History of the Building
Financed by the John Hancock Mutual Life Insurance Company, the building was originally conceived to be the world's second tallest building. Construction of the tower was interrupted in 1967 due to a flaw that was discovered in an innovative engineering method used to pour concrete in stages. The engineers were getting the same soil settlements after the first 20 stories had been built as they expected for the entire 99 stories. This forced the owner to stop development until the engineering problem could be resolved, and resulted in a credit crunch. The owner went bankrupt, which resulted in John Hancock taking over the project, which retained the original design, architect, engineer, and main contractor.
The building was completed in 1969. Its first resident was Ray Heckla, the original building engineer, responsible for the residential floors from 44 to 92.
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).
The observatory is a member of the World Federation of Great Towers. It has won various awards for its distinctive style, including the Distinguished Architects Twenty-five Year Award from the American Institute of Architects in May 1999.
Design & construction highlights
- 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.
- 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.
- 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.
- Enough steel to make 33,000 cars was used to make the frame, which took three years to complete and weighs 46,000 tons.
- Its four corner columns weigh up to 100 tons each.
- The building's 1,250 miles of wiring carries enough power to supply a city of 30,000 people
- There's enough aluminum in the building to cover 12 football fields.
- Its 11,459 extra-thick, bronze windows contain enough glass to produce a single, 5 ft sheet 13 miles long.
- Because of the John Hancock Center's lakeside location, caissons had to be sunk into 10 ft wide holes drilled 190 ft into bedrock.
- 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.
- Prefabrication of the immense corner joints meant construction proceeded at a rapid pace - up to three floors a week.