The Sears Tower in Chicago was the world's tallest building when it was built in 1973. Today it is the tallest building in North America.Historically Named: Sears Tower
Current Name: Willis Tower
Location: Chicago, Illinois, USA
Architect: Bruce Graham, Skidmore, Owings and Merrill (SOM)
Year: 1973
Height: 442 meters / 1,450 feet
Stories: 110
About the Sears Tower
To provide stability against high winds, architect Bruce Graham used a new form of tubular construction for Sears Tower. Two hundred sets of bundled tubes were laid into the bedrock. Then, 76,000 tons of prefabricated steel in 15-foot by 25-foot sections were put into place. Four derrick cranes moved higher with each floor to lift these steel "Christmas Trees" into position.
Facts about the Sears Tower:
The roof rises 1/4 of a mile - 1,454 feet (442 meters).
Its highest occupied floor is 1,431 feet above the ground.
The foundation and the floor slabs have some 2,000,000 cubic feet of concrete - enough to build an eight-lane highway 5 miles long.
The Tower has more than 16,000 bronze-tinted windows and 28 acres of black duranodic aluminum skin.
The 222,500-ton building is supported by 114 rock caissons socketed into the bedrock.
A 106-cab elevator system (including 16 double decker elevators) divides the Tower into three separate zones with skylobbies in between.
Two domed entrances, one with skylights, were added in 1984 and 1985.
The Ledge was added 2009.
As part of a rental deal, Willis Group Holdings, Ltd. renamed the Sears Tower in 2009.
Architect Bruce Graham talks about Sears Tower:
"The stepback geometry of the 110-story tower was developed in response to the interior space requirements of Sears, Roebuck and Company. The configuration incorporates the unusually large office floors necessary to Sears' operation along with a variety of smaller floors. The building plan consists of nine 75 x 75 foot column-free squares at the base. Floor sizes are then reduced by eliminating 75 x 75 foot increments at varying levels as the tower rises. A system of double-deck express elevators provides effective vertical transportation, carrying passengers to either of two skylobbies where transfer to single local elevators serving individual floors occurs."
-from Bruce Graham, SOM, by Stanley Tigerman.