Can You Tell Me About The Construction Of The World Trade Center?

In time the building foundations were sunk into bedrock. And from that base the twin towers rose rapidly. At the peak of construction as many as 3,500 men worked on the project, and many are still working on it. The first steel for the north tower was placed in August 1968, and six months later work began on the south tower.

Huge cranes swung large, twenty-two-ton prefabricated steel panels into place. These formed the exterior walls of the towers. Just to put siding on the walls required 2.2 million square feet of aluminum, equivalent to that needed to cover 9,000 homes. Also, over 600,000 square feet of glass were required for the 43,600 floor-to-ceiling windows. Unmanned automatic window washers keep them clean.
Unlike conventional skyscrapers, which have the weight-bearing columns on the inside, the towers' exterior walls carry most of the buildings' weight. The only columns inside are in the core, which contains the elevators. Thus the floors have a maximum of open, column-free space.

Another unique construction feature is the 102 elevators in each building. In conventional skyscrapers, elevator shafts service all the floors. This consumes large areas of floor space. The World Trade Center divided each tower building into three zones, and introduced a system of express and local elevators connected by transfer points called "skylobbies." As a result, space requirements for elevator shafts were considerably reduced