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Skyscrapers start with a very large hole in the ground which will contain the foundations, several floors, and possibly even a metro or subway station. 1 _______. Usually they are made by drilling narrow, deep holes and filling them with reinforced concrete to form piles. 2 _______. A thick raft of concrete is laid on top of the piles.
Vertical steel columns are bolted to the foundations. 3 _______. Steel girders are fixed horizontally from column to column by Steel Erectors to form a strong framework. Metal decking is laid across the girders and filled with lightweight liquid concrete which is pumped up from the ground. When it sets, it forms the floors.
Ducts are installed below the floors to carry all services: electricity, water, drains. 4 _______. If a fire happens, it is important that the structure can withstand high temperatures without buckling.
The same process is repeated as the building rises. In some construction methods, entire floors are built at ground level and hoisted into position by cranes.
The outside of the building is covered in cladding. This consists of prefabricated panels of materials such as stainless steel, aluminium, and glass.
The type of foundations depends on the nature of the ground.
Another method is to drive steel piles, as much as twenty metres in length, into the ground.
Each column rests on a platform of steel to spread the load.
All exposed metalwork is fireproofed.