Uploaded February 2022 | Updated September 2026, 2 weeks ago
NOVEMBER 10, 2001
In his first address to the United Nations General Assembly President Bush talked about joint counterterrorism efforts and the global threat of terrorism.
NOVEMBER 10, 2001
In his first address to the United Nations General Assembly President Bush talked about joint counterterrorism efforts and the global threat of terrorism.
![Frank De Martini, Construction Project Manager... WTC 1 & 2 designed to resist jetliner impacts.
At the time the Twin Towers were built, the design approach of moving the support columns to the perimeter and the core, thereby creating large expanses of unobstructed floor space, was relatively new, and unique for a skyscraper. However, that approach is commonplace in contemporary skyscrapers.
Frank A. Demartini, on-site construction manager for the World Trade Center, spoke of the resilience of the towers in an interview recorded on January 25, 2001. The building was designed to have a fully loaded 707 crash into it. That was the largest plane at the time. I believe that the building probably could sustain multiple impacts of jetliners because this structure is like the mosquito netting on your screen door this intense grid and the jet plane is just a pencil puncturing that screen netting. It really does nothing to the screen netting.
Demartini, who had an office on the 88th floor of the North Tower, has been missing since the 9/11/01 attack, having remained in the North Tower to assist in the evacuation. Demartini had first worked at World Trade Center when Leslie E. Robertson Associates hired him to assess damage from the truck bombing in 1993.
Like All Skyscrapers, the Twin Towers Were Over-Engineered. One aspect of engineering that is not widely understood is that structures are over-engineered as a matter of standard practice. Steel structures like bridges and buildings are typically designed to withstand five times anticipated static loads and 3 times anticipated dynamic loads. The anticipated loads are the largest ones expected during the life of the structure, like the worst hurricane or earthquake occurring while the floors are packed with standing-room-only crowds. Given that September 11th was not a windy day, and that there were not throngs of people in the upper floors, the critical load ratio was probably well over 10, meaning that more than nine-tenths of the columns at the same level would have to fail before the weight of the top could have overcome the support capacity of the remaining columns.
There is evidence that the Twin Towers were designed with an even greater measure of reserve strength than typical large buildings. According to the 1964 white paper cited above, a Tower would still be able to withstand a 100-mile-per-hour wind after all the perimeter columns on one face and some of the columns on each adjacent face had been cut. Also, John Skilling is cited by the Engineering News Record for the claim that live loads on these [perimeter] columns can be increased more than 2000% before failure occurs.
http://911research.wtc7.net/wtc/analysis/design.html Frank De Martini, Construction Project Manager... WTC 1 & 2 designed to resist jetliner impacts.](https://i.ytimg.com/vi/MYRYzLX4oQE/mqdefault.jpg)









