One World Trade Center / SOM / United States

One World Trade Center

• Architects:  Skidmore, Owings & Merrill LLP
• Location:  New York, United States
• Client/Developer:  Port Authority of New York and New Jersey, The Durst Organization
• Past Owner: Silverstein Properties;  Current Owner: 1 World Trade Center LLC
• Project Proposed:  2005;  Construction Start: 2006;  Completed: 2014
• Site Area:  74,328 ft2  
• Project Area:  3,500,000 ft2  
• Building Height:  541.32 m / 1,776 ft  (104 Stories)
• Function:  Commercial + Office, Mixed-Use
• Structural Engineer:  WSP Group, Schlaich Bergermann and Partner, Leslie E. Robertson Associates
• MEP Engineer/Vertical Transportation:  Jaros, Baum & Bolles
• Main Contractor:  Tishman Construction
• Civil/Traffic Consultant:  Philip Habib & Associates
• Cost Consultant:  AECOM
• Environmental Consultant:  Arnold & Porter LLP
• Facade Consultant:  Viridian Energy & Environmental LLC, Banson Industries
• Geotechnical Consultant:  Mueser Ruttedge Consulting Engineers
• Wind Consultant:  RWDI (Rowan Williams Davies & Irwin)
• Elevator Consultant:  Thyssenkrupp
• Building Monitoring:  Viridian Energy & Environmental LLC
• Structural Material:  Composite (Core: Reinforced Concrete; Columns: Steel; Floor Spanning: Steel)
• Construction Cost:  USD $3.9 Billion

Completed in 2014, One World Trade Center recaptures the New York Skyline, reasserts downtown Manhattan's preeminence as a business center, and establishes a new civic icon for the country. It is a memorable architectural landmark for the city and the nation - a building whose simplicity and clarity of form will remain fresh and timeless. Extending the long tradition of American ingenuity in high-rise construction, the design solution is an innovative mix of architecture, structure, urban design, safety, and sustainability.

One World Trade Center is a bold icon in the sky that acknowledges the adjacent memorial. While the memorial carved out of the earth, speaks of the past and of remembrance. One World Trade Center speaks about the future and hope as it rises upward in a faceted form filled with and reflecting light. This tower evokes the slender, tapering, triangular forms of the great New York City icons such as the Chrysler Building and Empire State Building and replaces almost one quarter of the office space lost on September 11, 2001.

Even with all of these high-profile projects, 1 WTC will dominate the site, not merely as New York City's tallest building, but as an icon representing perseverance, innovation, and urban-modernism. While, in an era of super-tall buildings, big numbers are the norm, the numbers at One World Trade are truly staggering: 5,660 cubic meters (200,000 cubic feet) of concrete, 92,920 square meters (1,000,000 square feet) of exterior glazing, 40,800 metric tonnes (45,000 US tonnes) of structural steel, and 241,550 square meters (2,6 million square feet) of office space. But the real story of One World Trade Center is the innovative solutions sought for the unprecedented challenges faced in building a project of this size on such a difficult site.

Site

One World Trade Center is seamlessly into the northwest corner of the World Trade Center Site, on land claimed from the Hudson River over centuries of development in Manhattan. The site, several blocks east of the river and in the heart of the financial district, will ultimately house more than ten million square feet of commercial development in towers, a performing arts center, 500,000 square feet of retail, a transportation hub, and at its center, the National September 11 Memorial & Museum. 

The project team was confronted with unprecedented challenges. The site sits over a vast tangle of existing subterranean obstacles. The new tower must bridge existing PATH train tracks adjacent to existing subway tracks, as well as accommodate a planned network of new development. The new World Trade Center Transportation Hub alone will occupy 74,300 square meters (800,000 square feet) to serve 250,000 pedestrians a day.

Bridging over the tracks was certainly, an engineering challenge. "We used state-of-the-art methods of analysis in order to design one of the primary shear walls that extends all the way up to the tower and is being transferred at its base to clear the PATH train lines that are crossing it," explains Yoram Ellon, Vice President at WSP Cantor Seinuk, the structural engineers for the project. " we designed a steel structure that bridges over the tracks, which supported the wet concrete loads during construction and was eventually integrated into the permanent structure."

Podium

The tower rises from a podium whose square plan measures approximately 204 feet by 204 feet, the same footprints as the original towers. The podium is 186 feet tall and is clad in triple-laminated, low-iron glass and horizontal, embossed stainless steel slats. The more than 4,000 glass, each measuring approximately 13 feet by 2 feet, are fixed and positioned at varying angles alone the vertical axis to form a regular pattern over the height of the podium. This pattern both accommodates ventilation for the mechanical levels behind the podium wall and, in combination with a reflective coating, refracts and transmits light a create a dynamic, shimmering surface. The podium's heavily reinforced concrete walls serve as a well-disguised security barrier.

Safety Design

Seven World Trade Center, the first rebuilt structure near Ground Zero, was completed in 2005. The 52-storey, 226 meters (741 foot) tower provided with an opportunity to enhance the tower's pure form with precision detailing. Simultaneously, integrating the next generation of the life-safety standards subtly into the infrastructure. The structure incorporates enhanced fireproofing for the structural steel that exceeds current codes. Its core is enclosed by up to 3 feet of reinforced concrete. There are dual interconnected fire standpipes and extra water storage to allow for high capacity sprinkler heads, if a standpipe is cut or broken, the interconnected valve automatically cuts off water supply to that standpipe and redirects it to the other standpipe, ensuring that every other floor has sprinkler protection.

In addition, to a concrete-enclosed core, the tower includes a protected tenant collection point on each floor and a separate stairwell for first responders. From an architectural perspective, all of these features are integrated into the design without lessening efficiency or constructability. The building incorporates highly advanced state-of-the-art life safety systems that exceed the requirements of the New York City Building Codes. Designed in collaboration with landscape architects Peter Walker & Partners, the collective vision is to connect the tower with nearly neighborhoods and allow views and access into the memorial.

Structural Design

The tower's structure is designed around a massive, redundant steel moment frame consisting of beams and columns connected by a combination of welding and bolting. Two large Manitowoc cranes - the largest ever used in New York City - positioned the steel columns and nodes, the largest weighing as much as 72.5 metric tons (80 US tons). Paired with a massive 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.

One World Trade Center is the first project in which 14,000 psi concrete has been used in a New York City project.The standard for high-rise buildings in New York was maxed out at 8,000 psi.The use of a hybrid system of high strength concrete core and structural steel moment frame at the tower perimeter results in an efficient structure. Additionally, the fact that the tower tapers as it rises coupled with the chamfered corners on the floor's footprint forms an aerodynamic and structurally efficient shape. In New York City skyscrapers design is governed by wind loads. The geometrical shape of the tower reduces exposure to such loads, as well as the amount of structural steel needed, and thus demand on the lateral system of the tower

Architectural Design

As the tower rises from a cubic base, its edges are chamfered back, resulting in a faceted form composed of a eight elongated isosceles triangles. At its middle the tower forms a perfect octagon in plan and then culminates in a glass parapet whose plan is a 150 foot by 150 foot square rotated 45 degrees from the base. Its overall effect is that of a crystalline form that captures an ever evolving display of refracted light. As the sun moves through the sky or we move around the tower, the surfaces appear like a kaleidoscope, and will change throughout the day as light and weather conditions change.

Eventual tenants will be educated on building infrastructure, from simple, metal walk-off grilles at major entrances to MERV 16 high-efficiency particulate filters and gas-phase filtration to serve the outside-air intake system and air-handling units on each floor. Ultimately, written guidelines and an exemplar space will help tenants incorporate sustainable strategies in their fit-outs.

For example, individual electrical-supply meters will encourage tenants to reduce energy consumption and meet the building goal of a 25 percent reduction in energy consumption. In addition, strategies for using low-emitting materials - paint, adhesives, wood, fabrics, and carpet - are outlined. The tower will be partially powered by 12 hydrogen fuel cells, expected to generate 4.8 megawatts of power for 1 WTC and other buildings on the site.

Spire

The spire will perform multiple functions, most of which will involve broadcasting and digital communication. It's a hybrid structure, consisting of two major components: a 137 meter (450 feet) spire and a three level communications platform ring. At the base of the spire, the circular lattice ring will support point-to-point microwave dishes, steerable Electronic News Gathering antennas, and whip-type radio communication antennas.