Wood And Steel

Front 1

Other than defects, name 5 things that can affect wood

Back 1

Duration of load, rate of loading, preservative treatment (pressure treatment), temperature,moisture content, size, cyclical loading (fatigue), direction of loading (axis), species

Front 2

What is the role of lignin in the tree

Back 2

Lignin acts as the glue that binds the cellulose units and cells together

Front 3

What is the role of hemi-cellulose in the tree?

Back 3

together wth lignin, the hemi-cellulose surrounds the cellulose units, bonding themtogether

Front 4

What is the typical tensile strength range of small clear pieces of wood parallel to the grain?

Back 4

70 to 150 MPa

Front 5

State the microfibril orientation in the following cell wall layers

Primary Wall

Secondary Wall, Outer Layer (S1)

Secondary Wall, middle layer (S2)

Back 5

Primary Wall - Random

(S1) - double spiral/left and right hand or helix inclined at 50 70 degrees

(S2) - Single/right-hand helix inclined at 10 to 30 degrees

Front 6

What are four things needed for fungi to survive

Back 6

Warmth

Moisture

Food

Oxygen

Front 7

What is the structural significance of the tube structure of wood cells

Back 7

Tube structure provides high strength to weight raio. They are orientated in the same direction held together in a matrix for high strength

Front 8

What are 2 advantages of wooden I joists to sawn lumber joists

Back 8

strength to weight raio

dimensional stability

Front 9

What is a stress modification factor? give an example

Back 9

Applied to the allowable stress for a structure to account for a specific condition

Ex: Duration of Load (Kd) - Can either increase or decrease allowable load. Short term loads increase the stress allowable and long term loads decrease the stress allowable.

Front 10

What is the most abundant cell type in trees and what is its role or purpose?

Back 10

Tracheids - provide mechanical support in the vertical direction and conducts water in the vertical direction

Front 11

What are microfibrils made of and where are they located and their orientation?

Back 11

Made up of bundles of tracheids.

Held together by hemicellulose and lignin.

They are orientated axial (longitudinal) direction.

Located in the trunk within the bark

Front 12

Machine stress rated lumber uses what mechanical property to predict what other property?

Back 12

It uses the modulus of elasticity to predict the ultimate tensile strength. (using force deflection)

Front 13

Do the mechanical properties of wood increase or decrease with density? Suggest a reason why?

Back 13

Generally increase with density. As density increases porosity decreases.

Since the cell wall is very strong and dense, an increase in cell wall thickness will lead to an increase in strength and density

Front 14

Is wood isotropic or anisotropic?

Back 14

Anisotropic, microfibrils are orientated in the longitudinal direction. Properties are not the same in each direction.

(Ex. Tensile strength parralle to the grain is much higher than perpendicular to the grain.

Front 15

What are two primary disadvantages to wood as a structural material?

Back 15

Variability

Food source (fungi, termites)

Front 16

Why can austenite accomodate more carbon than ferrite or delta iron?

Back 16

Bc austenite has an FCC lattice structure

Front 17

Pearlite consists of what two phases?

Back 17

Ferrite and iron carbide

Front 18

What are the 3 ways that veneer and PSL and LVL are sorted?

Back 18

Visual quality, strength, and moisture content

Front 19

Advantages to wood

Back 19

Reusable, recyclable, biodegradable

renewable resource

good aesthetics

cost effective

locks up CO2

Front 20

Microfibrils

Back 20

Threadlke bundles of cellulose molecules that are arranged approximately parallel

Bound together be hemi-cellulose and lignin

Front 21

Softwood vs Hardwood

Back 21

Softwood: needle trees, used more for structural

spruce, pine, douglas fir (Primary bld material), cedar

Hardwood: broadleaf trees, used more for furniture and cabinetry

oak, maple, birch

Front 22

2 states of moisture in wood

Back 22

Free water: liquid in the cell cavities

Bound water: pysically absorbed in the cell wall

Front 23

Fibre saturation point

Back 23

Condition at which all the free water is evaporated, but cell walls are still fully saturated

Typically occurs at a moisture content of 25 to 30%

Below FSP the molecular structure is compacted resulting in shrinkage and increased strength

Front 24

Mechanical Properties in wood

Back 24

Modulus of elasticity

Tensile strength

Compressive strength

Flexural strength

Shear strength

Effects of temperature

Front 25

Knots and Checks

Back 25

Portion of limb surrounded by subsequent wood growth

Lengthwise sepation of wood which usually extends across the growth rings. Caused by the outer surfaces of lumber drying more rapidly than the inner core

Front 26

Wanes and Shakes

Back 26

Lack of wood on the face of a piece for any reason at all

Separation along the grain bt the annual growth rings

Front 27

Pitch pocket and warp

Back 27

Opening bt growth rings containing resins or bark

bow, twist, crook, cup

Front 28

Stress Modification Factors

Back 28

Load Sharing Factor

Load Duration Factor

Treatment Factor

Service Condition Factor

Size Factor

Temperature Factor

Front 29

What are the main cells in softwood lumber

Back 29

Parenchyma and trachiads

Front 30

What are cracks in wood due to wind damage called?

Back 30

Shakes

Front 31

Rebar is normally protected from corrosion in concrete due to what condition?

Back 31

The concrete has high pH

Front 32

Why does pearlite have a layered structure?

Back 32

bc carbon atoms need to diffuse only a short distance to form this structure

Front 33

What type of wood has the lowest moisture content at manufacture?

Back 33

plywood and OSB

Front 34

The movement of dislocations and the resulting interference or locking up bt dislocations describes the process of what?

Back 34

work (strain) hardening

Front 35

What is cellulose made of?

Back 35

glucose

Front 36

What is used to predict if a type of steel can be welded?

Back 36

summation of weighted values of various steel alloy elements

Front 37

What is the major difference bt laminated veneer lumber and plywood?

Back 37

the grain direction of plywood veneers alternate 90 degrees, in LVL the do not

Front 38

Mill Test Certificates

Back 38

Chemical - Samples are taken from the molten metal

Physical - Samples from finished products; tensile yield, strength and elongations tests are done

Front 39

Potential problems with rebar

Back 39

low elongation

low strain hardening ratio

plastic strain not uniform along bar

Front 40

Purpose of rebar

Back 40

To carry tension

crack control

restraint of bursting stress

absorb energy during seismic loading

Front 41

Properties of steel are generally controlled by

Back 41

chemical composition

temperature of rolling

rate of cooling

re-heating treatments

Front 42

increased carbon results in

Back 42

increased strength

increased hardness

decreased ductility

decreased toughness

Front 43

Strengthening mechanisms of steel

Back 43

alloying

work (strain) hardening (cold working)

heat treatment

Front 44

Corrosion control of steel

Back 44

Coatings

galvanizing

cathodic protection

corrosion resistant metal

Front 45

3 Primary Categories of shear in wood

Back 45

Parallel to grain

Perpendicular to grain

Rolling shear