One World Trade Center, which is also known as One World Trade, One WTC, or Freedom Tower, is the main building of the rebuilt World Trade Center complex, which was destroyed in the terrorist attacks of September 11, 2001 (9/11), in Lower Manhattan, New York. Standing at an impressive height of 541.3m, it is the tallest building in New York City, the tallest in the whole of the United States, and the tallest in the Western Hemisphere.
One World Trade Center is also the sixth-tallest building in the entire world behind Lotte World Tower in Seoul, South Korea at number five, Ping An Finance Center in Shenzhen, China at number four, Makkah Royal Clock Tower in Mecca, Saudi Arabia at number three, Shanghai Tower in Shanghai, China at number two, and Burj Khalifa in Dubai, the United Arab Emirates at number one.
Construction and development
The cornerstone of the One World Trade Center was laid in a ceremony on July 4, 2004, however, construction was delayed due to disputes over money, security, and design. By December 18, 2006, the first 30-foot steel beam was installed and welded onto the building’s base by December 19, 2006.
Foundation and steel installation began shortly afterward, so the tower’s footings and foundation onto which 310 cubic meters of concrete was poured, were nearly complete within 12 months.
In January 2008 construction of the tower’s concrete core began and had reached street level by May 17 the same year. However, construction of the base was not finished until two years later, after which construction of the office floors and installation of the first glass windows began subsequently, during 2010, floors were constructed at a rate of about one per week. The tower reached 52 floors and was over 600 feet tall by December 2010.
The tower’s steel frame was halfway complete by then but grew to 82 floors by the tenth anniversary of the September 11 attacks, at which time its concrete flooring had reached 72 floors and the glass cladding 56 floors.
By March 2012, One World Trade Center’s steel structure had reached 93 floors growing to 94 floors and 1,240 feet by the end of that month. However, because the floor numberings were based on standard measurements, the 94th floor was numbered “floor 100”, because the extra space was occupied by the high-ceilinged 91st floor, which was used for mechanical purposes.
One World Trade Center’s steel structure topped out at the nominal 104th floor, with a total height of 1,368 feet, in August 2012. The tower’s spire was then shipped from Quebec to New York in November the same year, and the first section of the spire was hoisted to the top of the tower on December 12, 2012, and was installed on January 15, 2013. By March 2013, two sections of the spire had been installed.
The spire’s completion was scheduled for April 29, 2013, but bad weather delayed the delivery of the final pieces to May 10, 2013, when the final piece of the spire was lifted to the top of One World Trade Center, bringing the tower to its full height of 1,776 feet.
In subsequent months, the exterior elevator shaft was removed, the podium glass, interior decorations, and other finishing’s, as well as concrete flooring and steel fittings, were installed.
On November 1, 2014, the tower’s first occupying tenant moved in, and the building opened officially on November 3, 2014.
The building occupies a 200-foot square, with an area of 40,000 square feet, nearly identical to the footprints of the original Twin Towers. The tower is built on a 185-foot tall windowless concrete base, designed to protect it from truck bombs and other ground-level attacks.
Originally, the base was to be covered in decorative prismatic glass, but a simpler glass-and-steel façade was adopted when the prisms proved unworkable. The current base cladding consists of angled glass fins protruding from stainless steel panels. LED lights behind the panels light the base when it is dark or rather at night.
Cable-net glass façades on all four sides of the building for the higher floors are consistent with the other buildings in the complex. The façades are 60 feet high, and range in width from 30 feet on the east and west sides, 50 feet on the north side, and 70 feet on the south side. The curtain wall was manufactured and assembled by Benson Industries in Portland, Oregon, using glass made in Minnesota by Viracon International.
From the 20th floor upwards, the structure begins to gently taper at the corners forming 8 isosceles triangles. Near its middle, the tower forms a perfect octagon and then culminates in a glass parapet, whose shape is a square oriented 45 degrees from the base.
A 408-foot sculpted mast containing a broadcasting antenna, which was designed by Skidmore Owings and Merrill (SOM), in collaboration with artist Kenneth Snelson, who invented the tensegrity structure, and lighting designers, and engineers, is secured by a system of cables and rises from a circular support ring that contains additional broadcasting and maintenance equipment.
From the base to the parapet, the building is also the same height as the twin towers i.e. 1,368ft before its crowning mast takes it up to the height of 1,776ft. Its height in feet is a deliberate reference to the year when the United States Declaration of Independence was inked.
At night, an intense beam of light is projected horizontally from the spire and shines over 1,000 feet above the tower.
The Project team
- Developer: The Durst Organization
- Architect: Skidmore Owings & Merrill LLP
- Structural Engineer: WSP Group
- Peer Review: Leslie E. Robertson Associates
- Special Elements: Schlaich Bergermann und Partner
- MEP Engineer: Jaros Baum & Bolles
- Main Contractor: Tishman Construction
- Acoustics Consultant: Cerami & Associates
- Code Consultant: Code Consultants Inc.
- Cost Consultant: AECOM
- Façade Consultant: Permasteelisa Group
- Façade Maintenance Consultant: Lerch Bates
- Geotechnical Consultant: Mueser Rutledge Consulting Engineers
- Lighting Consultant: Brandston Partnership Inc.
- Wind Consultant: RWDI
- Cladding Supplier: Kuraray, POHL Group, CS Group Construction Specialties Company
- Elevator Supplier: thyssenkrupp
- Sealants Supplier: Dow Corning Corporation, Sika Services AG
- Steel Supplier: ArcelorMittal