This weekend's tragic crane collapse in New York stirred up my fascination with tall construction site cranes called tower cranes. One day there is no crane, the next day it is there, and another day it is gone. I never seem to get the chance to witness the construction of a crane. How do they erect and dismantle these giant structures so quickly? I did some research and here is what I found.
The construction company pours a huge concrete slab and the crane’s base is bolted to it.
On top of the base is the “mast” (the steel tower). On top of the mast is the “slewing unit”—the gears and motor that rotate the crane. On top of the slewing unit are the operator’s cab; the “jib” (the horizontal arm that does the work); the machinery arm that contains the electronics and motors that lift the loads; and concrete counterweights.
To assemble the tower crane a mobile crane is used to erect two six metre sections of the mast and a section called a climbing frame. These rise from the base. On top of this latticed tower structure, the mobile crane places the slewing unit, the jib, machinery arm, and the counterweights.
The tower crane is on its own now. It reaches high into the sky by itself, one mast section at a time. To accomplish this, hydraulic rams (insanely strong jacks) lift up the climbing frame and everything on top. A six metre space is opened up for the crane to insert another section of mast, which is then bolted into place. This goes on and on until the tall building is finished. The crane then dismantles itself, one section at a time.
On top of the base is the “mast” (the steel tower). On top of the mast is the “slewing unit”—the gears and motor that rotate the crane. On top of the slewing unit are the operator’s cab; the “jib” (the horizontal arm that does the work); the machinery arm that contains the electronics and motors that lift the loads; and concrete counterweights.
To assemble the tower crane a mobile crane is used to erect two six metre sections of the mast and a section called a climbing frame. These rise from the base. On top of this latticed tower structure, the mobile crane places the slewing unit, the jib, machinery arm, and the counterweights.
The tower crane is on its own now. It reaches high into the sky by itself, one mast section at a time. To accomplish this, hydraulic rams (insanely strong jacks) lift up the climbing frame and everything on top. A six metre space is opened up for the crane to insert another section of mast, which is then bolted into place. This goes on and on until the tall building is finished. The crane then dismantles itself, one section at a time.
source: http://www.yesmag.ca/Questions/crane.html
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