WTC - Engineering / Code question.

Factual Questions
1

My roomate, who is an engineer, mentioned that while he was in school, an instructor commented that the twin towers of the World Trade Center would not be legal to construct here in Canada, because and our building code requires a load-bearing core, and the WTC towers’ load bearing walls were all on the exterior of the building.

Is this true?

If so, wouldn’t such a structure be unsafe in less extreme circumstances than have transpired? (Like an earthquake?)

2

Too freaked out to preview.

3

It’s true such a design would be poor in a seismic zone, such as Los Angeles. However, NY has mild tremors, at worst - and they’re relatively rare. The code fits the expected conditions of the area.

The load-bearing walls would explain the collapse like a house of cards - looking quite like an implosion.

  • Jinx
4

IANAE(ngineer) however, the WTC was designed to withstand large shear forces from the wind. Twisting forces are what destroy most large buildings in earthquake. I was told (at a WTC tour of course) that the WTC was the building MOST likely to withstand an earthquake in New York, sincece it was already designed to withstand twisting.

The outer walls were definately load bearing. Inside the Towers there were big open floors with hardly any bearing walls.

5

This is incorrect. The towers also had a load-bearing core, aside from the load-bearing outer walls, like so:


O O O O O O O O O O
O                 O
O                 O
O                 O
O    O O O O O    O
O    O       O    O
O    O       O    O
O    O       O    O
O    O O O O O    O
O                 O
O                 O
O                 O
O O O O O O O O O O
6

Terminus Est got it right - it is described as a tube in a tube.

7

In a nutshell, for the layman…
Twisting IS NOT shear! Wind shear is one thing creating one type of stress; a twisting action creates a different stress. It’s not so much the load, but the resulting stress from the load. These two types of stresses must always be accounted for in any design.

I is a engineer - suffered through too many STRESS classes!

  • Jinx
8

I found an article that talks about the design a bit…

This is essentially what my buddy said, I misunderstood him. Not that extra load-bearing walls would have made a lot of difference, I’m guessing.