Crossing is the horizontal part of the structure of almost any structure, is the carrier, and therefore it accounts for a very large load, especially when comparing the inter -story and attic types of overlap.
As the main elements from which the ceilings are collected, most often heavy, usually reinforced concrete, floor slabs are used. Sometimes tightly laid beams are used for these purposes, but this method is not typical, the main material is the slabs.
Since the cost of ceiling structures usually is about 15-20% of the total cost of the structure, it is extremely important to choose the right plates, correctly calculate the design for maximum use of standard models, and also order a supply from a reliable manufacturer.
The main material of the manufacture of floor slabs is reinforced concrete, less often – concrete. Concrete is used either light or ordinary heavy brand at least 200. Often you can see plates in which a round section cavities are located along their entire length: this approach is used to maximally reduce its own weight of the plate without any significant loss of its strength-in hollow slabs a special knitting of the reinforcement is used. In ribbed reinforced concrete floor slabs, the additional strength of the structure is achieved due to 1.5 m of stiffness located at a distance of 1.5 m.
The standard sizes of the floor slabs can have different values within 0.6-2.4 m in width and from 2.4 to 6.6 m along the length. In special cases, according to a special order, 12-meter plates can also be made for the implementation of large off-line spans.
Due to the increased loads that the floor slab should withstand, its bearing in nature, as well as the use of residential, household and industrial facilities in the construction, the standards of the production of floor slabs provide their following most important characteristics:
a) strength;
b) stiffness – a separate category, not to be confused with strength. Rigidity is determined by resistance to deformations, bending under the influence of loads. You can judge the degree of estimated hardness by permissible values: for inter -story floors, this is only 1/250 span, for attic – 1/200;
c) refractory;
d) thermal protection;
e) small acoustic permeability (soundproofing);
e) industriality of all their elements;
g) efficiency in production is characterized by the maximum permissible decrease in the thickness and weight of the plate without lowering its strength characteristics and rigidity.
Depending on the features of a particular project, the floor slabs are installed both by the transverse and longitudinal way.