Building Materials, Structural Collapse, and Effects of Fire Suppression

Question 1

What are the nine most common building materials?

Answer 1

• Wood and engineered wood
• Metals
• Gypsum
• Fiberglass
• Composite materials
• Masonry
• Reinforced concrete
• Lath and plaster
• Plastic

Question 2

What is the most common building material in North America?

Answer 2

Wood

Question 3

What are the two factors that affect wood’s resistance to fire?

Answer 3

• Wood from young farmed trees is less dense than wood from old growth trees, and they typically have smaller dimensions, which affects ability to ignite and strength after ignition.
• The higher the moisture content of the wood, the slower it will burn. However, the higher the moisture content the more likely it is to have rot. There are some wood products that are pressure treated with fire resistant chemicals to slow burning.

Question 4

How does masonry react to fire?

Answer 4

Concrete can spall
Concrete blocks can crack
Brick mortar can crack and fall out

Question 5

True or false, all metals react is the same way to heat.

Answer 5

False, metals all have different failing temperatures.

Question 6

What are the two kinds of Iron commonly found in buildings?

Answer 6

Cast iron, used in the 19th century for structural support.

Wrought iron, was used for rails and straps in 1800s but then was mostly used for rail tracks.

Question 7

What happens to cast iron when it is heated by intense fire?

Answer 7

Cast iron performs well under intense heat, but if it is cooled rapidly by water it can crack.

Question 8

What is steel primarily used for in building construction?

Answer 8

Structural support in large buildings

Question 9

How does steel react to heat?

Answer 9

It depends on the thickness of the steel beam, the load it’s carrying. Also, whether the iron is insulated by concrete of insulation. But it will expand under heat and can bend.

Question 10

At what temperature does A36 steel begin to lose its load barring capabilities?

Answer 10

300C

Question 11

When Steel is exposed to flashover temperatures, how much weight can it bare?

Answer 11

40% or less of its designed load.

Question 12

What is steel elongation?

Answer 12

When steel is exposed to high temperatures, it can elongate and can push out load barring walls and cause a collapse.

Question 13

True or false, Aluminun has a greater heat tolerance than steel.

Answer 13

False.

Question 14

Why is reinforced concrete so strong?

Answer 14

It has the tensile strength of steel and the compressive strength of concrete.

Question 15

What are some of the weaknesses that reinforced concrete can experience when exposed to extreme heat?

Answer 15

Spalling, and disconnection between steel and concrete.

Question 16

True or false, rebar in reinforced concrete can become corroded by long term chemical exposure.

Answer 16

True

Question 17

True or false, Gypsum contains moisture, but drywall contains none.

Answer 17

False, Gypsum and drywall are the same thing and it does contain moisture. Not sure why it’s callled drywall if it’s wet.

Question 18

What is lath and plaster?

Answer 18

Horizontal strips of wood (Lath) are nailed to vertical studs and plaster is spread on the surface of the lath. not typially found in structures built after the 1950s

Question 19

How does glass react to high temperatures?

Answer 19

It will likely shatter if cooled quickly after being heated.

Question 20

How is fiberglass used in construction?

Answer 20

Most commonly as insulation.

Question 21

What are some of the dangers associated with plastic as a building material?

Answer 21

Plastic is flammable and the smoke is a carcinogen.

Plastic is often used for piping, which fail faster than metal pipes.

Question 22

What are some of the advantages of composite materials over traditional wood products?

Answer 22

• Corrosion resistance
• Resistant to chemical wear
• Resistant to heat

Question 23

Name the five most common composite wood products.

Answer 23

• Plywood
• Fiberboard
• Paneling
• Particle Board
• Oriented Strand Board

Question 24

Name the five most common composite builing materials

Answer 24

• Finger-jointed timber - Small pieces of wood that are glued together to form longer boards
• Laminated timber - Plywood
• Medium density fiberboard - laminated wood that emulates hardwood
• Particle board - uses formaldehyde glue
• Synthetic wood - made from plastic

Question 25

What kinds of events cause a structural collapse that cannot be anticipated?

Answer 25

• Natural events like, wind, snowfall, earthquakes, flood etc.
• Unatural causes like explosions

Question 26

What kinds of events lead to collapse that can be anticipated and planned for?

Answer 26

Structure fires

Question 27

What are some important structural qualities that affect the collapse due to fire?

Answer 27

• Modifications
• Weather
• Construction type
• Length of fire exposure
• Stage of fire
• Building contents
• Age of the structure
• Loads on the structure

Question 28

Explain a Type 1 structure collapse.

Answer 28

High-rises are designed to be collapse resistant, so they are very unlikely to collapse. If there is a fire in a high rise, it is likely to be a localized event.

Remember that in a type 1 fire, the buildings contents are on fire, not the structure itself.

Question 29

What causes collapse in type 2 structures?

Answer 29

The exposed metal supports expand when heated, which pushes out weight barring walls. Also when the beams are cooled, the constrict, which causes furhter movement to the structure and further collapse.

Question 30

What happens to a structure in a type 3 collapse?

Answer 30

The roof is made of wood so it contributes to the fire load, and the walls are made of cement or masonry, which can spall or crack and cause localized or widespread collapse. Type three collapse can send debris a long distance and can contribute to the collapse of other structures.

Question 31

What happens during a type 4 structural collapse?

Answer 31

Heavy timber structures are very resistant to collapse. They need to be exposed to intense fire for a very long time to collapse.

Question 32

Rank the types of contruction in terms of likelyhood of collapse from most to least likely.

Answer 32

• Type 5
• Type 3
• Type 2
• Type 4
• Type 1

Question 33

True or false, Type 5 structures are designed to only collapse inwards.

Answer 33

False, they can collapse inward and outwards, but inward collapses are much more rare, which is why it is important to plan for a collapse zone for any type 5 structure.

Question 34

True or false. When a non load-barring brick or masonry wall tips over and falls and lands flat as a single piece it is called a curtain collapse.

Answer 34

False, it is when a brick or masonry wall falls into a pile.

Question 35

True or false, there is little difference in collapse time between steel bar joists and wood joists.

Answer 35

True, both are prone to rapid collapse.

Question 36

What is the difference between a balloon structure and a platform structure?

Answer 36

Balloon structures have studs that extend from the basement to the roof on a two story building, whereas a platform structure has two seperate sets of studs for each floor.

Question 37

True or false, abandoned and poorly maintained structures pose greater fire hazards than well maintained ones.

Answer 37

True, as the supports could be rotten of cracked, the fire prevention systems are unlikely to function and the gypsum is often exposed from gutting.

Question 38

What factors influence the length of time the structure will maintain its structural integrity when on fire?

Answer 38

• Construction type
• Contents
• Size
• Compartmentation

Question 39

Why is collapse so likely to occur in post suppression activities?

Answer 39

The structural members are at their weakest and there is the added weight of water used for suppression.

Question 40

In which ways do the contents of the structure influence the collapse of the structure?

Answer 40

• They could contribute to the fire
• The added weight can cause a collapse earlier than anticipated
• The added water retention weight could further increase the weight

Question 41

Where are the heavy contents of a structure that could influence collapse likely to be kept?

Answer 41

During pre-incident surveys, the contents on the roofs are documented and included in the tactics, however, the contents in attics are not known and are therefore the most dangerous location for collapses.

Question 42

How do you calculate the distance of a collapse zone?

Answer 42

1.5 times the height of the structure

Question 43

Where is the safest position to be in around the outside of the structure?

Answer 43

At the corners, because they are less likely to fall towards you.

Question 44

When is the only time that personnel are allowed inside of a collapse zone?

Answer 44

When placing an unmaned master stream.

Question 45

What are the two types of dangerous conditions that may be posed by a building?

Answer 45

• Conditions that contribute to the spread and intensity of the fire
• Conditions that make the building susceptible to collapse