JК
11 сентября 2001 :: Мейссан Тьерри
Страница: 285 из 286Detailed modeling of the fires shouldbe conducted and combined with structural modeling to develop specific failure modes likely to have occurred.
• The floor framing system for the two towers was complex and substantially more redundant than typical bar joist floor systems. Detailed modeling of these floor systems and their connections should be conducted to understand the effects of localized overloads and failures to determine ultimate failure modes. Other types of common building framing should also be examined for these effects.
• The fire-performance of steel trusses with spray-applied fire protection, and with end restraint conditions similar to those present in the two towers, is not well understood, but is likely critical to the building collapse. Studies of the fire-performance of this structural system should be conducted.
• Observation of the debris generated by the collapse of the towers and of damaged adjacent structures suggests that spray-applied fire proofing may be vulnerable to mechanical damage from blasts and impacts. This vulnerability is not well understood. Tests of these materials should be conducted to understand how well they withstand such mechanical damage and to determine whether it is appropriate and feasible to improve their resistance to such damage.
• In the past, tall buildings have occasionally been damaged, typically by earthquakes, and experienced collapse within the damaged zones. Those structures were able to arrest collapse before they progressed to a state of total collapse. The two WTC towers were able to arrest collapse from the impact damage, but not from the resulting fires when combined with the impact effects of the aircraft attacks. Studies should be conducted to determine, given the great size and weight of the two towers, whether there are feasible design and construction features that would permit such buildings to arrest or limit a collapse, once it began.
2.5 References
BBC News. 2001. «We Ran for Our Lives.» Account of Mike Shillaker. September 13.
Cauchon, D. 2001a. «For Many on Sept. 11, Survival Was No Accident,» USA Today.com. December 19. Cauchon, D. 2001b. «Four Survived by Ignoring Words of Advice,» USA Today.com. December 19. Computers and Structures, Inc. (CSI). 2000. SAP-2000. Berkeley, CA. Dateline NBC. 2001. «The Miracle of Ladder Company 6.» September 28. Hearst, D. 2001. «Attack on America: Survivors: Suddenly they started to yell out, `get out now': Bravery and fear mingled with disbelief,» Guardian Home Pages, page 15. Account of Simon Oliver. September 13.
Labriola, J. 2001.
• The floor framing system for the two towers was complex and substantially more redundant than typical bar joist floor systems. Detailed modeling of these floor systems and their connections should be conducted to understand the effects of localized overloads and failures to determine ultimate failure modes. Other types of common building framing should also be examined for these effects.
• The fire-performance of steel trusses with spray-applied fire protection, and with end restraint conditions similar to those present in the two towers, is not well understood, but is likely critical to the building collapse. Studies of the fire-performance of this structural system should be conducted.
• Observation of the debris generated by the collapse of the towers and of damaged adjacent structures suggests that spray-applied fire proofing may be vulnerable to mechanical damage from blasts and impacts. This vulnerability is not well understood. Tests of these materials should be conducted to understand how well they withstand such mechanical damage and to determine whether it is appropriate and feasible to improve their resistance to such damage.
• In the past, tall buildings have occasionally been damaged, typically by earthquakes, and experienced collapse within the damaged zones. Those structures were able to arrest collapse before they progressed to a state of total collapse. The two WTC towers were able to arrest collapse from the impact damage, but not from the resulting fires when combined with the impact effects of the aircraft attacks. Studies should be conducted to determine, given the great size and weight of the two towers, whether there are feasible design and construction features that would permit such buildings to arrest or limit a collapse, once it began.
2.5 References
BBC News. 2001. «We Ran for Our Lives.» Account of Mike Shillaker. September 13.
Cauchon, D. 2001a. «For Many on Sept. 11, Survival Was No Accident,» USA Today.com. December 19. Cauchon, D. 2001b. «Four Survived by Ignoring Words of Advice,» USA Today.com. December 19. Computers and Structures, Inc. (CSI). 2000. SAP-2000. Berkeley, CA. Dateline NBC. 2001. «The Miracle of Ladder Company 6.» September 28. Hearst, D. 2001. «Attack on America: Survivors: Suddenly they started to yell out, `get out now': Bravery and fear mingled with disbelief,» Guardian Home Pages, page 15. Account of Simon Oliver. September 13.
Labriola, J. 2001.