World Trade Center NY Architect : Minoru Yamasaki.
Location : New York, NY, USA.
Date of construction:1966 to 1977.
Demolished by Muslim terrorist attack on 9/11/2001.
Building Type : commercial office tower.
Construction System : steel frame, glass, concrete slabs on steel truss joists.
The WTC was one of the first skyscrapers ever built with an open floor system, this is concrete slabs with reinforced steel rods suspended over corrugated sheeting on top of steel trusses that were spot welded on the I-Beams around the perimeter of the building. There was no interior support from each floor as the building took to rising, all the weight of each individual floor was supported by the outside steel beams.
For the 1,400 people in the top 19 floors of the north tower, there was no escape after the first jet smashed into the 94th through 98th floors at 8:46 a.m. But the people on the top floors of the south tower still had the chance to run, and for them, delay meant death.
The 9/11 planes hit the North and South WTC buildings at the 94th and approx. the 78th floors respectively and the ensuing jet fueled blaze weakened the support trusses and all it took was for one floor from above the impact area to collapse inward and all the following floors above would act as a giant sledge hammer to all the lower floors and down went the buildings, collapsing inwardly, see NYFD Chief's report below.
Why the World Trade Center Buildings Collapsed "A Fire Chief ’s Assessment"
By: Deputy Chief Vincent Dunn ret. World Trade Center tower construction. In terms of structural system the twin towers departed completely from other high-rise buildings. Conventional skyscrapers since the 19th century have been built with a skeleton of interior supporting columns that supports the structure. Exterior walls of glass steel or synthetic material do not carry any load.
The Twin towers were radically different in structural design as the exterior wall is used as the load-bearing wall. The only interior columns are located in the core area, which contains the elevators. The outer wall carries the building vertical loads and provides the entire resistance to wind. The wall consists of closely spaced vertical columns (21 columns 10 feet apart) tied together by horizontal spandrel beams that girdle the tower at every floor.
Bearing walls and Open floor design; When the jet liners crashed into the towers based upon knowledge of the tower construction (KHALID SHEIKH MOHAMMED WAS A MECH ENG GRAD) and high-rise firefighting experience the following happened: First the plane broke through the tubular steel-bearing wall. This started the building failure. Next the exploding, disintegrating, 185-ton jet plane slid across an open office floor area and severed many of the steel interior columns in the center core area. Plane parts also crashed through the plasterboard-enclosed stairways, cutting off the exits from the upper floors. The jet collapsed the ceilings and scraped most of the spray-on fire retarding asbestos from the steel trusses.
The steel truss floor supports probably started to fail quickly from the flames and the center steel supporting columns severed by plane parts heated by the flames began to buckle, sag, warp and fail. Then the top part of the tower crashed down on the lower portion of the structure. This pancake triggered the entire cascading collapse of the 110-story structure.
Note * Ground-breaking for the construction of the World Trade Center was on August 5, 1966.
Bill Warner Private Investigator Sarasota Fl at www.wbipi.com