Design Claims
Worthington, Skilling, Helle & Jackson White Paper
A white paper on the structure of the Twin Towers carried out by the firm of Worthington, Skilling, Helle & Jackson contained eleven numbered points, including:
The buildings have been investigated and found to be safe in an assumed collision with a large jet airliner (Boeing 707-DC 8) traveling at 600 miles per hour. Analysis indicates that such collision would result in only local damage which could not cause collapse or substantial damage to the building and would not endanger the lives and safety of occupants not in the immediate area of impact.
--City in the Sky, p 131
Glanz and Lipton summarize the findings of the white paper:
The Vierendeel trusses would be so effective, according to the engineers' calculations, that all the columns on one side of a tower could be cut, as well as the two corners and several columns on the adjacent sides, and the tower would still be strong enough to withstand a 100-mile-per-hour wind.
--City in the Sky, p 133
The Richard Roth Telegram
A telegraph from the architectural firm Richard Roth, partner at Emery Roth & Sons, was distributed to reporters on February 14, 1965. The telegraph was in response to claims by real estate baron and Lawrence Wien that the design of the Twin Towers was unsound.
THE STRUCTURAL ANALYSIS CARRIED OUT BY THE FIRM OF WORTHINGTON, SKILLING, HELLE & JACKSON IS THE MOST COMPLETE AND DETAILED OF ANY EVER MADE FOR ANY BUILDING STRUCTURE. THE PRELIMINARY CALCULATIONS ALONE COVER 1,200 PAGES AND INVOLVE OVER 100 DETAILED DRAWINGS.
...
4. BECAUSE OF ITS CONFIGURATION, WHICH IS ESSENTIALLY THAT OF A STEEL BEAM 209' DEEP, THE TOWERS ARE ACTUALLY FAR LESS DARING STRUCTURALLY THAN A CONVENTIONAL BUILDING SUCH AS THE EMPIRE STATE BUILDING WHERE THE SPINE OR BRACED AREA OF THE BUILDING IS FAR SMALLER IN RELATION TO ITS HEIGHT.
...
5. THE BUILDING AS DESIGNED IS SIXTEEN TIMES STIFFER THAN A CONVENTIONAL STRUCTURE. THE DESIGN CONCEPT IS SO SOUND THAT THE STRUCTURAL ENGINEER HAS BEEN ABLE TO BE ULTRA-CONSERVATIVE IN HIS DESIGN WITHOUT ADVERSELY AFFECTING THE ECONOMICS OF THE STRUCTURE. ...
--City in the Sky, p 134-6
Engineering News Record
The Engineering News Record (ENR) contained a number of articles on the design and construction of the World Trade Center. The article "How Columns Will Be Designed for 110-Story Buildings" quotes lead architect John Skilling:
"live loads on these [perimeter] columns can be increased more than 2000% before failure occurs."
--John Skilling, in Engineering News Record, 4/2/1964
Construction
9-11 Research pages on the history, architecture, and construction of the Twin Towers:
The Towers' History: Origins of the World Trade Center and the World's Tallest Buildings
Towers' Design Parameters: Twin Towers' Designers Anticipated Jet Impacts Like September 11th's
The Towers' Architecture: The Innovative Design of the World Trade Center Towers
Twin Towers Construction: Photographic Evidence of the Twin Towers' Construction
Destruction
On the day of 9/11, 2001, the three skyscrapers of the World Trade Center complex were totally destroyed, Structural collapse due to a combination of structural damage and fire is the reason given by official reports for the leveling of 110-story WTC 1 (the North Tower), 110-story WTC 2 (the South Tower), and 47-story WTC 7, with strong emphasis on the role of fires. That would make these the only three cases in history tall steel-framed structures collapsing mostly or entirely due to fires.
Visual Records
The attack on New York City was captured by numerous photographers and videographers, in many cases at great personal risk. Of the five major events -- the two jetliner impacts and total destruction of the three skyscrapers -- all but the first were recorded by numerous photographs and videos.
