22 Structural Collapse

Question 1

Which class of building construction shows the greatest resistance to collapse?

Answer 1

Class 1 fireproof construction

Question 2

What is the maximum fire resistance rating of Class 1 fireproof buildings?

Answer 2

Up to 4 hours

Question 3

How does collapse usually occur in Class 1 buildings?

Answer 3

Collapse is usually localized such as concrete spalling or sagging I-beams

Question 4

Which construction class is second best in resistance to collapse?

Answer 4

Class 4 heavy timber construction

Question 5

Why are Class 4 heavy timber buildings generally stable?

Answer 5

Because of large load-bearing members such as 12x12 wooden columns and brick walls

Question 6

How does collapse typically occur in Class 4 buildings?

Answer 6

Collapse is large scale affecting walls and floors

Question 7

At advanced fires in Class 4 buildings, how far should apparatus be removed?

Answer 7

At least 1.5 times the height of the wall for the full frontage

Question 8

Which construction class is third most resistant to collapse?

Answer 8

Class 3 ordinary construction

Question 9

What materials define Class 3 ordinary construction?

Answer 9

Brick walls with wood joists

Question 10

In Class 3 buildings, what fails first during fire exposure?

Answer 10

Floor or roof sheathing burns through before joists fail

Question 11

Which construction class ranks fourth in resistance to collapse?

Answer 11

Class 5 wood frame construction

Question 12

Which construction class is least resistant to collapse?

Answer 12

Class 2 construction

Question 13

How much will a 100 ft steel I-beam expand at 1,000°F?

Answer 13

Approximately 9.5 inches

Question 14

At what temperature does steel lose about half its strength?

Answer 14

Approximately 1,500°F

Question 15

What happens to steel at 1,500°F?

Answer 15

It may twist, sag, or drop its load

Question 16

What are buildings with protected steel or concrete frames called?

Answer 16

Framed structures

Question 17

How does collapse typically occur in framed structures?

Answer 17

Collapse is localized

Question 18

What are buildings called where weight rests mainly on bearing walls?

Answer 18

Unframed structures

Question 19

Why is collapse in unframed structures usually extensive?

Answer 19

Because bearing wall failure removes floor supports

Question 20

Which is more serious: failure of vertical or horizontal members?

Answer 20

Failure of vertical members

Question 21

Why is failure of a column more serious than a beam?

Answer 21

Columns support other structural members

Question 22

What is the most important structural component in collapse hierarchy?

Answer 22

Bearing walls

Question 23

What ranks second in importance in the structural hierarchy?

Answer 23

Columns

Question 24

Which component supports beams?

Answer 24

Girders

Question 25

What is the least important structural component in the hierarchy?

Answer 25

Floor or roof decking

Question 26

What is the approximate burn-through rate of wooden structural elements?

Answer 26

About 1 inch every 45 minutes

Question 27

How fast can a 2x8 joist burn through with fire on both sides?

Answer 27

In less than 45 minutes

Question 28

At what temperature will unprotected steel Lally columns fail?

Answer 28

Around 800°F

Question 29

What happens when Lally columns fail?

Answer 29

Upper floors and walls collapse

Question 30

How much lateral pressure can topple a brick wall?

Answer 30

As little as 1 psi

Question 31

What must firefighters do when a backdraft is suspected?

Answer 31

Vent at the top before entry and cool the atmosphere

Question 32

How much weight does a 1,000 gpm master stream add per minute?

Answer 32

Approximately 8,500 pounds

Question 33

How much weight does 1 foot of water over a 20x20 area add?

Answer 33

Nearly 25,000 pounds

Question 34

What tools should be used where structural weakness is suspected?

Answer 34

Low impact and low vibration tools

Question 35

Give an example of a low-impact cutting method.

Answer 35

Using a circular saw instead of an axe

Question 36

Which businesses commonly indicate overloaded floors?

Answer 36

Plumbing supply stores, appliance dealers, printing shops

Question 37

How long of heavy fire exposure suggests withdrawal should be considered?

Answer 37

More than 20 minutes

Question 38

What simple method can track expanding wall cracks?

Answer 38

Marking crack ends with tape

Question 39

What indicates a roof is pulling away from a wall?

Answer 39

Gaps at wall joints or clean beam ends

Question 40

Sagging floors or roofs indicate what stage of collapse?

Answer 40

One of the last warning signs

Question 41

What sounds may accompany partial collapse?

Answer 41

Creaking, groaning, cracking, deep rumbling

Question 42

Which construction class commonly shows distorted door and window frames?

Answer 42

Class 5 wood frame construction

Question 43

How much does masonry typically weigh per cubic foot?

Answer 43

Approximately 80 to 130 pounds

Question 44

How should aerial devices be positioned relative to building height?

Answer 44

No closer horizontally than vertically

Question 45

How many types of collapse are identified?

Answer 45

Five

Question 46

Name the five types of collapse.

Answer 46

V-shape, A-frame, supported lean-to, unsupported lean-to, pancake

Question 47

Which collapse type is common in Class 3 and 5 buildings?

Answer 47

V-shaped collapse

Question 48

What causes V-shaped collapses?

Answer 48

Burned, overloaded, or unsupported wooden joists

Question 49

What causes an A-frame collapse?

Answer 49

Strong center support with outer ends falling

Question 50

In what situation are A-frame collapses common?

Answer 50

Explosions

Question 51

What is the safest action for an unsupported lean-to collapse?

Answer 51

Pull it down after checks are complete

Question 52

What must be checked after a pancake collapse?

Answer 52

That the load is safely transferred to ground

Question 53

Why are pancake collapse victims easier to locate?

Answer 53

Floors maintain their physical relationship