"We calculated that the floors that would be hit would be three or four floors. I was the most optimistic of them all," he is reported to have said. "Due to my experience in this field, I was thinking that the fire from the gas in the plane would melt the iron structure of the building and collapse the area where the plane hit and all the floors above it only. That is all we hoped for."

The twin towers are the first steel-reinforced skyscrapers to have ever collapsed in a fire.

Why did the World Trade Center collapse when its builders claimed it could withstand the impact of a Boeing 707? Were hundreds of firemen sent to their deaths due to lack of information on the punishment the buildings could take? Was the capitalist profit drive reflected in the design of the buildings, and does it provide an explanation for the massive death toll that resulted from the complete destruction of the towers on September 11 after hijacked 767 jet airplanes smashed into each one of them?

Three months after the destruction of the World Trade Center buildings new facts are emerging on these questions, in part prompted by bin Laden's observations.

Officials with the Port Authority of New York and New Jersey, the longtime owner of the buildings, have insisted that the two 110-story structures came apart because of the intense fire generated by burning jet fuel.

However, a growing discussion and debate points to different explanations. Frederick Mowrer, an associate professor in the fire protection engineering department at the University of Maryland and an expert in the field, said that burning jet fuel may not have been the decisive factor in the twin towers' collapse, since much of this fuel blew out of the buildings and burned off quickly.

Instead, he and others point to the lack of adequate fireproofing as the reason the structural steel became so hot, causing it to give way. Once the floors around the impact area were destroyed, the top of each building fell, collapsing the floors underneath it like a deck of cards.

But before undertaking further exploration of the lack of fireproofing, the basic design of the twin towers is itself of interest. Media reports often describe it as "innovative," "unusual," or a "technological breakthrough." They point out that far from being a solid steel structure, the towers more resembled 110 stories of spider webs surrounding a tree branch.  
 
Unusual construction
A September 17 article by The Society for New York City History entitled, "How Could the World Trade Center Collapse So Quickly?" says that part of the answer "may lie in the buildings' unusual construction, which is very different from the steel frame construction of most high-rise buildings."

The trade center was comprised of a reinforced concrete "central core" and, around the outside of the structure, 19-inch-wide steel columns spaced 22 inches apart. Steel trusses, only 33 inches wide, spanned the 60 feet between the core and the small steel columns. A fact sheet from the University of Sydney Department of Civil Engineering says the trusses "support the concrete slab of each floor and tie the perimeter columns to the core, preventing the columns from buckling outwards."

The Sydney document says that the "structural integrity of the World Trade Center depends on the closely-spaced columns around the perimeter." High temperatures from the fire "caused a failure of the truss system supporting a floor, or the remaining perimeter columns, or even the internal core, or some combination."

Constructing a tall building in this manner, various articles point out, is not only less expensive for the builders but allows the greatest possible square footage of leaseable space--a virtual gold mine in lower Manhattan. There were no columns cutting into the floors to be rented, making the total prime office space available equal to 7.9 million square feet, or about 50 city blocks. Upper floors had as much as 40,000 square feet of office space.

In a BBC news dispatch, John Knapton, professor of structural engineering at Newcastle University in the United Kingdom, said that the collapse of the buildings was predictable. Given what was widely known about the structure of the buildings, Knapton said the firemen and rescue workers "should not have gone in at all," or for an hour at the most. "You would have thought someone with technical expertise would have been advising them," he said.

The lack of such advice or information about the vulnerability of the buildings is the subject of a growing number of questions by relatives of those killed when the buildings collapsed.  
 
Long history of fireproofing problems
True to the Big Apple, the history of fireproofing at the World Trade Center begins with companies saving a buck and cutting corners, includes a mob-connected construction firm whose owner was later gunned down, and is the subject of numerous lawsuits, government investigations, and ongoing "inspections."

Fireproofing in modern steel-reinforced buildings is a mixture of mineral fibers and concrete-like materials called binders. The mixture is sprayed onto columns and beams, where it dries and sticks. If a fire breaks out, the fireproofing insulates the steel to prevent it from heating to the point at which it becomes soft and unable to support the weight above.

At a December 12 conference held at New York University, Mowrer said that fireproofing applied to everything at the twin towers--from structural columns to floor trusses to bolted connections--had peeled off or was inadequately installed over extensive parts of the building, and that at the very least this safety violation would have sped up the pace of the collapse.

"There may be issues related to the condition of the buildings before September 11 that need to be factored into the analysis" of why they collapsed, he said. Along with several other scientists, Mowrer is being financed by the National Science Foundation to study the disaster. "It seems as if the fireproofing was not up to what it should have been," he said.

Among the evidence cited is an extensive archive of some 1,200 photographs of scores of floors in the World Trade Center buildings taken by architect Roger Morse between 1986 and 2000. The photographs show that large areas of fireproofing are missing from core columns and that much of it was applied improperly to rusty steel. Morse took the pictures in his capacity as a consultant to the manufacturer of the spray-on fireproofing. His photos show that stretches of the tube-like structural steel supporting the trusses have no fireproofing and other areas had an extremely thin coating.

The New York and New Jersey Port Authority reacted sharply to the findings, insisting that whenever damaged fireproofing was discovered in regular inspections it was repaired. But even officials there acknowledged that problems with maintaining the fireproofing have plagued the structures for years.

Alan Reiss, a Port Authority official since 1984 who became director of the department in charge of day-to-day operations of the trade towers, admitted that engineers had been aware of difficulties in keeping the fireproofing on the structural columns in the core of the building around elevator shafts.  
 
DiBono and Gambino
The company first contracted to apply fireproofing material was run by Louis DiBono, reputed to be a member of the Gambino crime family. According to Morse, DiBono's firm had improperly sprayed the fireproofing onto rusted steel, which would have caused it to slough off.

The first fireproofing material applied by the company, starting in 1969, contained asbestos. This caused a stir, and city officials ordered the application of a new material. DiBono's firm got the contract to remove the asbestos mix. The manner in which DiBono obtained this work was one matter examined in a criminal investigation into Port Authority construction contracting, although no charges were ever filed against him. In 1990 DiBono was gunned down on the orders of mafia boss John Gotti.

In a December 4 New York Times article titled "Wounded Buildings Offer Survival Lessons," James Glanz drew a comparison between what happened to two tall buildings engulfed in fire after being hit by debris from the twin towers. One was the 47-story skyscraper at 7 World Trade Center, which collapsed, and the other was a 1907 landmark at 90 West Street, which survived even though it was completely gutted.

In comparison to the skimpy fireproofing done on the 7 World Trade Center building, which was completed in 1987, Glanz described the extensive fireproofing system put in place at the 1907 high rise. "Most of the dozens of steel columns holding up the building were encased in four-inch-thick blocks of tile," he explained, according to the New York Times. "Fireproofing on the floors was still more impressive, with an archlike arrangement of tile a foot thick having stopped the flames from burning through one story to the next." Aside from a few structural columns that had slightly buckled on the upper floors, the building "had battled the fire and essentially won," the article noted.

"The cost and installation of such tile today would probably be prohibitive," the report stated, getting to what is the bottom line for the profit-hungry capitalists who run the construction industry. However, it continued, the reason why one collapsed and the other didn't "remains one of the deepest mysteries" that engineers have faced.

Responding to this assertion, Ross Firestone, a materials scientist with 40-years experience developing substances to protect structures from high temperatures, wrote a letter to the Times.

"It is no mystery: the fireproofing on the steel structural elements of the World Trade Center was inadequate," he wrote. "I hope architects and engineers will learn from this disaster and construct adequately fireproofed buildings again."  
 
 
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