Reclaiming the skyline

The 2014 completion of One World Trade Center marked a major milestone in the history of New York City. More than 13 years in the making, the 104-story, 3.5-million-square-foot, 1,776-foot tower — the tallest in the Western Hemisphere — recaptured the New York skyline, reasserted Lower Manhattan’s preeminence as a global business center, and established a new civic icon for the country.

One World Trade Center was designed as a memorable architectural landmark — a symbol of the American spirit, with a simplicity and clarity of form that will remain fresh and timeless. While the adjacent World Trade Center Memorial speaks of the past and of remembrance, One World Trade Center’s faceted form speaks about the future and about hope. As the tower rises from a cubic base, its edges are chamfered back, resulting in a faceted form composed of 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. The building’s 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 as viewers move around the tower, the surfaces appear like a kaleidoscope, changing with the weather and position of the sun.

Anatomy of a landmark

Entrances are situated on all four sides of the building, each 60 feet tall. Glass canopies and large cable-net walls framed by metal portals define the entrances, which provide for separate access to the observatory lobby on the concourse level, transportation systems, and commercial office space in different sections of the building. These transparent entrances encourage building occupants to flow out into the surrounding plazas, which create areas for people to gather, sit, relax, and reflect. These generous open spaces, filled with trees and places of respite, help connect the tower with the adjacent neighborhoods and allow views and access to the adjacent memorial.

Rising from the plaza level, the building’s 50-foot-tall public lobby and mechanical floors form a monumental podium, clad in shimmering glass fins and embossed steel slats. Seventy-one glass-clad office stories rise above the base to an elevation well over 1,000 feet, above which sits a three-level observatory at elevations that culminate in a parapet marking the heights of the original Twin Towers. Communication platform rings rise above the parapet, and a 441-foot, cable-stayed spire and innovative LED beacon crown the tower.

For the curtain wall, SOM worked with industry experts to develop glass of a new monumental scale that is capable of withstanding the wind loads of a supertall building as well as stringent security requirements. The 5-foot by 13-foot-4-inch insulated glass panels span the full floor-to-floor height, with no intermediate structure — a first in skyscraper construction. These glass units, the largest ever mass-produced for a building of this scale, help give the massive tower its crystalline elegance. Windows have twice-laminated outer lites and were treated with a low-E coating for maximum energy efficiency.

Setting new standards

In structural engineering and building performance, One World Trade Center stands unsurpassed. The building features a hybrid structure comprised of a high-strength concrete core surrounded by a perimeter moment frame of steel. Paired with the massive concrete shear walls of the core, the steel frame adds rigidity and structural redundancy. Both bolted and welded together for maximum connection strength, the steel members were hoisted into place by two Manitowoc cranes — the largest ever used in New York City. The tower’s tapered, aerodynamic form reduces exposure to wind loads while simultaneously reducing the amount of structural steel needed. Rising a quarter mile into the sky, the tower is brute strength veiled in glass.

One World Trade Center also led the way in utilizing new technologies to maximize efficiency, minimize waste and pollution, and reduce environmental impact. The building’s sustainable design strategies, including water and energy efficiencies, go beyond the criteria established for LEED CS Gold certification. The tower features a high-tech building management system that optimizes energy use and indoor air quality based on data collected by thousands of sensors. The building also generates some of its own power through elevators with variable voltage/variable frequency drives and hoist motors that produce energy through regenerative braking. Under certain conditions, the elevator motors turn into small generators supplementing power in the building’s power distribution grid, thus reducing demand for electrical utility power.

In addition, over 40 percent of the materials used in the construction of the tower were made from post-industrial recycled content, including gypsum boards, ceiling tiles, and glass. The structural steel was produced from 95 percent recycled materials, and the building features “green concrete,” made from waste fly ash collected from coal plants. Thirty-four percent of construction materials were extracted, harvested, or recovered as well as manufactured within 500 miles of the project site, further reducing the project’s carbon footprint.