Basic Structure of the Original World Trade

The North and South Towers [3]

The picture on the left shows a cross section of the buildings. The towers were 208 ft by 208 ft with a structural core in the middle. This core is where the elevators are housed as well as other service areas such as bathrooms. This center column was believed to be the downfall of the towers in the 9/11 attacks because it acted like a chimney and quickly burned. Although the structure held strong after the impact, the prolonged fire damage was irreversible.

The picture on the right highlights the revolutionary elevator system and also shows the height of the building. The building is a massive 110 stories and 1368 feet tall. Since the building is too tall for an elevator to reach the top, a system of express and local elevators was put in place to get occupants to the higher stories faster.[1]

This is the basic structure of the floors. The joists were resting on angle clips that were attached to the inner core and the outer shell. These clips are also speculated to be one of the main causes of the building collapse. The floors were only designed to hold the 1,300 tons of weight. They would have failed when the weight from rubble, other floors, and airplane fuselage were resting on them. The buildings collapsed within themselves by the floors falling onto the floors below them. This caused a domino effect of collapsed floors and it brought down the entire building[1].

[2]


This is an original blueprint of the twenty fourth floor. This picture shows the lightweight steel core structure that the rest of the building was constructed around. This was considered to be a new way of making skyscrapers when the twin towers were constructed and is still in common practice today. The core was 138 ft by 88ft  in size.

[1] Eager, Thomas, and Christopher Musso. "Why Did the World Trade Center Collapse? Science, Engineering, and Speculation." Why Did the World Trade Center Collapse? Science, Engineering, and Speculation. N.p., n.d. Web. 07 May 2015.
[2] 9-11research.com. N.p., n.d. Web. 7 May 2015. <http://www.tms.org/pubs/journals/jom/0112/eagar/eagar-0112.html>.
[3] "The Towers' Design." 9-11 Research:. N.p., n.d. Web. 07 May 2015. <http://911research.wtc7.net/wtc/arch/plan.html>.