At what distance does the reinforcement fit?

How to tie reinforcement for a strip foundation

The foundation is the basis of the entire structure, the guarantor of its durability and strength. Strip foundation reinforcement, drawings and diagrams must be prepared and calculated in advance.

The need for reinforcement

The foundation is a monolithic reinforced concrete structure. Concrete itself is a material that can withstand significant loads only in compression. To increase the tensile and bending strength of the foundation, it is necessary to make a metal frame. Moreover, strength indicators increase only due to the arrangement of working longitudinal rods.

Therefore, thick profiled rods with a diameter of 10÷14 mm are used as them. Transverse elements are designed to create the spatial geometry of the foundation; they do not allow the longitudinal bars to move when pouring concrete mortar, and keep them in the right place.

For these purposes, you can use smooth or profiled rods with a diameter of 6÷9 mm.

Requirements of regulatory documents for reinforcement materials

You can learn how to properly reinforce a strip foundation by reading the regulatory documents. The requirements that must be observed when reinforcing a monolithic strip reinforced concrete foundation are set out in SNiP (No. 52-01-2003).

Types of steel rods recommended for reinforcement:

• hot-rolled smooth or profiled (Ø=3÷80 mm);
• thermomechanically strengthened profiled (Ø=6÷40 mm);
• cold-rolled profiled or smooth (Ø=3÷12 mm).

Important! Compared to smooth ones, profiled rods have better adhesion to concrete: this can significantly increase the reliability of the structure.

Requirements for the arrangement of rods in the reinforced frame for a strip foundation:

• the distance between the longitudinal rods should be no more than 0.4 m;
• the pitch of the transverse fixing elements should be no more than 0.5 m.

The minimum relative content of working longitudinal rods in a reinforced concrete element must be at least 0.1%.

For tying elements of reinforced concrete structures, only special baked steel wire (Ø=0.8÷1.2 mm) should be used.

Example of calculation of foundation reinforcement

Let's try to calculate how much materials will be needed to arrange the reinforcement of a specific strip foundation with drawings. Let's say we are building a small country house with overall (external) dimensions of 5x8 m from building blocks (0.4 m wide).

The nature of the soil on our site allows us to make the height of the strip 0.9 m, its width 0.4 m, which corresponds to the width of the building material of the walls.

In the reinforcement cage for the strip foundation we will use longitudinal working rods with a diameter of 12 mm and □-shaped transverse clamps made from rods with a diameter of 8 mm.

Reinforcement of a shallow strip foundation:

The photo shows that the distance between the working longitudinal rods (0.4 m) and the pitch of the □-shaped transverse clamps (0.5 m) were chosen in accordance with the requirements of regulatory documents.

We check the relative content of longitudinal working rods in our reinforced concrete structure. To do this, we will use the following terms and notations:

• h – foundation height (900 mm);
• w – foundation width (400 mm);
• Sₒ – cross-sectional area of ​​the foundation;
• Sₐ – total cross-sectional area of ​​longitudinal rods (6 pieces);
• r is the radius of the longitudinal rod (6 mm), which is equal to d/2, where d is the diameter of the rod (in our case d=12 mm);
• D – relative content of working rods in the “body” of the foundation.

Source: https://zamesbetona.ru/armirovanie/armirovanie-lentochnogo-fundamenta-chertezhi.html

Reinforcement of strip foundations - rules, diagrams, instructions!

Reinforcement of a strip foundation significantly increases its strength characteristics and allows you to create stable structures while reducing weight.

Strip foundation reinforcement

Calculations of reinforcement and reinforcement schemes are carried out in accordance with the provisions of the current SNiP 52-01-2003. The document has detailed requirements for calculations, provides footnotes to regulatory documents and codes of practice.

SP 63.13330.2012 Concrete and reinforced concrete structures. Basic provisions. Updated version of SNiP 52-01-2003. File for download

SNiP 52-01-2003

The strip foundation must meet the requirements for durability, reliability, resistance to various climatic factors and mechanical loads.

Requirements for concrete

The main characteristics of the strength of concrete structures are the resistance to axial compression (Rb,n), tensile strength (Rbt,n) and transverse fracture. Depending on the normative standard indicators of concrete, its specific brand and class are selected. Taking into account the responsibility of the design, reliability correction factors can be used, which range from 1.0 to 1.5.

Diagram of bending moments

Requirements for fittings

During the reinforcement of strip foundations, the type and controlled values ​​of the quality of the reinforcement are established. The standards allow for the use of hot-rolled construction reinforcement of periodic profile, heat-treated reinforcement or mechanically strengthened reinforcement.

Construction fittings

The class of reinforcement is selected taking into account the guaranteed value of the yield strength at maximum loads. In addition to tensile characteristics, ductility, corrosion resistance, weldability, resistance to negative temperatures, relaxation resistance and permissible elongation before the onset of destructive processes are standardized.

Table of reinforcement classes and steel grades

Profile type Class Diameter, mm Steel grade

Smooth profile	A1 (A240)	6-40	St3kp, St3ps, St3sp
Periodic profile	A2 (A300)	10-40, 40-80	St5sp, St5ps, 18G2S
Periodic profile	A3 (A400)	6-40, 6-22	35GS, 35G2S, 32G2Rps
Periodic profile	A4 (A600)	10-18 (6-8), 10-32 (36-40)	80С, 20ХГ2Ц
Periodic profile	A5 (A800)	10-32 (6-8), (36-40)	23Х2Г2Т
Periodic profile	A6 (A1000)	10-22	22Х2Г2АУ, 22Х2Г2Р

The calculation of the strip foundation is carried out in accordance with the recommendations of GOST 27751, the indicators of limiting loaded states are calculated by group.

GOST 27751 (page 1) GOST 27751 (page 2) GOST 27751 (page 3) GOST 27751
(page 4) GOST 27751 (page 5) GOST 27751 (page 6)
GOST 27751 (page 7)

The first group includes conditions that lead to complete unsuitability of the foundation, the second group includes conditions that lead to partial loss of stability, complicating the normal and safe operation of buildings. According to the maximum permissible states of the second group, the following are produced:

• calculations for the appearance of primary cracks on the surface of a strip foundation;
• calculations based on the time period of increase in cracks formed in concrete structures;
• calculations of linear deformations of strip foundations.

The main indicators for resistance to deformation and strength of building reinforcement include maximum tensile or compressive strength, determined in laboratory conditions on special test benches.

The technology and test methods are prescribed in state standards. In some cases, the manufacturer may use regulatory and technical documentation developed by the enterprise.

At the same time, regulatory and technical documentation must be approved by regulatory authorities.

For concrete structures, these values ​​may be limited by the maximum rates of change in concrete linearity.

Actual diagrams of the state of reinforcement under short-term one-sided exposure to design standard loads are taken as generalized indicators.

The nature of the state diagrams of building reinforcement is established taking into account its specific type and brand. During the engineering calculation of a reinforced foundation, the state diagram is determined after replacing the standard indicators with actual ones.

Reinforcement requirements

Reinforcement cage - photo

1. Requirements for the dimensions of reinforced concrete structures. The geometric dimensions of the foundation should not interfere with the correct spatial placement of reinforcement.
2. The protective layer must provide joint resistance to the loads of reinforcement and concrete, protect against the influence of the external environment and ensure the stability of the structure.
3. The minimum distance between individual reinforcement bars should guarantee its joint work with concrete, allow for correct joining and ensure correct technological pouring of concrete.

Reinforced strip foundation diagram

Source: https://banya-expert.com/fundament/armirovanie-lentochnogo-fundamenta.html

How to knit reinforcement for a monolithic slab?

There are two types of monolithic foundation:

• slab, created from special concrete slabs, which are also used as floors;
• monolithic, created from concrete and metal reinforcement of the required diameter.

Both types of foundations have a similar feature, which is that they have slabs at their base, which are made of reinforced mesh (interconnected metal reinforcement of the required diameter) and concrete.

This gives the foundation strength, since concrete protects the metal from corrosion, and it, in turn, gives the concrete rigidity and prevents it from cracking under the influence of various loads.

Foundation and floor slabs may have:

• corrugated surface on both sides or one;
• smooth surface.

This feature affects the scope of their application. The corrugated surface has good adhesion, and therefore such slabs are ideal for foundations, as they adhere well to the ground. Smooth slabs are most suitable for various floors inside the house and they are not recommended for use in the ground.

It's no secret that the use of ready-made reinforced concrete slabs increases the cost of construction several times, since you have to pay for a finished product. And if you do it yourself, you can save some money. Therefore, we will talk specifically about making a foundation with your own hands.

What materials will be needed to create a monolithic foundation?

The monolithic foundation will consist of two main components: iron and concrete. With metal everything is clear - the following materials will be used here:

• fittings, preferably with a diameter of 10 mm;
• metal rod, diameter 6-10 mm;
• knitting steel wire with a diameter of 1.2 mm.

The wire will be used to create a frame, i.e. for tying reinforcement and rods together. It is better not to use welding, since in the places where it is used the metal loses its properties and quickly collapses under the influence of water, which will be present in the concrete solution for some time.

What is the best wire to choose? Definitely - only steel.

Tying the reinforcement of a monolithic slab.

Now you can move on to the next element - concrete. It will be made from the following materials:

• sand (river or quarry);
• cement, better grade M300 or 400;
• crushed stone of medium fraction to give the foundation a relief surface.

Having figured out what we need to create a monolithic foundation, we can move on to other work.

Preparing to create a monolithic foundation

Creation of a metal frame from reinforcement.

This process can be divided into two stages:

1. Digging a pit. This needs to be given special attention. First of all, you need to correctly calculate its perimeter. In order for everything to be done according to the standard, you need to have an idea of ​​​​the size of the entire house and the total weight of the structure. The dimensions can be found from the finished drawing, and the weight can be calculated using a construction reference book. The depth of placement will depend on the general data. You should also take into account the characteristics of the soil, the depth of freezing, the presence of heaving and hard layers of soil.
2. Creation of a metal frame from reinforcement of the required diameter directly in the pit or next to it. This will be discussed below.

Source: https://FundamentClub.ru/armirovanie/vyazka-armatury-monolitnoj-plity.html

Secrets of knitting reinforcement for slab foundations

During operation, compressive and tensile forces are observed in a monolithic foundation slab. If concrete easily copes with the former on its own, then to compensate for the stretching it is necessary to use reinforcement.

This structural material increases the tensile strength of the slab base by 10 times.

Moreover, the rods must be knitted correctly, in accordance with the standards SP 52-101, according to the reinforcement scheme, the mesh must be laid in two layers with a minimum vertical distance of 10 cm, a protective layer of 3 cm.

Rules for reinforcing a slab foundation

The basic requirements for a monolithic slab are given in 52-101-2003. They contain recommendations on the location and knitting of reinforcing mesh, and what supports to use to provide a lower protective layer. The use of rods with flaking rust is not allowed.

The periodic cross-section rods provide high adhesion, and the binding wire is more reliable than plastic clamps. However, reinforcement should begin in stages: choosing a rational scheme, calculating the cross-section of the rods, fixing the frames in space using special elements.

Reinforcement schemes

The recommendations of SP 63.13330 for reinforced concrete structures have a special section on the manufacture of main load-bearing structures (10.4). In particular, the following requirements are specified for a slab foundation:

• the reinforcement is laid in two directions (mesh with a maximum cell size of 30 x 30 cm), connected by wire knitting or welding;
• the meshes are placed as close as possible to the top and bottom edges, taking into account a protective layer of 3 cm;
• Using U-shaped clamps, the mesh rods are tied together at the ends;
• in places where monolithic walls and columns are installed, vertical rods are released or anchored with hooks to strengthen the slab;
• under load-bearing walls, the cell pitch decreases compared to the rest of the slab;
• It is allowed to discharge the mesh cell in the central part to the minimum permissible percentage of reinforcement (0.3%).

The grids can be positioned correctly taking into account the lateral protective layers (minimum 4 cm between the rod and the formwork), the location of the communication input nodes (relevant for non-buried slabs).

In practice, for low-rise cottages the following scheme is used:

• mesh of 6 mm wire in the top layer;
• similar mesh in the bottom layer;
• reinforcement of USHP ribs or a smooth slab (thickness 30 cm or more) with frames around the perimeter of 10 - 14 mm periodic cross-section rods.

This is due to the absence of heaving forces when using a warm blind area, ring drainage around the foundation, replacing soil with non-metallic materials to a depth of 40 cm. The recommended cell size in the discharged part is no more than 1.5 of the slab thickness, under walls 10 x 10 - 20 x 20 cm In the absence of a footing, the lower protective layer increases to 5 - 7 cm.

Openings

In non-buried slabs it is impossible to do without openings in the monolithic structure for the entry of utility systems. This issue is very poorly described in the specialized literature. An individual developer should refer to the design guidelines for reinforced concrete buildings:

• cutting holes in welded mesh with bending the rods upward;
• edging of openings larger than 30 cm with rods 10 - 14 mm diagonally located to the mesh cells;
• There is no need to reinforce the perimeter of holes smaller than 15 cm.

In deep slabs there are no communication entry nodes by default. To increase the maintainability of engineering systems, sewerage and water supply are run through the basement walls.

Plate/tape interface

It is possible to correctly install reinforcement bars in the formwork of a buried slab foundation with a basement, taking into account the following conditions:

• walls on a recessed slab are prohibited from being placed close to its edges; the minimum perimeter offset is equal to the thickness of the foundation strip (from 10 to 40 cm);
• The anchoring scheme for the interface between the tape and the monolithic basement wall has several options.

Reinforcement outlets in the slab under the walls.

For example, a U-shaped clamp can be extended upward from the slab, the distance between the rods of which corresponds to the size of the tape frame, in order to subsequently connect these two structures. In addition, you can tie rods bent at right angles to the lower and upper mesh of the slab and extend them 40 - 60 cm outwards in the same way as the previous option.

If the project does not have a rigid connection between the tape and the wall with a deep slab, in these places the mesh is reinforced with U-shaped clamps to avoid pushing through.

What reinforcement is needed for a slab foundation

Any rod used in the foundation frame must comply with the requirements of GOST 5781 of 1982. However, reinforcement, like most structural materials, has a classification:

• AIII – corresponds to the A400 marking, has a variable cross-section, popularly called “corrugated”;
• AII – corresponds to the current class A300, the cross-section is periodic, discharged;
• AI – new A240 marking, smooth profile.

For the foundation, reinforcement A400 (AIII) is used, it has a crescent-shaped profile.

Rods of class A500C (for welded mesh, frames) or A500 are more expensive and are rarely used by individual builders. They are made from alloy steels, in contrast to conventional reinforcement of the first three classes, for which 32G2Rps, 25G2S or 35GS steels are used.

We recommend: What reinforcement is needed for the foundation.

Due to the complexity of calculations and the small dimensions of buildings in low-rise construction, a simplified scheme is recommended. Two grids at a distance of 10 cm vertically with at least identical cells. If the developer wants to save on pouring the slab, the calculation should be ordered from specialists who will calculate the minimum required reinforcement, use thin reinforcement in the center of the foundation, strengthen the perimeter, and the places where the internal walls pass.

If the foundation dimensions are more than 3 m on any side of the slab, it is recommended to use rods of at least 12 mm. To determine the minimum possible cross-section, the following method is used:

• calculation of the slab cross-section - length multiplied by thickness (for example, 6 m x 0.3 m);
• calculation of the minimum allowable cross-sectional area of ​​the rod - the previous figure is divided by the minimum percentage of reinforcement (0.3% for concrete B20, 0.15% for grade B22.5, 0.1% for grade B15), for this example 1.8 m²/0 .15 = 27 cm²;
• calculation of the reinforcement area in each row - the result obtained is divided in half (in the example 27/2 = 13.5 cm²);
• determination of the minimum permissible cross-section of a rod depending on the mesh pitch (13.5 cm² / 31 rods every 20 cm for a slab 6 m long = 0.42 cm²;

GOST 5781 contains a table of assortments with reinforcement sections of different diameters. For example, for rod diameters 14 mm, 12 mm, 10 mm, this value will be 1.54 cm², 1.13 cm², 0.785 cm², respectively. Thus, even 10 mm reinforcement provides twice the reinforcement percentage compared to the minimum. Mating is done in the building spot after laying out in rows.

Template for laying reinforcement.

Then it is necessary to correctly calculate the total number of rolled metal products of each diameter. The rods are sold in 11.7 m lengths, the overlap for longitudinal anchoring is 40 - 60 cm. The length of the workpiece for each U-shaped clamp is equal to 5 dimensions of the slab thickness, their number coincides with the total number of longitudinal and transverse rods in one mesh. You can convert the length into kilograms using tables from the same GOST, but each construction market has similar conversion tables.

The upper mesh is laid on supports; the most popular in private construction are:

• spider - a U-shaped clamp with legs curved in opposite directions;
• the supporting frame is a lattice curved at a right angle.

The length of each of them is calculated individually, taking into account 2 pieces/m².

The spider is made of reinforcement with a diameter of 8 mm; such elements must be made in advance for laying the upper mesh.

Laying reinforcement in a slab foundation

A typical TTK map for installing reinforcement in the formwork of a foundation slab provides for the following sequence of actions:

• control of formwork - linear dimensions, compliance with the axes of the walls;
• the first row of the lower mesh - polymer clamps for the lower protective layer are placed on the concrete base, longitudinal rods are laid out in their nests (increased in length with an overlap of 40 cm if necessary);
• second row - ladders are laid on the rods, shifted as needed, transverse rods are laid out sequentially with the design grid spacing;
• knitting - at the intersection points, the reinforcement is tied (less often welded);
• stands - have several names (spider, frog, table, supporting frame), designs, tied to the lower grid in a checkerboard pattern;
• upper grid - made in a similar way or large format cards tied in the building spot are placed;
• knitting U-shaped clamps along the ends of the slab;
• under load-bearing walls, the grid spacing is reduced by 1.5-2 times.

Longitudinal overlap of at least 50 reinforcement diameters.

Depending on the design of the foundation slab (smooth, with a strip, side walls), at the last stage vertical rods are installed to connect with the structures that will be concreted on its surface. These are L-shaped or U-shaped clamps with design dimensions. When bending rods yourself, it is prohibited to use metal heating to avoid changing the structure. All elements of the slab foundation must be bent using jigs, clips or manual pipe benders.

The slab is reinforced at the ends with U-shaped clamps.

To provide a lateral protective layer, plastic supports of various shapes can be used. This is necessary to prevent accidental shifting of the frame while laying concrete and workers walking along the ladders.

Knitting of reinforcement is done in several ways:

• hand hook - standard twist;
• mechanized hook – has a spiral handle, doubles the knitting productivity;
• a gun for tying reinforcement - is expensive, more often used by professional teams on large volumes.

A special plastic cup provides a protective layer.

Experts often soak the reinforcement to increase adhesion to concrete. The SP standards only prohibit flaking rust; there is no information about fresh corrosion. For example, in ACI-318 this point is specifically highlighted; rusty reinforcement is allowed inside concrete.

This guide covers the key points of reinforcing slab foundations. This will allow the individual developer to implement the project independently to reduce the construction budget.

Source: https://GidFundament.ru/plitnyj/kak-pravilno-vyazat-armaturu-dlya-monolitnoj-plity.html

Knitting reinforcement: why you need to knit reinforcement for the foundation and how to do it yourself

The foundation is a stable support and foundation of any structure, so its manufacture must be approached with all responsibility. A reinforcing metal frame makes the foundation of buildings more durable, reliable and of high quality.

It will provide the foundation of any building with high performance characteristics.

What does it mean to “knit” the reinforcement?

The reinforcement frame is an integral part of the foundation, which helps create a reliable and durable foundation for a house or any other structure. In order for the finished metal frame to last for decades and withstand serious loads, the reinforcement must be knitted using special wire and observing certain technological requirements.

Durable and high-quality reinforcement binding is necessary to preserve the spatial shape of the fundamental basis of the structure when it is poured. The reinforcement for the foundation consists of metal rods with a length of 6 meters and a diameter of 6 mm. The strength characteristics of this type of rods directly depend on their thickness: the larger the diameter of the metal rod, the higher the reliability of the frame.

The metal profile of the rod can be smooth, with periodic edges, corrugated, with notches or ribs. The presence of the above features contributes to better adhesion of the metal to the concrete solution. The adhesion of a smooth rod to concrete is 2 times lower than the adhesion of a corrugated rod. To create a high-strength foundation, channel bars or metal corners can be used for reinforcement.

The knitting pattern can be of two types:

1. Flat . In this case, metal rods are fastened together in one plane, most often in a horizontal one.
2. Spatial . This is the most common knitting method and is used for strip foundations for any soil. The spatial scheme allows you to create a three-dimensional frame that will withstand longitudinal and lateral loads, thanks to its elasticity and flexibility.

Why knit reinforcement?

The main element in the foundation of a structure is longitudinal reinforcement. The transverse rods support the position of the longitudinal ones. Their main task is to ensure that when the process of pouring concrete begins, the entire structure remains in an unchanged position. Since when the reinforcing mesh shifts, the protective layer of concrete will decrease, which will subsequently lead to a decrease in the strength of the structure, corrosion of the reinforcement, the appearance of irregularities, cracks, etc.

In order to make a reinforcement cage, it is necessary to install formwork around the foundation pit. Formwork is made from edged boards and nails . The joints can be additionally fastened with metal corners to provide the finished box with rigidity and strength.

Steel wire with a diameter of up to 8 mm is wound outside and inside the formwork. The bottom of the pit and the walls of the formwork are covered with polyethylene film to prevent rapid dehydration of the concrete solution.

Then metal rods are driven at a distance of 20–30 cm from each other and 5–10 cm from the edge of the trench. To ensure a level surface, bricks are laid at the bottom of the pit. It is advisable to make a “cushion” of sand before laying bricks to minimize the force of heaving on the foundation.

After laying out the bricks, you can lay out the reinforcement and use wire to tie together the places where they connect and intersect.

To manually tie reinforcement with wire, the simplest method is used: when the wire is tightened when twisted, and its ends are fixed with wire cutters . The wire should be folded in half, and the cutters should have blunt teeth so as not to bite the wire. You can use pliers for these purposes.

How to tie foundation reinforcement: knitting methods

In order to connect reinforcing bars into a spatial frame or mesh, reinforcement is performed by welding or knitting. This is done with wire or plastic clamps.

Recently, knitting reinforcement for foundations remains the most popular compared to welding.

Disadvantages of welded joints:

• during welding, the strength of the steel decreases at the fastening points, and when concrete is poured, destruction of the welded joints may occur;
• the strength and reliability of the welded joint directly depends on the experience and qualifications of the worker, so poorly executed seams when laying concrete can simply collapse under dynamic loads;
• The disadvantages include the fact that the prices for welding work, which can only be done by a qualified specialist - a welder, are quite high.

The welding process for connecting reinforcement is used quite rarely, despite such advantageous indicators as ease of installation and high speed of work performed.

Flat knitting of slab foundation reinforcement is performed in an overlap. Special tools are not needed for this knitting. The disadvantage of this method is that it has low productivity.

Knitting work is carried out where the reinforcement formwork was installed. For this:

1. There is no need to waste time on delivery and transportation of materials.
2. There is no need to move them from place to place.
3. The time required to prepare the reinforcing mesh for pouring concrete is reduced.

The disadvantages of tying reinforcement with wire include the fact that the quality of the tying is inconsistent, and the tying unit may shift.

There are several ways to tie foundation reinforcement, here are the main ones:

• using pliers;
• using a special hook;
• using a screw hook;
• using a screwdriver;
• when using special paper clips;
• using a knitting gun.

Materials and tools for tying reinforcement

For tying reinforcement, baked steel wire with a diameter of 1–1.4 mm is used, depending on the diametrical dimensions of the reinforcing bars. This wire is supplied in coils , so before use it must be cut into pieces 150-200 cm long for ease of use and, depending on what tool will be used when knitting.

Burnt wire has a number of advantages that are necessary for the production of tying reinforcement, namely:

• the wire bends well;
• fits very tightly to the fittings;
• When knitting, it practically does not tear.

As an alternative to steel wire, the construction market offers plastic clamps , which have appeared quite recently. Their main advantage is ease of use and high speed of execution. In addition, the price of clamps is quite low.

Necessary tool for tying reinforcement:

1. Fittings (channel, angle).
2. Reinforcement cutters.
3. Screwdriver.
4. Pliers.
5. Knitting gun (mechanical or electric).
6. Special hook.
7. Welding machine.
8. Steel wire.
9. Paper clips (staples, clamps).

Source: https://plita.guru/raboty/armirovanie/kak-proizvodit-vyazku-armatury-dlya-fundamenta.html

standard reinforcement schemes for strip foundations

The foundation is the most vulnerable part of the structure. Due to the fact that the upper part of the building is subject to compression loads and the lower part is subject to tensile loads, proper foundation laying plays an important role. To perform the correct reinforcement of a strip foundation with your own hands, you need to perform a calculation according to the diagram.

Such a base is, in fact, a reinforced concrete strip running along the outer part of the building and under the load-bearing walls inside.

In compression, concrete structures can withstand 50 times more than in tension . Both the upper and lower parts of the structure experience overloads, so it is necessary to reinforce both parts. There is almost no load on the middle part. Metal fittings help solve these problems.

To ensure the strength, reliability, and durability of a building, any foundation must be reinforced . After all, the foundation is subject to various loads. This includes the weight of the entire house and various movements of the soil. The reinforcement scheme for a strip foundation resembles the skeleton of a structure, which is assembled from steel rods . In order to choose the necessary scheme for it, you need to understand what it is.

Reinforcement of a strip foundation can be easily done with your own hands, without the involvement of specialists. It is important, first of all, to correctly select the required diameter of the reinforcement

Reinforcing material

The choice of material is a fairly important step. To reinforce a strip foundation with your own hands, use steel rods of different sections or fiberglass reinforcement. But most often metal is used.

The main horizontal reinforcement has a cross-section of rods from 12 to 24 mm. The rods that will be positioned vertically are auxiliary. Therefore, usually the cross-section of vertical rods is from 4 to 12 mm . Such a large difference is due to the variation in loads on the foundation and is directly dependent on the type of soil and the weight of the structure.

Auxiliary vertical rods are installed if the height of the foundation exceeds 15 cm . In this case, reinforcement with a cross section of 6-8 mm of class A1 is used. The frame is assembled from rods and clamps, cleaning them from rust. If necessary, the rods are straightened and cut. Knitting wire and a hook are used to connect the rods. Welding work can be performed if the rods are marked “C”.

The choice of diameter is influenced by the number of horizontal levels and the reinforcement scheme of the strip foundation.

Calculation of strip foundation reinforcement

The number of reinforcement elements must be calculated based on the size of the base. For foundations whose width is 40 cm, 4 longitudinal rods are sufficient - two at the top and two at the bottom. To install a row of frames in a strip base measuring 6x6 m, you will need, on average, 24 m of reinforcement . If you lay 4 rods at a time, you will need 96 m of longitudinal rods.

For transverse and vertical reinforcement of a foundation, the width of which is 0.3 m and the height of 1.9 m for each fastening at a distance of 5 cm from the surface, according to the concrete calculator, it is necessary (30-5-5)x2+(190-5-5)x2= 400 cm or 4 m of smooth shaped reinforcement elements.

If the mounting step of the clamps is 0.5 m, the number of connections will be: 24/0.5+1=49 pcs. This means, based on the calculations, you will need 4x49 = 196 m of transverse and vertical rods.

The total cross-sectional area of ​​the reinforcement and its weight, based on the diameter of the rods, can be calculated from the table:

Diameter of fittings, mm	Calculated area of ​​the transverse rod, mm2, with the number of rods	Theoretical weight of 1 m length of reinforcement, kg
1	2	3	4	5	6	7	8	9
6	28,3	57	85	113	141	170	198	226	254	0,222
8	50,3	101	151	201	251	302	352	402	453	0,395
10	78,5	157	236	314	393	471	550	628	707	0,617
12	113,1	226	339	452	565	679	792	905	1018	0,888
14	153,9	308	462	616	769	923	1077	1231	1385	1,208

The minimum area of ​​foundation reinforcement is regulated by regulatory documents, and the strength of the foundation depends on this

Which scheme is better to choose?

There are two main reinforcement schemes that are most often used to strengthen the foundation for low-rise buildings:

• four rods;
• six rods.

In accordance with SNiP 52-101-2003, adjacent reinforcement bars should be located at a distance of 40 cm (400 mm) in one row. The extreme longitudinal reinforcement should be at a distance of 5-7 cm (50-70 mm) from the side walls of the base. Therefore, if the width of the base is more than 50 cm, then it is better to use a six-rod reinforcement scheme .

Depending on this, the diameter of the steel rods is selected.

Typically, for a strip base, the rods are laid “in a cage.” In this case, all the rods are attached at an angle of 90° . For longitudinal arrangement, reinforcing materials of class A3, having a round shape, are used.

How to reinforce corners

The corners bear a lot of load. Therefore, when reinforcing, care must be taken to strengthen them.

In this case, the following rules must be taken into account:

• the rod must be bent so that one side of it is buried in one wall of the foundation, and the other in the other wall;
• if the rod is not long enough to make a bend, then L-shaped profiles can be used to fasten the rods at the corner.

Most often, class A3 fittings are used for this.

How to do reinforcement yourself

To do this, take a square or rectangle as a basis.

Before installing the frame, a sand cushion 1 m deep must be laid on the bottom of the trench.

The frame is installed as follows:

• bricks are laid at the bottom of the trench, the height of which is 5 cm (in order to create a gap between the lower part of the base and the frame);
• to install rack rods, it is necessary to make a sample in advance, according to which the rods will be cut;
• longitudinally shaped rods are laid on the bricks;
• Horizontal jumpers with a length slightly less than the thickness of the base (approximately 5 cm on each side) are tied to the longitudinal rods in increments of 50 cm using knitting wire;
• rods are attached vertically to the corners of the formed cells, 10 cm long less than the height of the base;
• the upper longitudinal rods are mounted to the vertical reinforcement;
• The upper transverse rods are tied to the resulting corners.

When reinforcing a strip foundation, it is necessary to adhere to the requirements of SNiP 52-01-2003

Basic provisions of SNiP 52-01-2003

The main provisions of SNiP 52-01-2003 concern the distance between the horizontal ribs of the steel frame and the diameter of the reinforcement. So, between the longitudinal rods there should not be less than 25 cm and more than 40 cm .

The cross-section of the rods is selected according to the number of longitudinal rods. For a strip foundation, it must be at least 0.1% of the working sectional area of ​​the base. For example, if the height of the foundation is 1 m and the width is 0.5 m, the cross-sectional area should be approximately 500 mm2.

You can see the minimum diameter of the reinforcement more clearly in the table of examples:

Terms of use of fittings	Minimum diameter of reinforcement	Regulatory document
Longitudinal working reinforcement along a side 3 meters or less	10 mm	Reinforcement of elements of monolithic reinforced concrete buildings
Longitudinal working reinforcement along a side of more than 3 meters	12 mm	Reinforcement of elements of monolithic reinforced concrete buildings
Structural reinforcement	The cross-section is equal to 0.1% of the cross-sectional area along the height of the distance between the layers of reinforcement and half the width of the tape	Guidelines for the design of concrete and reinforced concrete structures made of heavy concrete
Transverse reinforcement (clamps) of compressed elements	Not less than ¼ of the largest diameter of the longitudinal reinforcement and not less than 6 mm	SP 52-101-2003 Concrete and reinforced concrete structures without prestressing reinforcement.
Transverse reinforcement (clamps) of knitted bending frames	not less than 6 mm	SP 52-101-2003 Concrete and reinforced concrete structures without prestressing reinforcement.
Transverse reinforcement (clamps) of knitted frames with a section height of 80 cm or less	6 mm	Guidelines for the design of concrete and reinforced concrete structures made of heavy concrete
Clamps for knitted frames with a section height of more than 80 cm	8 mm	Guidelines for the design of concrete and reinforced concrete structures made of heavy concrete

Reinforcing a strip foundation is easy to do with your own hands; all you need to do is follow the technology and perform the calculations correctly. If it is difficult to do this on your own, it is better to seek the help of professionals. After all, a reliable and solid foundation is the price and guarantee of the stability of the entire building.

More information about reinforcing a strip foundation with your own hands can be seen in the video:

Books on the topic:

Source: https://obetone.com/fundamenty/lentochnye/armirovanie-lent/sxemy-armirovaniya-fundamenta.html

How to properly knit reinforcement for a foundation: several options

Before you start knitting rods when creating a frame for the base of a building, many questions arise. How to knit reinforcement for the foundation correctly? Or is it better to use welding? It is necessary to understand this issue in detail.

Disadvantages of welding

First you need to remove all doubts about knitting using welding. There are advantages to choosing wire connection as the main method for attaching reinforcement to the foundation. But the welding method is much more dangerous, and more complicated, requiring equipment, special knowledge and design calculations.

For this method, you need to attract a specialist to the construction site and install electricity. This method is less reliable. To strengthen the foundation, the welder must go through several dozen connections, and he will not be able to check every seam. When a compound is heated, the metal becomes brittle and its chemical structure changes.

It becomes less bendable and stronger, which is precisely why reinforcement is installed in the base to withstand such loads.

For the frame, special marked reinforcement is used, marked “C” - this means that this class allows elements to be welded. Using welding, it is not always possible to reach the right places, so sometimes you have to switch to an alternative method. Wire knitting is much more efficient and convenient, and it costs several times less. Now we need to consider: how it is more convenient to tie the reinforcement, and what materials will be needed.

What to use for knitting?

The standard is to use baked steel wire. Some builders prefer galvanized ones; this will protect the structure from corrosion, but when pouring a foundation, this does not matter (it already seals the entire frame). If you purchased wire that has not been fired, then you will have to do it yourself. You need to make a fire, put the wire, it will glow red, then you just need to let it cool.

In shape, all rods should have a round cross-section; such wire is easier to knit. A suitable diameter is 1 or 2 mm, it depends on the load and the thickness of the reinforcement itself. If a strip foundation is used for the house, then you need to take a wire with a larger size. If you want to save money on buying wire, you can use old tires from a car, only a truck. In order to get the metal, you need to burn the tires.

Nowadays plastic clamps are used quite often; their functions are similar to metal, but they are also more expensive, but they save time.

What tool will you need?

You can use many tools to knit reinforcement; one of the simplest is a hook. This is not only the simplest, but also the most widely used method. You don’t have to buy a hook in a store; you can make it yourself. Although the method is simple, when you need to make a lot of knots, your hands get tired quickly.

There is another type of hook - semi-automatic. It is only supplemented with a spiral, thanks to which it rotates when the handle moves. You can also make an attachment for a drill, then the process will go even faster.

This method is often used for significant volumes of work, when knitting meshes, but it is not suitable for a strip base made of reinforced concrete.

You can purchase or rent a special pistol. This is a professional tool that knits joints with high quality. All tools except the last one are inexpensive and quite suitable for the job.

DIY knitting

How to tie reinforcement for a foundation correctly? The procedure itself is not as complicated as it might seem. After an hour of work, the hands themselves will remember all the actions, and the work will proceed automatically. For knitting you will need a 20 cm piece of wire; it needs to be bent in half, but not all the way. After this, it should be carried diagonally to the intersection of the two rods. The pieces of wire are connected, a hook is inserted, they need to be twisted clockwise several times until it stops.

Some people like to do the tying twice - crosswise, this is a completely useless activity, and more time and material are spent. A connection with similar strength may be needed when laying only a strip foundation.

Tying rules

When working, you must follow certain rules:

• any strapping must provide the necessary level of fixation to the rods;
• the main task is to immobilize the reinforcement and ensure the correct shape of the frame before pouring the foundation;
• the reinforcement must be inside the base and not extend beyond it;
• to protect the reinforcement from moisture, air and soil, a layer of stone, approximately 50 mm, is used;
• if the height of the structure is large, it is better to use spacers; they will prevent the frame from touching the walls of the trench;
• if the nodes are fastened with plastic clamps, you need to use pliers for a stronger connection;
• plastic can be installed only before the onset of frost; it will not withstand negative temperatures.

These are the basic rules that should be followed when tying foundation reinforcement to ensure a reliable and durable connection.

Selection of fittings

The metal frame is made up of rods with a round cross-section. They can be smooth or ribbed, which provides better adhesion to the mixture. Such rods can be from 5 to 30 mm, usually 8 or 16 mm are used. Smooth rods are used for the transverse plane, and ribbed rods for the longitudinal line.

Fiberglass reinforcement consists of heat-resistant resin with fiberglass filler. Such fittings are easy to transport and tie. It is also made smooth or ribbed, it can withstand any load.

How to knit rods correctly?

What is a frame? This is a shell with cells; when poured with the mixture, concrete does not flow, there are no bubbles or the appearance of voids. If you want to assemble the frame correctly, you need to know how to tie the reinforcement. Here you need wire or clamps.

If transverse rods are used, pallets will also be required (they are installed immediately before starting work; you need to calculate the pitch of the cells in advance). You can install cup holders after installing the frame. The choice of window spacing depends on the building; it is taken from 150 to 350 mm. Sometimes a distance of up to 600mm is maintained. The longitudinal rods must be laid out on the selected segment and marked with a marker.

Next, the jumpers are attached at an angle of 90 degrees. These rods can also have a smooth surface. It is better to attach the jumpers from the bottom of the frame. All clamps are tightened tightly; the nodes should not diverge after pouring. First, the first row of the reinforcement mesh is laid out, then the remaining layers are applied. The corners need to be fastened especially well.

For such connections, you can buy ready-made parts or knit them manually.

It is strictly forbidden to cook corners. The rods can be fastened together with wire or clamps. Wire knitting is, of course, more difficult, but it is also used more often, providing the required structural strength. There is another option - this is knitting reinforcement by spot welding, which is quite difficult and time-consuming. It is used mainly for mounting rods with a diameter of 24 mm.

Knitting metal rods

It is worth considering the basic steps when knitting metal structures:

1. Take a wire 1.5 mm in diameter and a hook or pliers. Such a tool is required for high-quality fastening of elements. You can also choose a screwdriver or a drill with a special attachment. A hook made independently or purchased in a store is used as a nozzle.
2. The rods are attached using the same principle as fiberglass. To avoid jumpers sticking out of the ground, you need to lay plastic pallets. It is very important to carry out the correct binding; this affects not only the quality of the foundation as a whole, but also the strength of the building in the future.
3. To connect the frame, you need to take a piece of wire 25-30 cm (it must be pre-burnt), wrap it around two rods to make a loop.
4. A hook is inserted into it and scrolled clockwise to the end. The basic rule is not to twist the connection too much, the wire may break and the procedure will have to be repeated again.
5. Knitting corners is carried out according to general rules, but there is a nuance - the bend of the rods is at a right angle. But a too even angle is also not desirable, so they must be rounded using a reinforcement bending machine.

As you can see, there are many nuances in knitting reinforcement for the foundation, but correct execution of all stages of work will allow you to quickly and reliably create a metal frame, thereby strengthening the foundation for the building. If you have a question about how to properly knit reinforcement for the foundation, the video will help in this difficult task. Fortunately, today there are enough such videos.

Source: https://profundamenti.ru/armirovanie/kak-pravilno-vyazat-armaturu-dlya-fundamenta-neskolko-variantov.html

Strip foundation reinforcement

• 8864
• strip foundation reinforcement

The most popular foundation in private buildings is strip foundation. Most often this is a concrete strip on which the walls of the house rest.

Concrete can withstand large static loads (because it can withstand enormous compressive forces), but is vulnerable to dynamic loads.

Under tensile stress, which often occurs during movement and frost heaving of the soil, the tape may crack.

To prevent this from happening, it is reinforced with a metal rod. How to properly reinforce a strip foundation with your own hands?

Which reinforcement is best for a strip foundation?

Reinforcement of a strip foundation can be done with steel or composite materials, i.e. metal or fiberglass rods. They are sold in coils from 50 to 100 meters, sometimes in the form of cut metal from 6 to 12 meters.

Steel reinforcement Fiberglass rods

The advantages of fiberglass reinforcement for foundations are corrosion resistance, chemical inertness, non-magneticity, lack of electrical conductivity and static electricity. This material is used, for example, when constructing foundations for technical structures, for which the absence of radio interference is important.

It is rarely used in private buildings: due to poor bending stretch, it does not perform its main function very effectively.

Features and diameter of reinforcement for strip foundations:

• for verticals and crossbars, a smooth or corrugated rod about a centimeter thick is used;
• for the longitudinal part of the frame, which takes on the main loads, choose corrugated material up to two centimeters (for a private house this is enough);
• for knitting use steel wire or clamps;
• sometimes welding is used to connect the rods. Metal marked “C” is suitable for it.

For foundation reinforcement it is not allowed to use:

• profile corners;
• metal pipes;
• chain-link mesh, incl. with a large cell;
• iron cables;
• plastic bottles, etc.

How to calculate reinforcement for a strip foundation

For shallow foundations (no deeper than 90 centimeters), the frame is made of two longitudinal rows, two rods per row. For buried ones (below the freezing of the soil, i.e. deeper than one and a half meters), longitudinal rods are placed at three to four levels.

For shallow foundations For deep foundations

Distances:

• between verticals the step is from 40 to 80 cm;
• between horizontal lines – from 30 to 60.

note

01/52/2003 SNiP specifies the minimum amount of metal: 0.1% of the foundation cross-section. For example, if the height of the tape is 1.2 meters and the width is 0.4, then the total cross-section of the reinforcement is from 480 square millimeters.

The minimum diameter of the rods depends on the reinforcement conditions:

• longitudinal rod for a side up to 3 meters long - 1 centimeter;
• more than three – 1.2;
• crossbars with a frame height of up to 80 cm - 0.6 cm;
• more than 80 – 0.8 cm.

Initial data:

• Construction: 5 by 5 meters;
• Ribbon height: 0.6 meters (a two-level frame will be required);
• Width: 0.3 m;
• Step between verticals: 0.5 m.

Quantity of reinforcement for strip foundation: (to the obtained figures you need to add a margin of about 10%):

• Length of longitudinal rods: 20 meters multiplied by 4 = 80 meters;
• Vertical pins, with a five-centimeter indentation from the surface: 1.4 meters multiplied by the number of intersections (51) equals 71.4 meters;
• Cross members: 40*0.3*2 = 24 meters;
• The intersection requires 30 centimeters of wire for knitting, four joints per section. With a reserve - about 70 meters.

The procedure for reinforcement is as follows:

1. Cover the bottom of the ditch with a cushion of sand and crushed stone.

2. Fill the concrete base with a layer of 5 centimeters to protect the metal from corrosion. Instead of a sole, you can use a more economical option: place stones or broken bricks under the vertical rods. But this is a long and energy-intensive method.

3. Install the formwork.

4. Place the calculated number of transverse rods on the concrete in increments of 0.8 cm.

5. Lay two rows of longitudinal rods along the walls of the ditch. Link intersections. Fragments of horizontal lines are overlapped together. The overlap length is 50 rod diameters minimum.

6. Install vertical rods at the joints. They are placed perpendicular to the laid lower level; there should be no deviations from the vertical. Bind.

7. Attach the upper tier of crossbars to the verticals. The overlap of the ends of the frame should be at least 20 centimeters.

8. Lay the upper longitudinal rods and fasten them to the rest of the structure with clamps or wire.

9. Fix the frame relative to the formwork. There should be at least five centimeters between the metal and the boards. The same minimum distance is left between the rods and the upper border of the concrete.

How to properly knit reinforcement for a strip foundation

To protect both the frame itself and the concrete from the development of corrosion, the reinforcing bars should be cleaned of rust and dirt before installation.

To work, you will need a tool: clamps, special hooks for tying wire, cloth or metal scissors.

A homemade hook can be made from a piece of reinforcement: sand the end of the rod 6 or 8 millimeters, bend it and put a wooden or plastic tube on the opposite end. The handle should be located at an obtuse angle to the working part of the hook. It is fixed on both sides with thrust washers, and the washers are secured by welding.

Actions when linking:

1. Place a wire bent in half under the desired joint of the rods.
2. Hook the fold loop.
3. In two or three turns, tie a loop to the other (double) end of the wire.

A problematic point during installation is the reinforcement of the corners of the strip foundation. Concentrated tension is formed in the corners; these are the most loaded points. To compensate for the load, L-shaped or U-shaped reinforcements with clamps are used. L-shaped ones are used for obtuse angles.

A) using an overlap and a paw, B) using an L-shaped clamp. 1. horizontal reinforcement, 2. overlap, 3. tab, 4. vertical reinforcement, 5. transverse reinforcement, 6. additional transverse reinforcement, 7. L-shaped clamp, d - reinforcement rod diameter

Clamps of the required size and cross-section are installed instead of ordinary vertical rods. In corner connections there should be twice as many clamps as in linear sections.

Source: http://www.vogorodah.ru/armirovanie-lentochnogo-fundamenta/

Foundation reinforcement

The foundation serves as the basis for any structure, so it must be strong, durable and safe. Reinforcement is like the skeleton of a structure, which strengthens the structure, making it more durable.

When building the foundation of a house, it is necessary to choose only high-quality reinforcement. Concrete itself has good strength properties, but only in compression. And when stretched, concrete cannot withstand the load and breaks. It can withstand a load 50 times higher in compression than in tension.

When we add reinforcement to concrete, we get a new building material - reinforced concrete, which differs from conventional concrete in its increased tensile strength.

Characteristics and types

It is mainly made from steel, but modern technologies make it possible to make it from fiberglass or, scientifically, composite. Manufacturers claim that composite reinforcement is several times stronger than metal reinforcement. Whether this is so, I cannot say.

One of the important characteristics of reinforcement is its diameter. It is available in several sizes from 5.5 mm to 32 mm. When building a private house, rods with a diameter of 8 to 16 mm are mainly used.

Each type of foundation involves the use of rods of a certain diameter. You probably noticed that its surface varies. Some rods come with a smooth surface, while others have a ribbed surface.

The question arises - “which reinforcement to choose, smooth or better ribbed.” For stronger adhesion to concrete, the material must have a large area, so the reinforcement that is subjected to tensile loads must be ribbed.

The smooth one is used as a structural element, that is, so that the ribbed one does not move. Therefore, reinforcement with a smooth surface is used with a smaller diameter.

Knitting 16 mm reinforcement for the foundation

Of course, it is easiest and simplest to weld it. The result is a finished frame. As they say - simple and most importantly fast. However, there is one “but”: the metal in the welding areas loses strength. Therefore, it is not recommended to use a welded frame for the foundation.

The ideal option is to tie the rods with a special knitting wire. At first, this process seems quite labor-intensive, but with proper skill, one connection will take about 5 seconds.

To do this you will need pliers or a special hook. In addition to manual knitting, there is also automatic knitting using a special gun. But the cost of such guns is high, so it is not advisable to buy it in order to fill one foundation. It is important that more than half of the intersections are connected.

Strip foundation

For example, let’s take a tape for a house 6 by 6 meters, 40 cm wide and 70 cm high. For this type of foundation, regardless of the depth, two reinforced belts are usually used. For these belts, it will be enough to use 4 rods laid horizontally, two at the top and two at the bottom.

If the house is assumed to be massive or the soil on the site is heaving, then it is necessary to increase the number of rods to 3 or 4 in each belt. The size of the house is 6 by 6, so the perimeter will be: 6 * 4 + 6 (main wall) = 30 m. For reinforcement with four rods: 30 * 4 = 120 m.

We will install additional smooth rods (vertical and transverse) every 50 cm. The width of the foundation is 40 cm, the height is 70, so taking into account the 5 cm indentations from the edge, it turns out: 30 + 30 + 60 + 60 = 180 cm (1.8 m) .

There should be approximately 60 connections in total. 1.8 m * 60 = 108 m. As a result, it turns out that we need 120 meters of reinforcement with a ribbed surface and 108 meters of a smooth one.

Columnar foundation

Columnar foundations are reinforced with thinner rods, 10 mm will be enough. Ribbed reinforcement is used for vertical placement, and smooth reinforcement is used to connect them into one frame.

For 1 column there are 2 - 4 reinforcement bars, the length equal to the height of the column. For a pole 2 meters high and 20 cm in diameter, four 10 mm rods will be enough. The distance between them will be 10 cm, dressing with smooth reinforcement in 4 places.

We calculate the consumption per 1 column: 2 * 4 = 8 m (ribbed), 0.4 m * 4 = 1.2 m (smooth).
Now we need to multiply the number of pillars by the results obtained and we will find out how much reinforcement is needed for a columnar foundation. The cost can also be calculated by multiplying the price by the results obtained. On average, the price of 1 ton = 25,000 rubles. The weight of 1 meter of rod with a diameter of, for example, 14 mm = 1.21 kg.

Important Tips

Many nugget builders reinforce corners and junctions using cross connections. This is a gross violation of the rules for reinforcing corners and junctions, which leads to weakening and damage to the base. Tensile reinforcement must be bent.

When bending, it should not be heated or cut. This weakens the rods, which leads to their rupture under heavy load.

Some builders say that any metal is suitable for reinforcement: pipe, flat sheets, chain-link mesh, wire, rails, etc. None of the listed materials has the necessary characteristics to withstand compressive or tensile loads, and cannot prevent deformation or cracking in concrete.

Some builders advise watering the reinforcement several days before laying it in the foundation. This is not considered a violation, but is done so that it becomes covered with rust. In this case, the concrete will stick better, but only if the rust does not flake off.

The official ACI-318-08 standard in paragraph R7.4 states:

“Ordinary surface non-flaking rust enhances the bond strength of concrete.”

Watch the video: Knitting wire. Crochet reinforcement.

Source: https://alina-sharapova.ru/stroitelnye-materialy/armatura-dlya-fundamenta.html

Rules for tying reinforcement for strip foundations

When building a foundation for a house, it is necessary to take into account all the requirements imposed by SNiPs. Because the quality of the final result depends on correctly carried out construction work. This fully applies to tying reinforcement under a strip foundation. Despite the apparent simplicity of the process, the requirements for it are quite stringent.

Although the binding itself does not require rigid fastening of the reinforcement to each other, because an important component of a metal structure is maintaining volume and the ability to balance when pouring and hardening the concrete mixture. That is, without changing the size and shape, the frame takes on an ideal position under the influence of loads acting on it from the concrete.

Types of fittings

Today in construction, conventional steel reinforcement and new composite reinforcement are used to fill strip foundations. Both types are used for the construction of frame structures, but the question of which is better is one of the pressing ones today. So, let's figure out what kind of reinforcement should be chosen for pouring a strip foundation.

There are three types of material in this category: cold-deformed, thermomechanical and hot-rolled.

We won’t get into the weeds of production technologies for each type; we’ll just point out that to create a high-strength foundation, a hot-rolled type of class AIII is used.

This is reinforcement with a corrugated surface, which is laid in the longitudinal direction. It is she who bears all the main loads (tensile and bending) that act on the foundation of the house.

 There are two more elements in the design of the reinforcing frame: vertically installed rods and transverse ones. The former, together with the longitudinal ones, form the basis of the frame grids, the latter are responsible for connecting several reinforcing meshes to each other.

Therefore, for these two groups you can use reinforcement of a lower class and a smaller diameter. For example, for vertical elements, rods of class AII (also with a corrugated surface) are used, for crossbars of class AI (smooth).

As for the diameter, in private housing construction reinforcement with a diameter ranging from 8 to 18 mm is used. The same size is typical for vertical rods, but crossbars can be made from reinforcement 6 - 8 mm or wire (rod rod) with a diameter of 6 mm. The most popular type for crossbars is wire rod. Let us add that the selected diameter of the transverse elements depends on the height of the assembled frame.

• If this figure does not exceed 80 cm, then the frame is tied with 6 mm wire rod.
• If above this value, then 8 mm.

Steel type reinforcement is tied with special wire. It is soft and does not tear with frequent bending cycles.

Fiberglass

 Plastic reinforcement is often called composite because it consists of several different materials.

Their base, of course, is plastic, but the fillers can be different: basalt, glass and carbon.

The most popular among them is fiberglass reinforcement. It has excellent technical and operational characteristics, but the price is much lower than other types.

Here are the advantages of fiberglass rods over steel ones.

1. They do not corrode, although these processes occur slowly inside the foundation.
2. They have low thermal conductivity.
3. They are not afraid of changes in temperature and humidity.
4. Tensile strength – 1000 MPa. For steel reinforcement this figure is 390 MPa.
5. Fiberglass reinforcement is 3.5 times lighter than metal.
6. It does not conduct electricity.

As for the disadvantages, again in terms of comparison, the elasticity of fiberglass reinforcement is much lower. When heated, they quickly soften and lose their quality. In addition, reinforcement of this type can be classified as slightly flammable materials. Today they produce special plastic rods that are better in terms of flammability. But this still cannot be compared with metal analogues.

The construction canons do not yet have certain standard approaches on which to rely when answering the question for which foundations fiberglass reinforcement can be used. Just from personal experience, builders recommend that this variety is best used for assembling a frame for a strip foundation, if the latter is laid under small, lightweight buildings.

Knitting tools

 Literally twenty years ago, no one even thought about inventing a tool for tying reinforcement.

At all times, an ordinary hook was used, and there was no replacement for it for the simple reason that this is the simplest device, cheap, which you can easily make with your own hands.

Using a hook, it was possible to knit a large amount of steel material in just a couple of hours. The main thing that was required of the work manufacturer was to have the skill to work with this tool (experience) and to know several methods of knitting.

But the requirement to increase the speed of work gave impetus to inventors who began to offer various designs of hooks. These are mechanical and electrical tools. The first is an inertial action hook. This is a tool with a handle, inside of which slots are made in a spiral. The metal hook itself has protrusions that fit into these slots.

It turns out that when you pull the handle towards you, the crochet hook begins to come out of it, rotating about its central axis. That is, it turns out that by inserting the hook into the wire loop and starting to pull the handle towards you, the tool twists, thereby twisting the wire.

 But the electric pistol showed itself best in this regard. Its design includes a coil of wire (it is replaceable), from which the latter is fed to a special working element.

When the button is pressed, the wire comes out and twists itself under the rotational action of the tool head.

Speed, high quality – these are the main parameters when it comes to using a tying gun for rebar.

The only disadvantage of this tool is the high price. Therefore, when the task is to correctly knit reinforcement for a strip foundation with your own hands, you will have to abandon the method with a gun. You can get by with a regular crochet hook.

How and with what to bend?

There are special bending machines that can be used to bend reinforcement. This is done in one case, when the corners of a strip foundation are reinforced. But you should not purchase equipment of this type if you are constructing the foundation yourself. There are methods that are no worse than machine methods, but in terms of ease of production, the work is much simpler.

To do this, you only need two pipes, which are driven into the ground with a distance of 2 cm between them. The main thing is that the pipes themselves do not bend under the influence of pressure from the fittings. Therefore, you will have to bury at least half a meter. The reinforcing bar is inserted between the pipes and bent manually relative to one of them. And the larger the diameter of the pipes, the larger the bending radius, and vice versa. For the manufacture of corner frame elements, this is the simplest option.

 We knit correctly

There are a large number of ways to connect elements of a reinforcing frame using knitting wire. The simplest of them is to fold a piece of wire 25 - 30 cm long in half, and tie it to the overlap of two rods using a hook. This reinforcement knitting pattern is so simple that you don’t even have to understand it.

But there are more complex methods of knitting that you will have to learn. Therefore, the question of how to properly knit reinforcement for a strip foundation is still relevant. After all, the owner of the house tries to get the maximum result at minimal cost. And the correct tying of the strip foundation reinforcement is a guarantee of high quality of the final result. So let's look at several ways of tying.

Schemes and techniques

Before knitting reinforcement, you need to understand that it is not always possible to use simple knitting patterns. After all, foundation structures are sometimes subjected to enormous loads amounting to hundreds of tons. Therefore, more complex fastening methods must be used.

Look at the photo below, which shows one of the reinforcement knitting patterns. It differs from the others in that the wire folded in half makes a double loop, with the help of which one rod is pressed to another.

Connecting frame elements in this way is not entirely convenient, but it is an effective scheme that guarantees high strength of the connection. It should be noted that in the transverse direction the rods are firmly connected, but in the longitudinal direction there is freedom to move.

In this way, reinforcement is usually tied in the corners of the foundation structure.

Simple methods of strapping also include another technology:

1. One free end of the wire is inserted into the double loop.
2. Two turns are made with a crochet hook.
3. Then the second end is inserted into the loop.
4. The required number of turns is made to clamp the two rods.

Corner reinforcement

Reinforcement in corners must be approached with special attention, because these areas are the most loaded, and high-magnitude vacuums are formed in them.

Therefore, the connection of the reinforcement in them is carried out according to special schemes, in which part of the structural elements in one trench extends into the adjacent one with the mating ends overlapping.

To make it clear what we are talking about, here are a few photographs that indicate possible ways to connect two adjacent sections of the reinforcing frame.

Please note that the differences in these two schemes are clearly defined. If in the first the overlap and connection of two frames occurs due to longitudinal reinforcement, which is bent and directed into the adjacent trench, then in the second the connection is made by an L-shaped clamp made of the same reinforcement as the longitudinal elements of the reinforcing frame.

It is necessary to understand that corner elements are always reinforced with vertical and longitudinal reinforcement or special U-shaped clamps made of rods, like vertical elements. The reinforcement for the foundation is tied in the corners of the structure with clamps or wire.

It is also necessary to pay attention to the fact that closer to the corners of the structure, the installation step of vertical and transverse rods is reduced to half the main distance between them. This primarily strengthens the structure. Of course, these are material costs, but without additional strengthening we cannot talk about high reliability of the structure.

The photo above shows only two patterns for tying reinforcing bars in the corners of a strip foundation. There are many more of them, and each has its own specifics of carrying out work, its own precise joining and tying technology.

Conclusion on the topic

Constructing a strip foundation with your own hands involves several construction operations, where one of the most important is knitting a reinforcing frame. How important this operation is can only be understood after the foundation becomes covered with cracks. There are several reasons: the load on the side of the building was calculated incorrectly, the concrete mortar was not formulated accurately, the reinforcing frame was incorrectly connected, which simply disintegrated in the body of the concrete under the influence of loads.

This does not happen so often, because the process of knitting a frame for a strip foundation is quite simple. But keep in mind that if you deviate from the rules and nuances discussed in this article, you can reap the fruits of your inattention, and sometimes even laxity.

Source: https://OsnovaPodDom.ru/vidy-fundamentov/lentochnyj-fundament/pravila-vyazki-armatury