Christian Newswire: Sears Tower vulnerable to TERRORIST ATTACK!!!

They are just not letting this tangent go.

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Sears Tower Susceptible to Terrorist Attack
Availability: Structural Engineer on Vulnerability of Sears Tower to Terrorist Attack, Suggests Sears Tower Design is Very Similar to World Trade Center

Contact Thomas Harmon,, 314-935-4536, tharm@wustl.edu; Tony Fitzpatrick, Public Affairs, 314-935-5272, 935-5230, tony_fitzpatrick@wustl.edu

ST. LOUIS, June 24 /Standard Newswire/ -- Chicago's Sears Tower, named as a possible target by an alleged terrorist group based in Miami, shares many of the architectural design features that contributed to the collapse of the World Trade Center in the 9/11 terrorist attack, says Thomas Harmon, a structural engineer at Washington University in St. Louis.

Harmon, the Clifford W. Murphy Professor of Civil Engineering and director of the University's Construction Materials and Management Center, did an analysis of Chicago's Standard Oil Building in the early 1970s. He says all three buildings are designed as structural tubes -- a system of small, closely spaced columns that resist two sets of loads, vertical and lateral.

Although these structures are vulnerable to attack, the Sears Tower design has features that make it somewhat less susceptible to catastrophic collapse in the event of either a bomb explosion or airplane crash attack.

"Since the Sears Tower design has fewer columns, the mass of each column is greater than with either World Trade Center or the Standard Oil building," says Harmon. "So in my opinion, it would be a little harder to knock down the Sears building using an airplane, as compared to the Standard Oil building and World Trade Center."

If the Sears Tower had been attacked using explosives, as the Miami-based terrorist group is believed to have considered, such a bomb would do the most damage if planted near the top of the Sears Tower, Harmon suggests.

"The structural mass of the building decreases the higher you go in the building, so it is easier to cause damage at the top than at the bottom," he explains. "One thing that was clearly learned on 9/11 is that a collapse at the top of a building causes collapse of the total building. This logic says that less explosive is needed if placed near the top of a building than if placed at the bottom."

"The problem with this for the Sears building is that there may be enough structural redundancy so that severe damage to a single column may not cause collapse of an entire floor, which would in turn likely cause total collapse due to successive impacts and story failures as the structure falls on floors below."

Although not an explosives expert, Harmon can imagine several scenarios for how a bomb attack might lead to a collapse of the Sears Tower.

"I can think of several possibilities," Harmon says. "One would be to take enough columns to cause a local collapse that would lead to progressive collapse. Another would be to take out enough of the floor system to destabilize enough columns and allow them to buckle, again leading to progressive collapse."

Harmon says that both the Standard Oil Building and the World Trade Center were/are tubes with a "leaner" core.

"That means that the outer wall of the building forms a vertical tube that resists all lateral loads, primarily wind in Chicago and New York," he explains. "The structure of the inner core is designed to take gravity loads only, not wind. The floor system consisting of lightweight trusses and a concrete deck braces the core against the outer tube."

"In addition, the floor system braces the individual columns. The two buildings used two different methods to reduce 'shear lag' in the walls. The World Trade Center used closely spaced small columns, (I think about 3 feet apart) to reduce the length of the spandrel beams and make them very stiff."

"The Standard Oil building used the concept of a perforated tube according to its structural engineer, Al Picardi. The columns were spaced ten feet on center, but were shaped like chevrons and were five feet wide, basically consisting of two plates welded together to form a V. The spandrel beams were also folded plates formed into a 'c' shape."

"Since the columns were so wide, the spandrels were only five feet long. They were also very deep, I think around 5 feet, or a little less, so therefore very stiff. Both buildings are very efficient in that the weight of steel per square foot of building is extremely low for such tall buildings."

Harmon says the Sears Tower is actually a "bundled" tube according to the structural engineer, F. Kahn, who like Al Picardi was an exceptionally innovative engineer.

"The idea was that there were 9 bundled tubes, each 75 feet square, arranged in a 3 by 3 grid," he says. "The tubes were cut off at different heights. I am uncertain of the floor framing system of the building, however, I know that the columns were arranged around the perimeter of the tubes and spaced at 15 feet on center."


http://www.earnedmedia.org/st0624.htm

Chicago about 13 hrs after warning the cut an ran VP showed up in Chicago for a fundraiser he said"A Week Ago I Warned You Attacks Would Come From Within" Rove at his best known the VP was going to be in Chicago if it smells like a fish it is