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case study and information compilation of John Hancock Centre, Chicago, Illinois.
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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.