One World Trade Center... and 9 More Feats of Mega-Engineering

From the top of the house, as construction workers at One World Trade Center call it, the view on a clear day extends deep into neighboring Connecticut and New Jersey and out into the Atlantic Ocean. It's just days after the building surpassed the 1250-foot-high roofline of the Empire State Building, and there is a debate swirling between the lead architect, David Childs, and the Port Authority of New York and New Jersey, which owns the site, about the design of the antenna mast, which may or may not qualify One World Trade as the tallest building in the Western Hemisphere at 1776 feet when complete. The ironworkers here are focused on floor 96, installing rebar as thick as tree limbs to form the tower's reinforced concrete core, the "building within a building," according to Port Authority director of WTC construction Steve Plate. "The core walls aren't sheetrock like the original towers, they're more than 6 feet of concrete in places. We're rewriting the book on security for office towers."

One hundred floors below, crowds gather near the young oak trees and twin waterfalls of the 9/11 Memorial. The memory of nearly 3000 lost here a decade ago is never far from mind at the World Trade Center site?not for the workers with NEVER FORGET stickers on their hardhats or the designers of the crowning, chamfered replacement for the Twin Towers. "Not many office buildings have been attacked twice by terrorists," says Port Authority executive director Patrick Foye, referring both to Sept. 11, 2001, as well as the bombing of the north tower in 1993. "This tower is a bold symbol of recovery from that."

After consultation with the CIA, FBI, New York Police Department, and security firms, designers implemented a raft of safety measures?including extra-strong fireproofing, redundant water tanks at the top and bottom of the building to feed sprinkler systems, and biological and chemical filters in the air-intake system. Then there is the massive "podium" that forms the building's base?a concrete slab 187 feet tall and 200 feet wide.

Inside the reinforced core, designers plan for egress stairwells almost one and a half times wider than code, an additional stairwell for first responders, and a fireman's lift leading to a pressurized fireman's lobby. "The core is basically an isolated bunker," Plate says.

When completed at the end of 2013, at a cost of roughly $4 billion, the 104-story building will have office space on 71 floors, a grand public lobby with 50-foot ceilings, and an observation deck more than 1265 feet off the ground. "Rebuilding on this site shows our unwillingness to just accept the attacks of Sept. 11," Foye says. "No one can bring those people back, but this tower will help make sure they're remembered."

Source: http://www.popularmechanics.com/technology/engineering/architecture/one-world-trade-center-and-9-more-feats-of-mega-engineering?src=rss

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