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15 Cards in this Set
- Front
- Back
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Describe LVL |
LVL - Laminated Veneer Lumber - Made form laminating thin sheets of wood - most laminates in longitudinal direction - Deep and long sections, with high strength Page 2-4 |
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Describe a Glulam beam |
- Made from gluing many small pieces together to form a deep member - Strength > individual pieces - Makes curved and tapered beams Page 2-5 |
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Describe plywood |
Made by gluing and pressing thin laminates, where the grain is placed in alternating directions, to develop the strength in the two directions. Page 2-7 |
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Manufactured wood products are designed to limit the effect of strength reducing characteristics. What does this mean? |
Plywood and LVL are thin glued laminates, so the characteristics of one layer have little effect on the overall properties, due to the small area involved. This causes lower variability in the properties and higher properties and reliability. Page 2-9 |
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What two grades are used to characterise wood products? |
Appearance grade and structural grade Page 2-10 |
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What are some of the grading criterion for appearance grading? |
- Knot size and frequency (location unimportant) - Splits, cracks and checks (size and frequency) - colour, grain uniformity - utility - cup, bow, spring, twist Page 2-11 |
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What can you say about the structural properties of a high appearance grade timber? |
It will generally have good structural properties, because there will be fewer strength reducing characteristics Page 2-12 |
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Describe some structural grading methods |
- Visual stress (presence or absence of physical features) - Machine Stress (stiffness on flat (minor axis Modulus of Elasticity) - Proof Grading (samples pass if the remain unbroken after a proof load is applied) - Quality control (verification of grade properties by testing Page 2-14 |
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Briefly describe the visual stress grading process for structural timber. |
Examined by a trained grader - knots (size, location, angle, position relative to others) - slope of grain (on each face or edge) - splits and checks 1. Materials are given a structural grade 2. Depending on species, each structural grade has an F grade 3. F grade is stamped on each piece Page 2-17, Page 2-18 |
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Briefly describe machine stress grading |
- Each piece is tests in non-destructive bending about minor axis over most of the length - Minimum E value determines grade Page 2-20 |
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What is scanning in terms of searching for defects in timber? |
EM radiation passes through timber, to give an indication of: - density - slope of grain - internal perfections Page 2-21 |
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How does proof grading work? |
The pieces of timber are initially sorted, then put through the proofing process. A significant major axis bending load is applied, and pieces that pass are sold as proof graded timber. Page 2-22 |
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What does durability mean in terms of timber properties? |
Capacity to perform satisfactorily for a specified period Page 2-24 |
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Durability is affected by...? |
- Weathering - Fire - Chemicals - Fungi - Marine conditions Page 2-25 |
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Understand what conditions are more hazardous for wood. |
- Inside is less hazardous - Above ground is less hazardous - Out of water is less hazardous Page 2-27 |
