Comments:
Floor panels are the main part of any building. They include load-bearing elements that exert load on the walls, or individual supporting elements. Based on the material of the supporting element, they are distinguished reinforced concrete structures. The cost of flooring is 20% of the total cost of the building.
Floor panels contain load-bearing elements that exert load on the walls.
Precast concrete floors - the main panels in the construction industry
Currently, potential developers prefer to use reinforced concrete panels. In turn, they are divided into:
- Prefabricated.
- Monolithic.
The panels must have characteristics such as strength, rigidity, fire resistance, reliability, and quick installation properties. If a building is being built where high humidity is expected during operation, then the floor panels must be resistant to moisture. IN country houses You can often see the use of these structures from reinforced concrete panels with the presence of round voids. Basically, their length can reach up to 6800 mm, and their width - up to 2400 mm.
Reinforced concrete structures have a huge number of advantages. They have high strength, long operational period, and most importantly, they are fire resistant. When creating a project for the construction of a house or any other building, potential developers try to enlarge them in order to reduce the number of installation actions and joint contacts. Prefabricated type reinforced concrete floors are divided into 3 main classes:
- In the form of flooring (tile form).
- Large panel.
- Beam.
Deck-shaped structures have flat or ribbed components of the same type that must be tightly installed. Their connection is carried out using a special cement mortar. Consequently, they include load-bearing reinforced concrete parts with high thermal insulation and sound insulation.
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Interfloor large-panel reinforced concrete structures
By design feature interfloor large-panel structures made of reinforced concrete can have a layered floor. They are lightweight, soundproofing capabilities are achieved using a special layered floor structure or the presence of a continuous air gap in the thickness of the ceiling. The floor panels themselves can be solid, hollow, or tent-shaped. The tent panel is special type slab, which is framed along the contour by ribs. The ribs are always directed downwards.
Regarding attics and plinth panels, then they must be insulated, and the interfloor ones are soundproofed. Consequently, for these actions, expanded clay or sand bedding, layered coatings with elastic gaskets are used. It is worth considering that the increase in sound and thermal insulation characteristics must be done by increasing mass building structures. Since the components beam floors Because they are lightweight, they are used on construction sites. If reinforced concrete floor panels are involved in the construction of sanitary facilities or in rooms with high humidity, then it is necessary to apply a waterproofing layer.
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What are monolithic panels?
Monolithic floors are mounted using installed formwork. Installation of monolithic floor panels is not easy. They transfer the load from the floor to existing load-bearing walls. They can also serve as an additional rigid frame for any structure. Their design requires working only with a professional who has the skills and experience in working with these structures. Compared to other panels, monolithic ones have a number of advantages:
- There is no need to use special equipment for loading and lifting.
- It is enough to use small mechanization.
- High tensile strength.
- Long service life.
- Reliable design that can withstand heavy loads.
Floors consist of a load-bearing part that transfers the load to the walls or individual supports, and an enclosing part, which includes floors and ceilings. Based on the material of the supporting part, they are distinguished reinforced concrete ceilings, on wood and iron supports, also armosilicate and clay. The price of floors and floors in the total price of the house reaches 20% of its total price.
The main material for floor devices V modern construction is reinforced concrete. Reinforced concrete floors divided by prefabricated And solid, concreted in formwork. IN last years mainly used prefabricated And solid floors.
Floors must meet the requirements of strength, rigidity, fire resistance, durability, sound and thermal insulation, if they separate heated rooms from unheated ones or from the external environment. Floors in rooms with wet processes they must be waterproof, and in rooms with the emission of gases they must be gas-tight.
In suburban houses with brick walls use floors made of reinforced concrete panels with round voids, the length of which varies from 4800 mm to 6980 mm, width from 1000 to 2400 mm, height 220 mm, also with flat ones - length 2700-4200 mm with gradation of 300 mm, width 1200, 1500 mm, width 120 and 160 mm . Panels laid (Fig. 1) on a layer of freshly laid masonry mortar 10 mm wide with termination on supports of more than 120 mm. In one panel(pitch 2400-3000 mm) are connected to the walls with anchors 8-10 mm in diameter, which are fastened to the hinges and inserted into the masonry 250 mm from the end of the panel, ending with a bend at an angle of 90° horizontally at 380 mm.
Seams between panels filled with a cement substance of composition 1: 4 (by volume). Installation of panels produced using truck cranes. Reinforced concrete floors
Such floors have a number of valuable properties, the main of which are great strength, durability and fire resistance. When designing parts structures prefabricated reinforced concrete floors one should strive to enlarge them to reduce the number of installation operations and butt joints.
Prefabricated reinforced concrete floors
Prefabricated reinforced concrete floors are divided into three main groups: in the form of decking (slabs), large-panel and beam. Ceilings in the form of floorings consist of flat or ribbed parts of the same type, laid flush; They are connected by filling the gaps with cement. Such floors consist of a load-bearing reinforced concrete part (usually textured at the bottom), a sound or thermal insulation layer and a floor structure. The supports for the decking are walls and purlins. More common hollow flooring 160 mm high for clearances up to 4 m and 220 mm for clearances over 4 m. There are longitudinal voids in the floorings round section(Fig. 2, a).
When making decks with vertical voids, concrete consumption is reduced to 15% compared to round-hollow ones. Vertical round voids are formed using pipe liners (the liners are welded to the channels). Floorings, which can cover entire rooms, are called large panels. Lack of connections in floor panels within the boundaries of the room increases their sound insulation and ensures a higher quality of ceiling finishing.
To ensure standard soundproofing parameters from airborne noise single-layer structures interfloor panel ceilings, made of heavy concrete, must have a mass exceeding 300 kgf/sq.m.
At installation of floors separate type, in which the soundproofing capacity of the air gap between the upper and lower communication floor panels is used, also when installing layered floors, ensure the regulatory soundproofing ability possible with a floor mass of less than 300 kgf/sq.m.
By design interfloor large-panel reinforced concrete floors can be with a layered floor, a separate type (with a separate floor, a ceiling or from 2 separate load-bearing panels) and with a layered floor and a separate ceiling (Fig. 3). All these floor structures have a relatively small mass (less than 300 kgf/sq.m.); Standard noise insulation is ensured by a layered floor structure or the presence of a continuous air gap in the thickness floors.
Floor panels They produce solid, hollow (with round voids) and tent-shaped ones. The load-bearing single-layer panel (Fig. 4, a) is reinforced concrete slab constant cross-section with a lower surface ready for coloring and a flat upper surface.
Solid single-layer reinforced concrete panels 140 mm wide, cover gaps up to 3.6 m. To cover huge spans (6-6.6 m), they mainly use solid single-layer for previously stressed reinforced concrete panels 14-16 cm wide or expanded clay-reinforced concrete 18 cm wide.
Tent panel(Fig. 4, b) has the form of a slab, framed along the contour with ribs facing down in the form of a cornice. Satisfied interfloor ceilings and from flat reinforced concrete panels 14-16 cm wide.
Floors on reinforced concrete supports
Prefabricated reinforced concrete interfloor slabs(Fig. 5) beam type consist of T-profile beams and filling between them. The filler here is a roll of gypsum concrete or lightweight concrete slabs 80 mm wide and 395 mm long, reinforced with wooden slatted or timber frames, and in attic floors - lightweight concrete slabs 90 mm wide and 395 mm long, reinforced with welded iron mesh. The seams between the supports and slabs are filled with cement and rubbed. Attics and basements floors They are sure to be insulated and soundproof between floors. To do this, use expanded clay or sand bedding, layered coatings with elastic pads. With all this, it is better that heat and noise insulation is not carried out at the expense of increasing the weight of the building structures.
Because the elements beam floors have a relatively small weight, they are used on buildings equipped with low-capacity cranes (up to 1 t).
At installation of reinforced concrete floors th in sanitary facilities a waterproofing layer is included in the ceiling design. To do this, they usually stick on top of the flooring or panels. bitumen mastic 1-2 layers of roofing material.
Solid floors
Solid floors made using installed formwork. Transferring loads from the floor to load-bearing walls, solid floors serve as an additional rigid frame for the structure. Their design requires a certain professional skill and should be done according to a project under the supervision of a specialist builder. Manufacturing floors The location has its own advantages. At the same time, no special transport or lifting equipment is required. To lift and move concrete, small-scale mechanization is sufficient. To the database solid floors laid down Monier plate, in which the reinforcement is located in places of tension, in other words, in the lower part of the slab. This is justified by the fact that steel has 15 times greater tensile strength than concrete. Reinforcement frame the slabs should be placed at a distance of more than 3-5 cm from the formwork walls so that concrete can fill this space. Length of the gap to be covered solid slabs, should not exceed 3 m. For plumbing pipelines, special iron or vinyl sleeves with an internal diameter larger than the pipeline being laid are installed in the ceiling. The gap between the sleeve and the pipeline is minted with tarred tow.
To the shortcomings solid floors This may include the need to install wood formwork virtually over the entire area of the house. But this does not mean that the formwork must be laid out all at once. Overlap can be done in separate gaps, moving the formwork as the concrete sets.
Load bearing capacity solid floors is provided with reinforcement, the diameter of which must be at least 8-12 mm. With all this, intermediate connections of rods along the entire length of the floor are undesirable. A small layer of concrete with outside the overlap must be more than 2 cm. The clearance must be concreted in one working cycle.
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Design characteristics
Floors consist of a load-bearing part, which transfers the load to individual supports or walls, and an enclosing part, which includes ceilings and floors. Based on the material of the load-bearing part, one can distinguish reinforced concrete (reinforced concrete) floors, steel and wooden beams, ceramic and armosilicate. The cost of floors and ceilings will reach 20% of the total cost of the house. The consumption of reinforced concrete for flooring will be up to 60% of the total consumption.
It is worth understanding that the cost of covering should be minimal.
In modern construction, the main material for flooring is reinforced concrete. made of reinforced concrete (reinforced concrete) can be divided into monolithic and prefabricated, concreted in formwork. IN Lately For the first floor, only monolithic reinforced concrete floors and prefabricated floors are used. Prefabricated ones allow you to cover a span of up to 12 m. Speaking about which one is needed, you should know that the consumption of this mortar per 1 m² will be 0.223 m³, and steel - 6.5 kg. This consumption is approximate and may vary slightly.
It is worth knowing that floors must meet the requirements of rigidity, strength, fire resistance, durability, sound and heat insulation if they will separate heated rooms from the outside environment or from unheated premises. Floors in rooms in which wet processes will occur must be waterproof, and in rooms in which gases are emitted - gas-tight.
In country houses with brick walls, people most often prefer precast reinforced concrete floors with round voids. Their length ranges from 4800 to 6980 mm, width - from 1000 to 2400 mm, and height - 220 mm. Designs with flat voids with a length of 2700-4200 mm with a gradation of 300 mm, a width of 1200-1500 mm, and a thickness of 120 and 160 mm are also used.
Panels for the first floor should be laid on a 10mm thick layer of freshly laid masonry mortar, with a minimum of 120mm of support sealed. In increments of 2400-3000 mm, they are connected through one panel with anchors with a diameter of 8-10 mm. The anchors are attached to the hinges and inserted into the masonry 250 mm from the end of the panel. It is necessary to finish with a bend at an angle of 90 degrees horizontally at 380 mm.
The seams between the panels are filled cement mortar. Speaking about what composition should be, it is worth knowing that it is 1:4 by volume. The panels are installed using truck cranes.
Installation of reinforced concrete floors
Such designs for the first floor have some valuable qualities. The main ones are durability, great strength and fire resistance. To reduce the number of butt joints and installation operations when designing structures of prefabricated floor elements made of reinforced concrete (reinforced concrete), it will be necessary to strive to enlarge them.
Next we will talk about precast reinforced concrete floors. It is divided into 3 main groups: beam, large-panel and in the form of flooring (slabs). Structures in the form of decking will consist of flat or ribbed elements of the same type, which are laid closely. Speaking about which connection method should be used here, it is worth knowing that you need to fill the gaps with cement mortar.
Similar structures for the first floor consist of a load-bearing part made of reinforced concrete, a thermal and sound insulating layer and a floor structure. The walls and purlins will serve as supports for the decking. The most common are hollow-core decks, having a height of 160 mm if there is a span of up to 4 m, and 220 mm if there is a span of more than 4 m.
In the process of manufacturing decks with vertical voids, concrete consumption will be 15% less than with round-hollow decks. Round vertical voids are formed using pipe liners (the liners are welded to the channels). Flooring that can cover entire rooms is called large panels. IN in this case consumption will be less. The absence of joints in panels within rooms will increase their sound insulation and provide more high quality ceiling finishing.
In order to ensure regulatory sound insulation properties from airborne noise, single-layer panel structures of the first floor, which are made of heavy concrete, must have a mass that exceeds 300 kgf per 1 m².
In the process of installing split-type floors, in which the soundproofing ability of the air gap between the bottom and top panels prefabricated reinforced concrete floors, and when installing layered floors, it will be possible to ensure sound insulation capacity with a floor mass of less than 300 kgf per 1 m².
Interfloor large-panel reinforced concrete (reinforced concrete) floors can be designed with a layered floor, with a layered floor and a separate ceiling, of a separate type (of two separate load-bearing panels, with a separate ceiling or with a separate floor). All of the above floor structures have a relatively small mass (less than 300 kgf per 1 m²). Standard sound insulation can be provided by a layered floor structure or by the presence of a continuous air layer in the thickness.
Floor panels for the first floor are made solid, hollow (with round voids) and hipped. A single-layer load-bearing panel is a reinforced concrete slab with a lower surface of a constant cross-section, which is ready for painting, and a flat upper surface.
Single-layer solid reinforced concrete (reinforced concrete) panels, which have a thickness of 140 mm, can cover a span of up to 3.6 m. In order to (about 6-6.6 m), single-layer solid reinforced concrete prestressed panels, which have a thickness of 14- 16 cm, or expanded clay-reinforced concrete, which have a thickness of 18 cm.
The tent panel has the form of a slab, which is framed along the contour by ribs facing in the shape of a cornice. They are also made from flat reinforced concrete panels with a thickness of 14-16 cm. The type of overlap will depend on which span should be covered. Maximum span - 12 m.
Installation of beam structure
Interstorey prefabricated reinforced concrete beam-type structures consist of T-beams and infill between the beams. The filler in this case will be a roll of lightweight concrete and gypsum concrete slabs having a thickness of 80 mm and a length of 395 mm, reinforced with slatted wooden or timber frames. The attic floors are made of lightweight concrete slabs, which have a thickness of 90 mm and a length of 95 mm, reinforced with welded steel mesh.
The joints in the slabs and beams are filled with cement mortar and rubbed. Basement and attic floors must be insulated, and interfloor floors must be soundproofed. To do this, sand or expanded clay bedding, a layered coating with an elastic gasket should be used in the slabs.
It is recommended that sound and heat insulation in slabs should not be achieved by increasing the weight of building structures. Due to the fact that the elements beam structures have a relatively small weight, they are often used in buildings that are equipped with cranes of low lifting capacity (about 1 t).
When installing reinforced concrete beam floors in sanitary units, a waterproofing layer should be included in the slabs. For this purpose, 1-2 layers of roofing felt on bitumen mastic are most often glued on top of decking or panels. Beam floors are used if you need to cover a span of 3-7.5 m.
Installation of monolithic buildings
Monolithic structures are made using pre-installed formwork. Such floors on slabs will serve as an additional rigid frame for the building in the process of transferring the load to the load-bearing walls from the floor. Their installation requires a certain professional skill. It must be carried out according to the project under the guidance of a construction specialist.
Manufacturing similar designs location has some advantages. To do this, you do not need to have special transport or any lifting equipment. To move and lift concrete, it is enough to have small-scale mechanization equipment.
The basis of monolithic structures is laid in Monier slabs. In it, reinforcement is placed in places of tension, meaning the lower part of the slab. This is due to the fact that steel has a tensile strength 15 times greater than concrete. The reinforcement frame of the slab should be located at a distance from the formwork walls by minimum distance 3-5 cm. This is necessary so that the concrete has the opportunity to fill this space.
The span that is covered with a monolithic slab must have a maximum length of 3 m. For plumbing pipelines, care should be taken to install metal or vinyl sleeves that have an internal diameter larger than the pipeline being laid. The gap between the pipeline and metal sleeves must be embossed with tarred tow.
The disadvantage of such monolithic structures is the installation of wooden formwork over almost the entire area of the house. However, this does not mean that you need to install the formwork all at once. The overlap can be done in separate spans, while moving the formwork as the concrete sets.
Load-bearing capacity will be provided using reinforcement. Intermediate joints of rods along the entire length are undesirable. WITH outside overlap, the minimum layer of concrete must be at least 2 cm. The span must be concreted in one working cycle.
Installation of formwork
To install a monolithic reinforced concrete floor, you will need to install horizontal removable formwork.
Such formwork can be made from wooden shields(from cut boards that are 25-35 mm thick) or waterproof plywood that is at least 20 mm thick. If the formwork panels, which are made of boards, have gaps, a layer is needed on top of the formwork waterproofing film. It will be needed in order to liquid solution couldn't flow out.
Removable formwork should be laid on beams, which will be supported by supporting vertical posts. The racks can be telescopic, made independently from round timber with a diameter of 8-15 mm and beams, or factory-made.
The formwork must be installed without cracks, strictly horizontally. By horizontal design steel reinforcement is laid and tied using soft knitting wire in the form of a mesh with cells measuring 200x200 mm.
Rebar frame
The reinforcement on the formwork is laid in such a way that there is a gap of at least 25 mm between it and the formwork. To do this, you should use standard special plastic stands or make them yourself from wood, plywood or other material. What material to choose is up to everyone to decide. Any of the above will be needed.
Floors consist of a load-bearing part, which transfers the load to walls or individual supports, and an enclosing part, which includes floors and ceilings. Based on the material of the load-bearing part, a distinction is made between reinforced concrete, wooden and steel beams, as well as armosilicate and ceramic. The cost of floors and floors in the total cost of the house reaches 20% of its total cost.
The main material for flooring in modern construction is reinforced concrete. Reinforced concrete floors are divided into prefabricated and monolithic, concreted in formwork. In recent years, prefabricated and monolithic floors have been mainly used.
Floors must meet the requirements of strength, rigidity, fire resistance, durability, sound and heat insulation if they separate heated rooms from unheated ones or from the outside environment. Floors in rooms with wet processes must be watertight, and in rooms with gas emissions - gas-tight.
In country houses with brick walls they use floors made of reinforced concrete panels with round voids, the length of which varies from 4800 mm to 6980 mm, width from 1000 to 2400 mm, height 220 mm, as well as with flat ones - length 2700-4200 mm with gradation of 300 mm, width 1200, 1500 mm , thickness 120 and 160 mm. The panels are laid (Fig. 1) on a layer of freshly laid masonry mortar 10 mm thick with a seal on the supports of at least 120 mm. Through one panel (pitch 2400-3000 mm) they are connected to the walls with anchors with a diameter of 8-10 mm, which are attached to the hinges and inserted into the masonry 250 mm from the end of the panel, ending with a bend at an angle of 90° horizontally at 380 mm.
The seams between the panels are filled with cement mortar with a composition of 1:4 (by volume). The panels are installed using truck cranes.
Reinforced concrete floors
Such ceilings have a number of valuable qualities, the main ones being greater strength, durability and fire resistance. When designing the structures of elements of prefabricated reinforced concrete floors, it is necessary to strive to enlarge them to reduce the number of installation operations and butt joints.
Prefabricated reinforced concrete floors
Prefabricated reinforced concrete floors are divided into three main groups: in the form of decks (slabs), large panels and beams. Ceilings in the form of floorings consist of flat or ribbed elements of the same type, laid closely; connect them by filling the gaps with cement mortar. Such floors consist of a load-bearing reinforced concrete part (usually textured at the bottom), a sound or thermal insulation layer and a floor structure. The supports for the decking are walls and purlins. The most common are hollow decks with a height of 160 mm for spans up to 4 m and 220 mm for spans of more than 4 m. The decks have longitudinal voids of circular cross-section (Fig. 2, a).
When making decks with vertical voids, concrete consumption is reduced by up to 15% compared to round-hollow ones. Vertical round voids are formed using pipe liners (the liners are welded to the channels). Flooring that can cover entire rooms is called large panels. The absence of joints in floor panels within a room increases their sound insulation and ensures a higher quality of ceiling finishing.
To ensure standard sound insulation properties from airborne noise, single-layer interfloor panel structures made of heavy concrete, must have a mass exceeding 300 kgf/sq.m.
When installing separate-type floors, which use the sound-insulating ability of the air gap between the upper and lower panels of the communication floor, as well as when installing layered floors, it is possible to ensure the standard sound-proofing ability with the weight of the floor less than 300 kgf/sq.m.
By design, interfloor large-panel reinforced concrete floors can be with a layered floor, a separate type (with a separate floor, a ceiling or two separate load-bearing panels) and with a layered floor and a separate ceiling (Fig. 3). All these floor structures have a relatively small mass (less than 300 kgf/sq.m.); Standard sound insulation is provided by a layered floor structure or the presence of a continuous air gap in the thickness of the floor.
Floor panels are made solid, hollow (with round voids) and hipped. The load-bearing single-layer panel (Fig. 4, a) is a reinforced concrete slab of constant cross-section with a lower surface ready for painting and a flat upper surface.
Solid single-layer reinforced concrete panels with a thickness of 140 mm cover spans up to 3.6 m. To cover large spans (6-6.6 m), solid single-layer prestressed reinforced concrete panels with a thickness of 14-16 cm or expanded clay-reinforced concrete panels with a thickness of 18 cm are mainly used.
The tent panel (Fig. 4, b) has the form of a slab, framed along the contour with ribs facing down in the form of a cornice. Interfloor ceilings are also constructed from flat reinforced concrete panels 14-16 cm thick.
Prefabricated reinforced concrete interfloor floors (Fig. 5) of the beam type consist of T-profile beams and filling between them. The filler here is a roll of gypsum concrete or lightweight concrete slabs 80 mm thick and 395 mm long, reinforced with wooden slats or timber frames, and in the attic floors - lightweight concrete slabs 90 mm thick and 395 mm long, reinforced with welded steel mesh. The seams between the beams and slabs are filled with cement mortar and rubbed. Attics and basement floors They must be insulated and soundproof between floors. To do this, use expanded clay or sand bedding, layered coatings with elastic gaskets. At the same time, it is desirable that heat and sound insulation is not carried out at the expense of increasing the weight of building structures.
Since the elements of beam floors are relatively light in weight, they are used on buildings equipped with low-capacity cranes (up to 1 t).
When installing reinforced concrete floors in sanitary facilities, a waterproofing layer is included in the floor structure. To do this, 1-2 layers of roofing felt are usually glued on top of the decking or panels using bitumen mastic.
Monolithic floors
Monolithic floors are made using installed formwork. By transferring loads from the floor to load-bearing walls, monolithic floors serve as an additional rigid frame for the building. Their installation requires a certain professional skill and should be carried out according to the project under the guidance of a specialist builder. Making floors on site has its advantages. This does not require special transport or lifting equipment. To lift and move concrete, small-scale mechanization equipment is sufficient. Monolithic floors are based on a Monier slab, in which reinforcement is placed in tension areas, that is, in the lower part of the slab. This is because steel has 15 times more tensile strength than concrete. The reinforcement frame of the slab must be located at a distance of at least 3-5 cm from the formwork walls so that concrete can fill this space. Length of span covered monolithic slabs, should not exceed 3 m. For plumbing pipelines, special metal or vinyl sleeves with internal diameter larger than the pipeline being laid. The gap between the sleeve and the pipeline is minted with tarred tow.
The disadvantages of monolithic floors include the need to install wooden formwork over almost the entire area of the house. However, this does not mean that the formwork needs to be installed all at once. The overlap can be done in separate spans, moving the formwork as the concrete sets.
The load-bearing capacity of monolithic floors is ensured by reinforcement, the diameter of which must be at least 8-12 mm. In this case, intermediate joints of rods along the entire length of the floor are undesirable. Minimum layer There must be at least 2 cm of concrete on the outside of the ceiling. The span must be concreted in one working cycle.
Precast reinforced concrete floor slabs are important design in building a house. On average, about 20% of the total production costs of a building are spent on slabs.
Types of prefabricated reinforced concrete floor slabs.
Exist different kinds floor slabs.
Tent - is a tray with ribs directed downwards or upwards, 140 - 160 mm thick. Thanks to this design and the existence of a reinforced layer, concrete consumption is significantly reduced while maintaining high strength indicators. This prefabricated floor can resist deformation. Several transverse ribs provide additional reliability. The disadvantages of this type of slab include low heat and sound insulation compared to hollow slabs. A very common U-shape used in construction non-residential premises such as a garage or shed. We do not recommend using tent slabs for the construction of interfloor partitions, because they do not give the ceiling a very respectable appearance, and finishing and installing communications will not be easy.
Hollow - inside these slabs there are parallel longitudinal voids, usually round in shape. Such prefabricated reinforced concrete floor slabs are more common and are actively used in the construction of buildings. Hollow core slabs are usually presented in the form of a structure, with several numbers of cavities of different sections: round, semicircular and oval shape. They have excellent insulating properties. This type flooring significantly reduces the load on the foundation and walls of the house.
Solid are floors with no voids. They have higher strength, but lower sound and thermal insulation compared to hollow core slabs and weigh more.
Standard sizes of reinforced concrete slabs.
Usually, sizes reinforced concrete slabs floors are important factor when planning the construction of a future building. Floors for which slabs of non-standard shapes or sizes will be used can have very high price. For this purpose, the design should take into account the use standard formats: thickness - 220 mm, width 1, 1.2, 1.5 m, length from 2.4 to 9 m, multiple of 100 mm.
Prefabricated reinforced concrete floor slabs - marking.
Precast concrete floors are marked with letters and numbers indicating what type of product we are dealing with, as well as the possible load capacity.
The first numbers for ribbed slabs indicate the existence of a special technical hole of a certain diameter. Usually, the numbers 1.2.3 appear at the beginning. These designations indicate that holes measuring 40, 70 and 100 cm are used. Multi-hollow products are characterized by similar markings, only these numbers mean hole sizes of 159, 140 and 127 mm.
Letter abbreviations: PC - hollow core slabs with round diameter. PNO is a lightweight product. PG PB - deckless multi-hollow, NV, VNK, VNKU - product with significant amount voids. PG - silver plates. PF, PV, PS - U-shaped products with ventilation holes. PR - ribbed slabs are designated. P, PTVs - the name of solid boron products. If the letter O is in the center, this means that the slab has a vault-like exterior. The letter indicates the number of supports: T-3, K-4 supports.
Advantages and disadvantages of precast concrete floor slabs.
Factory-made reinforced concrete floor slabs are the most common material for construction. They have their advantages.
- Low price.
- Installation speed.
- Durability in operation and reliability.
- Simple assembly - the slabs are laid by a truck crane with the help of several slingers.
- Noise insulation. The noise level in the slabs is reduced by voids.
The disadvantages include:
- Less rigidity compared to monolithic floors.
- The presence of a gap between the plates.
- The need to use lifting equipment.
Installation of reinforced concrete floor slabs.
Prefabricated reinforced concrete floor slabs are structures that are designed to bear a specific load. Any such ceiling can function only when the pressure on it can be absorbed by the working fittings. In such slabs, the reinforcement is located exclusively in the lower part of the slab and only along it. This means that the ceiling can bend without harm, exclusively in the longitudinal direction; it is also necessary that the deflection of the slab is directed strictly downward.
Concrete resists compression well, but poorly in tension. The ceiling is subject to compression in the upper part, and tension in the lower part. Therefore, reinforcement is placed in the lower part of the slab, which resists tension.
Installation of floor slabs.
1. Classic installation method.
The reinforced concrete floor rests on two sides, bends under the weight of the load, and the working frame takes on the tension; if the load does not exceed the permissible weight, there will be no damage.
Supporting a reinforced concrete slab on both sides.2. Supporting the slab on three sides - one long and two short.
The long part of the slab slides onto the wall. It is used when the width of the span does not fit the slabs. Installing floor slabs in this way is somewhat worse than the first method, but in principle, it is allowed. We must not forget: the long part of the panel cannot be inserted into the wall deeper than the height of the reinforced concrete slab. We will consider the concept of pinching further.
In the case considered, it is not the entire slab that bends, but only the free edge. Nevertheless, a longitudinal frame comes into play, which takes tensile stress - not along the length of the slab, but only in its fragment.
Supporting a reinforced concrete slab on three sides.How not to install floor slabs.
1. Installation of floor slabs on two long sides.
The working frame in the slab is only in the longitudinal direction. In the transverse one there is only a small mesh that can take the load from the slab’s own weight during its installation, when it is lifted by a crane. When we install prefabricated reinforced concrete floor slabs along two long sides, they will bend under pressure, and there will simply be no reinforcement in this direction, and the floor will collapse. At first, the mesh can take the load, but we must remember that the reinforcement area of this mesh is only intended to support the weight of the slab itself.
Supporting a reinforced concrete slab on two long sides.2. Installation of floor slabs with additional support in the span.
Precast concrete slabs are used only as single-span slabs. When there is a wall or column in the span, the slab between the supports bends downwards, and above the support a bend appears in the other direction - with a tightened zone at the top. There is no frame in the upper part of the ceiling, and we have nothing to absorb the tensile bending pressure. The result may be the formation of deformations in the upper part of the floor, as indicated in the figure. The probability of a crack appearing increases over time, which will lead the reinforced concrete floor to emergency condition.
Installation of a reinforced concrete slab with additional support in the span.3. Installation of floor slabs on two walls with removal of part of the slab.
The top of the panel, in in this example, is subject to tension, and there is no reinforcement there to take the load. The longer the console is and the stronger the load on it, in particular at the edge, the sooner destruction can occur.
Supporting and removing part of a reinforced concrete slab.4. Installation of the slab on columns.
Installing prefabricated reinforced concrete floor slabs not on walls or beams, but directly on columns is strictly prohibited. The frame in the slab works as follows - the stretched reinforcement can take on stress when its ends are placed behind the support. If there is no support at the end of the reinforcing bar, the slab stops working correctly.
The slab will bend in the longitudinal and transverse directions, which will lead to the destruction of the slab.
Only two outer reinforcements are supplied to the support; the rest “hang in the air” and are not included in the work. This means that the working reinforcement in the slab is reduced many times compared to the required one. It is clear that the prefabricated reinforced concrete floor will collapse. The best option The solution to this problem will be to install beams in right place supporting the slab, namely between nearby columns.
Supporting a reinforced concrete slab at four points.5. Pinching of the prefabricated floor slab.
In our case, pinching is the insertion of the slab onto the wall by more than the height of the slab. A pinched panel functions completely differently than a hinged panel. All such slabs are designed for hinged support - when the slab bends, as if turning on a support. IN technical documentation, according to prefabricated floors, the depth of possible support is indicated, which, in fact, should be less than specified.
Pinching of the precast floor slab.Let's look at the image. It shows what the pinching of precast reinforced concrete floors on a support leads to. With hinged support, the slab simply rotates a little on the support and stretches in the lower zone - there its lower frame begins to turn on.
When pinched, the slab is inserted too deeply and does not have the ability to rotate, and then it bends in such a way that the stretched lower part of the floor is in the center, and the upper part is at the supports. There is not enough reinforcement at this location to absorb the tensile stress. The result of this will be the formation of cracks, which are dangerous because they are invisible, since they are located under the floor. Prefabricated reinforced concrete floor slabs will fall into disrepair over time. Installation of floor slabs must be carried out strictly following the installation rules.