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Histar® steel lightens Hearst Tower's external diagrid structure
The vertical extension of Hearst Headquarters' Art Deco building from the 1920ies is a 182 m high tower that set new standards for sustainable high-rise office buildings in New York. ArcelorMittal's high strength steel HISTAR® was used for the external diagrid structure and contributes to optimizing the weight and sizes of the steel shapes used.
Creative dialogue between New and Old
When the six-storey Headquarter building on Eighth Avenue was finished in 1928, Hearst already anticipated that the Art Deco block would eventually form the base for a landmark tower, though no scheme was ever advanced. The architectural approach for the design of the new tower was to establish a creative dialogue between old and new.
The modern 42-storey tower rises above the 1920ies Art Deco building, linked on the outside by a transparent skirt of glazing that floods the spaces below with natural light and encourages an impression of the tower floating weightlessly above the base.
The main spatial event is a lobby that occupies the entire floor plate and rises up through six floors. Like a bustling town square, this dramatic space provides access to all parts of the building. It incorporates the main elevator lobby, the Hearst cafeteria and auditorium and mezzanine levels for meetings and special functions.
Efficient use of steel: structural optimization
The Hearst Tower's load bearing structure consists of a steel core with a perimeter diagonal structural system (diagrid) forming four-storey triangular frames visible as as diagonal lines over all faces of the skyscraper.
With its corners peeled back between the diagonals it has the effect of emphasising the tower’s vertical proportions and creating a distinctive facetted silhouette.
ArcelorMittal supplied Histar® steel (ASTM A913 grade 65) in form of HD 400 shapes (per ASTM A6) which are used in the wind bracing and gravity load system. In fact, these inclined structural members function as bracing and column at the same time. The structural diagrid is extremely weight-efficient as it contains roughly 20% less steel than a conventional perimeter frame . In case of the Hearst Tower the saving was approximately 2,000 tons of steel. The use of high strength steel for the diagonal members contributed to further weight and material savings.
The total amount of steel used for the tower was 10,480 tonnes, 85% of which was produced from recycled material.
The external cladding of the tower's diagrid is made of profiled stainless steel, set within the diagrid is high-performance low emission glass that forms the floor to floor glazing . A unitised system with integral roll-down blinds ensures control of direct sun light.
Sustainability & LEED Gold
This modern high-rise building is also distinctive in environmental terms. Not only is it built using 85% of recycled steel, but it is also designed to consume 26% less energy than a building that minimally complies with the respective state and city energy codes. As a result, it is the first new occupied office building in the city to have been given a Gold rating under the US Green Buildings Council’s Leadership in Energy and Environmental Design (LEED) program.
International Highrise Award 2008
Norman Foster was awarded the International Highrise Award 2008 for his design of the Hearst Tower. According to the Jury, the project can be seen as “a new standard for office buildings in the high-rise metropolis", and in their statement they explain their decision as follows: "the transparent high-rise building, which is set on an historic plinth, is attractive because of its impressive form. Its load-bearing triangular steel structure creates floors of various sizes and could be a new prototype.”
- New York
Foster and Partners
- Engineering Firm:
Cantor Seinuk Group (structure)
Turner Construction (Construction Manager)
Chuck Choi and Nigel Young for Foster and Partners