Vertical Slip Formwork

The slip forming technique was in use by the early 20th century for building silos and grain elevators. James MacDonald, of MacDonald Engineering of Chicago was the pioneer in utilising slip form concrete for construction. His concept of placing circular bins in clusters was patented, with photographs and illustrations, contained in a 1907 book, "The Design of Walls, Bins, and Grain Elevators". In 1910, MacDonald published a paper "Moving Forms for Reinforced Concrete Storage Bins," describing the use of moulds for moving forms, using jacks and concrete to form a continuous structure without joints or seams. This paper details the concept and procedure for creating slip form concrete structures. On May 24, 1917, a patent was issued to James MacDonald of Chicago, "for a device to move and elevate a concrete form in a vertical plane". Honolulu, Hawaii, in 1969. Another shear wall supported structure was the Casa Del Mar Condominium on Key Biscayne, Miami, FL in 1970.From the 1950s, the vertical technique was adapted to mining head frames, ventilation structures, below grade shaft lining, theme and communication tower construction; high rise office building cores; shear wall supported apartment buildings; tapered stacks and hydro intake structures, etc. It is used for structures which would otherwise not be possible, such as the separate legs of the Troll A deep sea oil drilling platform which stands on the sea floor in water about 1000 feet (300 m) deep, has an overall height of 472 meters (1,549 ft), weighs 656,000 tons, and has the distinction of being the tallest structure ever moved (towed) by mankind. In addition to the typical silos and shear walls and cores in buildings, the system is used for lining underground shafts and surge tanks in hydroelectric generating facilities.