Plate foundations, part 1

Plate foundations

Buildings with a frame or longwall structure are placed on slab foundations in the following cases:
a) there is low load-bearing soil under the foundation,
b) the total surface of the benches - unidirectional or longitudinal and transverse (grates) - or the footing takes over 60% the projection area of ​​the building and their construction is much more difficult than the foundation slab,

c) the foundation is placed below the water table, and in the underground part of the building there are utility rooms, who are made demands, keep them dry.

tmp724b-1Plate foundation: a) throw, b) cross-section, c) reinforcement detail; 1 - foundation plate, 2 - ceiling slab, 3 - wall, 4 - poles, 5 - ground floor wall, 6 - upper and lower reinforcement mesh, 7 - wall reinforcement, 8 - column reinforcement, 9 - Lean concrete, 10 - insulation.

A foundation with a constant slab thickness is usually used for smaller spacings of load-bearing walls or columns. Large bending moments occur in the slab at larger distances, which entails the need to increase its height. To avoid an increase in the height of the slab and its mass, ribs protruding above the slab or downwards can be used.

tmpc50a-1Plate-rib foundation: a) general view of the plate-rib foundation, b), c) - construction details of the slab, d) plate with holes; 1 - upper reinforcement mesh, 2 - bottom reinforcement mesh, 3 - column reinforcement, 4 - rib reinforcement.

Foundation slabs with channels can also be used. Channels (Lynx. d) can be obtained by concreting asbestos or plastic pipes in the slab. These holes reduce the weight of the plate, and, moreover, they can be used to route installation cables.

The ribs protruding upwards from the baseplate obstruct communication for pedestrians and vehicles (trolleys), therefore, the spaces between the ribs are filled with sand or gravel, and a floor is laid on top.

A slab foundation with downwardly projecting beams is used in the case of, when the ground is cohesive, the sides of the beams do not require formwork, especially when the walls of the excavation are properly sloped. Most often, however, the substrate and the sides of the lean concrete beams are concreted first, and then the reinforcement and construction concrete are laid.