Quiz Questions: |
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| 1. |
For simplicity and economy in use, pieces of lumber of similar mechanical properties are placed in categories called stress grades, which are characterized by |
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one or more sorting criteria |
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a set of properties for engineering design |
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a unique grade name. |
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All of the above |
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| 2. |
The National Grading Rule provides guidelines for writing grading rules for lumber in this thickness range and specifies grading characteristics for different grade specifications. |
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True |
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False |
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| 3. |
What does ASTM stand for? |
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American Standard for Testing and Materials |
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American Society of Testing and Materials |
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American Standard of Transportation and Materials |
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None of the above |
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| 4. |
Visual grading is the original method for stress grading. |
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True |
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False |
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| 5. |
Approval process for acceptance of design values for foreign species:
- Rules-writing agency seeks approval to include species in grade-rule book.
- Agency develops sampling and testing plan, following American Lumber Standard Committee (ALSC) foreign importation guidelines, which must then be approved by ALSC Board of Review.
- Lumber is sampled and tested in accordance with approved sampling and testing plan.
- Agency analyzes data by ALSC Board of Review and ASTM D1990 procedures and other appropriate criteria (if needed).
- Agency submits proposed design values to ALSC Board of Review.
- ALSC Board of Review and USDA Forest Service, Forest Products Laboratory review submission.
- Submission is available for comment by other agencies and interested parties.
- ALSC Board of Review approves (or disapproves) design values, with modification (if needed) based on all available information.
- Agency publishes new design values for species.
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True |
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False |
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| 6. |
In general, knots have a greater effect on strength in tension than compression; in bending, the effect depends on whether a knot is in the tension or compression side of a beam (knots along the centerline have little or no effect). |
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True |
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False |
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| 7. |
The presence of a knot has a greater effect on most strength properties than on stiffness. The effect on strength depends approximately on: |
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the proportion of the cross section of the piece of lumber occupied by the knot |
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knot location |
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distribution of stress in the piece |
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All of the above |
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| 8. |
Slope of grain (cross grain) reduces the mechanical properties of lumber because the fibers are not parallel to the edges. |
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True |
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False |
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| 9. |
Checks are separations of the wood through the piece to the opposite surface or to an adjoining surface caused by tearing apart of the wood cells. Splits are a separation of the wood that normally occur across or through the annual rings, usually as a result of seasoning. |
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True |
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False |
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| 10. |
Shake is a separation or a weakness of fiber bond, between or through the annual rings, that is presumed to extend length-wise without limit. |
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True |
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False |
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| 11. |
Properties assigned to lumber are sometimes modified by using the rate of growth and percentage of late wood as measures of density. |
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True |
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False |
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| 12. |
Decay in most forms should be prohibited or severely restricted in stress grades because the extent of decay is difficult to determine and its effect on strength is often greater than visual observation would indicate. |
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True |
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False |
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| 13. |
Wane refers to bark or lack of wood on the edge or corner of a piece of lumber, regardless of cause (except eased edges). |
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True |
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False |
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| 14. |
For a beam containing an edge knot, the bending strength ratio can be idealized as the ratio of the bending moment that can be resisted by a beam with a reduced cross section to that of a beam with a full cross section:
Where:
SR=strength ratio,
k=knot size, and
h =?
What does h mean? |
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Width of face containing the knot |
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Height |
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Size of the beam |
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None of the above |
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| 15. |
What does figure 6-2 illustrate about? (Refer Pg 6-6) |
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Effect of edge knot: A, edge knot in lumber and B, assumed loss of cross section (cross-hatched area). |
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Visual grades described in National Grading Rule |
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Relation between strength and strength ratio
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None of the above |
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| 16. |
Modulus of elasticity E is a measure of the ability of a beam to resist deflection or of a column to resist buckling. |
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True |
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False |
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| 17. |
Quality control procedures are necessary to ensure that stresses assigned by a machine-grading system reflect the actual properties of the lumber graded. |
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True |
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False |
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| 18. |
As wood is cooled below normal temperatures, its properties increase. When heated, its properties decrease. The magnitude of the change depends upon moisture content. |
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True |
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False |
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| 19. |
Machine-graded lumber is lumber evaluated by a machine using a nondestructive test followed by visual grading to evaluate certain characteristics that the machine cannot or may not properly evaluate. |
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True |
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False |
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| 20. |
Pitch pockets ordinarily have so little effect on structural lumber that they can be disregarded in stress grading if they are small and limited in number. |
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True |
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False |
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