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?

<p>As a percentage of weight before and after drying. (C)</p> Signup and view all the answers

Which of the following applications does Glulam NOT typically serve?

<p>Residential plumbing (C)</p> Signup and view all the answers

What does the fiber saturation point indicate in wood?

<p>The point where cell walls are fully saturated with water. (C)</p> Signup and view all the answers

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

<p>Orthotropic nature (C)</p> Signup and view all the answers

What defines timber in the context of engineering construction?

<p>Wood processed by a mill for construction purposes (D)</p> Signup and view all the answers

Which of the following is not a recognized timber defect?

<p>Sway (C)</p> Signup and view all the answers

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

<p>Strength (B)</p> Signup and view all the answers

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

<p>Elasticity (C)</p> Signup and view all the answers

Which aspect of Glulam contributes to its resistance against fire?

<p>Inherent fire-resistance treatment (A)</p> Signup and view all the answers

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

<p>Greater flexibility (C)</p> Signup and view all the answers

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

<p>Removes excess moisture from the timber. (B)</p> Signup and view all the answers

What is a common misconception about the durability of Glulam?

<p>It is weaker than solid wood alternatives. (B)</p> Signup and view all the answers

What is a characteristic of hardwood trees?

<p>They shed leaves annually. (B)</p> Signup and view all the answers

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

<p>Plywood (B)</p> Signup and view all the answers

What is the primary material used in chipboard production?

<p>Wood particles (C)</p> Signup and view all the answers

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

<p>The amount of paint applied (A)</p> Signup and view all the answers

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

<p>Heartwood only supports the tree. (C)</p> Signup and view all the answers

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

<p>Strength varies based on grain structure (C)</p> Signup and view all the answers

Which property makes plywood an excellent insulator?

<p>Its layered structure (C)</p> Signup and view all the answers

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

<p>It is generally more cost-effective for structural applications. (D)</p> Signup and view all the answers

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

<p>The grains are parallel (C)</p> Signup and view all the answers

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

<p>Softwood (D)</p> Signup and view all the answers

What is a significant drawback of chipboard compared to plywood?

<p>Greater vulnerability to moisture (A)</p> Signup and view all the answers

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

<p>Sapwood (D)</p> Signup and view all the answers

In what temperature range does plywood undergo charring and hollowing?

<p>90 to 150 degrees Celsius (D)</p> Signup and view all the answers

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

<p>It increases strength and ease of working. (B)</p> Signup and view all the answers

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

<p>Fast growing cells produced in the spring (D)</p> Signup and view all the answers

Which characteristic of glulam enhances its usability in construction?

<p>Ability to be manufactured in curved shapes (A)</p> Signup and view all the answers

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

<p>Its grain is oriented at right angles (C)</p> Signup and view all the answers

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

<p>Application of a load to the ends of a column. (B)</p> Signup and view all the answers

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

<p>Tensile strength (C)</p> Signup and view all the answers

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

<p>Oil type (B)</p> Signup and view all the answers

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

<p>Janka hardness test (D)</p> Signup and view all the answers

Transverse strength in lumber refers to what scenario?

<p>Strength in a bending test. (C)</p> Signup and view all the answers

Which type of preservative is typically dissolved in organic solvents?

<p>Organic solvent type (D)</p> Signup and view all the answers

What does shear strength measure in lumber?

<p>Ability to endure slipping of parts along the grain. (B)</p> Signup and view all the answers

What is a major disadvantage of using oil type preservatives?

<p>Difficult to handle due to odor and poor paint adhesion. (A)</p> Signup and view all the answers

What is a characteristic of leachable type preservatives?

<p>They are odorless. (D)</p> Signup and view all the answers

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

<p>Brushing (A)</p> Signup and view all the answers

What is the primary use of the charring method?

<p>To burn the surface for protection against fungi (D)</p> Signup and view all the answers

What distinguishes fixed type preservatives from leachable type preservatives?

<p>They include fixative salts like dichromate. (A)</p> Signup and view all the answers

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

<p>Spraying (B)</p> Signup and view all the answers

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

<p>It can only be performed in special treatment plants. (C)</p> Signup and view all the answers

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

<p>Soaking the lumber for enhanced effectiveness (B)</p> Signup and view all the answers

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

<p>Creosote oil (D)</p> Signup and view all the answers

Flashcards

What is timber?

Wood that is suitable for construction or engineering purposes.

What is moisture content in timber?

The moisture content in wood refers to the amount of water it contains. This can affect its strength, durability, and workability.

What is the difference between hardwood and softwood trees?

Hardwood trees have broad leaves that they shed annually, while softwood trees have needle-like or scale-like leaves. Hardwoods are typically denser and stronger than softwoods.

What is sapwood and heartwood?

Sapwood is the outer layer of a tree that transports nutrients and water, while heartwood is the inner layer that provides structural support and is often more resistant to decay.

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What is earlywood and latewood?

Earlywood is the lighter and softer wood produced during the early part of the growing season, while latewood is the denser and harder wood produced later in the season. Earlywood grows fast (big cells), while latewood grows slow (small cells).

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How is timber manufactured?

Timber is made from trees. The trees are felled, debarked, and then sawn into planks or beams. The wood can be further processed to create various products.

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What are the advantages of using timber?

Timber is a natural material that is strong, durable, and renewable. Because it comes from trees, it is sustainable when managed responsibly. Timber is also versatile and can be used for a variety of purposes.

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What are some challenges of using timber?

Timber can be affected by factors such as moisture, pests, and temperature changes. It's important to treat timber properly to protect it from these factors and increase its longevity.

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Latewood (Summerwood)

The denser, stronger wood formed during slower growth in the summer.

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Earlywood (Springwood)

The less dense, weaker wood formed during faster growth in the spring.

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Wood Grain

The pattern formed by growth rings in wood. It can be straight, cross, or spiral.

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Wood Texture

The fineness or coarseness of the wood structure, determined by the width of growth rings.

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Moisture Content

The percentage of water in wood, expressed as a ratio of the weight of water to the weight of dry wood.

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Fiber Saturation Point

The point at which the cell walls of wood are fully saturated with water, typically around 30% moisture content.

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Seasoning

A process of drying wood to reduce its moisture content, usually done in a kiln or by air drying.

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Plywood

A layer of wood veneer glued to a core of plywood, creating a strong and stable sheet.

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What is plywood?

A type of wood panel made by bonding together thin layers of wood veneer, with the grain of each layer running at right angles to the one next to it. This construction provides strength in both directions and minimizes warping and cracking.

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What is a key property of plywood?

Plywood is an excellent insulator, meaning it helps to prevent heat from escaping or entering a space. Its layered structure contributes to its insulating quality.

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What happens to plywood under high heat?

When exposed to extreme heat, plywood undergoes a process called charring and hollowing. This means the surface turns black and forms cavities. This occurs at temperatures between 90 and 150 degrees Celsius.

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What is chipboard?

Chipboard is a sheet material made from mixing wood particles or wood waste with an adhesive. It is a cost-effective material often used for furniture and interior construction.

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What are some limitations of chipboard?

Chipboard is more prone to warping and splitting than plywood due to its shorter wood fibers. It is also less resistant to impact damage and can deform under prolonged weight.

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What is Glulam?

Glued Laminated Timber (Glulam) is a strong and versatile material made by bonding together layers of wood with glue, with the grain of all layers running in the same direction.

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What is a unique feature of Glulam?

Glulam allows for the creation of large and complex shapes, including curved beams. This makes it suitable for architectural designs that require unique forms.

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What are the materials used to make Glulam?

Glulam can be made from both softwood and hardwood, giving builders flexibility in choosing the type of wood that best suits their needs.

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Water-soluble wood preservative

A type of wood preservative that dissolves in water and is applied to lumber.

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Leachable wood preservative

A type of water-soluble preservative containing salts that can be washed away by rain or water.

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Fixed wood preservative

A type of water-soluble preservative with additional salts that prevent leaching.

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Charring wood

A traditional wood preservation method that involves burning the wood surface.

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Brushing wood preservatives

A simple method of applying wood preservatives using a brush.

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Spraying wood preservatives

A method of applying wood preservatives using a sprayer.

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Injecting wood preservatives

Applying preservatives under high pressure to penetrate deep into the wood.

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Dipping and wetting wood preservatives

A method of preserving lumber by soaking it in preservative solution.

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Compression perpendicular to the grain

The load is applied perpendicular to the grain direction, such as when a beam or column is supporting a weight from above.

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Compression parallel to the grain

The load is applied parallel to the grain direction, which means force is applied along the length of the wood.

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Tensile strength

The maximum strength of the wood before it breaks when stretched or pulled. Grain structure plays a big role in the material's ability to withstand tension.

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Shear strength

The strength of the wood against slipping or shearing along the grain, usually tested by applying force parallel to the grain.

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Transverse strength

The strength of the wood before it yields in a bending test. This is important for beams that need to withstand bending loads.

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Hardness

The resistance of wood to wear, measured by how deep a steel ball can penetrate.

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Oil type preservative

A type of wood preservation that uses coal tar creosote oil, a distillate of coal tar.

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Organic solvent type preservative

A type of wood preservation that uses salts dissolved in organic solvents.

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What are some applications of Glulam?

Glulam is used as an alternative to steel or concrete in construction, offering advantages in both strength and aesthetics.

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What is the nature of wood's strength?

Wood is a directional material, meaning its properties vary based on the direction of the grain. It's stronger along the grain than across it.

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What are the important mechanical properties of lumber?

The strength of lumber is a measure of its ability to withstand loads. This can be compressive (pushing), tensile (pulling), or transverse (sideways).

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What is hygroscopicity in lumber?

The ability of wood to absorb water and expand or shrink based on moisture content. This can affect dimensional stability and strength.

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What is durability in lumber?

The ability of wood to resist decay and insect attack. This depends on the type of wood and how it's treated.

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What are preservatives used for in lumber?

Chemicals are used to protect lumber from decay, insects, and fire hazards. They are applied to the surface or injected into the wood.

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How are preservatives applied to lumber?

Preservatives are applied using various techniques, including dipping, brushing, pressure treatment, and vacuum impregnation. The method depends on the wood type and desired protection level.

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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.

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