At 3 World Trade Center, Silverstein Properties is employing an uncommon construction method once shunned by union workers.
The developer is building the 80-story office tower using a “composite” structural design: a concrete core and a steel perimeter.
The technique was long resisted by Local 40 of the International Association of Bridge, Structural, Ornamental and Reinforcing Iron Workers, who balked at the idea of working below a concrete pouring team.
The novel approach means the building’s topping out will be marked with a bucket of concrete signed by workers, rather than the traditional topmost steel beam, the New York Times reported.
But the terrorist attacks of Sept. 11, 2001 demonstrated the vulnerability of skyscrapers built with steel-framed cores.
The core of 2.8 million-square-foot Rogers Stick Harbour & Partners-designed tower is three feet thick on average, and reinforced with steel bars.