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CIVE40007 – Materials > Wood > Flashcards

Wood Flashcards

1
Q

How much timber is harvested worldwide each year?

A

1.6 billion cubic metres

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2
Q

How much timber is used in the UK annually?

A

Approximately 50 million m^3

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3
Q

What amount of timber is produced by the UK per year?

A

16 million m^3 per year

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4
Q

Where does most softwood come from?

A

Scandinavia and the Baltic States

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5
Q

What is hardwood used for?

A

Furniture and interior design

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6
Q

What are the two types of tree types?

A

Coniferous and deciduous

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7
Q

Where is hardwood imported from?

A

Eastern and Western Europe and North America

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8
Q

What are glulam beams?

A

Type of structural timber product composed of several layers of dimensioned lumber bonded together with durable, moisture-resistant adhesives.

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9
Q

What is glulam short for?

A

Glue laminated

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10
Q

What is wood compatible with?

A

glass and steel

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11
Q

What is glulam used for?

A

Mainly arches, curved roofs, domes

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12
Q

What are characteristic of glulam?

A
  • better structural properties
  • dimensional stability
  • large sizes
  • reduced wastage of timber resource
  • less material variability
  • aesthetic variety
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13
Q

Why are timber framed houses beneficial?

A

Huge savings

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14
Q

What type of wood scaffolding can you have?

A

Bamboo

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14
Q

What are the advantages of wood?

A
  • Excellent combination of physical properties
  • High compressive and tensile strength
  • Relatively low cost
  • Good durability under certain conditions
  • Predictable fire behavior
  • Sustainable material if harvested from a sustainable forest
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15
Q

What are the disadvatnges of wood?

A
  • Certain level of variability in performance
  • Properties vary in different directions → the grain
  • Wood often contains inherent flaws → inhomogeneous
  • Durability can be poor under partially wet conditions (in soil)
  • Transport costs – forests are often not near markets
  • Dimensional stability → changes dimensions with moisture
  • Needs to be dried before use
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16
Q

What country produces large amounts of wood?

A

Canada, Sweden, USA

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17
Q

How much timber is produced by Canada from the global market?

A

20%

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18
Q

Why is energy used in producing wood?

A

Zero energy to use apart from transport and drying out

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19
Q

Is wood a high or low embodied energy consumption material?

A

Low

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20
Q

Why is wood a low embodied energy material?

A

Converting timber into a usable building material takes far less energy and generates far fewer greenhouse gases than any other mainstream alternatives, including aluminum, steel and concrete

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21
Q

How much energy do conrete and steel use compared to timber?

A

Concrete uses 5 times, and steel 6 times more energy to produce than timber

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22
Q

What is photosynthesis?

A

Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods.

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23
Q

What happens during photosynthesis?

A

During photosynthesis, plants convert carbon dioxide and water into glucose and oxygen, using light energy trapped by chlorophyll.

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24
Q

How much carbon dioxide do trees absorb?

A

On average a tree absorbs 1 tonne of carbon dioxide for every cubic meter of growth

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25
Q

What makes a sustainable forest?

A

Uses recognised harvesting principles and crop
rotation techniques

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26
Q

True or false, wood is an excellent insulator?

A

True

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27
Q

True or false, wood is energy efficient?

A

True

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28
Q

What is the FSC?

A

Forest Stewardship Council -> non-governmental organization

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29
Q

What do the FSC promote?

A

Dedicated to promoting responsible management of the world’s forests

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30
Q

What do the FSC aim to combat?

A

Aims to combat both illegal, unethical and environmentally damaging logging

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31
Q

What can timber be defined as?

A

Timber is an organic, non-toxic, and naturally renewable building material

32
Q

What role do forests play in the carbon cycle?

A

Carbon sink

33
Q

What is the typical composition of dry wood?

A
  • Glucose - glucose monomers
  • 70 weight percent carbohydrate = cellulose and hemicellulose
34
Q

How much cellulose and hemicellulose in dry wood?

A
  • Cellulose - 50% of weight → crystalline
  • Hemicellulose and pectin - 20 % of weight → semi crystalline
35
Q

What are glucose monomers made from?

A

H and OH bonds

36
Q

What is the shape of the structure of glucose?

A

Ring structure

37
Q

How are glucose molecules linked?

A

Glucose molecules are linked by α or β linkages to form polysaccharides

38
Q

How are mircofibrils formed?

A

Strong cross linking between strands forms microfibrils containing ~100 cellulose molecules

39
Q

What is lignin?

A
  • Lignin is a massive random polymer of phenylpropane alcohol
  • Nonbiodegradable part of wood
40
Q

How much moisture does cut wood have?

A

85%

41
Q

How can wood be dried?

A

Air dried or kiln dried

42
Q

What does the visible structure of wood consist of?

A
  • Growth rings and rays
  • Bark and the cork
43
Q

What type material is wood?

A

Heterogeneous

44
Q

What are the differences between heartwood and sapwood?

A
  • Colour (sometimes)
  • Durability
  • Permeability
45
Q

How are heartwood and sapwood similar?

A

Strengthwise

46
Q

What does SEM stand for?

A

Scanning electron microscopy

47
Q

What does the mircostructure of wood look like?

A
  • Collection of longitudinal cells
  • Close-packed drinking straws → vary in size
48
Q

What are the key characteristics of wood microstructure?

A
  • multi-component
  • hygroscopic
  • anisotropic
  • inhomogeneous
  • discontinuous
  • inelastic
49
Q

What are some features of wood affecting strength?

A
  • Growth rings
  • Wane
  • Fissure
  • Knot
50
Q

What is a wane?

A

Untrimmed bark or wood that is missing along the edge or corner.

51
Q

What does green mean in terms of wood?

A

The wood directly after it is cut?

52
Q

How much mositure in green wood?

A

50%

53
Q

How much moisture in dry wood?

A

12%

54
Q

What is the ultimate bending strength in douglas fir during its green and dry phase?

A

green - 53%
dry - 91%

55
Q

How can you test bending strength on wood?

A
  • Wood will deflect when you do a 3 point bending test
56
Q

How does wood behave when bending?

A

Behaves like a fibre reinforced composite material with significant toughness

57
Q

The loading and unloading curves do not correspond, true or false?

A

True

58
Q

How does water affect bonding?

A

Water reduces the bonding between fibers and cell walls making it easier to buckle

59
Q

Does wood have low or high density and tensile strength?

A

Low density and high tensile strength

60
Q

How can wood rot?

A
  • Dry rot and wet rot
  • Fungal decay
61
Q

What are some common insects that can infest wood?

A
  • Common furniture beetle
  • Deathwatch beetle
  • House longhorn
  • Powderpost beetles
62
Q

What are some marine borers?

A
  • Shipworm (Teredo)
  • Gribble (Limnoria)
63
Q

What are some structural timber composites?

A
  • New types of wood products
  • Glulam
  • OSB – Oriented Strand-board
  • LVL – Laminated Veneer Lumber
64
Q

Why are reonsititued timbers used?

A
  • More consistent behaviour than normal wood
  • Redistribution/removal of defects
  • Reduced variability
65
Q

What does PRF stand for?

A

Phenol resorcinol formaldehyde

66
Q

What are orientated strand lumber used for?

A

Used in timber frame wall panels

67
Q

How are laminated veneers produced?

A

Produced by bonding together veneers peeled from a log (c. 3mm thick)

68
Q

What are lengths of veneers?

A

26 m

69
Q

What are laminated veneer lumbers used for?

A

Typical used for roof beams, floor beams, beams in factory built housing flanges of I-joists footbridges and bridge decking

70
Q

How are successive veneers usually orientated?

A

Orientated in a common grain direction

71
Q

How are parallel strand lumber produced?

A

Produced by cutting peeled veneer into long strands (up to 2400mm), applying glue, and forming structural-sized sections through a heat and pressure quasi-extrusion process.

72
Q

What are the characteristics of I-Joists?

A
  • Strong
  • Stiff
  • Light
  • Dimensionally stable
  • Cost-effective
  • Easy to handle
  • Quality assured
73
Q

What is the fastest-growing method of house construction in the UK?

A

Timber frame

74
Q

How many homes have timber frames now?

A

One in four new homes

75
Q

How much CO2 is saved from timber-framed homes?

A

4 tonnes

76
Q

Why are timber-framed homes beneficial?

A
  • The operational cost of a house can be reduced due to the improved thermal efficiency of timber frame houses
  • Lighter construction
77
Q

What is timber frame wall construction?

A

Timber frame wall construction is a method of building that uses heavy timber framing as the structural support for the walls

CIVE40007 – Materials (16 decks)

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