NEW YORK, Sep 14, 2001 (United Press International via COMTEX) -- Two teams of experts organized and funded by the American Society of Civil Engineers will begin a painstaking analysis of the World Trade Center site and damage at the Pentagon in the aftermath of Tuesday's terrorist attacks.

The specialists hope to determine the exact sequence of events that led to the collapse of the World Trade Center towers and to make recommendations as to how buildings can be constructed in the future that might be more resistant to similar attacks.

The teams will include structural engineers, materials engineers and fire protection engineers. Consultation with aircraft designers will be part of the investigations.

The fire from jet fuel released upon impact is thought to be largely responsible for the collapse of the towers. According to a prepared statement released by ASCE: "The damage from the impact, though significant, weakened the structure but did not cause it to collapse. Rather, the intense heat of the resulting fire fed by great quantities of jet fuel further weakened the already damaged structural system."

Gene Corley, an expert on building collapse who will lead the investigation at the World Trade Center site, told United Press International Friday: "The unknown here is whether or not the building was designed to exceed the normal requirements for fire design and whether or not the amount of fuel that did come from these aircraft was considered in any way -- and that would probably be above the requirements for the building code."

Corley added: "We don't know at this point what role additional fireproofing would have played. We anticipate it would have increased the time before collapse, but we can't quantify that at this moment. That is one of the things we expect to come out of this investigation."

Jane Howell, spokeswoman for ASCE, said her organization had yet to confirm published reports the World Trade Center design included an ability to survive a direct hit from a Boeing 707 aircraft. Different models of the Boeing 707 can carry from 15,000 to 23,000 gallons of jet fuel, while the Boeing 767s used in the attacks against the towers have a capacity of 24,000 gallons.

Corley told United Press International, "What we intend to do is collect all the information we can about the physical damage done by the crashes, collect information about the fire, then analyze what we would expect the performance of the building to be so we can determine the sequence of events before the collapse occurred. Then based upon that, see if there are any recommendations that might be appropriate for design that would have even greater resistance than these buildings did to any future terrorist attacks."

Corley, senior vice-president of Construction Technical Laboratories, led the engineering investigation of the Murrah Federal Office Building for the Federal Emergency Management Agency after the Oklahoma City blast.

"Whatever information we get we will use to make calculations of what would happen from the impact of the two aircraft through beginning of the fire. We can model the fire itself, determine what effect that is having on the structural members and come up with a predication of how long it would be able to stand up under that fire load," he said. "Then based on that, compare it with what really happened. Then we can feed in other possibilities if it had been constructed differently. But we can't preclude the possibility that we will find things that can be done to even better resist the initial impact."

Although it is possible a thicker application of fire retardant on steel beams during construction might have resulted in slowing the collapse, it is too early to draw that conclusion, Corley told UPI. "Clearly the longer the fire resistance of the structural members, the better off you are in a fire. That will be one of the things we'll be looking at very carefully."

Corley is a structural engineer who does forensic work. Forensic investigations use technology to establish facts, most often for use in legal cases, but also for other types of investigations.

ASCE said it would cooperate with FEMA. The American Institute for Steel Construction, American Concrete Institute and the Society for Fire Protection Engineers also will conduct forensic investigations at the World Trade Center site.

Leading the investigation of the Pentagon damage will be Paul Mlakar, an engineer with the Army Corps of Engineers and an expert in blast-resistant design. Fire also played a significant role in the structural damage at the Pentagon, Mlakar said.

"This is really one investigation with two parts and there are really a lot of similarities between the two, for example, the forces created by the impact and explosion of the aircraft," he said.

The Pentagon is involved in a 10-year renovation plan that includes increasing its perimeter resistance to the effects of bomb blasts. But the work is not designed to take a direct hit from a jetliner loaded with fuel.

Out of concern a bomb attack on the Pentagon most likely would affect the outer perimeter, windows on much of the outside of the outer ring of offices are being replaced with windows designed to be blast-resistant. The thick glass is installed in a hardened frame and is designed to withstand a blast without shattering into small pieces or coming out as one piece. Additionally, brick inside the outer wall is being wrapped in a very tough geo-textile mesh that is anchored to metal supports that are being installed inside the walls and bolted to the building's frame.

Small changes in construction can sometimes make big differences.

Following his investigation of the bomb attack on the Murrah Federal Building in Oklahoma City, Corley testified to House Committee on Transportation and Infrastructure in 1998. If the Murrah building had been built to modern seismic standards, at an additional cost of a few thousand dollars, "as much as 50 to 80 percent of the structural damage and presumably the fatalities could have been prevented," Corley testified. "Practicing engineers, who may not be intimately familiar with designing to mitigate the effects of a blast, need and want a mandatory consensus standard, thereby providing them the assurance that they are meeting their clients' needs," Corley told Congress.

(Reported by Joe Grossman in Santa Cruz, Calif.)

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