10 Lightweight Steel Roof and Floor Collapse

Question 1

Steel can do what when it is heated?

Answer 1

1. Expand
2. bend
3. Twist
4. Sag
5. Buckle

Question 2

Does steel melt?

Answer 2

No. (Ok, it does start to melt at more than 2,400 degrees F)

Question 3

Steel starts to distort and lose strength when temperatures reach _________________.

Answer 3

1,000 to 1,100 degrees F

Question 4

What are two of the most common structural elements formed by bending steel?

Answer 4

1. Bar joist truss
2. C-beam

Question 5

What are other common shapes of steel to increase load-bearing capability?

Answer 5

1. Hollow tube steel
2. Steel partition wall studs
3. Fluted floor decking

Question 6

Steel failure depends on:

Answer 6

1. The load it carries
2. The dimensions of the steel
3. The span of the steel beam
4. Fire protection insulating covering

Question 7

What are the three common methods of protecting steel from the heat of fire?

Answer 7

1.Encasement with concrete
2. Installation of a fire-retarding ceiling between occupancy and steel above
3. Spray-on Fire Retarding Material (SFRM) (most popular but least effective)

Question 8

When SFRM fails to protect the steel it is because:

Answer 8

1. The steel was not prepared properly (cleaned) to allow the SFRM to stick properly
2. The spray-on slurry is often not mixed properly
3. Workers do not apply the material evenly.
4. Other workers working nearby easily remove it
5. Even if applied correctly, over several years, vibrations and HVAC air movement causes the material to blow off

Question 9

What are three criteria that the construction industry now determines are necessary criteria for the SFRM to be effective on steel during a fire?

Answer 9

1. Adhesion
2. Consistency
3. Thickness

Question 10

What are the two reasons why FFs should view lightweight steel bar joist construction as extremely hazardous?

Answer 10

1. The failure characteristics of unprotected steel
2. Joist spacing

Question 11

How far apart can open-web steel bar joists be spaced apart?

Answer 11

8 feet

Question 12

What are the four factors that determine the speed with which unprotected steel will fail?

Answer 12

1. Temperature
2. Load stress
3. Steel thickness
4. Fire size

Question 13

What is the principal danger to a FF in a burning noncombustible structure that contains unprotected steel?

Answer 13

It’s potential for early collapse

Question 14

The fire service considers what temperature the failure temperature of steel?

Answer 14

1,100 degrees F

Question 15

At 1,100 degrees F steel will lose how much of it’s load-carrying capacity?

Answer 15

40%

Question 16

A 50-foot-long steel beam that is heated uniformly over its length from 72 degrees to 972 degrees F, the average increase in length can be what? The increase will either push out an enclosing wall or cause the steel beam to buckle.

Answer 16

3 feet 9 inches

Question 17

The two important facts of the time-temperature curve:

Answer 17

1. Within the first 5 minutes, the temp of the fire will rise to 1,000 degrees
2. At 10 minutes, the temp reaches over one-half the total temp rise (1,300 degrees) attained after 8 hours.