Sears Tower

There was much discussion on whether the Petronas towers are actually taller than the Sears tower as the height of the antennas on the Petronas towers are included in the total height, while the height of the antennas are not included in the height calculation of the Sears tower as they are not considered an actual part of the building. With the construction of the 508m high Taipei 101 tower in 2004 this discussion became irrelevant.

Anyhow, the Sears tower is still the tallest Chicago skyscraper, exceeding the height of the number 2, the Aon Center by 93 meter and the John Hancock Center by 95 meter.

The building consists of nine framed tubes, which are actually nine skyscrapers on themselves taken together into one building. Originally, the plan included no less than 15 tubes, but when the planned hotel was taken out of the project, only nine tubes were used in the final designs. The nine tubes all reach forty-nine stories. At that point, two tubes end. The other rise up to the sixty-fifth floor. From the sixty-sixth to the ninetieth floor, the tower has the shape of a crucifix. Two tubes, creating a rectangular, reach the full height of 443 meter (1457ft).

The result is an interesting tower, which looks different from all angles. The construction, designed by Fazlur Kahn (1929-82), has other advantages : the construction with separate tubes provides lateral strengths to withstand the strong Chicago wind loads, as each tube only needs to take a part of the pressure.