Wood Science and Engineering Basics

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Questions and Answers

What is the primary difference between latewood and earlywood in tree growth?

Latewood is denser and stronger than earlywood. (correct)

Latewood is less dense than earlywood.

Earlywood is primarily formed during winter months.

Earlywood has wider growth rings than latewood.

What is one of the primary benefits of using Glulam in construction?

It is only suitable for temporary structures.

It is environmentally friendly. (correct)

It requires extensive maintenance.

It is less aesthetically pleasing compared to steel.

Which term describes the natural defects found in timber as a result of growth?

Wane

Checks

Knots (correct)

Cup

How is moisture content in wood expressed?

As a percentage of weight before and after drying. Signup and view all the answers

Which of the following applications does Glulam NOT typically serve?

Residential plumbing Signup and view all the answers

What does the fiber saturation point indicate in wood?

The point where cell walls are fully saturated with water. Signup and view all the answers

What characteristic of wood affects its strength properties in different directions?

Orthotropic nature Signup and view all the answers

What defines timber in the context of engineering construction?

Wood processed by a mill for construction purposes Signup and view all the answers

Which of the following is not a recognized timber defect?

Sway Signup and view all the answers

Which property of lumber is related to its ability to withstand loads?

Strength Signup and view all the answers

Which of the following properties of timber allows it to perform better under tension than compression?

Elasticity Signup and view all the answers

Which aspect of Glulam contributes to its resistance against fire?

Inherent fire-resistance treatment Signup and view all the answers

What is one of the main advantages of plywood compared to traditional timber?

Greater flexibility Signup and view all the answers

What does the drying process known as 'seasoning' achieve?

Removes excess moisture from the timber. Signup and view all the answers

What is a common misconception about the durability of Glulam?

It is weaker than solid wood alternatives. Signup and view all the answers

What is a characteristic of hardwood trees?

They shed leaves annually. Signup and view all the answers

What type of lumber is specifically designed for strength and stability through bonding layers of wood?

Plywood Signup and view all the answers

What is the primary material used in chipboard production?

Wood particles Signup and view all the answers

Which factor does not influence the rate at which wood reaches equilibrium moisture content?

The amount of paint applied Signup and view all the answers

How does heartwood differ from sapwood in terms of its function?

Heartwood only supports the tree. Signup and view all the answers

Which of the following best describes the mechanical properties of lumber?

Strength varies based on grain structure Signup and view all the answers

Which property makes plywood an excellent insulator?

Its layered structure Signup and view all the answers

In terms of cost-effectiveness, how does Glulam compare to traditional materials?

It is generally more cost-effective for structural applications. Signup and view all the answers

Which feature distinguishes glued laminated timber (glulam) from plywood?

The grains are parallel Signup and view all the answers

Which type of timber is commonly used for most structural purposes due to its workability?

Softwood Signup and view all the answers

What is a significant drawback of chipboard compared to plywood?

Greater vulnerability to moisture Signup and view all the answers

Which layer in a tree stops storing nutrients and transforms into heartwood?

Sapwood Signup and view all the answers

In what temperature range does plywood undergo charring and hollowing?

90 to 150 degrees Celsius Signup and view all the answers

What is the significance of the straight-grain characteristic of timber?

It increases strength and ease of working. Signup and view all the answers

What is earlywood, in relation to the growth of trees?

Fast growing cells produced in the spring Signup and view all the answers

Which characteristic of glulam enhances its usability in construction?

Ability to be manufactured in curved shapes Signup and view all the answers

Why is plywood less likely to warp and crack compared to chipboard?

Its grain is oriented at right angles Signup and view all the answers

What is meant by compression parallel to the grain in lumber?

Application of a load to the ends of a column. Signup and view all the answers

Which of the following is a measure of the maximum strength before breaking when wood is stretched?

Tensile strength Signup and view all the answers

Which type of lumber preservative is known for being highly toxic and providing termite protection?

Oil type Signup and view all the answers

What measurement is used to evaluate the resistance of wood to wear?

Janka hardness test Signup and view all the answers

Transverse strength in lumber refers to what scenario?

Strength in a bending test. Signup and view all the answers

Which type of preservative is typically dissolved in organic solvents?

Organic solvent type Signup and view all the answers

What does shear strength measure in lumber?

Ability to endure slipping of parts along the grain. Signup and view all the answers

What is a major disadvantage of using oil type preservatives?

Difficult to handle due to odor and poor paint adhesion. Signup and view all the answers

What is a characteristic of leachable type preservatives?

They are odorless. Signup and view all the answers

Which method of applying preservatives is known to be the simplest?

Brushing Signup and view all the answers

What is the primary use of the charring method?

To burn the surface for protection against fungi Signup and view all the answers

What distinguishes fixed type preservatives from leachable type preservatives?

They include fixative salts like dichromate. Signup and view all the answers

Which method of preserving lumber is described as being more effective than brushing?

Spraying Signup and view all the answers

What is a disadvantage of the method of injecting preservatives under pressure?

It can only be performed in special treatment plants. Signup and view all the answers

What type of application is well-suited for dipping and wetting?

Soaking the lumber for enhanced effectiveness Signup and view all the answers

Which material is commonly associated with the injecting method of preservation?

Creosote oil Signup and view all the answers

Study Notes

Timber

Timber is organic matter from trees
Timber is primarily cellulose
Wood suitable for engineering construction is called timber
Lumber is processed wood for construction
Unprocessed wood or standing trees are timber
Timber is fibrous and elastic.
Timber performs better under tension than compression.
Timber undergoes variations in moisture content.
Straight-grain timber is stronger and easier to work with compared to irregular grain timber.

Timber Characteristics

Trees are divided into hardwoods and softwoods
Hardwoods have broad leaves that fall annually
Hardwoods have a specific gravity between 0.15 and more than 1.0 for some dense species
Hardwoods are strong, durable, and have color variations.
Hardwoods are more expensive than softwoods
Softwoods have needle-like or scale-like leaves
Softwoods may shed leaves when damaged or unused
Softwoods have a specific gravity between 0.25 and 0.65
Softwoods are used in structural timbers due to their softness and straight grain.
Trees grow by adding new layers
Sapwood stores nutrients and supports trees
Heartwood stores no nutrients, but supports the tree
Heartwood is often resistant to decay in some species, without any difference between sapwood and heartwood specific gravities
Earlywood/springwood is fast-growing cells
Latewood/summerwood is slower-growing cells
Latewood is denser and stronger than earlywood.

Timber Defects

Timber defects include splits, knotholes, wane, cup, crook, checks, shake, bow, and twist
Shakes and knots are natural defects

Moisture Content

Water is found in cell cavities and walls of wood
Moisture content is expressed as a percentage using the weight of the piece of wood prior to oven-drying and after oven-drying.
Freshly sawn wood from living trees has a moisture content greater than 100%
Fiber saturation point is when saturated cell walls are reached, usually associated with 30% moisture content
Equilibrium moisture content is reached based on surrounding humidity and temperature
Temperature kilns are used to dry the wood to a specified moisture content
Oven-dry is used to dry the wood until no further moisture is removed
Seasoning is the process of removing water from timber to produce seasoned timber

Rate of Equilibrium Moisture Content

The rate at which wood reaches its equilibrium moisture content depends on
The degree the wood has been enclosed
The environmental conditions
The wood species

Types of Lumber

Plywood
Chipboard
Glulam (structural glued laminated timber)

Plywood

Plywood is made by bonding veneers at right angles
Plywood is strong, flexible, and resistant to impact damage.
Plywood is an excellent insulator.
Plywood undergoes charring when exposed to extreme heat

Chipboard

Chipboard is made from mixing wood particles with an additive
Chipboard is primarily used for furniture
Chipboard is susceptible to warping and splitting
Chipboard is less likely to withstand impact damage than plywood
Chipboard is prone to creep
Chipboard absorbs moisture easily and will crumble

Glulam

Glued laminated timbers are produced by bonding dry lumber under controlled conditions and temperature
Glulam has parallel grains
Glulam is available in any size and can have curved shapes
Glulam is made from softwoods and hardwoods
Glulam is strong in tension and compression, but defects reduce structural strength

Manufacturing Process of Glulam

Glulam is manufactured by converting and cutting lumber, applying adhesives, planing, drying, strength grading, finger joining, pressing, and curing by final planing
https://techlam.nz/about/how-techlam-glulam-is-manufactured/

Benefits of Using Glulam

Environmentally friendly
Aesthetically pleasing
Strong, sturdy, and durable
Stable
Fire resistant
Cost-effective
Versatile

Applications of Glulam

Glulam is used as an alternative to steel or concrete in construction
Glulam is commonly used for beams and columns
Glulam can be used for roofs, domes, and bridges

Lumber

Mechanical properties of lumber
Preservatives used to treat lumber
Methods of applying preservatives

Mechanical Properties of Lumber

Wood is an orthotropic material (properties depend on the direction of the grain)
Strength differs in longitudinal, tangential, and radial directions.
Strength properties parallel to the grain are 20–30 times higher than properties perpendicular to the grain
Strength: the ability to bear loads.
Compressive Strength: withstands loads (e.g., columns, posts)
Compression perpendicular to grain: load applied at right angles to the grain
Compression parallel to grain: load applied to ends of a column
Tensile Strength: max strength before breaking when stretched or pulled (dependent on grain structure)
Shear Strength: measure of wood to slipping of one part along the grain (force is applied parallel to the grain)
Transverse Strength: strength of the material before yielding in a flexural test (e.g., beams, and static bending of a beam)
Hardness: a measure of the resistance of wood to wear

Preservatives of Lumber

Preservation of lumber is carried out to increase lumber life and durability.
Preservative types: oil, organic solvent, and water-soluble
Oil type: coal tar creosote (for outdoor use)
Organic solvent type: organic/inorganic salts dissolved in solvents (often flammable)
Water-soluble type: inorganic/organic salts soluble in water (leachable), mixtures of water-soluble salts

Methods of Application of Preservatives

Methods of application include brushing, spraying, injection under pressure, dipping, and wetting.
Brushing: simplest, used on well-seasoned lumber, multiple coats
Spraying: more effective than brushing, for water-based/organic solutions using a spraying gun
Injection under pressure: injecting under high pressure for creosote oil (applied at special plants)
Dipping/stepping: dipping lumber in preservative solution (more effective than brushing or spraying), wetting done over days or weeks.

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Description

Test your knowledge on the fundamental concepts of wood science and engineering with this quiz. Covering topics such as wood growth, defects, properties, and applications in construction, this quiz offers a comprehensive overview for students and professionals alike. Ideal for those studying timber and its uses in engineering.