Support of floor slabs pc. Supporting the floor slab on the wall: permissible limits, SNiP. Minimum maximum limits

Reinforced concrete slabs are one of the most common types of floors. They provide high strength and allow the assembly of a rigid structure in the shortest possible time. Installation of floor slabs is a demanding task that requires certain knowledge in the field of construction. Everything in order.

Floor slab types

Before starting to mount the horizontal structure, you must select the type. Reinforced concrete prefabricated structures are produced in the form of:

• hollow;
• flat (PT);
• hip panels with perimeter ribs;
• with longitudinal ribs.

Most often, the use of reinforced concrete hollow-core... They are available in two types, depending on the manufacturing method:

• hollow-core (PC);
• continuous molding (PB).

Hollow core slabs are time-tested products that have been used in construction for several decades. Many regulatory documents and installation rules have been developed for them. Thickness - 220 mm. Products are installed according to serial dimensions, which creates inconvenience for individual construction.

The manufacturing technology of these slabs involves the use of reusable casting molds, and before the manufacture of atypical products, you first need to prepare the formwork. Therefore, the cost of the required size can increase significantly.... Typical PC slabs have a length of 2.7 to 9 meters in 0.3 m increments.

The width of reinforced concrete products can be:

• 1.0 m;
• 1.2 m;
• 1.5 m;
• 1.8 m.

Structures with a width of 1.8 m are extremely rarely purchased, since, due to the large weight, the process of installation in the design position is greatly complicated.

PB are used in much the same way as the previous type. But the technology of their manufacture allows you to give the product any length. Thickness - 220 mm. The width is the same as the PC series. The disadvantage is the little experience of use and the lack of processing of regulatory documents.

Flat PTs are often purchased as additional elements for hollow-core slabs. They are available with a thickness of 80 or 120 mm and have smaller dimensions, allowing to block narrow corridors, storage rooms, and bathrooms.

Supporting the plates

The laying of floor slabs is carried out after the preparation of the project or the scheme on which the products are laid out. Floor elements must be selected so that they are sufficiently supported on a brick wall or expanded clay concrete blocks and laid without gaps in width.

The minimum support for the PB and PC series depends on their length:

• products up to 4 m long - 70 mm;
• products longer than 4 m - 90 mm.

Most often, designers and constructors take the optimal value of support on the wall 120 mm. This value guarantees reliability with small deviations during installation.

It will be correct to pre-position the load-bearing walls of the house at such a distance that it is easy to lay the slabs. The distance between the walls is calculated as follows: length of standard slabs minus 240 mm. Series PK and PB must be supported on two short sides without intermediate supports. For example, PK 45.15 has a size of 4.48 m, 24 cm is subtracted from it. It turns out that the distance between the walls should be 4.24 m. In this case, the products will lie with the optimal amount of support.

The minimum support for the PT series products on the wall is 80 cm. Installation of such reinforced concrete slabs is possible with the location of support points on all sides.

The support must not interfere with the passage of the ventilation ducts. The optimum thickness of the bearing internal brick wall is 380 mm. 120 mm on each side goes under the reinforced concrete ceiling, and 140 mm remains in the middle - the standard width of the ventilation duct. In this case, it is necessary to lay as correctly as possible. Displacement of the product towards the ventilation opening will lead to a decrease in its section and insufficient ventilation of the premises.

Summarizing what was said:

• the PK and PB series up to 4 m are supported on both sides by at least 7 cm;
• series PC and PB more than 4 m - not less than 9 cm;
• PT series - on two, three or four sides at least 8 cm.

Storage of boards

After the scheme has been developed and the products are purchased, they need to be located on the building site for convenient installation in the design position. There are rules for storing materials:

• you need to lay the elements under a canopy;
• the storage place should be located in the access zone of the crane;
• lining is provided under the support points.

Failure to comply with the last rule will lead to a split in half. PC, PB and PT products work in such a way that the appearance of intermediate supports or a solid base leads to the appearance of cracks. Laying is performed in the following order:

• wooden blocks or boards are laid on the ground under the edges of the slab;
• on the boards with a crane from the machine I shift the overlapping element;
• boards or bars are again placed on the laid plate;
• unload the second plate from the machine;
• repeat points 3 and 4, the maximum storage height is 2.5 m.

Masonry requirements

In order to correctly install floor slabs, it is necessary to ensure that special requirements for a brick wall are met:

• evenness of the masonry in the place of laying the floors;
• laying in three rows until the overlapping of reinforcing meshes with a mesh of 5 by 5 cm from a wire with a diameter of 3-4 mm;
• the top row of masonry from the inside should be butted.

If the slabs are mounted on expanded clay concrete blocks, a monolithic belt is additionally arranged under the floors. Such a design will help to evenly distribute the load from heavy floors on expanded clay concrete blocks with less strength. Construction technology provides for pouring a monolithic tape of concrete 15-20 cm thick onto blocks.

Floor laying

To carry out the work, at least three people are required: one performs slinging, and two install them in the design position. If the installers and the crane operator cannot see each other, when installing the slab, another worker will be needed to give commands to the crane.

Fastening to the crane hook is performed with a four-branch sling, the branches of which are fixed at the corners of the slab. Two people stand on both sides of the support and control its evenness.

When installing a PC, pinching into the wall is carried out in a rigid way, that is, bricks or blocks are laid on top and bottom of the slab. When using overlappings according to the PB series, it is recommended to perform hinged fastening. For this, the plates are not pinched from above. Many builders mount the PB series in the same way as PCs and buildings stand, but it's not worth the risk, because human life and health depend on the quality of the installation of load-bearing structures.

Another important feature of the use of products from the PB series is that it is forbidden to make technological holes in them.

These punches are needed for heating, water supply and sewerage pipes. Again, many builders neglect this even when building multi-storey buildings. The difficulty is that the behavior of this type of floor under load over time has not been fully understood, since there are no objects built for a long time yet. The ban on punching holes has reasons, but it is rather preventive.

Slab cutting

Sometimes, in order to install a slab, you need to cut it. The technology provides for work with a grinder with a disc on concrete. It is impossible to cut the PC and PT slabs along the length, since they have reinforced reinforcement in the support zones. If you support such a cut slab, then one edge will be weakened, serious cracks will go along it. It is possible to cut PB slabs in length, this is due to the peculiarities of the manufacturing method. A timber or board is laid under the cut site, which will facilitate the work.

The division along the length is performed along the weakened part of the section - the hole. this method is suitable for a PC, but is not recommended for a PB, since the width of the walls between the holes is too small.

After installation, the holes in the areas of bearing on the walls are poured with lightweight concrete or clogged with mineral wool. This is necessary to provide additional strength in the pinch points in the walls.

What to do if it was not possible to evenly spread the product across the width

Sometimes the dimensions of the room do not correspond to the width of the products, in this case all the gaps are brought together into one. This space is covered with a monolithic section. Reinforcement occurs with curved meshes. In length, they rest on the top of the ceiling and seem to sag in the middle of the monolithic section. for floors, concrete is used at least B 25.

The technology of prefabricated floors for bricks or blocks is quite simple, but requires attention to detail.

Typical prefabricated reinforced concrete products are mainly used as load-bearing elements of floors in civil and industrial buildings of mass construction - plates.

Reinforced concrete floor slabs are subdivided:

By type of cross-section (fig. 2.1) - solid, hollow-core, ribbed, box-shaped;

By the number of layers (see fig. 2.1) - single-layer, two-layer, three-layer;

According to the support options - on four sides (along the contour), on three sides, on two opposite sides, at the corners (on the columns of the frame);

Precast floors made of reinforced concrete slabs are used mainly in buildings of wall and frame structural systems, resting them, respectively, on walls and beams (crossbars) (Fig. 2.1 a, b). In some cases, the slabs are supported directly on the columns of the frame, as well as on other floor slabs (Fig. 2.2 c, d).

Multi-slot reinforced concrete floor slabs(table 2.1, fig. 2.3) subdivided into types:

1pc- 220 mm thick with round voids with a diameter of 159 mm, designed to be supported on both sides;

1PCT

1PAC - then same, for support on four sides (along the contour);

2pcs- 220 mm thick with round voids with a diameter of 140 mm, designed to be supported on both sides;

2PKT- the same, for support on three sides;

2PZ

ZPK- 220 mm thick with round voids with a diameter of 127 mm, designed to be supported on both sides;

ZPKT- the same, for support on three sides;

ZPKK- the same, for support on four sides (along the contour);

4pcs- 260 mm thick with round voids with a diameter of 159 mm and cutouts in the upper zone along the contour for supporting on both sides;

5pcs- 260 mm thick with round voids 180 mm in diameter, designed to be supported on both sides;

6pcs- 300 mm thick with round voids with a diameter of 203 mm, designed to be supported on both sides;

7pcs- 160 mm thick with round voids with a diameter of 114 mm, designed to be supported on both sides;

Rice. 2.1. The main types of reinforced concrete floor slabs:

a - solid single layer; b - solid two-layer; c, d - solid three-layer; d - void; e - hollow two-layer; g - ribbed: h - ribbed (trough) sanitary-technical; and - ribbed type "PI"; k - ribbed insulated with a lower shelf; l - ribbed type "TT"; m - ribbed folded; n - box-shaped.

Table 2.1. Reinforced concrete hollow-core floor slabs (according to GOST 9561-91)

Note. For the length of the slabs, the size of the side of the slab that is not supported by the supporting structures of the building is taken for slabs intended to be supported on two or three sides; the smallest of the dimensions of the slab in plan - for slabs with support along the contour.

PG - 260 thick with pear-shaped voids, intended for support on both sides;

PB - 220 mm thick, manufactured by continuous molding on long benches and designed to be supported on both sides.

These types of hollow-core slabs are intended for use in residential and public buildings:

With walls made of bricks, stones and blocks;

With walls made of large panels;

With monolithic concrete walls;

Frame constructive system.

Plates 1PC can also be used for industrial buildings. The use of 7PK type slabs is limited to low-rise residential buildings.

Wide application of hollow-core slabs in construction (Figure 2.4) largely determine their merits:

Strength, stiffness and crack resistance;

Small reduced thickness due to the high voidness of the sections, reaching 50%;

Sufficient sound insulation of the floor, provided by the mass of the slabs in combination with the floor structure;

High fire resistance of the floor;

High level of prefabrication of prefabricated elements, which provides a smooth ceiling and an acceptable surface for flooring;

The possibility of a device in the plates of utilities.

Hollows in slabs designed to be supported on two or three sides, are located in the direction of the length of the plates. In slabs supported on four sides, voids are located parallel to either side of the slab.

Plates are made with grooves or grooves on the lateral edges for the formation of intermittent or continuous dowel, providing joint operation of floor slabs for shear in horizontal and vertical directions.

Plates designed to be supported on two or three sides with a length of more than 4.8 m have pre-stressed reinforcement.

Reinforcement of the ends of the plates, necessary when transferring the load, is achieved by reducing the cross-section of the voids on the supports (on the one hand) and filling the voids with concrete (on the other side).

Slabs can have (in accordance with the design of a particular building) embedded parts, outlets of reinforcement, local cutouts, holes, and other additional structural details. For lifting and installation of plates, mounting loops or special gripping devices (holes) are provided in them.

Hollow-core slabs are made of heavy concrete of classes B15-B25 and structural lightweight concrete of dense structure with an average density of at least 1400 kg / m 3.

Hollow-core slabs with support on two sides (beam slabs) are calculated in the longitudinal direction for bending as free-lying single-span beams. According to the calculated values ​​of bending moments and transverse forces, the required amount of longitudinal and transverse reinforcement is assigned. Longitudinal working armature with a diameter of 10-18 mm of classes A-IV and A-V is included in the lower grid. The transverse reinforcement is installed in the extreme edges of the section, and, if necessary, on average, according to the results of the calculation for the shear force. An example of reinforcing a hollow core slab is shown in rice. 2.5.

In the manufacture of plates of the PB type, modern continuous formwork method on heated long stands. The molding machine with targeted supply of concrete mix moves at a speed of 0.6-3.5 m / min. Addressable heating of the track guarantees the maturation of concrete up to 70% strength in 16 hours, after which a computer-controlled diamond disk cuts the reinforced concrete tape into slabs of any given length (2.4-9 m), including trapezoidal in plan. The nominal width of such slabs is 1.2 or 1.5 m. Reinforcement is performed with prestressing rods of wire reinforcement of classes VI and VR-I with a diameter of up to 8 mm or seven-wire rope reinforcement of class K-7 with a diameter of up to 15 mm.

Rice. 2.5. Reinforcement of the hollow core slab: a - cross section; b - longitudinal section; 1 - bottom welded mesh; 2 - longitudinal working reinforcement; 3 - vertical flat welded frames; 4 - mounting loop; 5 - top welded mesh; 6 - protective concrete layer; 7 - distributor fittings.

Hollow-core slabs are used in the floors of stone and monolithic concrete buildings with longitudinal-wall and cross-wall structural systems (fig. 2.6).

The role of ceilings as hard disks is in the perception of all vertical and horizontal loads that fall on them, as well as in ensuring the unity of the load-bearing frame when the walls of the building are absorbed by force. Therefore, the slabs have anchor links between themselves and with the load-bearing walls. (see fig. 2.6).

If necessary, the device of vertical communications between the slabs or between the wall and the slab, leave a gap of up to 300 mm, which is subsequently filled with concrete with the installation of flat reinforcing frames (nodes 5,6, 9 - fig. 2.6).

In buildings with monolithic concrete walls, hollow-core slab floors can be made according to carved or uncut schemes (fig. 2.7). At the same time, the design of the joints of the floors with the walls should ensure the unhindered passage of the vertical reinforcement of the walls through them.

Table 2.2 Solid reinforced concrete floor slabs for large-panel buildings (according to GOST 12767-94)

With free support on the walls (sectional diagram), the floor slabs must have support protrusions that extend beyond the wall edge to a depth sufficient for anchoring the longitudinal reinforcement of the slabs, but not less than 70 mm. In this case, the connection of the slabs at the ends, in addition to the indicated method, can be carried out by embedding the reinforcement cages in the voids of the slabs ( rice. 2.7 a).

With a rigid connection to the walls (continuous scheme), floor slabs must have reinforcing outlets - straight, looped, hooks. The rigidity of the nodes is achieved by welding the upper and lower outlets of the reinforcement (fig. 2.7 b), combining looped outlets and anchoring them with horizontal reinforcing bars (Fig.2.7 c, d).

Rice. 2.7. Interfacing of hollow core slabs with monolithic concrete walls:

a - freely supported slabs on the inner wall (split diagram); b, c - rigid joints of floor slabs with internal walls; d - the same, with an outer wall; 1 - inner wall; 2 - outer wall; 3 - hollow-core slab; 4 - plug; 5 - reinforcing cage; 6 - straight reinforcement outlet; 7 - loop reinforcement outlet.

In low-rise buildings and apartments on two levels, it becomes necessary to arrange stairways in the ceilings. These openings can be designed without any additional vertical supporting structures using rolled steel profiles supported by walls or main floor slabs. (fig. 2.8).

Reinforced concrete solid floor slabs for large-panel buildings subdivided into types according to their thickness and pattern of support on wall panels (Table 2.2).

The thickness of the slabs is taken from 100 to 200 mm. The most widely used slabs are made of heavy concrete with a thickness of 160 mm.

Slabs are supported on the walls on four sides (along the contour), on three or two opposite sides. Based on this, the working reinforcement of the slabs is located in two or one direction. Slabs with a length of more than 4.8 m, designed to be supported on both sides, have, as a rule, prestressed reinforcement.

Coordination dimensions of the slabs: length 3.0-7.2 m (through 0.3), width 1.2-6.6 m (through 0.3). The length of the slab is taken: when it is supported on four sides - the smallest of the dimensions of the slab in the plan; when it is supported on three or two sides - the size of the side of the slab not supported by the supporting structure. According to the transportation conditions, one of the dimensions of the slab should not exceed 3.6 m.

Plates have (fig. 2.9):

Steel embedded parts, outlets of fittings and other structural elements for connection with adjacent building structures;

Channels for hidden electrical wiring, sockets for boxes and sockets, plastic boxes with anchors for fixing luminaires;

Rice. 2.8. Arrangement of openings for intra-apartment stairs in ceilings with hollow-core slabs: a - when adjacent to one wall; b - when adjacent to two walls; A, B, C, D - nodes.

Holes and openings for the passage of utilities.

The side faces on the sides of the plates of the PD and PT types, intended for joining in the span (without leaning on the walls), are performed with closed or open recesses, the shape of which ensures the joint operation of the mating plates for shear in the horizontal and vertical directions after the grouting of the joints between the plates ... The slabs can have recesses for the formation of dowels also on the sides, supported by the wall panels.

The depth of the platform for supporting the slabs on the outer walls is 90 mm (fig. 2.10). The nominal size of the depth of the platform bearing on the inner walls is equal to half the thickness of the wall panel minus 10 mm, except for the cases when the plates are supported on the walls of the staircase, where the plates are supported for the entire thickness of the walls. The support of the floor slabs on the walls is carried out using a cement-sand mortar. All steel connections of floor slabs to each other and to external wall panels are welded. At least two ties are provided on each side of the floor slab.

Overlapping buildings with reinforced concrete frames are solved using three types of products:

Hollow-core slabs with a height of 220 mm;

Ribbed slabs with a height of 300 or 400 mm;

Plates type "TT" and "T".

Rice. 2. 9. Reinforced concrete solid floor slab, type PT for large-panel buildings:

1 - embedded corner for joining plates for welding; 2 - sling loop; 3 - loop outlet for connecting plates; 4 - hole for the ventilation block; 5 - hole for communications; 6 - hidden wiring channel; 7 - box for fixing the lamp.

Hollow-core slabs for buildings with reinforced concrete frames of the 1.020.1 series are designed to cover spans 3.0; 6.0; 7.2; 9.0 m (fig. 2.11). Coordination dimensions in width - 3 m (only for a span of 6 m); 1.5; 1.2; 0.9 m.Along with them, ribbed (trough) plates, also 220 mm high and 1.5 m wide, are used as plumbing plates in the places of passage of vertical engineering communications.

Hollow-core slabs are laid on the shelves of crossbars or stiffening diaphragms over a 10 mm thick layer of cement mortar. Flat reinforcing cages are installed in the seams between the slabs and poured with cement-sand mortar. Intercolumnar slabs of the frame floors are also installed on the shelves of the crossbars (stiffness diaphragms) along the internal axes of the buildings and, with the help of reinforcing assembly products, are connected to each other by arc welding (node ​​B - see fig. 2.11).

Rice. 2.10. Scheme of the assembly plan and joints of the floor slabs:

1 - floor slab; 2 - outer wall panel; 3 - inner wall panel; 4 - connecting rod; 5 - freeze-out concrete; 6 - connecting bracket; 7 - cement mortar; 8 - mounting loop; 9 - loggia floor slab.

Ribbed reinforced concrete floor slabs 300 mm high are intended for floors of multi-storey public and industrial buildings for various purposes with a column pitch of 6 m with a maximum load on the slab up to 26 kPa (2600 kgf / m 2). The shapes, sizes of the slabs and their purpose are indicated in tab. 2.3 and on Figure 2.12.

The slabs can have holes with a diameter of 400, 700 and 1000 mm, cutouts in the shelves, recesses on the outer edges of the longitudinal ribs for installing concrete dowels between adjacent slabs, additional embedded parts.

The ribbed slabs are installed "dry" on the ledger shelves or stiffening diaphragms and welded to the ledger shelves.

Slabs are made of heavy concrete with an average density of 2200 kg / m 3 or lightweight concrete of dense structure with a density of at least 1600 kg / m 3.

Rice. 2.11. Hollow-core slabs with a height of 220 mm and their location in the ceilings of frame buildings: a, b - in the span of girders 3 m; c, d - in the span of crossbars 6 m; d, e - in the span of crossbars 7.2 m; g, h - in the span of the girders 9 m; 1 - row plate; 2 - intercolumnar (tie); 3 - intercolumnar near-wall; 4 - sanitary ribbed plate; 5 - transverse crossbar; 6 - longitudinal girder; 7 - reinforcing cage; 8 - column; 9 - connecting rod.

Ribbed reinforced concrete floor slabs 400 mm high are intended for floors of industrial buildings for various purposes with a frame column pitch of 6 m with a maximum load on the slab up to 52 kPa (5200 kgf / mg 2).

Plates, depending on the way they are supported on the crossbars of the building frame, are divided into two types (table 2.4):

1P - with support on the shelves of the crossbars;

2P - leaning on the top of the crossbars (fig. 2.13).

Plates of type 1P are provided in eight standard sizes (1P1-1P8), type 2P - one standard size (2P1).

Reinforced concrete prestressed slabs of type "TT" and "T"(Figure 2.14) intended for floors of public and industrial buildings with a column pitch of 9 m (coordination length of slabs).

Rice. 2.12. Ribbed slabs with a height of 300 mm and their location in the floors of frame buildings:

a, b - in the span of the crossbars 3 m; c, d - in the span of crossbars 6 m; e, f - in the span of the girders 9 m; 1 - ordinary plate; 2 - ordinary and intercolumnar (tie); 3 - intercolumnar wall; 4 - additional solid section slab; 5 - transverse crossbar; 6 - longitudinal transom; 7 - reinforcing frame; 8 - embedment concrete.

Table 17.5. Reinforced concrete ribbed floor slabs 300 mm high

Slab "TT" with two ribs in the longitudinal direction has a width of 3 m and can be used both as a row and as an inter-column (tie) slab. Slab "T" with one edge has three standard sizes: 1.5m wide - row -

vaya and intercolumnar; 1.3 m - ordinary additional; 1.7 m - intercolumnar wall. The height of all slabs of type "TT" and "T" 600 mm - corresponds to the height of the crossbars of the reinforced concrete frame. The support is carried out on the ledges of the crossbars by the thickened ends of the plates with trimming of the longitudinal ribs (Fig.2.14 d), which allows you to solve the overlap without protruding individual elements.

Differ in architectural expressiveness coffered ceilings public buildings made of reinforced concrete slabs with not only longitudinal, but also transverse (sometimes diagonal) ribs of the same height (Figure 2.15). In this case, two types of slabs are used - ordinary and side (intercolumnar). The overlap is solved on a square grid of columns with a pitch of 6 or 7.5 m.The modular dimensions of the width of the slabs and the pitch of their ribs are assumed to be 1.5 m. three. The supporting parts of the slabs have undercuts from the bottom to the height of the girder flange.

Rice. 2.14. Slabs of type "TT" and "T" and their location in the floors of frame buildings:

a - in the span of the crossbars 3 m; b - in the span of crossbars 6 m; c - in the span of the girders 9 m; d - unit for supporting the slab on the crossbar; 1 - row and column slab 3 m wide; 2 - the same, 1.5 m wide; 3 - ordinary additional plate; 4 - intercolumnar wall; 5 - ri-gel at the end of the building; 6 - fine-grained concrete.

The fastest and most economical way of organizing the interfloor separation and separation of the residential part of the house from the attic and basement is to lay floor slabs on a brick wall. Monolithic structures are rarely preferred, when for some reason it is impossible to use ready-made slabs, for example, the road does not allow the crane to drive up to the object.

Product types

The installation of the floor must be approached responsibly. The strength of the structure depends on this.

Plates are flat or ribbed (PKZH). The large-panel reinforced concrete slab has a U-shaped section. They are used in the construction of industrial and technical facilities, in conditions of increased loads and long spans. Stiffeners increase the load-bearing capacity. In residential construction, they are used to separate the first floor from the basement, since a section of this type does not allow obtaining an even ceiling.

Flat slabs are produced with voids or with solid fill (PT). The technical underground slab is used in public buildings to cover the channels under the floor. In the construction of private houses, it can be used as an additional element for flooring over small spans of corridors, bathrooms. In residential construction, hollow-core products are used. They are cheaper, weigh less and are easier to install. Air voids help retain heat better and increase sound insulation. Depending on the method of production, they are divided into 2 types.

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Hollow-core formwork

PCs have been used in private construction for over 20 years. In the manufacture of reusable forms of sizes (formwork) are used. To reduce the cost of production, formwork of standard parameters is used. The price of a custom-made product will be much more expensive. The thickness of the plate is 220 mm, Depending on the width and length, options are provided, which are presented in the table:

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Continuous production

PB - made using a new technology on a continuous conveyor, then cut. They have a smoother surface, which greatly simplifies further finishing. Made from harder concrete. At the request of the client, the length can be any, with an accuracy of 10 mm. It is possible to cut the end side of the product at an angle. The only drawback is the width, it is standard - 1.2 m.

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The slabs must be laid on the walls without gaps in width. You need to be especially careful about the top row of brickwork. It needs to be well aligned and the inside of it should be laid with the butt side. Even before laying the PC or PB on the wall, it is necessary to close up the voids with liners or a piece of brick with mortar. The slab support unit is formed with the condition that a distance of 1-2 cm should remain between its end and the place of abutment in the stone. The solution for fixing the floor and masonry must be the same.

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Calculation of support parameters

The amount of overlap on the wall depends on the purpose of the building, the width of the wall, the thickness and weight of the ceiling, the seismic activity of the construction area, and the length of the span to be covered. The specific amount of support is calculated by the engineers during the design. As a rule, to guarantee reliability, taking into account deviations during installation, the maximum value according to SNiP is selected 120 mm. The laying of floor slabs PB and PC in a brick house is carried out with a support on two short sides. The smallest support is presented in the table:

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Features of masonry slabs

The installation of the ceiling is carried out using a crane. In addition to the crane operator, you need 3 workers. One hooks the slings to the fixing loops of the slab, and the other two are installed on the wall. If there is no visibility between the fitters and the crane operator, another person is needed. The PC must be laid rigidly, with bricks on top and bottom of the slab. When laying PB, a hinge is used.

It should be borne in mind that it is forbidden to make technological holes in the formwork plates and shorten them. This reduces the strength of the existing structure, since they have reinforced reinforcement in the support zones. The possibility of supporting hollow-core products on a third side should be checked with the manufacturer. This can lead to cracking. Do not overlap two spans with one PC or PB.

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Cracked

Sometimes cracking of the product occurs due to improper transportation or storage. If the cracks are 4-10 mm and there are many of them, it is better to cut off the damaged part and not use it. If the marriage is small, the product can be put into operation in compliance with the following installation rules:

• Use in a place where there will be the least stress, for example, for an attic floor.
• Mount between two complete PCs or PBs, carefully fastening them together.

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Insufficient width

If the existing standards were not taken into account in the design of the building, it happens that the width of the overlap does not coincide with the dimensions of the room. There are 4 ways to seal the missing space:

• Cut a strip of the required width from the PC or PB.
• Lay the gaps with sagging nets, which rest on the top of floors or ceilings and walls. Fill with concrete.
• Tie up the formwork from below, lay the reinforcement, pour.
• When the width is small, brickwork is sometimes preferred to the monolithic method. "Holes" are left against the walls, stones are poked in such a way that one edge they lay on the masonry, and the other rested against the slab. For reinforcement, in front of the floor screed, you can lay this place with mesh or thin reinforcement (6 mm).

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Sealing of seams

After all the slabs have been laid, anchoring is performed. Anchors are made in the form of a U-shaped bracket, the ends are bent into a loop, inserted into the eyes, cling to the mounting loops, pulled as tight as possible and welded. After that, the rusts (seams between the slabs) and holes with hinges are sealed with mortar. It is important to do this quickly, before debris gets in.

etokirpichi.ru

The main thing is where which slabs and on which sides can be supported:
GOST 9561-91
1.2.1. Plates are divided into types:
1PK - 220 mm thick with round voids with a diameter of 159 mm. designed to be supported on both sides;
1PKT - the same, for support on three sides;
1PCK - the same, for support on four sides;
2PK - 220 mm thick with round voids with a diameter of 140 mm, designed to be supported on both sides;
PG (260 mm thick with pear-shaped voids, designed to be supported on both sides;
PB (220 mm thick, continuously molded on long benches and designed to be supported on both sides.

1.2.8. Reinforcement methods and minimum dimensions of the fittings are set in the working drawings or indicated when ordering plates.

We look at working drawings and materials for design and technical requirements
Code 0-453-04.0, where paragraph 4.11 explains that the amount of pinching of the plates depends (one of the points) on the material of the walls:

4.11 When using slabs in the ceilings of buildings with support on the masonry of load-bearing walls made of
bricks, ceramic or concrete small blocks, as well as with large-block and
panel walls with platform nodes of floor support should be made
additional design checks for fracture toughness of normal sections along the edges
supports and inclined sections at the ends of the slabs.
At the ends of the slabs inserted into the masonry of the walls or clamped in the platform nodes of the panel
walls, from loads in excess of their own weight, support (negative)
bending moments to be taken by an unreinforced concrete section
slabs (along the length of reinforcement slippage and at the beginning of the anchorage zone). The quantities
pinching moments due to the resistance of the wall material to the rotation of the ends of the slabs
on supports, depend on many factors:
the magnitude and distribution of the load;
span length (angle of rotation of the axis of a freely supported slab under uniform load
proportional to the length of the span to the third degree);
deformation modulus and strength of the wall material;
characteristics of mortar joints around the sealed end of the slab and their level
compression.

4.13 A complex stress is formed at the ends of the slabs inserted into the walls under loading.
condition (Figure 2).
r /> Depending on the depth of support, strength and deformability of the wall material, different trajectories of crack propagation are possible (Figure 3).
In slabs with constructive longitudinal stress-free reinforcement at the upper edge and
transverse reinforcement in ribs, development of cracks with a decrease in the pinching moment
the working capacity of normal and inclined sections stops and remains.
For slabs reinforced only with longitudinal high-strength reinforcement, cracks in
normal and inclined sections at supports are unacceptable, since with their appearance they can
the shear strength of the slabs has been exhausted.

We read paragraph 9.12
the depth of insertion of slabs into the walls (length of support lon) should not exceed for
brick walls - 160 mm, for walls made of small blocks of classes B3.5 and B7.5 - 200 mm,
for buildings made of large concrete and reinforced concrete blocks - 120 mm.
The minimum length (depth) of support of the slabs on load-bearing reinforced concrete beams, walls and
panels made of dense concrete of class B10 and higher must be at least 65 mm; on brick
walls not less than 80 mm; on walls made of aerated concrete, polystyrene concrete, foam silicate
blocks - 100 mm.
Further on slabs TU-5842-001-01217316-05 (2005)

2.6.2 Slabs do not have horizontal and vertical transverse reinforcement, their
strength when lifting in longitudinal sections is provided only by concrete, therefore
strict adherence to those specified in the working drawings and technological documentation
rules for slinging and supporting plates, the use of only specially tested and
lifting devices equipped with approval labels is mandatory.
r /> 2.7 When operating slabs corresponding to TU, as part of the floors of buildings (structures)
danger is represented by possible cases of violation of the established in the working drawings
rules for their support on supporting structures (walls, floor beams).
The manufacturer is obliged to notify the consumer about the need to ensure:
compulsory support during installation of the support zone along the entire width of the slab per layer
solution to exclude the formation of longitudinal cracks along the voids from bending into
transverse direction;
on compliance with the minimum support length of at least 65 mm over the entire width (under
each of the ribs) of the plate;
on the need to limit the maximum length of embedding of slabs into the masonry of walls made of
bricks or concrete blocks to prevent the appearance of supporting bending
moments.

www.forumhouse.ru

When developing drawings for prefabricated floors, it is imperative to show the nodes for supporting these slabs on the walls, as well as fastening the slabs to the walls and to each other with metal anchors (in detail, such nodes are developed in series 2.140-1, issue 1 "Floor details of residential buildings").

This drawing shows a unit for supporting a hollow core slab on a brick outer wall. The depth of support of the slab is 110 mm, if we take into account the seam of 20 mm, then in total the niche for the slab is a multiple of the size of the brick, which is convenient for masonry workers. The slab rests on a masonry mortar. The joints between the slabs (10 mm) and between the wall and the slab (20 mm) are carefully filled with mortar. An anchor made of smooth reinforcement with a diameter of 10 mm (reinforcement class A240C or A-I) enters the wall seam with one end, and is hooked onto the loop and welded with the other. It is recommended to install one anchor for every second slab along each wall, it is optimal when the anchors are installed in a checkerboard pattern and cover all floor slabs (at least one anchor per slab). Then the overlap is considered a single disc, and all the slabs work together.

Welding is carried out in accordance with GOST 14098-91, type 42 electrodes.

The anchor is protected from corrosion with cement mortar of the M100 brand, the thickness of the mortar layer is 30 mm.

The voids of the slabs resting on the outer wall must be filled with factory-made concrete inserts, the installation of which is mandatory when the design resistance in the wall at the floor level is more than 17 kg / cm 2. If the liners are not installed, the slab will collapse under the load from the wall. It is recommended to support the slabs with the liner side on the less loaded external walls, and on the more loaded internal walls - with closed ends formed by molding.

You can download the drawing in pdf and dwg format here.

svoydom.net.ua

Types by support method

The slab used for the interfloor separation is a reinforced concrete structure with voids. The holes in the slabs come in various shapes and sizes to lighten the weight of the component.

The choice of interfloor overlap and the depth of its support depends on the structural features of the building. The following parameters are taken into account:

• the purpose of the building (residential, industrial, public);
• the material from which the structure was erected;
• wall thickness;
• types of loads acting both on the slabs and on the building;
• seismic characteristics of the building area.

By type of support interfloor slabs are divided into three categories... Their choice is carried out at the planning stage of the project, taking into account the calculations of the loads acting on the load-bearing elements of the building.

On two sides

These slabs are supported by two opposite load-bearing walls. They are laid on capital elements, with narrow (transverse) sides. Most often, for this type, floor slabs with round voids are used, marked with PC, 1 PC, 2 PC. They are capable of withstanding loads of up to 800 kg / m².

On three sides

They have reinforced end reinforcement and fit on three load-bearing walls. They are mounted in the corners of a building with a U-shaped structure of load-bearing walls. They are designated by the PKT marking, and can withstand a load of up to 1600 kg / m².

On four sides

Such plates are reinforced with reinforcement at all ends, they are more rigid and have an increased bearing capacity. They are used only in complex structures where maximum distribution of high loads is required, or in cases where additional superstructures are planned to be erected. They have the PKK marking, indicating increased strength. In low-rise construction, they are practically not used.

Depth of the establishment on the walls

All floors, regardless of the installation method, can be laid on a foundation or load-bearing walls made of bricks, reinforced concrete panels, aerated concrete or foam blocks.

It is important to know how much a hollow reinforced concrete product can be supported on. This depth depends on the material from which the supporting structures are erected.:

• brick - from 9 to 12 cm;
• panel - from 5 to 9 cm;
• aerated concrete or foam block - from 12 to 25 cm.

Failure to comply with the recommended laying depth is fraught with the destruction of the walls, due to incorrectly distributed loads. Insufficient depth leads to coloring of the inner layer of the masonry and plaster, or cracking panels. An excessive distance taken up under the support will lead to the destruction of the outer part of the wall.

Diagram of the correct and incorrect bearing on a brick wall:

Excerpt from SNIP

JV Large-panel structural systems. Design rules "

4.3.17 The depth of support of precast slabs of a solid section on concrete and reinforced concrete walls, depending on the nature of their support, is taken not less:

• 40 mm - when supported along the contour, as well as on two long and one short sides;
• 50 mm - on two sides and a span of 4.2 m or less, as well as on two short and one long sides;
• 70 mm - on both sides and a span of more than 4.2 m.

The support of hollow-core slabs without formwork on the wall panels is carried out on two sides, that is, according to a beam scheme with a support depth of at least 80 mm for slabs with a height of 220 mm or less, and at least 100 mm for slabs with a height of more than 220 mm.

In all cases, the maximum bearing depth of hollow-core slabs without formwork is taken no more 150 mm.

Support on three or more sides of hollow-core slabs without formwork (insertion of the longitudinal side of the slabs into the walls) not allowed.

Armopoyas

Before the installation of floors on the main structures, a monolithic armored belt is installed. It is carried out along the perimeter of the area of ​​the main walls, over their entire width. A formwork is installed along the edge, then a reinforced frame of longitudinal, transverse and vertical reinforcing bars is mounted, and poured with concrete.

When erecting an armored belt, be sure to comply with the following requirements:

1. The height of the armored belt is from 20 to 40 cm (not less than the height of a standard aerated concrete block).
2. The width must match the width of the structural member.
3. Reinforcement thickness - at least 8 mm. The frame is rigidly knitted with wire or fastened by welding.
4. The concrete must correspond to the grade of the mortar used for the masonry. The recommended grade of used concrete is at least B15 class.

Armopoyas serves to evenly distribute all loads. It also installs reinforcing fasteners, which are designed for reliable installation of interfloor ceilings. Since the armopoyas is a cold concrete layer, a thermal insulation coating is provided on it.

Supporting nodes

They are designed for reliable and correct fixing of floor slabs on capital elements. Laying the slab and fixing it to the wall is carried out using mortar and rigid reinforcing joints.

Nodal connections must meet the following requirements:

• the end sides of the slabs should not be closely adjacent to the masonry;
• thermal insulation is performed between the masonry and the ceiling;
• it is recommended to close the hollow holes with special liners to prevent heat loss;
• the connection of the ceiling and the armored belt is performed by rigidly connecting the armature of the armored belt with the reinforcing rods of the slab by means of welding.

The nodes depend on the number and type of capital elements. For support on two sides, they are performed on transverse load-bearing walls, and for support on three or four sides - both on transverse and longitudinal walls. Nodes are also performed when columns, trusses and floor beams act as load-bearing elements.

When laying floor slabs, it is necessary to take into account all the parameters necessary for their correct bearing on the supporting elements. The choice of slabs, the calculation of nodes, armored belts and the depth of support are carried out at the stage of building design.

Do not forget to seal the seams after installation.

Useful video

The video clearly tells why it is impossible to lean against the wall with a deep institution. Only I would argue with the value of the maximum depth of 30 cm.It should be no more than 15 cm.

izbloka.com

Parameters that determined the amount of support

The depth of the overlap on the walls depends on the following factors:

• purpose and type of buildings - residential, administrative, industrial;
• material and thickness of load-bearing walls;
• the size of the span to be covered;
• dimensions of reinforced concrete structures and their own weight;
• the type of loads acting on the floor (static or dynamic), which of them are permanent and which are temporary;
• values ​​of point and distributed loads;
• seismicity of the construction area.

All the factors listed above are necessarily taken into account when performing calculations of the reliability of the construct. In accordance with the current regulatory documents, the support of the floor slab on a brick wall is taken from 9 to 12 cm, the final size is determined by engineering calculations during the design of the building. With less overlaps, the heavy dead weight of the elements, together with the existing loads, will have a direct effect on the edge of the masonry, which can lead to its gradual destruction.

On the other hand, a larger overlap will already be a kind of pinching of reinforced concrete elements with the transfer of weight from the upper section of the wall to their ends. The result is cracking and slow destruction of the wall masonry. Also, when the ends of the products approach the outer surfaces of the walls, an increase in heat loss in reinforced concrete elements occurs with the formation of cold bridges, leading to the formation of cold floors. The cost of parts is proportional to their length, so excessive pinching will increase the cost of the structure.

When erecting brick buildings with precast concrete slabs, the laying is carried out in full thickness up to the design bottom of the ceilings. Further, the bricks are laid only on the outside of the walls to form a niche into which the slabs can be laid.

It is important to observe the following conditions in the support nodes:

• the ends should not rest against the brickwork, so for the overlap most often used in practice of 12 cm, the width of the niche is ≥ 13 cm;
• the mortar on which the slabs are laid is of the same brand as the masonry;
• the voids in the channels are sealed from the ends with the help of concrete inserts, which will protect the ends from destruction when squeezed under loads. The production of concrete liners is carried out in factories with delivery upon purchase of slabs; in the absence of liners, the channel voids are filled with B15 concrete directly at the construction site.

On the end brick walls, slab reinforced concrete products also fall on one side. In this case, the minimum support of the floor slab on the end walls is not standardized. But in order to avoid the destruction of the product when the hollow channel is squeezed, the installation should be carried out so that the masonry laid out above the overlap does not lie on the extreme void of the structure and the shoulders of the moments acting from the load should be of minimum values.

Requirements for the device of armored belts for floor slabs

In buildings with walls made of blocks made of lightweight concrete (aerated concrete, aerated concrete, aerated concrete, polystyrene concrete), with low strength characteristics, the overlap must necessarily rely on reinforced belts. Armopoyas is arranged around the entire perimeter of the building. The height of the armored belt under the floor slabs is from 20 to 40 cm. The connection of the reinforced belts with the floor details must be mechanically strong, for which anchoring devices or joining with reinforcing bars of a periodic profile using electric welding are used.

A number of the following requirements are imposed on the design:

• belts should fit the entire width of the walls; for external widths ≥ 50 cm, a decrease of ≤ 15 cm is permissible for laying insulation;
• reinforcement, made using engineering calculations, must provide sufficient mechanical strength to absorb the loads from the dead weight of reinforced concrete elements and upstream structures;
• concrete ≥ class B15;
• the belt is a kind of cold bridge, therefore, its mandatory insulation is necessary in order to prevent the destruction of aerated concrete blocks from accumulated moisture;
• reliability of adhesion to load-bearing walls.

The support of floor slabs on aerated concrete blocks of load-bearing walls along reinforced belts is carried out in compliance with the following standardized values:

• at the ends ≥ 250 mm;
• along the rest of the contour ≥ 40 mm;
• when supported on 2 sides of the span ≤ 4.2 m - ≥ 50 mm;
• the same with a span of ≥ 4.2 m - 70 mm.

Aerated concrete blocks are not able to withstand high loads, the material begins to undergo various deformations. Armopoyas, taking on all the loads, evenly distributes them, thereby ensuring that the structure is not destroyed.

Installation of floor slabs on gas silicate blocks is also performed with the obligatory installation of monolithic reinforced concrete belts. The required support values ​​correspond to the values ​​given above for walls made of aerated concrete blocks.

During the installation work, the following conditions must be met:

• compliance with the symmetry of the laying of elements in the spans;
• the ends of the plates must be aligned in one line;
• all elements must be located in the same horizontal level (control is carried out using a building level), the permissible deviation in the plane of the plates is ≤ 5 mm;
• mortar thickness under the boards ≤ 20 mm, the mortar must be freshly prepared, without starting the setting process. Additional dilution of the mixture with water is inadmissible.

It is unacceptable to lay rows of bricks or reinforcing meshes instead of an armored belt.

stroikadialog.ru

Appointment of floors

Reinforced concrete floor slabs are one of the main load-bearing structures of a building, therefore, enough attention is paid to them during construction. The main function of reinforced concrete floors is to transfer and distribute the load to its own weight, and then to other elements of the building.

By location, these building structures are divided into interfloor, above-basement and attic. Plates are manufactured at the factory and are of several types:

• prefabricated monolithic;
• hollow;
• made from heavy grades of concrete.

The main requirements that high-quality floors should have are strength, rigidity, fire resistance, sound and water resistance.

Most floor slabs are made with voids, this design is considered the most optimal in terms of weight and quality. Laying takes place on the load-bearing walls of the structure, the step of which can be up to 9 m.

Parameters for the amount of bearing

The maximum and minimum support of the slab overlap on the wall is determined by the following factors:

1. The purpose of the building is residential, industrial, administrative.
2. The material from which the load-bearing walls are made and their thickness.
3. The size of the span to be covered between the walls.
4. The size of the reinforced concrete floor slab and its weight.
5. Seismic indicators of the location of the building.

In accordance with the SNiP data, the support of the floor slabs on the walls is from 9 to 12 cm, depending on the factors described above. The final size is determined by the engineers when designing the building. It is important to correctly calculate the amount of overlap, otherwise the pressure of the floors can lead to gradual cracking and destruction of the building.

When building brick buildings, the masonry is carried out close to the future ceiling, while it is important to leave small niches for the installation of ceilings. The node for supporting the floor slab on the wall is created taking into account the following conditions:

• the ends of the slabs should not rest on brickwork. For example, with an overlap of 12 cm, the width of the niche should be 13 cm;
• the composition of the mortar for masonry and fixing floors must be identical;
• the voids formed in the channels should be filled with concrete liners. They are manufactured at the factory together with the slabs.

The minimum support of floor slabs on a brick wall is not standardized if a reinforced concrete product rests on the end walls with one side. Installation is carried out so that the masonry, which will be higher than the floor, does not lie on the formed extreme voids.

Installation of floors

Work on the installation of floors is carried out by a construction team of four people:

• crane operator who feeds the slab,
• a rigger performing slab sling,
• two installers coordinating the slab and placing it in a given location.

At the same time, supporting the floor slabs on a brick wall is one of the most important procedures that requires strict adherence to standards.

Before carrying out installation work, it is imperative to level the brickwork ridge. If this is not done, the stove will be unstable. The gaps between the slabs are sealed with cement mortar.

Features of installation of ceilings for aerated concrete buildings

The support of the slab overlap on the wall is carried out on an annular reinforced belt, which is mounted along its perimeter. Such a monolithic concrete tape covering the entire building is required if the support is less than 12 cm.The following parameters are recommended for an armored belt:

• thickness 12 cm;
• width 25 cm;
• the bearing depth is the same as for reinforced concrete slabs.

In combination with strong reinforced concrete slabs, the reinforced belt creates a rigid structure that provides sufficient resistance to the structure to emergency impacts, temperature extremes and shrinkage deformations.

If the amount of support of the ceiling on the wall is more than 12 cm, then the building does not need an additional reinforced belt. In such cases, it is sufficient to construct a reinforced belt from an annular anchor along the outer perimeter of the slabs.

Calculation of the bearing parameter

Regulates the amount of support of floor slabs on the walls of SNiP (otherwise, a set of rules and regulations), highlighting the following types of slab sizes:

• modular - the width of the span in which the structure is installed;
• constructive - the actual size of the ceiling slab from one end to the other.

For example, if the modular floor length is 6.0 m, then the real one is 5.98 m.To obtain a room size of 5.7 m, a slab should be installed with a support of 12 cm. warmth in the room. If the end is too close to the outer surface of the wall, cold air will penetrate inside. This design gives a cold floor in winter.

Basement floor slab

Installation of floor slabs for the basement floor is the easiest. In order to achieve a flat surface for laying reinforced concrete structures, the upper edge of the foundation should be leveled. Then formwork boards are placed along the upper edge of the poured foundation. This structure is filled with concrete. Thus, a perfectly flat cushion for the installation of the plates is obtained.

Installed on a smooth surface, the slabs form a flat ceiling, in which you just need to close up the seams, after which it is ready for finishing.

Sealing joints between slabs

After the optimal size of the support of the floor slabs on the walls has been determined, and the reinforced concrete structures themselves have been installed, you should start sealing the joints between them.
For this, a sand-cement mortar is used if the gaps are insignificant. If there are large gaps, you should use the following methods:

1. Formwork is arranged from wooden planks, into which the subsequent pouring of the solution takes place.
2. Large gaps can be filled with rebar debris, brick fragments and other materials. They are tamped into cracks, which are then covered with concrete.

It is important to seal the voids formed during the installation of the slabs immediately. This greatly simplifies the finishing work that will be carried out at the end of the construction.

The future strength and durability of the structure depends on the correct calculation of the amount of support of the floor on the wall. Therefore, this process is regulated by the rules of SNiP and is carried out by experienced designers.

Comments:

During the construction of a building, such an important issue as the support of floor slabs must be taken into account.

Building codes have special instructions in this regard.

Important structural element

Ceilings are load-bearing elements of a building made of reinforced concrete structures. They receive and distribute the loads from their weight and the people and equipment in the building on the walls and supports. With their help, the internal space of the building is divided into floors, and the attic and basement are separated.

Overlapping in a building must meet many requirements. They must be durable, tough, have good sound insulation characteristics, do not burn and do not allow water to pass through.

The material used for the production of floor slabs is reinforced concrete. Basically, these are hollow-hollow structures with voids of various shapes: polygonal, oval, round. Most often, elements with round voids are used in construction. They are highly durable, technologically advanced and completely ready for installation. Their bearing capacity is 800 kg / m². They are placed on load-bearing walls spaced about 9 m apart. Lean on two sides. They are distinguished by fire resistance, rigidity, long service life. Brick, aerated concrete, foam blocks and reinforced concrete panels are used as the material for the walls on which such overlapping elements will be laid.

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Some calculations

To find the amount of support for the floor slab, the base on which it is planned to be laid is of great importance. It is imperative to take into account the length and weight of the structure, the thickness of the support wall, the seismological stability of the building. In addition, the load and its nature must be taken into account, whether it will be temporary or permanent. Such calculations should be carried out by specialists. For an individual developer, when drawing up a project and installation, the marking of the manufacturer becomes the main reference point.

When using flat overlapping elements, the span can be calculated as follows: you need to add the thickness of this element and the distance between the two supports. As for the depth of support of the floor slab on the brick base, this value should be equal to the thickness of the structure itself, but not less than 70 mm. To calculate the minimum thickness of the outer wall, which will become the basis for the floor slabs, it is necessary to take into account the thermal insulation layer and the facing material on the end parts of the latter. So, a structure with a thickness of 140 mm must be supported by a base, the thickness of which is at least 300 mm.

The installation of often ribbed structures that have inserts assumes a minimum deepening of the floor slabs on the base - 150 mm. During installation, do not allow hollow liners to enter the wall. If the ribs are reinforced with two rods, then it is necessary to bend them after one at the support. If the rib has one bar, then the stirrups will take shear stress.

Reinforced stone structures are analogs of flat ones. Therefore, the minimum value of the bearing depth of these elements can be determined in the same way. They must be at least 90 mm thick, they are supported on two sides.

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Individual construction

In the specialized literature on construction work, a definition of the necessary standards for the depth of support of floor slabs is given. This figure is in the range of 90-120 mm. For a more accurate determination of this value, certain calculations must be made, which take into account the length and weight of the structure, the thickness of the supporting wall and the material from which it is made. The expected load must also be determined.

For example, the use of a slab, the length of which is 6 m, assumes a depth of support on a brick base of at least 100 mm. When using structures made of reinforced concrete or steel, a depth of at least 70-75 mm is permissible, on walls made of foam blocks and aerated concrete - at least 120 mm.

Floor slabs

Factory floor slabs are a very popular option for floors in IZHS, because the alternative - a monolithic concrete floor - is a much more time-consuming thing, difficult for inexperienced private developers. Unlike the monolith, the slabs come with a factory-guaranteed maximum load, which is more than enough in a private house.

Description

• GOST 9561-91 “Reinforced concrete hollow-core floor slabs for buildings and structures. Specifications. "
• GOST 26434-85 “Reinforced concrete floor slabs for residential buildings. Types and basic parameters. "

• 1PK - 220 mm thick with round voids with a diameter of 159 mm, designed to be supported on both sides;
• 1PKT - the same, for support on three sides;
• 1PCK - the same, for support on four sides;
• 2PK - 220 mm thick with round voids with a diameter of 140 mm, designed to be supported on both sides;
• 2PKT - the same, for support on three sides;
• 2PCK - the same, for support on four sides;
• 3PK - 220 mm thick with round voids with a diameter of 127 mm, designed to be supported on both sides;
• 3PKT - the same, for support on three sides;
• 3PCK - the same, for support on four sides;
• 4PK - 260 mm thick with round voids with a diameter of 159 mm and cutouts in the upper zone along the contour, intended for support on both sides;
• 5PK - 260 mm thick with round voids with a diameter of 180 mm, designed to be supported on both sides;
• 6PK - 300 mm thick with round voids with a diameter of 203 mm, designed to be supported on both sides;
• 7PK - 160 mm thick with round voids with a diameter of 114 mm, designed to be supported on both sides;
• PG - 260 mm thick with pear-shaped voids, designed to be supported on both sides;
• PB - 220 mm thick, manufactured by continuous molding on long stands and designed to be supported on both sides.

Manufacturers produce slabs of different sizes, you can almost always find the size you need.

Floor slabs in most cases are prestressed (paragraph 1.2.7 GOST 9561-91). Those. the reinforcement in the slabs is stretched (thermally or mechanically), and after the concrete has set, it is released back. Compression forces are transferred to the concrete, the slab becomes stronger.

Manufacturers can strengthen the ends of the slabs that participate in the support: fill round voids with concrete or narrow the cross-section of the voids in this place. If they are not filled by the manufacturer and the house turns out to be heavy (the load of the walls on the ends increases accordingly), then the voids in the area of ​​the ends can be filled with concrete yourself.

Plates usually have special loops on the outside, for which they are lifted by a crane. Sometimes the reinforcement loops are located inside the slab in open cavities located closer to the four corners.

Floor slabs in accordance with clause 1.2.13 of GOST 9561-91 are designated as: slab type - length and width in decimeters - design load on the slab in kilopascals (kilogram-force per square meter). The steel grade of the reinforcement and other characteristics may also be indicated.

Manufacturers do not bother with the designation of the types of plates and in the price lists they usually write the type of plate only PC or PB (without any 1PC, 2PC, etc.). For example, the designation "PK 54-15-8" means a 1PC slab 5.4 m long and 1.5 m wide and with a maximum permissible distributed load of about 800 kg / m 2 (8 kilopascals = 815.77 kgf / m 2 ).

Floor slabs have bottom (ceiling) and top (floor) sides.

According to paragraph 4.3 of GOST 9561-91, plates can be stored in a stack with a height of not more than 2.5 m. Spacers for the bottom row of plates and spacers between them in a stack should be placed near the mounting loops.

Supporting the plates

The depth of support of precast plates on the walls, depending on the nature of their support, is recommended to be taken at least, mm: when supporting along the contour, as well as on two long and one short sides - 40; when resting on two sides and a span of plates of 4.2 m or less, as well as on two short and one long sides - 50; with support on both sides and a span of plates of more than 4.2 m - 70.

But there are questions with the maximum depth of support of the plates. Different sources give completely different meanings, somewhere it is written that 16 cm, somewhere 22 or 25. One friend on Youtube assures that the maximum is 30 cm. Psychologically, it seems to a person that the deeper the stove is pushed into the wall, the more reliable will. However, there is definitely a limit to the maximum depth, because if the slab goes too deep into the wall, then bending loads “work” differently for it. The deeper the slab enters the wall, the usually lower the allowable stresses from loads on the support ends of the slab. Therefore, it is better to find out the value of the maximum support from the manufacturer.

Similarly, the slabs must not be supported outside the support zones. Example: On one side, the slab is lying correctly, while the other side hangs down from the middle load-bearing wall. Below I have drawn this:

If the wall is built of "weak" wall materials such as aerated concrete or foam concrete, then you will need to build an armored belt in order to remove the load from the edge of the wall and distribute it over the entire area of ​​the wall blocks. For warm ceramics, an armored belt is also desirable, although instead of it you can lay several rows of ordinary durable solid brick, which does not have such support problems. With the help of an armored belt, it is also possible to ensure that the plates together form a flat plane, therefore, expensive ceiling plastering is not required.

Laying slabs

Floor slabs must be laid on a mortar layer no more than 20 mm thick, aligning the surfaces of adjacent slabs along the seam from the side of the ceiling.

During installation, the plates are placed only on those sides that are provided for support. In most cases, these are only two sides (for PB and 1PK slabs), so you cannot "pinch" the third side with a wall, which is not intended for support. Otherwise, the plate clamped from the third side will not correctly perceive the loads from above, and cracks may form.

Floor slabs should be laid prior to the construction of interior partitions; the slabs should not initially rely on them. Those. first you need to let the slab "sag", and only then build non-load-bearing interior walls (partitions).

The gap between the plates (the distance between the sides) can be different. They can be laid close, or with a gap of 1-5 cm. The space of the gap between the floor slabs is then sealed with mortar. Usually the gap width is obtained "by itself" when calculating the required number of slabs, their size and the distance to be covered.

After laying, floor slabs can be tied together using, for example, welding. This is done in earthquake-prone regions (Yekaterinburg, Sochi, etc.), in ordinary regions it is not necessary.

In places where it is difficult to pick up a floor slab or it is not possible to mount it correctly, a monolithic floor should be poured. It must be poured after installing the factory plates in order to correctly set the thickness of the monolith. You need to make sure of the rigidity of the installation of a monolithic floor, especially if a staircase will rest on it. The space between floor slabs is not always trapezoidal or with slab protrusions on which to lean. If the monolith turns out to be rectangular and does not hold on to the beveled edges of adjacent slabs, then it can simply fall out.

Warming

The load-bearing outer wall 50 cm thick includes a plate with a support of 12 cm, which is insulated from the end with EPS (orange) 5 cm thick.