AAR 553 STRUCTURAL THEORIES & APPLICATIONS

TIMBER MATERIALS

MOHD HILMI FAKHRUDDIN B. ZAKARIA 2012417304

MOHAMED FIQRYN B. MD. SHAHRODIN 2012829808

MUHAMMAD FAIZ B. ABD. GHAFAR 2010121001

SHAFWANDIN BIN SHAMSUL BAHRI 2010984975

KHAIRUL ASYRAF BIN MOHD YUSOF 2010789227

Terminologies • Timber – wood suitable for use as building material• Wood – the tough, fibrous cellular substance that makes up

most of stem and branches of tree behind the bark• Log – a length of trunk of a felled tree ready for sawing• Lumber (timber) – timber product manufactured by sawing,

re-sawing, planed, cutting to length and grading• Dressed lumber (dressed timber) – lumber or timber that has

been smoothed by planing machine and of uniform size• Undressed lumber (undressed timber) – lumber that is sawn

edged and trimmed, but not planed smooth• Treated wood – wood that has been coated or impregnated

with chemicals to resist decay and insects infestation• Fire-retardant wood – wood impregnated with mineral salt

under pressure to reduce flammability or combustibility

The nature of timber

• Timber is a natural product, drawn from the wood in the trunks of trees.

• Its character is consistent with the species of tree and the form and growth over time of the wood in it.

Regrowth in a native forest

Tree growth• New wood on outside of tree

– oldest wood on the inside– youngest wood on the outside– diameter largest at the base– one ring (layer) per growing season

• Tree in forest grows toward light– trunk is straight– lower branches die– leaving small knots in wood

• Bark protects wood from damage– the tree sheds bark each year

Production of wood

Cambium - growth cells• wood cells created on the inside• bark cells created on the outside

Sapwood - newest wood• on the outside of tree (~ 1-3 cm)• takes nutrients from root to leaves

Heartwood - older wood• cells closed - can’t pass nutrients • storage for waste - extractives

Pith - the start of growth in the tree• the original sapling

Classification of Timber

• Softwood – usually found in temperate countries (cooler climate)

• Hardwood – usually found in tropical countries (warmer climate)

Softwood >> conifers / cone bearing plants, needle shaped leaves, naked/exposed seed

Hardwood >> broad-leaved plants, seed enclosed in pods

Variation: fibre & grain

• The cell structure is designed to serve particular functions in a tree.

• Its properties vary in different directions.

rays

rays

cells

fibres

vesselshardwood earlywood

rays

latewood

softwood

Variation: species & growth

• Species and genetics: – selected stock or

natural seed.

• Climate:– wet or dry, cold or

warm.

• Arrangement:– native forest or

plantation.

Each piece is unique

Myrtle burl veneer

Quarter sawn hardwood

Properties are variable

• Drying (seasoning) & shrinkage• Strength & hardness• Durability • Appearance

Timber & Timber by-products

• Timber is available in a wide range of products and species including: – Solid sawn, moulded pieces;– laminated timber;– Veneer;– Plywood; and– Wood panels.

Solid Timber: sawn timber (lumber)

• Hardwood or softwood. • Solid timber cut from a

log and dried. • It is a versatile material

used for moulding, frames and exposed structures.

• Size is restricted.

Solid Timber: mouldings

• Hardwood or softwood.

• Solid seasoned timber milled to a wide variety of shapes.

Timber products: glue laminated (glulam)• Small pieces of timber glued

together to form a larger element.

• Used as both a structural and finishing element.

• Size is limited only by transport capacity.

bench top

beam

Curved bar

curved glulam - Glue laminated material can be curved.

Timber products: veneer• Thin layers of solid wood sliced

from a flitch or peeled from a log and dried.

• High quality material is used as a decorative finish.

• Lower grade material is used to make plywood, LVL (laminated veneer lumber) and similar products.

Veneer leaf

Timber products: plywood

• Layers of veneer glued together so that the grain direction alternates between layers.

• Usually produced in sheets.

• Very good in a structure, as a lining and as a flooring surface.

Timber products: manufactured panels

• Panels made from wood or wood fibres bound together with glue, or other binder:– Particleboard /

woodchip board– Medium Density

Fibreboard (MDF)– Hardboard– Core board

MDF sheet

Advantages of Timber • Environmentally friendly

material• Good appearance, aesthetic

appeal• Low weight to strength ratio• Light, easy to handle, easily

joined• Suitable for prefabrication of

components (reduce amount of site work)

• Dry construction, faster completion period

• Good sound, thermal and electrical insulation property

• Capacity to withstand shock / vibration

Disadvantages of Timber

• Subjected to rot – dry rot / wet rot

• Is a combustible material• Being a living material, it is

subjected to attack by insects / termite

Traditional usage of timber • Main structure of Malay

house made of “heavy hardwood” – such as “cengal”, “cengal mas”, “cengal batu” and “balau”

• Floor of “balau”, “cengal”

• Walls made of “medium hardwood” – such as “meranti”

• Colonial buildings – other species of timber such as “keruing” and “merbau” for structures

Timber usage in brick buildings

• FLOOR – floor beams / bearers, floor joist, floor boards

• WALL – studs, wall panel / sheathing

• CEILING – beams, ceiling joists

• ROOF – beams, rafters, trusses, purlins, battens

• DOOR & WINDOW – frames, door panels, window leaves, sills

• VERANDA – balusters, handrails, flooring, stairs, columns