Lift-Slab Method

the construction of multistory buildings by lifting each floor slab to a height specified by the design. The reinforced-concrete slabs are made at ground level and lifted by a set of hoists. Walls, partitions, and plumbing or other technical equipment are mounted on the slab either before or after lifting, depending on the degree of completion of the associated structures.

Since 1950 the lift-slab method has been widely used in the United States, the People’s Republic of Bulgaria, the Czechoslovak Socialist Republic, the Federal Republic of Germany, and other countries for the erection of various types of buildings with as many as 21 stories. In the USSR this method has been used since 1959 for the erection of multistory buildings up to 15 stories high (for example, apartment houses in the Armenian SSR and public buildings in Leningrad and Moscow).

In the USSR the lift-slab method involves the fabrication of a set of girderless, reinforced-concrete slabs at the construction site. The number of slabs is determined by the number of floors in the building. Steel collars are inserted in each slab; their shape corresponds to the contour of the columns. The collar is used to grip the slab during lifting, which is done by electrical-mechanical hoists or, less frequently, hydraulic hoists. The hoists are mounted on the columns or attached by clasps.

The lift-slab method makes possible the construction of multistory industrial and public buildings with continuous floor slabs having an area up to 3,000 sq m and a weight of as much as 1,500 tons. The distance between columns may be 6 m or more. For spans exceeding 8 m, hollow or coffered slabs of either standard or prestressed reinforced concrete are used.

The lift-slab method is particularly effective in the construction of multistory buildings with operational, architectural, or structural requirements that preclude the use of sectionalized floor slabs prefabricated in large numbers in a factory. The lift-slab method is successfully used in seismic regions, at construction sites with limited space, and in regions where highly developed industrial construction materials and facilities are not readily available.