05 Collapse Dangers of Parapet Walls

Question 1

Building codes define a parapet wall as what?

Answer 1

The continuation of an exterior wall, a fire wall, or a party wall above the roof level.

Question 2

What is the most dangerous type of parapet?

Answer 2

The one constructed as the front wall of a one-story structure above several large display windows (found in supermarkets, shopping malls, and rows of stores)

Question 3

Five separate additional design defects in the construction of a parapet wall:

Answer 3

1. Freestanding wall
2. The steel lintel
3. Steel reinforcement rods embedded in a parapet wall
4. Coping stones and cornices of a parapet wall
5. Unfinished brick of a parapet wall

Question 4

A front, freestanding parapet wall over a store can be considered what type of beam?

Answer 4

A cantilever beam - it is a vertical cantilever wall supported from one end, the bottom.

Question 5

As all the trusses begin to fall, the weight of the roof will shift from the trusses to the front and rear parapet walls by way of the top roof rafters or purlins, which extend from the end bowstring trusses to the front and rear parapet walls. This shifting of weight from trusses to walls can cause what?

Answer 5

A violent front parapet wall collapse seconds after the entire roof caves in.

Question 6

If the masonry wall falls because of explosion or internal pressure, the wall will collapse outward for a distance equal to twice its height with force, and bricks may bounce or roll out farther.