by spitthedog » Mon Jan 04, 2016 10:46 pm
Seems pretty clear why the world trade centers collapsed. If you weaken one floor in a '' lightweight “perimeter tube” design building then the weight of the above floors will eventually pancake the floors below accelerating until it's just rubble on the ground.
''In essence, the building is an egg-crate construction that is about 95 percent air, explaining why the rubble after the collapse was only a few stories high''
''Nearly every large building has a redundant design that allows for loss of one primary structural member, such as a column. However, when multiple members fail, the shifting loads eventually overstress the adjacent members and the collapse occurs like a row of dominoes falling down.
The perimeter tube design of the WTC was highly redundant. It survived the loss of several exterior columns due to aircraft impact, but the ensuing fire led to other steel failures. Many structural engineers believe that the weak points—the limiting factors on design allowables—were the angle clips that held the floor joists between the columns on the perimeter wall and the core structure (see Figure 5). With a 700 Pa floor design allowable, each floor should have been able to support approximately 1,300 t beyond its own weight. The total weight of each tower was about 500,000 t''
http://www.tms.org/pubs/journals/jom/01 ... -0112.htmlSeems pretty clear why the world trade centers collapsed. If you weaken one floor in a '' lightweight “perimeter tube” design building then the weight of the above floors will eventually pancake the floors below accelerating until it's just rubble on the ground.
''In essence, the building is an egg-crate construction that is about 95 percent air, explaining why the rubble after the collapse was only a few stories high''
''Nearly every large building has a redundant design that allows for loss of one primary structural member, such as a column. However, when multiple members fail, the shifting loads eventually overstress the adjacent members and the collapse occurs like a row of dominoes falling down.
The perimeter tube design of the WTC was highly redundant. It survived the loss of several exterior columns due to aircraft impact, but the ensuing fire led to other steel failures. Many structural engineers believe that the weak points—the limiting factors on design allowables—were the angle clips that held the floor joists between the columns on the perimeter wall and the core structure (see Figure 5). With a 700 Pa floor design allowable, each floor should have been able to support approximately 1,300 t beyond its own weight. The total weight of each tower was about 500,000 t''
http://www.tms.org/pubs/journals/jom/0112/eagar/eagar-0112.html
