رسائل ماجيستير
English
2005
Collapse of World Trade Center Towers
أمجد أحمد ميرغني الأمين, محجوب عثمان محجوب
كلية الهندسة-جامعة الخرطوم · السودان
Buildings are designed to withstand loading events that are deemed credible hazards andto protect the public safety in the event such credible hazards are experienced. Buildings are notdesigned to withstand any event that could ever conceivably occur, and any building can collapse ifsubjected to a sufficiently extreme loading event. Communities adopt building codes to helpbuilding designers and regulators determine those loading events that should be considered ascredible hazards in the design process. These building codes are developed by the designers andregulatory communities themselves, through a voluntary committee consensus process. Prior toSeptember 11, 2001, it was the consensus of these communities that aircraft impact was not asufficiently 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 someconsideration of the probable response of the buildings to an aircraft impact, albeit a somewhatsmaller 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 controlthe spread of fire throughout buildings, to delay the onset of fire-induced structural collapse, and tofacilitate 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 designconsidering the impact of a jet air liner, the Boeing707, and have been designed to ACI and ASICcodes, which include the general safety requirement therefore stand for a long time before collapsedto give a chance for occupant to evacuate from towers with out injuring, and there was only 2,830from 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 incomparison with this large event and huge buildings occupants.The study of this collapse required; information reported from field observations at theWTC site and the results from tested samples of the collapsed structures. Hundreds of hours ofvideo and thousands of still photographs were viewed. Conducted interviews with witnesses andpersons involved in the design, construction, and maintenance of each of the affected buildingsreviewed & construction documents, and conducted preliminary analyses of the damage to theWTC towers. And I found that the structural damage sustained by each of the two buildings as aresult of the attacks was massive. The fact that the structures were able to sustain this level ofdamage and remain standing for an extended period of time is remarkable and is the reason thatmost building occupants were able to evacuate safely. Events of this type, resulting in suchsubstantial damage, are generally not considered in building design, and the ability of thesestructures to successfully withstand such damage is noteworthy.
