Collapse of World Trade Center Towers

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Mirghani, Amjad Ahmed
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Buildings are designed to withstand loading events that are deemed credible hazards and to protect the public safety in the event such credible hazards are experienced. Buildings are not designed to withstand any event that could ever conceivably occur, and any building can collapse if subjected to a sufficiently extreme loading event. Communities adopt building codes to help building designers and regulators determine those loading events that should be considered as credible hazards in the design process. These building codes are developed by the designers and regulatory communities themselves, through a voluntary committee consensus process. Prior to September 11, 2001, it was the consensus of these communities that aircraft impact was not a sufficiently credible hazard to warrant routine consideration in the design of buildings and, therefore, the building codes did not require that such events be considered in building design. Nevertheless, the design of world trade center towers (WTC) did include at least some consideration of the probable response of the buildings to an aircraft impact, albeit a somewhat smaller and slower moving aircraft than those actually involved in the September 11 events. Building codes do consider fire as a credible hazard and include extensive requirements to control the spread of fire throughout buildings, to delay the onset of fire-induced structural collapse, and to facilitate the safe egress of building occupants in a fire event. The world trade center towers, which attacked by Boeing 767-E 200 on September 11, 2001. were the first structure out side of the military and the nuclear industries whose design considering the impact of a jet air liner, the Boeing707, and have been designed to ACI and ASIC codes, which include the general safety requirement therefore stand for a long time before collapsed to give a chance for occupant to evacuate from towers with out injuring, and there was only 2,830 from 58,000 occupants died including 403 fire fighter & the two aircraft passengers with their crew, when we are calculating the percentage of death to the life, we say this number is so small in comparison with this large event and huge buildings occupants. The study of this collapse required; information reported from field observations at the WTC site and the results from tested samples of the collapsed structures. Hundreds of hours of video and thousands of still photographs were viewed. Conducted interviews with witnesses and persons involved in the design, construction, and maintenance of each of the affected buildings reviewed & construction documents, and conducted preliminary analyses of the damage to the WTC towers. And I found that the structural damage sustained by each of the two buildings as a result of the attacks was massive. The fact that the structures were able to sustain this level of damage and remain standing for an extended period of time is remarkable and is the reason that most building occupants were able to evacuate safely. Events of this type, resulting in such substantial damage, are generally not considered in building design, and the ability of these structures to successfully withstand such damage is noteworthy.
Collapse, World,Trade,Center,Towers