Table of Contents
At the heart of any floor and ceiling the hollow floor slab which plays role of the horizontal support directly affecting stability of construction lies. Any panel or frame building did not do without these plates which have executed all interfloor overlappings. Generally material is made of concrete of a different type. Characteristic – availability of longitudinal emptiness, and the main advantages – lightweight and long life cycle.
Main types and sizes of hollow floor slabs
Hollow reinforced concrete slabs of overlapping are everywhere used at construction of combined type of buildings. Depending on features of production of product are divided into round hollow and formless plates.
Width of hollow floor slab has several values:
- 1 m;
- 1.2 m;
- 1.5 m;
- 1.8 m.
Thickness of hollow floor slab generally invariable is also 22 cm though it is possible to meet also options 16 or 30 cm thick. Length can change depending on way of production that does not affect reliability of construction material in any way. Generally indicators of lengths are in range from 1.7 to 9 m.
In separate group it is possible to allocate the facilitated interfloor plates. The main difference from standard plates – height which equals not 22, but 16 cm.
Main types of markings: what data can be learned from the name
Standard marking of plates of overlappings, irrespective of version, has such values:
- letters designate type of product and construction feature;
- digits note length and width, height is considered rather constant value and in marking is not used;
- bearing capacity where unit of value corresponds to the maintained loading of 100 kg/m ²;
- the class of the used armature usually is specified right at the end.
Sometimes in marking also additional values, such as resistance to hostile environment, seismic influence, temperature drops meet. It is also possible to find the value indicating amount of emptiness in panels. On example it is possible to consider interpretation of marking of hollow product personal computer 23.15-8:
- The abbreviation of the personal computer means that overlapping is made by filling method in ready timbering, and the plate has round cavities.
- 23 – designates length in decimeters which is most often rounded up.
- 15 – the rounded width of plate of 14.9 dm.
- 8 – the value indicating bearing capacity of the hollow block which corresponds to indicator of 800 kg/m ².
Also designation of overlapping of PB 72.15-12.5 is similarly deciphered:
- The PB – these letters is marked the product executed by means of formless way. The abbreviation also means that it is plate with cylindricity cavities.
- 72 – the rounded value of length of 71.8 dm.
- 15 – width parameter.
- 12.5 – the coefficient designating bearing capacity of product which corresponds to value of 1250 kg/m ².
What is represented and as hollow plates are made
In production of hollow floor slabs of round hollow type timberings which limit plate on special contour are used. For this reason length of ready overlappings varies from 1.8 to 7.2 m, the size changes with step of 30 cm.
Process of production looks as follows:
- Solution from concrete is filled in in stationary metal formwork with the recorded armature and the metal gauze.
- The concrete mix is well rammed then ready plates give in to processing in hydrothermal boxes.
- After full hardening the ready panel is removed from timbering for in advance built in eyes.
Formless plates make without use of timbering at continuous casting of concrete. The final form to product is given by the forming machine therefore the long plate which already then is cut on the necessary sizes turns out, at the same time accuracy can reach several centimeters. The maximum length of floor slabs in this case reaches 9 m, height remains invariable and is 22 cm. The main advantage of formless plates is that at scrap the edge can give any form which corresponds to architectural idea of the building.
Most often on sale the plates executed by the shuttering principle because for their creation it is not required to use additional equipment meet. This type of plates is made practically at all plants which are engaged in production of precast concrete.
For convenience of transportation and construction all products are equipped with mounting loops. To give to plates big reliability, reinforcing is in addition carried out them. As armature the rope from wire or another high-strength material is used. Use of fittings increases the margin of safety of products and allows plates to resist to the raised loadings in use.
For production W4 brand concrete having strength index of A22.5 is used, and the bearing durability of overlappings is in limits of 2000-2400 kg/m3.
Most often such types of concrete are applied to production of panels:
In general multihollow floor slabs consist of such materials:
- Concrete. Products are made on the basis of the portlandtsement of M300 brand above. Strength indices of finished products also depend on quality of the applied concrete.
- Iron fittings. Use of the reinforcing material belonging to class A3 and A4 increases load properties of the plates applied as interfloor overlappings.
Hollow floor slab: design features
The main advantage of use of the hollow floor slabs meeting the standard – considerable simplification of process of construction and laying of utilities. In addition, features of production of panels provide to the ready building the raised heat insulation of interfloor overlappings. Also plates guarantee the improved sound insulation and prevent penetration of external noise into the room.
Such moments belong to the main design features:
- Correct geometrical form. Finished products differ in form of parallelepiped which has plain surfaces of edges.
- Presence of through holes from the edge parties. Availability of internal hollowness increases the soundproofing and heat-insulating properties and also reduces the final weight of floor slab.
- Correct shape of internal cavities. The configuration of longitudinal section of cavities has appearance of the correct circle or oval.
- Sizes of hollow floor slabs. In general length, thickness and width of plates, as well as diameter of internal section of openings, depend on the producer, but are generally regulated by norms.
- Quantity of internal openings. Hollow floor slabs have from 5 to 9 through holes.
Interesting information! Availability of emptiness in plates of overlappings also provides to products high operating ability. Unlike integral panels, the weight of hollow plate much below, respectively, on the base smaller impact will be made. At the same time hollow plates do not concede to integral panels neither on sound-proof, nor on heat-insulating properties.
Main advantages of use of hollow panels of overlapping
As the main advantages in which the hollow plate differs are considered:
- The reduced weight. At the identical sizes of hollow plate and the integral panel the weight of the first will be less. Availability of emptiness has no impact on decrease in margin of safety, but at the same time multihollow products load base basis of the building less.
- More available cost. The price of hollow floor slabs is much lower than the cost of monolithic panels because in the course of production the smaller volume of concrete is used, as allows to reduce manufacturing costs.
- The improved soundproofing and heat-insulating properties. Thanks to availability of emptiness the air layer which is in bulk concrete and provides high operating ability is formed.
- The reduced time expenditure on construction. Installation works are carried out with use of any size of hollow plates in quite short time, especially if to compare to construction of monolithic reinforced concrete construction using timbering.
- Big range of floor slabs. Producers have decent size range of products where products differ in parameters and characteristics. The wide choice of standard dimensions allows to pick up different plates for construction of overlappings of difficult designs.
Helpful advice! Only the products which are released in industrial conditions are capable to meet the requirements of the existing standards. The plates made in handicraft conditions by the small enterprises will have only small standard dimensions.
The main positive and downside of use of plates
Other advantages in which multihollow plates of overlappings differ the different size:
- Internal through holes can be used for any laying of communications and at the same time it is not necessary to prepare for them special grooves.
- The increased resistance of concrete products to fluctuations of humidity and ambient temperature.
- Ability to resist to vibration loads that gives the chance to apply plates to construction of buildings in regions with the increased seismic activity. At respect for norms of construction the building is capable to sustain pushes with an amplitude of 8-9 points.
- The plain surface of panels facilitates carrying out internal finishing work after completion of construction.
- Minimum exposure of multihollow products to shrinkage.
- The increased resistance of concrete to manifestation of corrosion processes.
In addition to the listed advantages, builders allocate also the fact that at application of hollow floor slabs the need in mounting of additional supporting poles disappears. Despite such amount of advantages, plates have also some negative sides.
So, the big weight of concrete slab leads to the fact that it will be required to use in addition in construction the load-lifting equipment. Because it is necessary to order the manipulator, first, it will be necessary to provide it the sufficient size construction site, secondly, it is necessary to include article of additional expenses in the estimate.
Besides, before beginning construction, it is required to calculate bearing capacity of hollow floor slabs and to estimate possible maximum load. At the same time it is necessary to consider actuating quantity of both static, and dynamic character and also to calculate load bearing capacity of walls.
It is important! Before creating overlappings of hollow panels, previously it is required to concrete armopoyas, located on box contour. To prevent freezing of plate, from within opening in edge corners are closed up by means of heater and cement.
Types of loadings which plates of overlappings are expected
According to the standard the size of bearing capacity of product equals 800 kg/m ², but there are also options expected the raised loading within 1200-1600 kg/m ². It is necessary to consider that the cost of hollow floor slabs of this kind will be higher.
Generally panels test two types of loadings:
Static load ‒ the cumulative impact on plate made by floor covering together with the mass of tie. Here also the mass of interroom walls belongs, the established furniture – all this makes the total pressure which is put upon product from above. From below there is additional loading in the form of surface mounted luminaires, gypsum cardboard of designs, the fixed eaves and all other hinged equipment at which installation the ceiling is used.
As for dynamic loads, they result from movement of all residents. In addition, dynamic load is created by the installed exercise machines and also sliding partitions which have fastenings on floor or on ceiling.
In separate category complex loading where, for example, it is possible to carry pressure put by the bathroom which changes depending on filling of bowl, presence or absence of the person in it is allocated. If the bathroom is established on legs, then each of support will create local pressure upon plate.
How to learn maximum load on hollow floor slab
That at construction to calculate pressure which the steel concrete basis with cavities is expected, it is required to perform such operations:
- To draw the detailed plan of construction taking into account quantity of support which after completion of works will render load of the bearing plate. To note how they will be located.
- Approximately to estimate the total mass of the elements putting pressure upon overlapping.
- To separate the calculated value into the number of concrete goods panels.
After calculation of most planned load of plate it is necessary to choose the product type which is most suitable on characteristics. At calculation you should not forget that plate deadweight is considered too. As for calculation algorithm for supporting structure with marking of personal computer 23.15-8 with bearing capacity of 800 kg which differs in the size of 1.49х2.29 m and with a lump of 1180 kg it will look as follows:
- To learn the area of the basis, it is necessary to increase length by width: 1.49х2.29=3.41 m ².
- For calculation of load of basis square lump is divided into the area of plate of 1180:3.41=346 kg/m ².
- Then from bearing capacity take away the received value of 800-346=454 kg.
The received indicator is also the maximum weight which the plate taking into account curb weight is expected. On m ² it is accepted to take the size equal of 250 kg for the total mass of all of the objects influencing from above plate. Thus, 454-250=204 kg – this weight can be considered margin of safety on m ² the areas of panels.
Interesting information! The most part of concrete products has bearing capacity of 800 kg/m ² which is considered optimum for premises.
Weight of plates of overlappings and other important parameters of products
If to order products under individual production, then all indicators can change depending on requirements of the buyer. Change of parameters should not affect reliability or manufacturing techniques at all. In spite of the fact that thickness of plates varies, in the majority of finished products it equals 22 cm.
Weight is considered especially important criterion, all products, differ in indicators from 750 to 4820 kg. It is important to consider the mass of product because, proceeding from value, the mounting mode of panels at construction is defined. Usually on small building involve cranes with a loading capacity up to 5000 kg. If the plate is heavier, it can lead to serious problems.
For example, the concrete slab of 2.91 m ³ with marking of personal computer 89-15.8 has length of 8.88 m, width of 1.49 m and standard height of 22 cm. The product with such parameters differs in the weight of 4150 kg, in that case use the crane with a loading capacity up to 5 tons can be dangerous. It should be noted that in certain cases the weight of plates is different to identical marking, but usually the difference does not exceed several kilograms therefore it does not play essential role when calculating. More often weight changes because of soaking of one of products.
Hollow steel concrete overlappings are widely used at construction of multi-storey buildings of both private, and state building. Panels have gained the distribution thanks to high utilization properties which were estimated by both users, and professional builders. To accelerate construction, main – it is correct to pick up the size, weight and type of plate, without forgetting to consider bearing capacity of products at the same time. As a result of construction with observance of rules and technologies when hollow interfloor overlappings are used, the qualitative and steady building turns out.