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TIMBER / WOODTIMBER / WOOD
Timber StructureTimber Structure
TIMBERTIMBER
Wood is one of the Wood is one of the oldest known oldest known materials used in materials used in constructionconstruction
It is the only It is the only naturally renewable naturally renewable building materialbuilding material
Species of wood in Species of wood in Malaysia – more Malaysia – more than 2500than 2500
Names of woodNames of wood
Vernacular – Vernacular – given by given by the local community e.g. the local community e.g. Cengal – Cengai or Cengal – Cengai or PenakPenak
Botanical – Botanical – given by given by botanical member e.g. botanical member e.g. Balanorcarpus Heimeii Balanorcarpus Heimeii (Cengal)(Cengal)
Commerce – Commerce – given for given for trading e.g. Cengaltrading e.g. Cengal
Design ConceptDesign Concept
Wood popular for Lightweight Wood popular for Lightweight ConstructionConstruction
Simplicity in fabricationSimplicity in fabricationLightnessLightnessReusabilityReusabilityMaterial availabilityMaterial availabilitySimpler connectionsSimpler connectionsEnvironmental Environmental compatibilitycompatibilityAdaptability to Adaptability to modifications and modifications and remodelingremodeling
Wood in ConstructionWood in Construction
In the form of lumber – In the form of lumber – pieces of wood cut from tree pieces of wood cut from tree trunkstrunks
Wood products – Wood products – glue glue laminated timber, pressed laminated timber, pressed wood, chip board etc.wood, chip board etc.
Tree trunks → Log → LumberTree trunks → Log → Lumber
USE OF TIMBERUSE OF TIMBER
Classification of WoodClassification of Wood
Hardwood – Hardwood – tree has broad tree has broad leaves, seeds with hard leaves, seeds with hard shell, mostly grow in shell, mostly grow in tropical climate e.g. jatitropical climate e.g. jati
Softwood – Softwood – species that species that has needlelike leaves, has needlelike leaves, seed without hard shell, seed without hard shell, mostly grow in mostly grow in seasonal climate e.g. seasonal climate e.g. Pine treesPine trees
This classification is based on the Botanical aspects, not the hardness of the woodThis classification is based on the Botanical aspects, not the hardness of the wood
Cont.Cont.
Generally, most Generally, most hardwoods are harder to hardwoods are harder to work with than softwoodwork with than softwood
The term The term hardwoodhardwood and and softwoodsoftwood do not do not necessarily indicate the necessarily indicate the relative hardness or relative hardness or density between the two density between the two categoriescategories
Growth Ring/Annual RingGrowth Ring/Annual Ring
Growth ringGrowth ring = = earlywood + latewoodearlywood + latewood
Earlywood – Earlywood – cell cell with larger opening, with larger opening, during winterduring winter
Latewood – Latewood – cell with cell with smaller opening, smaller opening, during summerduring summer
Growth RingGrowth Ring
Growth RingGrowth Ring
Wood CellWood Cell
Cell Cavity
Cell Wall
Wood CellWood Cell
Forest Research Institute of Malaysia Forest Research Institute of Malaysia (FRIM)(FRIM)
Hardwood in Malaysia – classified Hardwood in Malaysia – classified based on the based on the density and durabilitydensity and durability
Three categoriesThree categoriesHeavyweight hardwoodHeavyweight hardwood – density – density greater than 880 kg/mgreater than 880 kg/m33, very durable , very durable e.g. balau, cengale.g. balau, cengalNormal/Intermediate weight hardwoodNormal/Intermediate weight hardwood – – density in the range of 720 to 880 kg/mdensity in the range of 720 to 880 kg/m33, , less durable compared to heavyweight less durable compared to heavyweight hardwood, e.g. kempas, keruinghardwood, e.g. kempas, keruingLightweight hardwoodLightweight hardwood – density less – density less than 720 kg/mthan 720 kg/m33, not durable except , not durable except being preserved, e.g. merantibeing preserved, e.g. meranti
Properties of WoodProperties of Wood
The most important properties The most important properties that affect strength and durability that affect strength and durability of wood are:of wood are:
1)1) Moisture contentMoisture content
2)2) Specific gravitySpecific gravity
Effect of Moisture ContentEffect of Moisture Content
Moisture contentMoisture content
The weight of water in wood expressed The weight of water in wood expressed as a percentage of its oven-dry weightas a percentage of its oven-dry weight
Determining moisture content – oven or Determining moisture content – oven or moisture metermoisture meter
Wood is a hygroscopic substance – it Wood is a hygroscopic substance – it can absorb water/moisturecan absorb water/moisture
The ability to absorb or lose The ability to absorb or lose moisture depends on moisture depends on
environmental conditionsenvironmental conditions
Relative HumidityRelative Humidity
TemperatureTemperature
Variations of moisture content in Variations of moisture content in living treesliving trees
Moisture content 400%, specific gravity Moisture content 400%, specific gravity 0.20.2
Moisture content 100%, specific gravity Moisture content 100%, specific gravity 1.151.15
Typical trees contain water about two Typical trees contain water about two times the weight of its solid materialtimes the weight of its solid material
Water exist in woodWater exist in wood
FREE WATER – FREE WATER – in the cell in the cell cavitycavityBOUND or ADSORBED BOUND or ADSORBED WATER – WATER – in the cell wallin the cell wallThe amount of water in cell The amount of water in cell cavities varies with the cavities varies with the amount of dryingamount of dryingLumber has moisture Lumber has moisture generally in excess of 50% generally in excess of 50% at the time of its at the time of its manufacturemanufacture
FIBRE SATURETION POINT (FSP)FIBRE SATURETION POINT (FSP)
FSP is when the FSP is when the cell cavitycell cavity contains only air and the contains only air and the cell cell wallwall is saturated with water is saturated with water
Moisture content at FSP can Moisture content at FSP can vary from vary from 20 to 30%20 to 30% depending on the species ofdepending on the species of woodwood
Effect of Moisture ContentEffect of Moisture Content
Above FSP – Above FSP – volume volume and mechanical and mechanical properties unchanged properties unchanged or constant, although or constant, although the density of wood the density of wood decreasedecrease
Below FSP – Below FSP – wood wood shrink and strength shrink and strength increaseincrease
Amount of water in cell will affect:Amount of water in cell will affect:
Physical propertiesPhysical properties
Mechanical Mechanical propertiesproperties
DurabilityDurability
Dimensional Dimensional stabilitystability
Equilibrium Moisture ContentEquilibrium Moisture Content
The moisture content at The moisture content at which wood neither gains nor which wood neither gains nor loses moisture to the loses moisture to the surroundingsurrounding
Its values range between 5 Its values range between 5 and 17% at 70 °C and relative and 17% at 70 °C and relative humidity between 2 to 80%humidity between 2 to 80%
Specific GravitySpecific Gravity
Is the ratio of the weight of wood Is the ratio of the weight of wood (oven-dry) to the weight of an equal (oven-dry) to the weight of an equal volume of watervolume of water
Specific Gravity = (WSpecific Gravity = (Wss)/(w)/(wwwV)V)
WWss – oven-dry weight – oven-dry weight
wwww – density of water – density of water
V – volume of (green) woodV – volume of (green) wood
Wood is composed of:Wood is composed of:
Solid matterSolid matter
WaterWater
AirAir
Volume = VVolume = Vsolidsolid + V + Vwaterwater + V + Vairair
Specific gravitySpecific gravity
Determined in three conditions:Determined in three conditions:
1)1) Green (moisture content in excess Green (moisture content in excess of 19%)of 19%)
2)2) Air-dry (moisture content – 12%)Air-dry (moisture content – 12%)
3)3) Oven-dry (moisture content 0%)Oven-dry (moisture content 0%)
Cont.Cont.
Strength and stiffness of wood increase with Strength and stiffness of wood increase with the increase in specific gravitythe increase in specific gravity
Physical and mechanical properties of wood Physical and mechanical properties of wood are related to specific gravityare related to specific gravity
Density of wood is defined as the mass or Density of wood is defined as the mass or weight per unit volumeweight per unit volume
It is directly related to porosity or proportion It is directly related to porosity or proportion of voids and calculated using the total weight of voids and calculated using the total weight of woodof wood
PROPERTIES OF WOODPROPERTIES OF WOOD
Strength Strength is one of is one of the main properties the main properties that determines the that determines the suitability of wood suitability of wood in constructionin construction
Strength – Strength – the the ability of material to ability of material to resist external load resist external load without failurewithout failure
Strength of TimberStrength of Timber
Tensile strengthTensile strength
Compressive strengthCompressive strength
Flexural strengthFlexural strength
Shear strength hardnessShear strength hardness
Impact strengthImpact strength
Splitting strengthSplitting strength
Loading ConditionLoading Condition
Strength of woodStrength of wood
Varies according to the direction of Varies according to the direction of the applied loadthe applied load
1)1) Parallel to grainsParallel to grains
2)2) Perpendicular to grainsPerpendicular to grains
Wood grains – direction of wood Wood grains – direction of wood fibre with respect to the main axis fibre with respect to the main axis of woodof wood
Wood GrainsWood Grains
Straight grainStraight grain
Edge grainEdge grain
Flat grainFlat grain
Cross grainCross grain
Spiral grainSpiral grain
Diagonal grainDiagonal grain
The slope of grains will The slope of grains will affect the strength of affect the strength of woodwood
Effect of Wood GrainEffect of Wood Grain
Cont.Cont.
Tensile strength and Tensile strength and compressive strengths compressive strengths parallel to wood grains parallel to wood grains are higher than are higher than perpendicular to wood perpendicular to wood grains.grains.Compressive strength Compressive strength perpendicular to wood perpendicular to wood grains is between 12 and grains is between 12 and 18% of compressive 18% of compressive strength to wood grainsstrength to wood grains
Tensile strength parallel Tensile strength parallel to wood grains is to wood grains is approximately 2 to 4 approximately 2 to 4 times than compressive times than compressive strength parallel to strength parallel to wood grainswood grains
Shear strength Shear strength perpendicular to wood perpendicular to wood grains is higher than grains is higher than parallel to wood grains parallel to wood grains
Cont.Cont.
Hardness of wood is Hardness of wood is generally defined as generally defined as how easy the wood to how easy the wood to be work with i.e. cut, be work with i.e. cut, nailednailed
It depends on the It depends on the density, stiffness, and density, stiffness, and bonding between wood bonding between wood fibresfibres
Impact strength – Impact strength – the ability of wood the ability of wood to absorb sudden to absorb sudden external loadexternal load
It depends on the It depends on the hardness, elasticity, hardness, elasticity, plasticity of woodplasticity of wood
FACTORS AFFECTING STRENGTH FACTORS AFFECTING STRENGTH AND DURABILITY OF TIMBERAND DURABILITY OF TIMBER
Moisture contentMoisture content
DensityDensity
Wood grainsWood grains
DefectsDefects
Preservative Preservative TreatmentTreatment
Moisture ContentMoisture Content
Higher moisture Higher moisture content will reduce content will reduce the strength and the strength and durability of wooddurability of wood
Moisture will cause Moisture will cause wood to decaywood to decay
DensityDensity
Wood with higher Wood with higher density will have density will have higher compressive higher compressive strength and better strength and better durability durability due to due to dense microstructuredense microstructure
Wood DefectsWood Defects
Any irregularities in the Any irregularities in the structure of wood or structure of wood or lumber that will reduce lumber that will reduce the strength and the strength and durability durability
Types of defect:Types of defect:
1)1) Natural defectNatural defect
2)2) Defect during processingDefect during processing
3)3) Due to insects or fungusDue to insects or fungus
Natural DefectsNatural Defects
Natural DefectsNatural Defects
Design ConsiderationDesign Consideration
Effect of DefectEffect of Defect
Processing DefectsProcessing Defects
Generally is due to improper drying methodsGenerally is due to improper drying methods
Insects and FungusInsects and Fungus
Wood destroying insects – Wood destroying insects – termites, pin-hole borers, termites, pin-hole borers, beetlesbeetles
Fungi – Fungi – brown rot, white rotbrown rot, white rot
Conditions for fungal growthConditions for fungal growth
1)1) Proper temperatureProper temperature
2)2) Moisture greater than 19%Moisture greater than 19%
3)3) OxygenOxygen
4)4) Food (wood fibre)Food (wood fibre)
SEASONING OF WOODSEASONING OF WOOD
The process of controlled drying of The process of controlled drying of lumber (water in cell cavity and lumber (water in cell cavity and wall) to increase its structural wall) to increase its structural propertiesproperties
Reduction in moisture content:Reduction in moisture content:1)1) Increase strengthIncrease strength2)2) Reduce shrinkageReduce shrinkage3)3) Reduction in weightReduction in weight4)4) More durableMore durable
Methods of dryingMethods of drying
Air drying – Air drying – drying drying naturallynaturally
Kiln/Oven drying – Kiln/Oven drying – controlled drying controlled drying (temperatures and (temperatures and humidities)humidities)
Stacking lumberStacking lumber
Factors Affecting Drying ProcessFactors Affecting Drying Process
TemperatureTemperature
Relative humidityRelative humidity
Air circulationAir circulation
Duration of dryingDuration of drying
Types of wood – softwood, Types of wood – softwood, hardwoodhardwood
Size of lumberSize of lumber
Surrounding environmentSurrounding environment
Stacking methodStacking method
Air-drying vs Oven dryingAir-drying vs Oven drying
Preservative TreatmentPreservative Treatment
Is the process of Is the process of introducing or injecting introducing or injecting special chemicals into special chemicals into wood cell by special wood cell by special techniquestechniques
The purpose is to prevent The purpose is to prevent the destruction from fungi the destruction from fungi and insects and to inhibit and insects and to inhibit combustion combustion
Classes of Wood PreservativesClasses of Wood Preservatives
Creosote oilCreosote oil
Water-borne wood preservativesWater-borne wood preservatives
Light organic solvent preservativesLight organic solvent preservatives
It is important that the preservatives It is important that the preservatives must penetrate into the wood and to must penetrate into the wood and to such extent it is effectively protect the such extent it is effectively protect the woodwood
Attributes of Ideal Wood Attributes of Ideal Wood PreservativesPreservatives
Easy penetration into wood cellEasy penetration into wood cellPermanent in the wood cellPermanent in the wood cellToxic to insect and fungiToxic to insect and fungiSafe to handleSafe to handleColourlessColourlessCompatible with coatings and Compatible with coatings and finishesfinishesCheapCheap
Ease of Injecting PreservativesEase of Injecting Preservatives
Wood densityWood density
Microstructure of woodMicrostructure of wood
Chemical composition of cell Chemical composition of cell wallwall
Size of lumberSize of lumber
Moisture contentMoisture content
Methods of Treatment ProcessMethods of Treatment Process
Non-Pressure MethodNon-Pressure MethodBrushingBrushingImmersion Immersion Hot and cold open tank Hot and cold open tank treatmenttreatmentPressure TreatmentsPressure Treatments
1)1) Full cellFull cell2)2) Empty cellEmpty cell
Cont.Cont.
The only method to achieve any The only method to achieve any worthwhile degree of penetration is by worthwhile degree of penetration is by way of way of pressure treatmentpressure treatment
BrushingBrushing – not very effective, chemical – not very effective, chemical will not be able to penetrate into wood will not be able to penetrate into wood cell, need to repeat the processcell, need to repeat the process
ImmersionImmersion
Cold immersion – lumber is immersed in Cold immersion – lumber is immersed in tank for few weekstank for few weeksHot immersion – immersed in tank at Hot immersion – immersed in tank at higher temperature 90 °Chigher temperature 90 °C Hot-Cold immersion – immersed in tank at Hot-Cold immersion – immersed in tank at 90 °C, during heating air in cell cavity will 90 °C, during heating air in cell cavity will expand and pushed out, during cooling expand and pushed out, during cooling the cell will shrink and absorb the the cell will shrink and absorb the chemicalchemical
Pressure (full cell)Pressure (full cell)
Lumber is put in containerLumber is put in containerHalf vacuum (to pull out air)Half vacuum (to pull out air)Spray hot chemical, increase pressure Spray hot chemical, increase pressure (chemical enters wood cell)(chemical enters wood cell)Half vacuum to push out extra chemical from Half vacuum to push out extra chemical from the cellthe cellCell wall and cavity filled with chemicalCell wall and cavity filled with chemicalSuitable for construction in damp soilSuitable for construction in damp soilIn buildings, chemical may leach outIn buildings, chemical may leach out
Pressure (empty cell)Pressure (empty cell)
Lumber placed in containerLumber placed in containerApply pressure (compressed the air)Apply pressure (compressed the air)Spray chemicalSpray chemicalIncrease pressure (forcing chemical to Increase pressure (forcing chemical to penetrate into cell wall but air in cell cavity is penetrate into cell wall but air in cell cavity is compressed)compressed)Reduce pressure, half vacuum, air in cell Reduce pressure, half vacuum, air in cell cavity will expand pushing out extra cavity will expand pushing out extra chemicalchemicalCell wall filled with chemical but cell cavity is Cell wall filled with chemical but cell cavity is emptyemptyMore economical, cleaner lumberMore economical, cleaner lumber
TIMBER STRESS GRADETIMBER STRESS GRADE
Divided into two Divided into two categories:categories:
Wet condition – Wet condition – moisture greater moisture greater than 19%than 19%
Air-dry condition – Air-dry condition – moisture equal to or moisture equal to or less than 19%less than 19%
Design PurposesDesign PurposesFRIM divides stress timber into several FRIM divides stress timber into several gradesgrades
Basic stress – Basic stress – stress that can be sustained stress that can be sustained by timber without failureby timber without failure
GradeGrade Design stressDesign stress
SelectedSelected 80% of basic stress80% of basic stress
ParticularParticular 63% of basic stress63% of basic stress
GeneralGeneral 50% of basic stress50% of basic stress
Strength of TimberStrength of Timber
Divided into four groups i.e. Divided into four groups i.e. A, B, A, B, C, and DC, and D
Based on strengthBased on strength
Selection of timber Selection of timber based on based on strengthstrength from different groups from different groups
MANNER OF CUTTING A LOGMANNER OF CUTTING A LOG
The method of cutting a log will affect The method of cutting a log will affect shrinkageshrinkageShrinkage occurs in three mutually Shrinkage occurs in three mutually perpendicular directions:perpendicular directions:
1)1) Along its axisAlong its axis2)2) Along a radial directionAlong a radial direction3)3) Along tangent to the radiusAlong tangent to the radius
Tangential shrinkage Tangential shrinkage is the highest, about is the highest, about two times the radial shrinkagetwo times the radial shrinkageThe longitudinal shrinkage The longitudinal shrinkage is negligibleis negligible
WOOD PRODUCTSWOOD PRODUCTS
Wood in construction Wood in construction can be divided into two can be divided into two formsforms
1)1) In the form of lumberIn the form of lumber
2)2) In the form of wood-In the form of wood-based panel based panel
Two types of panels: Two types of panels: veneered panels and veneered panels and non-veneered panelsnon-veneered panels
PanelsPanelsVeneered panels – Veneered panels – also called plywood, also called plywood, made from thin sheet of woodmade from thin sheet of woodNon-veneered panels – Non-veneered panels – manufactured manufactured from wood particles or fibresfrom wood particles or fibres
Used for Used for structuralstructural applications such applications such as floor and wall panels, as floor and wall panels, non-structuralnon-structural applications such as in furniture and applications such as in furniture and cabinetscabinets
Wood-Based ProductsWood-Based Products
Manufactured by Manufactured by bonding together bonding together using using resin under resin under heat and pressureheat and pressure
Non-Veneered PanelsNon-Veneered Panels
Divided into two major Divided into two major categories:categories:
ParticleboardsParticleboards
FibreboardsFibreboards
ParticleboardParticleboard
Manufactured from Manufactured from discrete discrete pieces of wood pieces of wood particles particles (chipboard, flakeboard, splinterboard),(chipboard, flakeboard, splinterboard), combined with a synthetic combined with a synthetic resinresin or glue, bonded or glue, bonded together together under heat and pressureunder heat and pressure in a hot press in a hot press in which an entire interparticle bond is createdin which an entire interparticle bond is created
ParticlesParticles – piece of wood smaller than veneer – piece of wood smaller than veneer sheets but larger than wood fibresheets but larger than wood fibre
ClassificationsClassifications
Low-density particleboard – Low-density particleboard – density 590 density 590 kg/mkg/m33 and specific gravity of 0.59 and specific gravity of 0.59Medium-density particleboard – Medium-density particleboard – density density between 590 and 880 kg/mbetween 590 and 880 kg/m33 and specific and specific gravity between 0.59 and 0.80gravity between 0.59 and 0.80High-density particle board – High-density particle board – density density greater than 800 kg/mgreater than 800 kg/m33 and specific and specific gravity of 0.80gravity of 0.80
FibreboardFibreboard
Is a generic term for a Is a generic term for a homogeneous panel made homogeneous panel made from from wood fibreswood fibres
Fibreboard panels have Fibreboard panels have density between 160 and 500 density between 160 and 500 kg/mkg/m33, and specific gravity , and specific gravity between 0.16 and 0.50 between 0.16 and 0.50
Cont.Cont.
Veneer, plywood, and Veneer, plywood, and blockboard are blockboard are natural wood panelsnatural wood panels
Particleboard and Particleboard and fibre building board – fibre building board – are reconstituted are reconstituted wood panels which wood panels which are manufactured are manufactured mainly from mainly from various various wood wasteswood wastes
Wood PlyWood Ply
PlywoodPlywood
Is a panel comprising an assembly of plies Is a panel comprising an assembly of plies bonded togetherbonded together
Glulam or Glue-Laminated TimberGlulam or Glue-Laminated Timber
Consists of Consists of sawn sawn lumber laminations lumber laminations bonded with an bonded with an adhesiveadhesive so that the so that the grain of all laminations grain of all laminations runs parallel with the runs parallel with the long directionlong direction
Can be manufactured Can be manufactured in a in a variety of shapes variety of shapes and sizesand sizes
GlulamGlulam
Structural SectionStructural Section
Application of TimberApplication of Timber
Structural – Structural – column, beam, trusscolumn, beam, truss
Non-structural – Non-structural – frame, partitionframe, partition
Application in ConstructionApplication in Construction
Floor TileFloor Tile
Thank YouThank You