re: 57 story skyscraper built in 3 weeks - WYGII?

Tower cranes are Based on a tower crane concrete pad.... Typically 5+ feet in depth.....that sit in the center of the building foundation slab. Truck cranes are used up to about the 5th-8th floor.

A hydraulic lift is located at the base of the tower crane. Component vertical pieces are usually 8-10 feet tall. They assemble the crane up to the point where the truck mounted cranes become impractible to use. At that point, the boom is assembled and they start to use the tower crane.

As the building rises about a floor per 6-7 day cycle, the hydraulic system lifts the crane enough so as to fit another vertical segment at the base, thus, allowing it to increase in height with the building.

After the building is complete, the boom is disassembled at the top and the crane is brought down segment by segment using the hydraulic lift. It is lifted a few feet and the vertical segment is removed at the base. Keep doing that until it is gone.

They construct the building so as to leave room to remove the segments at the base.