Council on Tall Buildings and Urban Habitat
 

The John Hancock Center, Chicago
Posted March 2011
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The John Hancock Center is “gutsy, masculine, and industrial; reflecting the tradition of Chicago, where structure is of the essence.” – Bruce Graham, Skidmore, Owings and Merrill

Location
Chicago, USA
Completion
1969
Height
344 m (1128 ft)
Height to tip
457 m (1499 ft)
Stories
100
Area
260,126 sq m (1,214,530 sq ft)
Primary Use
Residential/Office

Owner/Developer

Jerry Wolman Associates
Architect
Skidmore Owings & Merrill
Structural Engineer

Skidmore Owings & Merrill
Contractor
Tishman Construction

Over forty years after completion, the John Hancock Center has established itself as one of the world’s most recognized skyscrapers and an iconic example of late 20th century Chicago design, construction and engineering. The building’s structural, programmatic and architectural innovations combine to create a design which has become a symbol of the city in which it exists.


Overview
Chicago 1969: the bustling city of over 3.3 million (nearly 700,000 larger than today’s city) celebrated the completion of the world’s second tallest building, the John Hancock Center. At 344 meters in height, the building also became the world’s second supertall (300 meter +) skyscraper to be completed (the first being New York’s 1931 Empire State Building). Historic not only in height, but also in the realms of tall building design, structural engineering, construction and architecture, the John Hancock Center is now one of the world’s most well-known tall buildings, and an integral piece of the Chicago skyline.


Planning

When builder/developer Jerry Wolman approached Chicago’s Skidmore, Owings and Merrill about the tower project, he had already obtained a site for the building. Located on Chicago’s Michigan Avenue, along the “Magnificent Mile,” the area was, in the 1960’s, primarily populated by upscale residences and boutiques. Wolman, however, believed the neighborhood could support a mixed-use tower containing commercial, office, and residential components. The SOM team, led by Bruce Graham and Fazlur Khan, proposed two potential tower schemes: a two-tower design consisting of separate office and residential buildings, and a single-tower, mixed-use option.

The single-tower scheme was advantageous in that it occupied a smaller portion of the site, allowing 60% of the block to be left open, and also encroached less upon the views of surrounding buildings. The site’s open area was designed as a simple urban plaza, something of an anomaly in Chicago’s dense downtown environment. Additionally, while the single-tower scheme’s significantly greater height would challenge designers, it would also allow the developer to advertise the project using the impressive slogan of “world’s highest residences.” Thus, the single-tower scheme was favored by both Wolman and the John Hancock Mutual Life Insurance Company, and was chosen to be developed and constructed.

As one of the world’s first mixed-use tall building projects, the John Hancock Center design was influential in its programmatic organization. The complex programmatic design placed commercial space on a sub-level concourse and the first five levels. This was followed by levels of parking, office, residential, and finally dining, observation, and broadcasting facilities.

Figure 1. The Center's facade
Structure
The most difficult task for the designers of the John Hancock Center was the development of an acceptable structural system. While conventional structural methods available at the time could have technically achieved the desired 100-story tower, the high costs and low space-efficiency of such systems at significant heights were highly undesirable. Structural engineer Fazlur Khan therefore chose to employ a non-conventional structural system which combined a diagonal bracing and exterior column system to create a “trussed” or “bundled tube” structure. This system had been successfully implemented by Khan in Chicago’s DeWitt-Chestnut Apartments, but needed to be further advanced and developed to accommodate the John Hancock Center’s 100-story structure. The bundled tube system developed proved to significantly reduce steel usage while simultaneously increasing floor plan efficiency. The diagonal truss organization is clearly expressed in the façade, creating the building’s distinctive structural “X’s” on all four elevations.
Due to soil conditions at the location of the Center and its proximity to Lake Michigan, caissons were sunk 190 ft into bedrock.  At the time, these were the deepest caissons employed in any building. At the height of construction, over 2,000 workers were involved in the project and its structure rose at a rate of three floors a day.

Architecture
The architecture of the Center is informed by its expressive structural system and gentle sloping façades. This innovative form was designed to efficiently accommodate the large number of programs contained in the building. The gentle inward slope creates optimally-sized floor plans for both the lower parking and office levels and the tower’s higher residential floors, with the first level consisting of 47,000 sq ft while the roof is only 17,000 sq ft. Additionally, the tapered form significantly reduces wind loads and therefore allowed for a reduction of structural members. For Chicago’s busy streetscape, the Center’s sloping façades increase the visual verticality of the building; adding perceived height to an already impressively tall tower.
Figure 2. The Center's tapered section and diminishing floor plans

The Center’s honest structural expression and simple tapering form, combined with its black aluminum cladding and extra-thick, glare-proof, bronze glass windowpanes create an architecture described by designer Bruce Graham as “Gutsy, masculine, and industrial; reflecting the tradition of Chicago, where structure is of the essence.”

Over forty years after completion, the John Hancock Center has established itself as one of the world’s most recognized skyscrapers and an iconic example of late 20th century Chicago design, construction and engineering. The building’s structural, programmatic and architectural innovations combine to create a design which has become a symbol of the city in which it exists.

Figure 3. Chicago Skyline

Related Links
CTBUH Skyscraper Center Profile:
Visit The John Hancock Center's profile

CTBUH Publications:
The John Hancock Center featured in 101 of the World's Tallest Buildings


CTBUH Technical Papers:
Reflections on the Hancock Concept

The CTBUH would like to thank Hancock Observatory for their assistance with this article. Images/drawings © John Hancock Center.