Citigroup Center

The Citigroup Center is a Modern Style skyscraper designed between 1973 and 1975 by Huge Stubbins, with as lead architect, in association with Emery Roth & Sons, and built between 1975 and 1976, for a reported $195 million dollars, in New York, NY.

Its precise street address is 601 Lexington Avenue, New York, NY. You can also find it on the map here.

The Citigroup Center is a structure of significant importance both for the city of New York and the United States as a nation. The building embodies the distinctive characteristic features of the time in which it was built and the Modern style. Because of that, the Citigroup Center was officially declared as a national landmark on December 6^th 2016.

The Evangelical Church that occupied the plot refused to give it up, however, they did allow for a building to be built above the existing church. This, as we will later see, was the reason why the structural system of the CitiGroup Center is sub-optimal, and did not come without severe complications.

The building has been restored 3 times over the years to ensure its conservation and adaptation to the pass of time. The main restoration works happened in 1978, 2010 and 2014.

Huge Stubbins, with as the lead architect, was the architecture firm in charge of the architectural design, in association with Emery Roth & Sons. But there was also one other architect involved, as far as we know. We are talking about Sigmar Truth.

That being said, architecture is a complex discipline involving many professionals from different fields, without whom this building would have not been possible. We will surely be leaving out a lot of names here, but here is a list of the people we do know also played their part in making the Citigroup Center a reality:

• Le Messurier Consultants in charge of Structural Engineering
• HRH Construction Corporation as the Main Contractor
• Otis Elevator Company as the company in charge of the elevators system
• First National City Bank as the Main Developer

The Citigroup Center can be categorized as a Modern Style building.

By their own nature, the Modern and International Styles can still look current, even in contemporary buildings. So that's not to say the Citigroup Center appeared old or outdated when it was completed, but Huge Stubbins certainly did not take many risks when it came to choosing the design style. This made the building look more "classic" and integrated within the city's architecture.

The Citigroup Center uses a trussed-frame structure made of steel columns and concrete and steel slabs.

A trussed-frame structure uses a combination of beams and columns to sustain the building's weight, and diagonal elements to provide stability against horizontal forces such as wind or seismic activity by triangulating the structure. The walls in this case are non-load bearing, which allows for more flexibility when distributing the interior spaces.

The facade uses a non-load bearing curtain wall system. This means the curtain wall modules are anchored to the building's structural frame, typically by being attached to the edge of the floor slabs. The curtain wall system connects to the slabs using brackets, anchors, and mullions, which transfer the loads imposed by wind and temperature changes, to the building's primary structural elements.

This setup allows the curtain wall to accommodate differential movement between the facade and the structural frame, such as thermal expansion, floor deflection, or sway from wind forces. This system's integration with the slab edges also allows for continuous insulation and weatherproofing layers.

Behind the smooth facade, there are six levels of V-shaped trussed steel structure that transfer the loads tot he four "super" columns and the center color, which also serves to enclose the stairs, elevators and mechanical ducts

From an aesthetic point of view, the facade features a double-glazed curtain wall alternating panels of blind bright, white anodized aluminum panels with translucent glass in horizontal bands, creating a very clean and rhythmic facade composition.

The building is crowned by a 45º degrees tilted roof which clearly stands out in the busy skyline of NYC.