JOHN HANCOCK CENTER

Overview:

ARCHITECT/ENGN.: BRUCE

GRAHAM/ FAZLUR KHAN/SOM

LOCATION: CHICAGO, ILLINOIS

DATE: 1970

BUILDING TYPE: COMMERCIAL

OFFICE TOWER, SKYSCRAPER

CONSTRUCTION SYSTEM: STEEL

FRAME

CLIMATE: TEMPERATE

CONTEXT: URBAN

STYLE: MODERN

The Construction of Big John:

• At the peak of construction, more than

2,000 people worked on the project;

• Some five million man-hours were

required to complete the development.

• The unusual design required innovative

construction methods, including the use

of "creeper cranes," previously used only

in bridge construction, to hoist steel

beams into place.

• Enough steel to make 33,000 cars was used to make the frame, which took three years to

complete and weighs 46,000 tons.

There's enough aluminum in the building to cover 12 football fields.

Its four corner columns weigh up to 100

tons each.

• The tower is situated on North Michigan

Avenue in a prestigious district with

expensive apartments, shops, offices, hotels, restaurants, and art galleries.

The building’s design allows only five to eight

inches of sway in a 60 mph wind; it’s been tested

to withstand winds of 132 miles-per-hour.

John Hancock Center is characterized by the

distinctive X-shaped external bracing that made it an

architectural icon.

• This bracing also eliminated the need for inner support columns, greatly increasing amount

of

available floor space.

Functions:

• The wish to continue this mixture initially gave rise to the idea of building a 70-story

apartment tower and a 45-story office tower. But the two towers would have occupied

most of the site and would have impaired each other's privacy and daylight conditions.

Moreover, the lower-level apartments would have suffered from noise nuisance from the

street. It was therefore decided to construct a single

tower where the offices would be on the lower floors

and the apartments on the higher levels.

• The tower's tapered shape was chosen in order to match

the different floor space requirements that decrease

from bottom to top from the entrance and commercial

zones at the base to the clusters of small apartments at

medium height and finally to the large apartments on top,

where relatively less space is

needed for ancillary rooms

with artificial lighting.

• Structurally, the exterior

members of the steel frame

represent a tube where the

necessary stiffness is

provided by diagonal members and by those

structural floors that coincide with the intersections of the

diagonals and the corner columns. In keeping with the

functional organization, this tubular body has its largest

cross-section where the stresses caused by wind

forces are greatest. Steel consumption, amounting to about 30-pounds-per-square-foot of

floor space, was no greater than for a 50-story conventional tower.Including its two

antennas, the John Hancock Center has a height of 1,500 feet (457.2 m), making it the

fourth highest building in Chicago and the thirty- third tallest building in the world when

measured to pinnacle height. The Observatory elevators of the John Hancock Center,

manufactured by Otis, travel 96 floors at a top speed of 1,800 ft/min (20.5 mph). It is a

mixed used building consisting of offices, restaurants and residential apartments.

• The office lobby was originally a high-ceilinged space on the second floor accessed by

escalators. It was shifted to ground level in the 1990s, and the old space was converted to

retail.

• The base of the building has dimensions of 80.77 by 50.29 meters (north-south by east-

west). The building narrows towards the top at 32 by 19.8 meters.

• Because of space constraints caused by the tower's tapering walls, common hallways and

elevator lobbies are narrower on higher floors.

Primary Usage:

1. commercial office

2. residential

condominium

Secondary Usage:

1. parking

2. restaurant

3. shops

• The slope of the windows

helps to reduce the feeling

of vertigo for people

looking out of high floors.

• The building tapers on all

four sides, narrowing by a

total of 105 feet on the east

& west sides and 65 feet on

the north & south.

• The base facade was

originally clad in white

travertine, but this was later replaced with a much darker granite. The black anodised

aluminium facade starts at the second floor.

• As an alternative to balconies, about one-third of the residential units have "sky terraces" -

a sort of tiled sunroom separated from living spaces by glass doors.

•  John Hancock Observatory allows a 360° view of the city, up to four states and over 80

miles. The Observatory has Chicago's only open-air Skywalk .The Observatory offers

what is claimed as the world's highest ice skating rink, using a synthetic surface that

enables the use of standard ice skates at normal room temperature.

The semicircular sunken plaza on the

west side is a public oasis with seasonal

plantings and a 12-foot waterfall.

Structural system visible in the interior

lobby with travertine and textured

limestone surfaces. 

America's highest indoor swimming pool is located

on the 44th floor near the sky lobby.

Structure:

Structure in general-

Structural system: trussed tube

Structural material: steel

Facade material: aluminum

Facade system: curtain wall

Facade color: black

Architectural style: structural expressionism

Roof System: flat roof with 1 box

• Construction of the tower was halted in 1967due

to a foundation engineering and soil mechanics

miscalculation. The engineers were getting the

same soil settlements for the 20 stories that had

been built as what they had expected for

the entire 99 stories. First trussed tube skyscraper

ever built.

• Building - structural expressionist   style .

Structural Expressionist architecture is a pure

expression of structure.

“Structural Expressionist” that was invented for

buildings that reveals their structure to the outside is

reflected appropriately in a building.

Prevalent in bridges and train stations of the past,

iron is the preferred material. 

High Tech Modern is the contemporary equivalent.

Proceeded By: Victorian

Succeeded By: Modern – Structural

• The John Hancock Center is actually a super-tall steel tube.

• Steel columns and beams are concentrated in the skyscraper's perimeter, and five

enormous diagonal braces on the exterior walls of the skyscraper give it extra strength in

the wind.

Tube (Structure):

• In structural engineering, the tube is the system where in order to resist lateral loads

(wind, seismic, etc.) a building is designed to act like a hollow

cylinder, cantilevered perpendicular to the ground. This system was introduced by Fazlur

Rahman Khan while at Skidmore, Owings and Merrill’s (SOM) Chicago office. The first

example of the tube’s use is the 43-story Khan-designed DeWitt- Chestnut Apartments

Building in Chicago, Illinois completed in 1963.

• T

h

e

system can be constructed using steel, concrete., or composite construction (the discrete

use of both steel and concrete). It can be used for office, apartment and mixed-use

buildings. Most buildings in excess of 40 stories constructed since the 1960s are of this

structural type.

The tube system concept is based on

the idea that a building can be designed to resist lateral loads by designing it as a

hollow cantilever perpendicular to the ground. In the simplest incarnation of the tube, the

perimeter of the exterior consists of closely spaced columns that are tied together with

deep spandrel beams through moment connections. This assembly of columns and beams

forms a rigid frame that amounts to a dense and strong structural wall along the exterior of

the building.

This exterior framing is designed sufficiently strong to resist all lateral loads on the

building, thereby allowing the interior of the building to be simply framed for gravity

loads. Interior columns are comparatively few and located at the core. The distance

between the exterior and the core frames is spanned with beams or trusses and

intentionally left column-free. This maximizes the effectiveness of the perimeter tube by

transferring some of the gravity loads within the structure to it and increases its ability to

resist overturning due to lateral loads.

Structure:

• The structure consists of a TUBULAR SYSTEM that

strengthens the building against wind and earthquakes.

• It is a three dimensional space structure composed of three,

four, or possibly more frames, braced frames, or shear walls,

joined at edges to form a vertical tube-like structural system

resisting lateral forces in any direction by cantilevering from

the foundation.

• Closely spaced interconnected exterior columns form the

tube. Horizontal loads (primarily wind) are supported by the

structure as a whole. About half the exterior surface is

available for windows. Framed tubes allow fewer interior

columns, and so create more usable floor space. Where

larger openings are required, the tube frame must be

interrupted, with transfer girders used to maintain structural

integrity.

• The cross-bracing on the exterior provides security against

horizontal movement while opening up the interior of the

building with more uninterrupted floor space.

X-BRACING

• Distinctive X-bracing exterior- actually a hint that the structure's skin is indeed part of its

tubular system.

• The five X's on each side go from floors 2-20, 21-37, 38-55, 56-74, and 75-91. A half-X

extends from 92 to 97.

• In order to fit the structural frame, the floors at the top of each X have extra-high ceiling.

• This X-bracing allows for both

higher performance from tall

structures and the ability to open

up the inside floor plan.

• This is one of the architectural

techniques which the architects

used to achieve a record height

(the tubular system is the structure

that keeps the building upright

during wind and earthquake loads).

• The diagonals, spandrels and

columns are clearly articulated to

depict the primary elements of this

tube. Less than thirty pounds of

steel per square foot of floor area

were used in the building, equaling

that of a forty- to fifty-story

traditional tower

• In order to achieve the height,

tower needed caissons to prevent it

from sinking into the soft ground.

• Such original features have made the John Hancock Centre an architectural icon.

• Although the X-bracing is massive and slightly blocks views from the interior, it is the

Hancock Building’s signature exterior feature and is structurally sound.

• The tapered form provides structural as well as space efficiency. The exterior columns and

spandrel beams, together with the diagonal members and structural floors, create the steel

tube.

Salient Features:

• The John Hancock Center, the world's first mixed-use

tower, is an architectural icon representing the close

collaboration between architect Bruce Graham and

structural engineer Fazlur Khan.

• Known locally as "Big John," the tower is situated on

North Michigan Avenue in a prestigious district with

expensive apartments, shops, offices, hotels,

restaurants, and art galleries.

• Moreover, the lower-level apartments would have suffered from noise nuisance from the

street. It was therefore decided to construct a single tower where the offices would be on

the lower floors and the apartments on the higher levels.

• The tower's tapered shape was chosen in order to match the different floor space

requirements that decrease from bottom to top — from the entrance and commercial zones

at the base to the clusters of small apartments at medium height and finally to the large

apartments on top, where relatively less space is needed for ancillary rooms with artificial

lighting.

• Structurally, the exterior members of the steel frame represent a tube where the necessary

stiffness is provided by diagonal members and by those structural floors that coincide with

the intersections of the diagonals and the corner columns. In keeping with the functional

organization, this tubular body has its largest cross-section where the stresses caused by

wind forces are greatest.