood in tea chests.

another type;

i) copper-chromate-arsenic composition.

ii) acid-cupric-chromate composition.

iii) chromate-zinc chloride composition.

iv) solvent treatment.

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TIMBER treatment and curing

3) Various treatment processes.

i) Surface application

by spraying, dipping or brushing the preservatives for a short period.

at least two coats should be applied.

the subsequent coats should not be applied until the first one has

dried or soaked into the wood.

used mostly for treating timber at site and re-treatment of cut

surfaces.

ii) Soaking treatment

submerging debarked timber in the preservatives solution for

sufficiently long period until the required absorption of the

preservative is obtained.

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TIMBER treatment and curing

iii) Hot and cold process ensures sterilisation against fungi and insects.

the timber is submerged in the preservation solution which is heated to

about 90°C to 95°C and maintained at this temperature. Then allowed

to cool until the required absorption is obtained. During the heating

period, air in the timber expands and is partially expelled.

while cooling, the residual air in the timber creates a partial vacuum

which causes the preservative to be sucked into the timber.

generally, two baths are used. First-containing the water to prepare the

hot treatment. Second-cold bath-containing the preservatives into which

the timber is transferred immediately after heating.

this to solve the danger of precipitation of chemicals at high

temperature. Also helps to make the process continuous in case the

quantity of timber is large.

Timber Products

Veneers (lapisan)

thin sheet of wood

manufacture in various grades.

it popular to make a furniture, concrete

mould.

Plywood

it used in beam making

easily can make curve shape for

designing

Boards

two types namely particleboard and

fiberboards.

Wood in constructions

Timber can be used for structural and non-structural member in construction. For the structural purposes, the properties have to be in compliance with the MS 544 standard requirements.

For Furnitures

Leban, Gading, Jati and Arang trees are used.

always this wood small sizes and expensive.

For Bridge

i.e. Cengal, Resak, Merbau

normally this wood is used to build high structure and exposed to weather.

this wood is strong and soft even easy to work but expensive.

For houses

piling foundation : Bakau, Kempas and Keruing.

Mast(tiang kapal) : Balau Merah, Cengal, Keruing, Meranti Merah Tua.

door and window frame : Meranti Merah Muda, Meranti Kuning.

stair : Keruing, Kapor, Mengkulang.

floor : Bintangor, Sepetir, Cengal.

For columns Balau, Balau Merah, Cengal.

Timber Standard Testing

1) Specific gravity

2) Volumetric shrinkage and swelling

3) Static bending strength

4) Impact bending strength

5) Compressive strength

6) Tensile strength

7) Brittleness test

8) Moisture content

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For example, if the initial weight of the piece was 30.51g and its dry weight

22.60g, then the difference of 7.91g is the weight of moisture initially in the

piece and its initial moisture content would be:

(30.51 - 22.60)/22.60 x 100 = 7.91/22.60 x 100 = 35.0%

Alternatively the formula can be written:

Moisture content (%) = [(Initial weight/Dry weight) - 1 ] x 100

So that only the division sum needs to be carried out:

[(30.51/22.60) - 1] x 100 = 0.35 x 100 = 35.0 %