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James Kovata
September 9th, 2004, 09:43 AM
I may like skyscrapers, but I know little about their construction and have the following questions: When a tower crane is positioned inside of a building that is under construction and remains there until a building is topped out, how is it removed, and what becomes of all of the openings in the floor plates through which the tower crane extended? Do they become an elevator shaft? :?:

ZippyTheChimp
September 10th, 2004, 09:04 AM
Until someone with experience visits the forum basement and responds to this post, I'll try my best.

The crane body breaks apart into sections. I've seen them being delivered to construction sites on several flatbed trailers. I suppose with multiple cranes as is the case with 7 WTC, one crane would lower the others, then a more portable derrick crane would be rigged to lower the last tower crane.

As for the shaftway left behind with interior tower cranes: each building situation is different. It would be logical to place the crane in an elevator or some other service shaftway.

If you look closely at the south side of 7 WTC, they took a different approach. The tower extends down about 10 storeys from the crane. Below that, the floorplates are completed. There are also temporary diagonal braces on the "box" where the tower rises, which are removed after concrete is poured.

The cranes are raised using jack sections. They are usually directly under the crane, as is the case in the outer crane at 7 WTC, but the interior crane has the jack section on the bottom because the entire assembly has to be lifted.

NoyokA
September 10th, 2004, 04:36 PM
The Kangaroo cranes employed at the original WTC were dismanteled and taken down piece by piece through the internal elevator.

James Kovata
September 11th, 2004, 12:08 AM
Thanks for the info, Zippy!