One World Trade Center reaches 20th floor

The Port Authority of New York has confirmed that steel works for One World Trade Center have reached the 20^th storey and the tower now stands 61 m above ground level.

One World Trade Center in New York, US is being built on the site of the World Trade Center twin towers which were destroyed in the 11 September 2001 terrorist attacks.

A Port Authority spokesman said, "To reach the 20^th floor, DCM Erectors, the steel contractor for the project, has already erected some 7300 tonnes of structural steel. Currently, DCM is installing 16 giant steel nodes on the twentieth floor, some of which stand three floors tall and weigh 159 tonnes."

The spokesman explained the steel nodes will act as joints between the steel framing for the building's podium and the steel for the remainder of the 541 m tall tower, and would represent one of the signature elements of the structure's unique design and appearance.

Since construction started in 2006 some 46000 m3 of concrete has been poured both above and below ground level. The Port Authority spokesperson said, "The above ground height is in addition to the 18 m, or four floors, of the building below street level. These floors will house mechanical space, fuel storage, water tanks, parking, retail space and a lobby for the elevators that will serve the observation deck."

"The initial 20 floors have required more complex construction due to their configuration and security," confirmed the spokesman. "The next 69 storeys will be standard office floors and will therefore be constructed at a much quicker rate. We are still scheduled for One World Trade Centre to be completed in 2013," he said.

Port Authority chairman, Anthony Coscia said, "The construction progress on One World Trade Center is great news, but we know more challenges lie ahead. The Port Authority will confront these challenges head-on as we continue with the rebuilding of the site."