Freedom Tower : Amazing Structures

1 World Trade Center, or the Freedom Tower, is the centerpiece building of the new World Trade Center complex currently under construction in Lower Manhattan in New York City. It is being developed by Silverstein Properties. The $2 billion project will be located in the northwest corner of the 16-acre (65,000 m²) World Trade Center site, and will be 1,776 ft (541 m) tall. Construction on below-ground utility relocations, footings, and foundations for Freedom Tower began on April 27, 2006.

On December 19, 2006, the first steel columns were installed in the building's foundation. Three other high-rise office buildings plus a residential tower are planned for the site along Greenwich Street, and collectively they will surround the World Trade Center Memorial, which is currently under construction. The area will also be home to a museum, highlighting many of the different aspects of the past and future World Trade Centers.

Following the destruction of the World Trade Center towers in the September 11, 2001 attacks, there was much debate regarding the future of the World Trade Center site. Proposals began almost immediately, and by December 2002, a design by Daniel Libeskind was selected. This design went through many revisions, largely because of disagreements with developer Larry Silverstein, who held the lease to the World Trade Center site on September 11, 2001.

A final design for the tower was formally unveiled on June 28, 2006. To satisfy security issues raised by the New York City Police Department a 187-foot (57 m) concrete base was added in April of that year. The final design included plans to clad the base in glass prisms to address criticism that the base looked like a "concrete bunker."

The final design tapers the corners of the base outward as they rise. Its designers stated that the tower will be a "monolithic glass structure reflecting the sky and topped by a sculpted antenna." In terms of a completion date, Larry Silverstein stated "By 2012 we should have a completely rebuilt World Trade Center more magnificent, more spectacular than it ever was."

It is projected that steel for the building will be visible above ground in 2008, with a topping out in 2010. The building is projected to be ready for occupancy in the first quarter of 2011.

The Freedom Tower's program includes 2.6 million square feet (241,000 square meters) of office space, as well as an observation deck, world-class restaurants, parking, and broadcast and antennae facilities, all supported by both above and below-ground mechanical infrastructure for the building and its adjacent public spaces. Below-ground tenant parking and storage, shopping and access to the PATH and subway trains and the World Financial Center are also provided.

An 80-foot-high (24 m) public lobby topped by a series of mechanical floors form a 200-foot-high (61 m) building base. 69 tenant floors rise above the base to 1,120 feet (341 m) elevation. Mechanical floors, two floors to be occupied by the Metropolitan Television Alliance, restaurants and observation decks culminate in an observation deck and glass parapet that mark 1,362 feet (415 m) and 1,368 feet (417 m) respectively — the heights of the original Twin Towers. Currently, only the Sears Tower and Taipei 101 have occupied floors higher than Freedom Tower. A shrouded antenna structure supported by cables rises to a final height of 1,776 feet (541 m).

The tower rises from a cubic base whose square plan—200 feet by 200 feet—(61 m by 61 m) is almost as wide as the 208 foot (63 m) Twin Towers. The base is clad in more than 2,000 pieces of prismatic glass; each measures 4 feet by 13 feet 4 inches (1.21 m by 4.06 m) with varying depths. It has been designed to draw upon the themes of motion and light; a shimmering glass surface drapes the tower's base and imparts a dynamic fluidity of form whose appearance will reflect its surroundings. Just as the rest of the building, the base will serve as a glowing beacon. Cable-net facades on all four sides of the buildings, measure 60 feet (18 m) high and range in width from 30 feet (9 m) on the east and west sides (for access to the restaurant and observation deck, respectively) to 50 feet (15 m) on the north side and 70 feet (21 m) on the south for primary tenant access, activate the building at street level.

As the tower itself rises from this cubic base, its square edges are chamfered back, transforming the square into eight tall isosceles triangles in elevation, or an elongated square antiprism. At its middle, the tower forms a perfect octagon in plan and then culminates in a glass parapet (elevation 1,362 feet (415 m) and 1,368 feet (417 m)) whose plan is a square, rotated 45 degrees from the base. A mast containing an antenna for television broadcasters—designed by a collaboration between SOM, artist Kenneth Snelson (who invented the tensegrity structure), lighting designers and engineers—and secured by a system of cables, rises from a circular support ring, similar to the Statue of Liberty's torch, to a height of 1,776 feet (541 m).

The spire will be an intense beam of light that will be lit at night and will likely be visible over a thousand feet (305 m) into the air above the tower. New York City is a suitable place to set such a light pointing towards the sky without complaints of light pollution by astronomers, as the night sky in locations near New York City is already far too bright for serious astronomical observers.

Other new safety features will include 3-foot (90 cm) thick walls for all stairwells, elevator shafts, risers, and sprinkler systems; extremely wide "emergency stairs"; a dedicated set of stairwells exclusively for the use of firefighters; and biological and chemical filters throughout its ventilation system.

The building will no longer be 25 feet (7.6 m) away from West Street—with the redesign and smaller base (the same width and length now as each of the previous towers), Freedom Tower will average 90 feet (27 m) away from the street.At its closest point, West Street will be 65 feet (20 m) away. The windows on the side of the building facing in this direction will be equipped with specially tempered blast-resistant plastic, which will look nearly the same as the glass used in the other sides of the building.

"Ultra-clear" glass, as opposed to reflective or tinted glass, is proposed for the fenestration generally. This will benefit internal daylight propagation; however, at this stage it is unclear how the corresponding issue of solar heat gain will be addressed. Although the roof area of any tower is comparatively limited, the building will implement a greywater recycling scheme involving rainwater collection. The robust, redundant steel moment frame, consisting of beams and columns connected by a combination of welding and bolting, resists lateral loads through bending of the frame elements. Paired with a concrete-core shear wall, the moment frame lends substantial rigidity and redundancy to the overall building structure while providing column-free interior spans for maximum flexibility^.

If the spire and antenna height (the criteria of two categories of the Council on Tall Buildings and Urban Habitat) are included, Freedom Tower will stand at 1,776 feet (541 m) (marking the year of the signing of the American Declaration of Independence). Freedom Tower was originally planned to be the tallest building in the world, but will no longer obtain this title, as the Burj Dubai has already broken the record for the tallest building at 1,822 feet (555 m), and it is expected to exceed 2,680 ft (818 m) by the time of its completion in 2009.

The Chicago Spire, currently under construction in Chicago, is set to be completed in 2010. It could also be taller than the Freedom Tower. At 150 floors, its roof will top out at 2,000 feet (610 m). The height of Freedom Tower will probably not be increased before completion, due to the symbolism of having an exact height of 1,776 feet (541 m).

Even though several buildings throughout the world will be taller than the Freedom Tower, the tower will still most likely obtain the record for tallest office building in the world; no taller all-office buildings are currently proposed, approved, or under construction.

As revealed on June 28, 2006, Freedom Tower will have a top floor denoted as 102, though the total number of floors is 82 (possibly with some uncounted floors). This is because the first office floor of the building atop the tall base will be designated as Floor 20. There are 69 office floors atop the base, ending at Floor 88, above which would be broadcasting space on the 89th and 90th floors. Three stories of mechanical space take up a floor count of 9. Finally, a restaurant will take up Floors 100 and 101, and the observation deck is at Floor 102. Six additional floors of mechanical space exist above to Floor 108.

In January 2008, two more construction cranes are expected to be placed at the construction site of the Freedom Tower. The steel is expected to be visible at street level by mid-2008, and the base is expected to be completed by September 1008. The opening of the supertall skyscraper is scheduled for the first quarter of 2011.

(Information comes courtesy of the Wikipedia amongst other sources.)