The current profile of 3 World Trade Center is unusual in New York City in that its concrete central core is being built ahead of the the steel surround.
Buildings in the city are usually “topped out” with a ceremonial signing of the highest piece. At 3 WTC, there will be two topping out ceremonies, one for the core next month, and one for the steel, most likely in October, writes David W. Dunlap in the New York Times.
Concrete cores are common around the world, but less so in New York. After the terrorist attacks on the World Trade Center, however, in which the steel cores of the towers were damaged by the hijacked planes, concrete cores are more common.
