Monolithic reinforced concrete buildings – Framework systems part 3
Column-plate structure: a) view, b) division of the disc into strands, c): top reinforcement mesh of the slab, d) bottom reinforcement mesh of the slab.
In recent years, slab and cassette ceilings have been widely used in the construction industry. Slab ceilings are heavy; this should be taken into account when designing multi-storey buildings, when using larger column meshes and when the building is founded on weak ground. Due to the consumption of concrete, Slab ceilings can be considered uneconomical, however, due to the simplicity of implementation, they have found wide application.
Too economical at variable load p ≤ 5,00 kN / m2, a slab thickness of approx. 20-25 cm, designed on a grid of posts 6,00 x 6,00 do 7,20 x 7,20 m. In the case when higher loads p > 5,00 kN/m2, e.g.. in warehouses, it is better to use mushroom ceilings (Lynx. a) or with head plates (Lynx. c).
Column-plate structure (head ceiling): a) view, b) cross-section through the head, c) cross section through the head plate.
Formwork consisting of inventory elements produced by various companies is used to make slab ceilings. The stands are mostly metal telescopic, while the bars with a full cross-section or lattice made of glued laminated timber, and the mold plates (sheet metal) from plywood.
Ceilings with head plates are easier to manufacture than mushroom ceilings and are most often made in warehouse buildings, garages etc.. Dimensions in the plan of square or rectangular head plates (Lynx. c) is assumed to be equal 0,33/ (l - slab span), while the thickness of the head plate, including the ceiling slab, is determined from the strength conditions, however, it should not be greater than 1.5 times the board thickness. The head plates may also be circular in shape, if the columns are circular or polygonal.
Execution of slab ceilings, yes with constant thickness, as well as with the head plate is simple. The plates are usually reinforced with meshes made of ordinary steel.
The plate band is divided into head and inter-head bands. In the head strips, the reinforcement is placed at the bottom of the slab, while in the head bands and over the supports - at the top.
In plates with a thickness greater than 18 cm, installation cables with a diameter of up to 10 cm (e.g.. for air conditioning devices).
