In the early 1970s, when the planning for the Citigroup Center began, the northwest corner of the proposed building site was occupied by St. Peter's Evangelical Lutheran Church which was founded in 1862. The church, occupying one third of the block on Lexington Avenue and 54th Street, was facing financial problems, thus sold its property to Citibank. However, it was only on the condition that a new church would be built on the same corner with no connection to the new office tower. Citibank needed to build the tower on the block while at the same time providing enough space at the base for the construction of a church building.
To accomplish these goals, the Citigroup Center was designed by architect Hugh Stubbins for Citibank, and construction of the tower started in 1972 by Hugh Stubbins & Associates, assisted by Emery Roth & Sons. Structural engineer William LeMessurier was responsible for the conception and design of the building's structural framing system.
The proposed solution to the agreement between Citibank and the church was to raise the building on four tall columns and a supporting core. The columns were placed at the tower's base with the church on the left center of each side rather than at the corners. This way, the design allowed enough space in the northwest corner for the new St. Peter's Church, also by Stubbins. In 1977, the office tower opened as the Citibank Center. The bright metal skin and the distinctive slanted top of the building quickly established it as one of the most recognizable skyscrapers of New York. With the company's expansion, the building was first renamed as the Citicorp Center and later as the Citigroup Center. The Citigroup Center was acquired by Boston Properties in 2001, and is the tallest building that bears the Citigroup name. The corporate headquarters of Citigroup are located across the street in 399 Park Avenue.
At 915-foot, the 59-story, aluminum and reflective glass clad tower known as the Citigroup Center is one of the tallest buildings in New York City, United States. The building’s slender body has a silvery shine that gives it an apparent weightlessness, making the building appear to be floating in space. Enhancing this effect are the four columns that support the building at the base, leaving the corners open and generating a colossal 114-feet open space.
At the top of the building is an unfenestrated crown, cut at 45-degree angle and facing south. The sloped roof was originally intended to contain solar panels to provide energy, however, this idea was eventually dropped when it was discovered that the utility savings would not recover the cost of its construction. Stubbins left the crown as a design element, rendering the building distinctive and imposing presence in midtown Manhattan's skyline. Although the solar collectors were not installed, the total demand for heating and cooling was reduced by using strip windows with wide spandrel panels of brushed aluminum to reflect light and heat without causing intense glare.
The building includes a large sunken plaza and a seven-story atrium at the base of the tower with three stories of restaurants and shops, and contains 1.3 million square feet of office space. The structure of the building’s shaft is similar to a donut-like tube. Cross bracing serves as a stabilizing device against wind pressure to reduce the effect of torque forces during strong winds. These wind braces are concealed behind the flush finish of glass and aluminum paneling that compose the exterior curtain wall. The extraordinary structural efficiency of the steel frame made the tower significantly lighter than a conventional structure of its height and therefore far more subject to lateral harmonic vibration due to the buffeting of winds. To help stabilize the building, a tuned mass damper, a block of concrete weighing more than four hundred tons floating on a film of oil is linked to the top of the structural frame by hydraulic springs. The damper is designed to diminish the accelerations caused by the vibration. The Citigroup Center was the first skyscraper in the United States built with a tuned mass damper. The building features double-deck elevators, which are separated to serve only odd or even floors. They reduce the area devoted to the vertical circulation core, leaving more space available for offices. The atrium, open-air concourse and office tower lobby were renovated in 1997. In 2004, the roof was reclad.
Many critics have hailed Stubbin’s significant work, and he is probably best known for the Citigroup Center. Paul Goldberger, the architecture critic for The New Yorker called it "the most important skyscraper built in New York in the 1970s because of its elegant and memorable shape, but also because of its engagement with the city at the base." 1 Stubbins had several favorites himself; among them were the Citigroup Center, the Federal Reserve, and the Ronald Reagan Presidential Library in Simi Valley, California. In an interview with the American Institute of Architects, Stubbins commented on the Citigroup Center: “A very tall building in New York has a unique top on it that's the genre of New York buildings.” 2
1. National Post, ‘Architect's tower became symbol of new york’, National Post [toronto edition], 2006, p. AL.11.
2. MARQUARD, Bryan, ‘Hugh stubbins, 94; architect whose iconic buildings spanned genres and usages’, Boston Globe [third edition], 2006, p. C.5.
Structural engineer William LeMessurier employed an ingenious, radically unconventional structural frame in the Citigroup Center. However, it was an engineering challenge, and changes during construction led to a finished product that was structurally unsound. In the original design, LeMessurier calculated for wind loads that hit the building straight-on, but he did not calculate for quartering wind loads. During the early 1970s, the New York Building Code made no mention of wind loads other than those produced by winds acting at right angles to building faces, although majority of the skyscrapers in New York and elsewhere had been designed considering the effects of quartering winds. Furthermore, there was another potentially fatal flaw in the building's construction; while LeMessurier's original design and load calculations were based on welded joints, a labor and cost saving change altered the joints to bolted construction after the building's plans were approved. In June 1978, shortly after LeMessurier found out that the problem was significantly critical, he informed the architect's attorney, his own liability insurance company, the architect, and the owner. Local building officials, the Red Cross, the police, and other emergency response agencies were told of the situation, and plans for remediating the structural inadequacies of the tower were developed and implemented. For the next three months, construction crews welded two-inch-thick steel plates over each of the skyscraper's 200 bolted joints during the night, after each work day. Information about the details of LeMessurier’s discovery and the actions that averted the crisis were kept hidden from the public until it was disclosed in the May 29, 1995 article in The New Yorker. Although LeMessurier was criticized for the oversight and for misleading the public, his professional behavior and ethical conduct, as well as that of the other participants, have received high praise. His act of alerting the owner to the problem inherent in his own design has became a staple element in engineering and architectural ethics teaching since then.
The Citigroup Center was designed and constructed during an extended period of economic malaise in New York City. Stubbins parted with the then prevalent skyscrapers with a flat top, and instead gave the building a distinctive angled roof line. The original plan to construct setback penthouses on the roof was abandoned due to zoning restrictions. It was then intended as a solar panel; however, this idea was also eventually dropped, leaving the crown as a distinctive and imposing design element. The construction of the Citigroup Center revitalized the area and several office towers were built in its vicinity, including Philips Johnson's postmodern Lipstick Building completed in 1986.
The Citigroup Center is not only distinctive in how its angled top meets the sky, but also in the way the building meets the street. The tower of which the lowest floor is perched above the ground on four legs with shops, restaurants, performance spaces, and a church tucked underneath added a dramatic new corporate icon to New York City's storied skyline. The new building epitomized Citibank’s intention to create a visible statement announcing its corporate identity and its commitment to innovation, and the tower still remains a New York landmark and an important symbol for the successor owner, Citigroup.
Overall, the building’s distinction lies in its design and its innovative structure, illustrating how sophisticated structure, technical excellence, and perfection of detail could serve business interests and yet preserve and enhance the life of the city street. Furthermore, it lies in the wisdom of ethicists that the Citigroup Center exemplifies in professional ethical behavior.
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