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CIVI 321 > CHAPTER 10 > Flashcards

CHAPTER 10 Flashcards

1
Q

2 types of growth

A

endogenous

exogenous

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2
Q

What is endogenous

A

intertwined growth.

very strong and lightweight

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3
Q

What is exogenous

A

outward growth

more predictable engineering properties

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4
Q

Difference between deciduous and confierous

A 
Deciduous = hardwood
Coniferous = softwood
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5
Q

Dark vs light ring

A

Early wood : light ring

Latewood : dark ring

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6
Q

What is early wood

A

rapid spring growth of hollow thin-walled cells

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7
Q

What is late wood

A

dense summer growth of thick-walled cells which are much harder and stronger

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8
Q

from center axis outwards

A
  • pith
  • heartwood (darker)
  • sapwood (ligher)
  • cambium (very thin layer)
  • inner bark
  • outerbark
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9
Q

Longitudinal properties

A

strongest and least shrinkage

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10
Q

Radial

A

perpendicula ro the growth rings

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11
Q

Tangential

A

weakest and most shrinkage

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12
Q

The direction influences

A

strength, modulus, thermal expansion, conductivity and shrinkage

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13
Q

Definition of anisotropic

A

properties change with direction

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14
Q

Chemical composition of wood

A 
Cellulose
Lignin
Hemicellulose
Extractives
Ash-forming
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15
Q

What is cellulose

A

polymer that forms strands (fibrils) that make up cell walls.

high density indicates higher strength

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16
Q

What is the lignin?

A

The glue

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17
Q

What are extractives?

A

tannins, coloring matters, essential oils, fats, resins, waxes, starches

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18
Q

What are ash-forming?

A

calcium, potassium, phosphate, silica

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19
Q

What depends on the moisture content?

A

shrinkage
strength
weight

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20
Q

What is EMC?

A

equilibrium moisture content.

moisture content for average atmospheric conditions

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21
Q

What is the FSP?

A

fiber saturation point

moisture content when cells are completely saturated with bound water but no free water inside cell cavities.

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22
Q

what is bound water

A

water held tightly in cell cavities, wood shrinks on removal

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23
Q

what is free water

A

water inside cell cavities

doesnt affect shrinkage

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24
Q

above fsp?

A

changes affect only wet weigth

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25
Q

below fsp?

A

small changes strongly affect all physical and mechanical properties

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26
Q

largest shrinkage is in

A

tangential direction

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27
Q

smallest shrinkage is in

A

longitudinal direction

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28
Q

zero shrinkage @

A

above fsp, regardless of direction

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29
Q

for glulam, assume

A

1% shrinkage per 5% change in m/c

30
Q

wood production steps (6)

A
  1. harvesting
  2. sawing
  3. seasoning (drying)
  4. surfacing (planing)
  5. grading
  6. preservative treating
31
Q

5 types of wood products for construction

A
  • dimensional lumber
  • heavy timber
  • round stock
  • specialty items
  • engineered wood products
32
Q

harvesting : 3 things

A
  • minimal sap wanted
  • concerns of fire hazard
  • other plant growth and underbrush is minimal
33
Q

3 types of sawings

A

live (plain)
quarter
combinatio0n

34
Q

3 types of board cuts

A

flat-sawn
rift-sawn
quarter-sawn

35
Q

describe flat sawn

A

worst quality, most problems and defects

grain is

36
Q

describe rift-sawn

A

45-80°

37
Q

describe quarter-sawn

A

80-90°

best quality, least shrinkage problem

38
Q

moisture content of green wood when leaving mill

A

approximately 15%

39
Q

3 methods of seasoning

A 
air drying (cheap and slow)
kiln drying (fast and expensive)
combination
40
Q

s4s means

A

surfaced 4 sides = dressed

41
Q

planing involves taking off

A

1/4 inch from each side

42
Q

4 types of grades for canadian timbers

A
  • select structural (ss)
  • no 1
  • no 2
  • standard utility
43
Q

causes of lumber defects (5)

A
  • natural wood growth
  • seasoning too fast
  • wood diseases
  • animal parasites
  • faulty processing
44
Q

what is the specific gravity of the cell wall?

A

1.5

45
Q

specific gravity closer to 1.5 means

A

more cell walls which is denser and stronger

46
Q

what is the R value?

A

1/conductivity

47
Q

what is thermal diffusivity

A

rate at which material absorbs heat from surroundings

48
Q

applying heat to wood

A

first expands the wood from thermal expansion

then shrinks from moisture loss (when below FSP)

49
Q

electrical properties of wood

A

good electrical insulator which decreases with moisture content. more water is a better electrical conductor

50
Q

modulus of elasticity of wood depends on

A
  • species variation
  • moisture content
  • specific gravity and
  • direction of grain
51
Q

which is better : tensile or compressive?

A

tensile

52
Q

which is stronger : parallel or perpendicular to grain for tensile strength?

A

parallel to grain 20x greater than perpendicular

53
Q

loads over time for wood?

A

wood can support higher loads of short duration than sustained loads

54
Q

load duration : what is the time assumed for design?

A

10 year loading and/or 90% full max load throughout life of structure

55
Q

short-duration loads, how to design?

A

multiply design values by load duration factors fr short-duration loads

56
Q

vibration damping and wood

A

vibration damping increases w/ moisture content up to FSP.

better than structural metals

57
Q

what are the two main testing techniques?

A
  • testing of timbers of structural sizes (ASTM D 198)

- testing of representative, small, clear specimens (ASTM D 143)

58
Q

3 types of tests

A
  • 2-point, 3rd-point or center-loading
59
Q

design considerations for wood

A
  • load duration
  • temperature
  • size
  • flat use
  • column stability
  • repetitive member
  • wet service
  • beam stability
  • volume (glulam only)
  • curvature (glulam only)
  • bearing area
60
Q

5 organisms that degrade wood

A
  • fungi caused dry rot
  • bacteria damage black heartwood
  • termite damage
  • spruce ips beetle
  • marine-borer damage to a buried pile
61
Q

wood preservation, 2 types

A
  • petroleum-based,

- waterborn preservatives (salts)

62
Q

2 applications techniques for wood preservation

A
  • superficial treatment (Generally not effective)

- liquid penetration (pressure treating at high temp, heat and moisture)

63
Q

what are engineered wood products?

A
  • made by bonding together wood strands, veneers, lumbers or other forms of wood fibers to produce large units.
64
Q

2 advantages of engineered wood products

A
  • produce specific and consistent mechanical properties that are better than natural large ppieces
  • hard to find high quality large natural pieces
65
Q

what is plywood

A

thin sheets (plies) flued together with the grain at right angles toeach other so it has the same propertiesin both direction

66
Q

how is plywood made?

A

veneer is peeled from a soaked log on a giant lathe

67
Q

what is particle board?

A

sawdust sized particles

68
Q

what is chip board

A

randomly oriented wood chips

69
Q

what is osb

A

wood chips and strand oriented in specific direction

70
Q

how are floor joists made of wood?

A

two 2x4s or 2x6s as flanges and an OSB web

71
Q

what is glulam?

A

lumber glued together with the parallel grain

72
Q

advantages of glulam

A
  • ease of manufacturing large pieces from standard commercial
  • can vary cross section along length
  • special architectural designs
  • can use lower wood grade in less stressed areas
  • minimizes shrinkage defects

CIVI 321 (7 decks)

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