Standing as the 12th highest skyscraper in the world, at 1127 feet at the top and at 1476 feet at the tip of its antenna, the John Hancock Center in Chicago Illinois, is still one of the world's most admired buildings both visually and architecturally. .
The John Hancock tower, known to Chicago locals as "Big John", is a multi-use building. The bottom floors are used for commercial storage and parking space, followed by 32 floors of office space, 50 floors of apartments consisting of 711 individual units, and finally topped off by television transmission spaces. The total usable area of the building is 2.8 million square feet. The interior of the tower also inhabits 50 elevators. Total weight of "Big John" comes to a staggering 384 million pounds. But if it weren't for the ingenious design of the engineers responsible for the 100 story building, it would have weighed more than twice as much. .
Chief Structural Engineer, Fazlus R. Kahn (who also designed the Sears Tower in Chicago Ill.) teamed with architects Skidmore, Owings & Merril, to complete the building in 1970 at a mere 95 million dollar price tag, the equivalent of a 45 story building at the time. Because the building was to be used for so many different things, a different design had to be used that would free up the interior from internal columns that would traditionally take up office space. This was made possible by the new "steel-braced-tube" system used in the building. The system consisted of the outside of the building carrying all of the lateral forces and some dead load, while the interior was able to focus on pure dead load. The design allows for a more flexible system in terms of how much steel was used. This made it possible to use 50 percent less structural steel that would have been required had they chosen to use interior columns. .
Because the design of the building was to be tapered from the bottom to the very top (168'-10" X 262'-2" at floor level and 99'-9" X 159'-6" at the top), a different approach had to be used aside from traditional methods.
