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Mon Dec 28, 2015, 12:19 AM

(1993) Seattle Times: Twin Towers Engineered To Withstand Jet Collision

Seattle Times | February 27, 1993

Engineers had to consider every peril they could imagine when they designed the World Trade Center three decades ago because, at the time, the twin towers were of unprecedented size for structures made of steel and glass.

"We looked at every possible thing we could think of that could happen to the buildings, even to the extent of an airplane hitting the side," said John Skilling, head structural engineer. "However, back in those days people didn't think about terrorists very much."



Skilling, based in Seattle, is among the world's top structural engineers. He is responsible for much of Seattle's downtown skyline and for several of the world's tallest structures, including the Trade Center. Concerned because of a case where an airplane hit the Empire State Building, Skilling's people did an analysis that showed the towers would withstand the impact of a Boeing 707.

"Our analysis indicated the biggest problem would be the fact that all the fuel (from the airplane) would dump into the building. There would be a horrendous fire. A lot of people would be killed," he said. "The building structure would still be there." ...snip
Full Article: http://community.seattletimes.nwsource.com/archive/?date=19930227&slug=1687698



NYC WTC 'designed to withstand multiple airliner impacts'

Frank De Martini WTC architect explains it would 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 Demartini's Statement

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. 6 Demartini had first worked at World Trade Center when Leslie E. Robertson Associates hired him to assess damage from the truck bombing in 1993. LINK 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. 7 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. 8 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."

1980s What if a plane hit the World Trade Center?



1945: Airplane Crashes Into The Empire State Building Killing 14



A United States military plane crashes into the Empire State Building on this day in 1945, killing 14 people. The freak accident was caused by heavy fog.

The B-25 Mitchell bomber, with two pilots and one passenger aboard, was flying from New Bedford, Massachusetts, to LaGuardia Airport in New York City. As it came into the metropolitan area on that Saturday morning, the fog was particularly thick. Air-traffic controllers instructed the plane to fly to Newark Airport instead.

This new flight plan took the plane over Manhattan; the crew was specifically warned that the Empire State Building, the tallest building in the city at the time, was not visible. The bomber was flying relatively slowly and quite low, seeking better visibility, when it came upon the Chrysler Building in midtown. It swerved to avoid the building but the move sent it straight into the north side of the Empire State Building, near the 79th floor.

Upon impact, the plane's jet fuel exploded, filling the interior of the building with flames all the way down to the 75th floor and sending flames out of the hole the plane had ripped open in the building's side. One engine from the plane went straight through the building and landed in a penthouse apartment across the street. Other plane parts ended up embedded in and on top of nearby buildings. The other engine snapped an elevator cable while at least one woman was riding in the elevator car. The emergency auto brake saved the woman from crashing to the bottom, but the engine fell down the shaft and landed on top of it. Quick-thinking rescuers pulled the woman from the elevator, saving her life.

Since it was a Saturday, fewer workers than normal were in the building. Only 11 people in the building were killed, some suffering burns from the fiery jet fuel and others after being thrown out of the building. All 11 victims were workers from War Relief Services department of the National Catholic Welfare Conference, into the offices of which the plane had crashed. The three people on the plane were also killed.

An 18 foot by 20 foot hole was left in the side of the Empire State Building. Though its structural integrity was not affected, the crash did cause nearly $1 million in damages, about $10.5 million in today's money.



Who would be silly enough to believe that Bush and Rice could lie to the nation and not be held accountable. Maybe James Clapper, who's still "on the job"? Liars Lie. Fools believe them.

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Reply (1993) Seattle Times: Twin Towers Engineered To Withstand Jet Collision (Original post)
nationalize the fed Dec 2015 OP
William Seger Dec 2015 #1
cantbeserious Dec 2015 #2

Response to nationalize the fed (Original post)

Mon Dec 28, 2015, 01:23 AM

1. Excuse me, but the buildings DID withstand the jet impacts

The lead structural engineer for the towers, Leslie Robertson, did an analysis that showed the buildings could survive the structural damage from a plane strike, and in fact they did. But it was the combination or fire and structural damage that brought them down. Regardless of Skillings' assertions that the building would stand after the fire, there was no analysis of the effects of fire when the building was designed because, according to Robertson, there weren't any tools then to do that kind of analysis, and no available systems that would withstand that kind of disaster, anyway:

The two towers were the first structures outside of the military and nuclear industries designed to resist the impact of a jet airliner, the Boeing 707. It was assumed that the jetliner would be lost in the fog, seeking to land at JFK or at Newark. To the best of our knowledge, little was known about the effects of a fire from such an aircraft, and no designs were prepared for that circumstance. Indeed, at that time, no fireproofing systems were available to control the effects of such fires.

http://www.nae.edu/Publications/Bridge/EngineeringandHomelandSecurity/ReflectionsontheWorldTradeCenter.aspx


And the unequivocal proof of that is that the fire mitigation systems were just "to code" -- intended for normal office fires with nothing at all special to handle a disaster like what happened -- and it is clear now that they were inadequate.

Once again, the "truth movement" gives us half-truths and fuzzy thinking instead of truth.

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Response to William Seger (Reply #1)

Mon Dec 28, 2015, 01:57 AM

2. Keep Dreaming The Impossible Dream - The People Know Better

eom

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