Chapter 10 Lightweight Steel Roof and Floor Collapse

Question 1

at what temperature does steel start to distort and lose strength during a typical structure fire

Answer 1

1000- 1100°

Question 2

steel bent and twisted into shape to increase its strength is called

Answer 2

shaped steel

Question 3

steel and alloy of

Answer 3

iron and carbon

Question 4

most common structural steel elements formed by bending steel

Answer 4

bar joist truss, C-beam

Question 5

what does steel failure depend on

Answer 5

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

Question 6

three common methods to protect steel from heat are

Answer 6

1. encasement of steel in concrete
2. installation of fire retardant ceiling between the occupancy and still above
3. spray on fire retarding material, most popular least effective

Question 7

what are the reasons that a membrane ceiling often fails at protecting steel

Answer 7

1. missing panels/ not properly in place

2. penetrations in the membrane

Question 8

one of the reasons prey on fire retardant material often fails to protect steel

Answer 8

1. the steel is not properly prepared
2. spray on slurry is not mixed properly
3. workers do not apply material evenly
4. subsequent work easily removes fire protection
5. HVAC air movement, blows off foam

Question 9

what are the three criteria the construction industry now determines are necessary for spray on foam material effectiveness

Answer 9

adhesion
consistency
thickness

Question 10

what are the two reasons lightweight steel bar of joist must be viewed by firefighters is extremely hazardous in roof and floor construction

Answer 10

failure characteristics of unprotected steel

joist spacing

Question 11

why can an experienced firefighter transfer his knowledge for safe operations time to a building with lightweight steel roof

Answer 11

firefighters have developed a sense of how long they can work inside a building or operate on roof based on roof construction used in ordinary construction this experience cannot be applied to type II noncombustible construction was steel trusses

Question 12

one is an important design difference between wood joist, steel part joists, and C-beam roof support system

Answer 12

open web steel bar joists can be spaced up to 8 feet apart

Question 13

4 factors determine the speed with which unprotected steel will fail during the fire

Answer 13

1. temperature of the fire
2. the load stress
3. steel thickness
4. fire size

Question 14

the fire service considers 1100° to be the failure temperature of steel at this temperature steel loses___ of its load carrying capacity

Answer 14

40%

Question 15

the 50 foot long steel being heated (972) uniformly will increase an average length of

Answer 15

3’9”

Question 16

what are the two important facts of the time temperature curve of a fire?

Answer 16

1. w/i the first five minutes the temperature will rise to 1000
2. at 10 minutes the temperature will reach over one half the total temperature rise (1300°)

Question 17

how much weight can a roof design only to support snow load handle

Answer 17

20 pounds per square foot

Question 18

roof deck is also load which can influence collapse of steel joist roof systems: which deck ( lightweight insulation or precast concrete plank) will reduce firefighter safe operating time

Answer 18

precast concrete plank… its heavier