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Shoddy Construction

The following excerpt from WikiPedia.org on 10/22/05 is typical of claims made by theorists claiming faulty construction was partly to blame for the collapses of the Twin Towers.

e x c e r p t
title: Collapse of the World Trade Center
authors: unknown
  1. Longspan floors supported by external columns are inherently weaker than the traditional box frame column/girder arrangement with internal walls.
  2. The bunching of all internal columns in a relatively narrow center shaft in a building is an "all your eggs in one basket" configuration-- if that region on any floor is catastrophically damaged (as it certainly was by the fire in the north tower), the entire building is doomed. This stands in stark contrast to earlier generations of skyscrapers which utilize full skeletons of stepped columns, usually one row approximately every 25 feet (7.6 m) from the center to the perimeter.
  3. The World Trade Center exclusively used lightweight materials, especially in the facade. Had the WTC facade contained even minimal masonry elements and/or traditional heavy steel outermost column rows, it is unlikely the aircraft would have cleanly penetrated to the core of each tower— a significant portion of debris and jet fuel would have remained outside, a much different scenario.
  4. Single-bolt connections binding the longspan floorplates with the load-bearing external columns were extremely lightweight for their assigned task. One study group from the Massachusetts Institute of Technology has concluded the proximal cause of the south tower collapse was failure of these bolts in the southeast corner of the building. Double-bolts should have been used.
  5. The use of gypsum cladding instead of reinforced concrete to shield stairwells. Almost all skyscrapers, including those built since the WTC, shield stairwells in reinforced concrete. On September 11th, it was the collapse of all stairways above the impact level that consigned all people above the impact zone in Tower One to death. Tower Two had two of its three stairwells taken out above the impact area by the plane. Some people above the impact zone survived, as they used the third stairwell. Computer models have shown that most of the stairwells in both towers would likely have remained usable until the general collapse had they been shielded in concrete.

The following debunking of the above 'design criticisms' was added to the Wikipedia article on 10/22/05, and and has since been deleted and restored a number of times.

The first criticism omits and the second criticism minimizes the massive core structures of the towers, which contained 47 steel box columns arranged in a footprint measuring 87 by 133 feet. Many of the box colums had outside dimensions of 54 by 22 inches. The denial of the existence of these massive structures is helpful in imagining the pancake-collapse of the floors. Perhaps it is for this reason that the 9/11 Commission Report stated "The interior core of the buildings was a hollow steel shaft, in which elevators and stairwells were grouped."

The second criticism asks us to imagine that the towers employed an unusual design, atypical of skyscrapers. In fact, most modern skyscrapers employ this design, which groups load-bearing columns in the core and around the periphery in order to create unobstructed office space.

The fourth criticism is contradicted by NIST's report, which states that the web trusses were both bolted and welded to the external columns, and that the truss-to-column connections probably did not fail. The failure of these connections would invalidate NIST's theory, which depends on the floor trusses pulling in the external columns.

It is interesting that the fourth design criticism (that only single bolts connected trusses to columns) was endorsed by a team of researchers from the Massachusetts Institute of Technology and then blatantly contradicted by FEMA's Report. 1   FEMA's Report showed that each truss was attached to the perimeter wall with it top chord connected with two 5/8" diameter bolts and a welded 3/8" gusset plate, and the bottom chord connected with two 1" diameter bolts. (See Figure 2-6 in the left margin.)

Shoddy Construction Theory Versus Towers' History

Aside from misrepresenting the Twin Towers' structural design, the idea that poor design was a factor in the collapses is contradicted by the fact that the buildings stood as long as they did without any indication that they were structurally deficient. They withstood many winter storms subjecting their upper reaches to windspeeds of over 100 mph.


1. Bolts Contributed To WTC Collapse, CBSNews.com, 10/28/02 [cached]

page last modified: 2006-01-30
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This video frame from the documentary Up From Zero shows the base of one of the core columns, apparently measuring 54 inches by 22 inches, excluding the flanges.
This photograph, on display at the Skyscraper Museum in New York City, shows one of the Twin Towers during construction. The left of the image is dominated by the edge of one building's core. It corroborates accounts that the columns forming the core's outermost edge were 54 inches wide.
Figure 2-6 from FEMA's Report, showing the truss-to-column connections