How to lay reinforcement in the grillage. What technology is used to reinforce the grillage of pile foundations? Grill reinforcement technology
Unlike a strip foundation, it is easier to calculate the reinforcement of a grillage. Without exception, all arising stresses are absolutely predictable, since heaving forces are completely absent. Above the piles, the upper belt is strengthened, and more powerful reinforcement is laid between them in the lower belt.
The advantage of a pile foundation is that it rests on layers with a guaranteed high bearing capacity. For example, if a strip foundation on bulk, undermined, swampy soils requires a huge budget to go through them, piles will cost 10 to 15 times cheaper. However, it is difficult to support small-format wall materials on them, so the heads are connected by monolithic beams, on which masonry or log crowns are erected without problems.
The only common thing for a strip foundation and a grillage is a drawing, the performance characteristics are different:
- the vertical bending moment in the tapes resting on the ground with the entire sole is an extremely rare phenomenon, with a grillage it is the norm;
- when swelling, the soils try to tear, push the MZLF tape to the surface, the beams on piles are separated from the ground by 15–20 cm by an air gap or polystyrene foam, which perceives the indicated loads on itself;
- therefore, the tape is reinforced in both belts in the same way, the lower layer of reinforcement is reinforced in the grillage, the upper one is above them (only in tension zones, which concrete cannot cope with without cracking).
The reinforcing cage in any reinforced concrete product is just designed to compensate for stretching. Composite rebars, popular with individual developers, have poor adhesion to concrete, are highly stretched, which leads to crack opening.
Therefore, experts recommend creating a reinforcing cage exclusively from steel rods of 8–14 mm of periodic section (in the longitudinal direction), bars of 6–8 mm of smooth section (clamps, transverse, vertical brackets).
The best option is class A400 (old marking A3). Which fully complies with the instructions (pile foundations), (reinforced concrete, concrete structures).
The technology of the reinforcing cage of a strip grillage
Despite the name of the pile foundation strip grillage, monolithic beams have a lattice structure. Therefore, the frame has several junctions of walls (external / internal), corners in which overlapping is not allowed. The bars in these places are bent, launched to the adjacent side, and overlapped with the frame.
Longitudinal reinforcement is similar to a strip foundation; rectangular clamps are also used to give the frames spatial geometry. However, in tension zones, other critical places, transverse vertical rods are added. The joints of the pile-grillage frame are tied with wire or joined by welding (only for reinforcement with the letter C in the marking).
Longitudinal reinforcement
Without professional education and knowledge of special programs, it is difficult for an individual developer to correctly calculate the cross section and number of longitudinal rods. The simplest option would be to use the ARBAT tool of the Scad Office computing complex with the simplest possible interface:
- unlike piles, the grillage is calculated by bending moments, for punching, cutting forces;
- the reinforcing cage is made of longitudinal bars 8 - 16 mm;
- unlike the strip foundation, in addition to the clamps, vertical bars are added near each longitudinal rod.
The laying technology is standard, the longitudinal bars are tied with clamps or welded to them. Then the reinforcing cage is placed in the formwork on the lower pads made of concrete, plastic (providing a protective layer), reinforcement elements (vertical rods) are added in place.
In projects of cottages with concrete or brick walls a two-row arrangement of piles can be used. Therefore, for the strip part of the pile foundation, a calculation in the transverse direction can be added, since torques also occur there, sometimes exceeding the value of the longitudinal ones. The reinforcing cage in some cases is reinforced with rods of 14 - 16 mm in increments of 20 cm.
Transverse reinforcement
Without clamps, it is impossible to give the frames the necessary spatial geometry. At the same time, these elements reinforce the armored belt. All joints are scalded or tied with wire twists. Additional vertical bars are mounted with a calculated step (usually 20 - 40 cm). In the above photo, there are almost all possible errors:
- protective layers are not observed on all sides of the tape, the reinforcement is in contact with the pile formwork;
- reinforcement of corners should be carried out according to special schemes, and not just bent bars;
- there are no concrete, plastic gaskets;
- armored belt is displaced relative to the center of the pile;
- instead of the middle belt, which does not perceive any loads, it would be necessary to strengthen the upper / lower levels with thicker reinforcement of the pile foundation or by adding additional bars (this option is preferable);
- incorrect connection of the reinforcing cages of the pile and the grillage.
To learn more about corner reinforcement, we recommend reading the article:. Corner reinforcement schemes for the strip foundation and grillage will be similar.
In the lower figure, all the elements of the armored belt are located correctly - two vertical rods of the pile are connected to the lower belt, the rest to the upper rods.
Scheme of the correct reinforcement of the grillage / pile interface.
Rules for reinforcing corners and junctions with diagrams
In most Soviet literature (for example, V. S. Sazhin's manual), incorrect schemes for laying reinforcement at junctions are given. According to the correct reinforcement of such L-shaped, T-shaped joints, it is necessary as follows:
- launching the U-shaped element on the adjoining wall, counter bending of the bar from the side tape at a right angle;
- two U-shaped elements over the crosshairs of the longitudinal rods from the corner of the structure outward;
Drawing of the correct reinforcement of the corners and junctions of the grillage.
As a reliable foundation for the construction of buildings, a pile-type foundation is used. The foundation on supporting elements is necessary when building objects on problematic soils. A pile foundation is the best solution in many situations, including if the building is being built on permafrost or weak soil with close aquifers, as well as if there are significant elevation changes at the construction site. Reinforcement of the pile foundation grillage makes it possible to ensure the strength of the foundation, to form a reliable base for the building under construction.
The grillage is a responsible, horizontally located part of the load-bearing frame, connecting the supporting columns into a single circuit. It ensures the verticality of the pillars, prevents them from moving. Ensuring the strength characteristics of the supporting structure is achieved by strengthening with steel reinforcement. To strengthen the support contour, a drawing is required, calculations of the expected forces acting on the base during the operation of the building are required.
Pile foundation - a universal foundation for the construction of brick, wooden, aerated concrete and foam concrete low-rise buildings
Consider how the grillage foundation is strengthened. Let us dwell on the features of the main stages of work, the professional implementation of which will ensure the reliability of the foundation being built.
What is a grillage?
For those who do not know construction terminology, we inform you that the grillage is a critical part of the pile foundation, connecting the pile heads into a single power circuit.
There are various types of grillages used in pile foundations:
- tape type, representing a monolithic concrete tape. It is located along the perimeter of the supports, successively located under load bearing capital walls;
- slab construction, in the form of a monolithic slab, the dimensions of which correspond to the contour of the base of the building and cover all the supports.
The grillage is a tape structure connecting free-standing piles to each other
Depending on the characteristics of the grillage foundation, it can be made in the following versions:
- Whole variant. Production is carried out by pouring a concrete solution into a previously prepared formwork. The formation of a monolithic base occurs after the hardening of the concrete mixture.
- Composite form. The base is a prefabricated surface of industrially produced reinforced concrete products, connected during installation to the supporting columns, as well as to each other.
Regardless of the design features, the grillage forms a supporting surface intended for the construction of the walls of the building. The tying of columns located in the ground ensures high rigidity of the spatial system and resistance to the effects of existing forces.
Reinforcement of the pile-grillage base allows you to strengthen the monolithic base with steel bars, which contribute to the integrity of the structure and increase durability.
Design features
To form a strip foundation located on piles, grillages are made at different heights relative to the zero mark. Depending on the location of the contour relative to the ground level, the following types are distinguished:
- high, the lower mark of which exceeds the ground level by 10 cm or more. It is constructed for light buildings located on any type of soil. On problem soils, its device is especially important. The design needs to be seriously reinforced with reinforcement, which is associated with the presence of cavities under the concrete monolith located above the soil surface;
It is in the case of the installation of a monolithic pile grillage, which is used in the construction of houses made of heavy materials, that it is necessary to reinforce the strapping
- ground version, made on gravel-sand bedding without deepening into the soil. Its feature is the lack of free space between the concrete monolith and the ground. Installation is carried out on non-problematic soils. If the soil is susceptible to frost heaving, cracking and separation of the hardened concrete mass from the supporting columns is possible;
- shallow type, formed by deepening the lower part into the soil on a previously prepared sand and gravel bed. The design of such a foundation resembles a strip foundation, the base of which rests on piles. The formation of a deep foundation is associated with significant costs and is used for the construction of massive buildings located on soils characterized by low bearing capacity.
Pile-type foundations are formed mainly for light buildings. That is why the device of a grillage foundation is quite common, the basis of which is a hanging tape made of concrete reinforced with steel reinforcement. With a base height of up to 40 cm, its width depends on the type, size of the material used for the construction of walls, and is 30-40 cm.
On the feasibility of reinforcement
The need to strengthen the base of the building with steel reinforcement is associated with the characteristics of concrete. The material has increased resistance to compressive forces, but is susceptible to bending moments and stretching, causing damage to the integrity and deformation of the base.
Note that foundations are subject to reinforcement, in which two types of piles are used - driven and bored
Reinforcement of the pile grillage structure helps to prevent the probability of destruction, increase the stability, service life of the building under construction. The reinforcing cage located inside the concrete mass perceives tensile loads and bending forces, ensuring the stability of the foundation under construction.
Regardless of the design of the piles used, located inside the soil, the supporting columns are also reinforced with reinforcement. Steel bars located in piles are connected in general design with a reinforcing cage of the supporting surface.
Reinforcement of the pile foundation grillage allows:
- To prevent the destruction of the monolithic array as a result of soil reaction.
- Significantly increase the strength of the base, which perceives the load from the mass of the structure.
- Avoid shrinkage of the structure caused by low strength characteristics basics.
Strengthening the grillage foundation avoids negative phenomena.
Reinforcement specifics
Reinforcement of the pile foundation grillage is carried out with a pre-fabricated three-dimensional frame, consisting of two tiers of rods, combined into a single structure using steel lintels.
Reinforcement of the tape grillage is carried out by means of a spatial reinforcement cage, consisting of two longitudinal belts of reinforcement
No modern house can now be imagined without a foundation. It is the foundation that collects all the loads from load-bearing structures, and transfers them to the ground. There are different types of foundations.
In some cases, it is appropriate to create strip monolithic foundations, while in others, one-piece monolithic structures are used. We will now talk about the features of the pile foundation, as well as such an important process as the reinforcement of all the supporting structures of the foundation.
Features and design of the pile foundation
A pile foundation is one of the types of load-bearing supporting structures, on which the rest of the structure is then mounted.
Just like other foundations, this type of foundation is designed and built using SNIP and other regulatory documentation. However, the drawing, calculation and type of specific elements will be slightly different from the tape or solid one, since its tasks are slightly different.
Unlike tape bearing structures, in pile foundations, piles are the bearing elements and the main stress transmitters.
They are great for use when you need to mount a house on soft soils. In such cases, the large sole of the tape foundation models is too expensive, but the creation of spot piles is considered more appropriate.
When constructing such a structure, piles of bored, driven and several other manufacturing technologies are used. Their calculation and rationing is regulated by the appropriate SNIP.
Without taking into account regulatory documentation, create such important elements the future structure is prohibited, as this can lead to rather unpleasant consequences. Moreover, it does not matter what type of structure you have to build, in any case, SNIP will be a priority document.
Apart from pile foundation out of several dozen elements, not a single pile foundation design can do without a grillage. It should be understood that the type of pile foundation provides for the installation of piles directly at a distance of about 2-4 meters from each other.
The specific distance regulates the drawing, SNIP, type of foundation and a few more parameters. But in any case, it will be quite impressive.
To assemble this entire structure together, they use the creation of a grillage tying belt or slab. Moreover, it does not matter whether a grillage is used for tying bored or driven piles. In any case, its presence is simply necessary.
The grillage itself is a consistent and rather impressive part of the pile foundation, it can consist of a large number beams or monolithic slabs.
It is on the structure of the grillage that all the main load from the supporting structures of the house falls, and he, in turn, transfers it to the piles, which put pressure on the ground and distribute the load over the soil.
The pile foundation is characterized by the use different types piles (bored, driven) and different materials. In this case, we consider only as the most durable, reliable and in need of reinforcement.
Reinforcing piles and directly the entire pile foundation is an absolutely necessary process. Without reinforcement, concrete, although it performs its functions, is not so good.
The fact is that concrete itself is a fairly strong material, but any SNIP, GOST or the results of official studies indicate that, for all its strength, it does not work well in bending. Namely, bending loads put pressure on the structure of the grillage pile foundation.
If all these structures are not reinforced, then there is a high risk of their destruction or serious damage. In this case, the whole house will have to be recognized as emergency, since the foundation is perhaps the most important part of it.
For the implementation of high-quality reinforcement, a specific calculation is used. It is also regulated by the current design drawing, as well as its type and regulatory documentation, which will give you all the additional information (SNIP, GOST, reference books, etc.).
For reinforcement, welded reinforcing cages are used in the form of a grid with a certain step. The specific type of metal or, its length and all other parameters determine the design calculation. The type of reinforcement section determines how the welded mesh will be assembled.
Types and differences of grillage foundations
As we mentioned above, there are several varieties of grillage-type foundations, as well as grillage and pile structures. All of them are of rather serious importance not only due to the features of their design, but also due to how the reinforcing welded mesh will be used to reinforce them.
It is quite obvious that the tape grillage in its shape, dimensions and purpose differs from the solid one. This means that the welded mesh for reinforcement will be different for them.
Foundations of this type start from piles. Piles can be assembled and mounted according to:
- bored technology;
- Driving technology.
The bored technology of arrangement is characterized by the creation of piles with a powerful bottom cushion. They are formed according to the technology of immersing special tools into the ground and its displacement, and then laying the reinforcing mesh and concreting the entire structure.
Calculation of grillage mesh reinforcement
Now let's move on to the most important point - the calculation of the reinforcing mesh (framework). The welded mesh for the grillage will differ primarily depending on its type.
The use of bored, driven or other types of piles will be of secondary importance, since in this case the piles are only required to release connecting reinforcing pins to the outside, to which the grid of the grillage will be attached. But no more.
The calculation is performed according to the drawing of a specific type of grillage. So, a linear grillage has the shape of a large beam. He ties all the piles, forming a kind of belt. According to the same scheme, columns are tied in load-bearing frame structures.
The lower part of the grid will be assembled from thicker reinforcement with a diameter of 20 mm or more. The upper one will have a cross section of 8-15 millimeters.
Since the main loads on the surface bending will put pressure on the grillage tape only at the points of contact with the piles, serious reinforcement should be done in the sections of the tape under the piles.
Moreover, it is enough just to stretch the reinforcement by 1.5-2 meters from the center of the pile along the tape in both directions. In other places, it is recommended to make such powerful structures of the upper grid, but not at all necessary.
The welded mesh-frame in this case is calculated quite easily. Take into account the width of the tape and its height. The reinforcement of the lower level is laid in increments of 8-10 cm. As a rule, at least 4 rods go to the lower grid of one of the grillage tapes. On the top can go from 6 rods.
This calculation applies to tapes 25 centimeters wide. If the tape is much wider, then the reinforcement will have to be spent on it more. Also, the upper and lower nets are tied and fastened to each other with resistant clamps made of durable reinforcement. This should also be taken into account.
Thus, having calculated the length and width of the grillage tapes, as well as creating a drawing of its grid, you can perform a full-fledged reinforcement calculation, find out the amount of material needed, its cost and a bunch of other useful points.
For a solid grillage, since it is, in fact, an enlarged monolithic slab overlappings, the welded mesh will already be a little different. First, it will cover the entire area of the house. Secondly, it must be very durable and reliable.
Here, in increments of 20-25 cm, it is necessary to lay reinforcement minimum diameter from 20-25 mm. The rebar is laid crosswise to create an extremely strong foundation.
But the upper grid has interesting features. It is not always necessary to mount it over the entire area. This is due to the fact that the lower reinforcement mesh dampens almost all loads.
Any upper mesh must dampen the bending loads that come from the interaction of load-bearing structures and the upper elements of the building. And this means that it needs to be installed only near the load-bearing elements that will be placed on top or the load-bearing elements that support it.
In frame monolithic houses the upper reinforcing mesh of the floors covers only areas in 2x2 or 3x3 square meters, centered at each supporting column. All other places are either supplied with a safety net made of thin reinforcement, or remain without it at all.
If you calculate the dimensions of a solid grillage, as well as its usable area, you can find out all the information you need in the same way.
Grill reinforcement technology
It is quite easy to describe the reinforcement technology itself, since it is, in fact, almost identical in all cases.
Stages of work:
- We assemble the formwork, monitor its strength and reliability.
- We collect the lower frame of the reinforcing mesh.
- We mount the clamps supporting the racks and other elements.
- We collect the top in the right places.
There are no related posts.
The arrangement of foundations for any building is a very responsible and important stage from which the main construction work begins. It is recommended to manufacture the foundations in strict accordance with the design documentation.
For monolithic structures a fairly important part of the work is the reinforcement of the grillage. The strength of the entire structure largely depends on the quality of the associated reinforcement. You can make reinforcement yourself, having previously familiarized yourself with the technology of this type of work.
What is a grillage
A grillage is a monolithic element of the foundation of a building, connecting free-standing pillars or piles in single system. It is made in the form of a strip foundation, on which the supporting and external enclosing structures of the building are installed. The tape evenly distributes the loads over the entire base of the building, which in turn transfers them to the ground.
Scheme of the grillage device The grillage can be made not only in the form of a monolithic strip foundation. It is also made of wooden, metal and reinforced concrete products located between columnar supporting structures. Such a device in the form of beams is used much less frequently than a monolithic one.
Distinguish between hanging and recessed structures Depending on the height of the grillage foundation relative to the ground level, there are hanging and recessed versions of the device. During the construction of a recessed grillage, a monolithic design is selected. If a hanging one is made, then the base of the grillage can be made of horizontal beams.
A monolithic grillage contains concrete and reinforcement at its core. Reinforcement takes the bulk of the time when constructing this type of foundation. When carrying out work on the reinforcement of the strip foundation, it is necessary to be guided by building codes and rules 52-01-2003.
The grillage should serve as a reliable support and protect the structure from moisture. The pile-grillage foundation is suitable for the construction of buildings with no more than three floors.
The device of a monolithic grillage
To make a monolithic grillage foundation, you will need to perform several stages of work.
- Formwork installation.
- Reinforcement grillage.
- Concreting.
- Stripping.
- Tape waterproofing.
Formwork installation
Formwork must be installed strictly at an angle of 90 degrees The grillage foundation is made hanging or buried in the ground. The design of the formwork directly depends on its shape.
Regardless of the design, the side walls of the formwork must be assembled in a strictly vertical level, and the corners must correspond to 90 °, unless otherwise provided by the project.
When making a tape in the ground, you can use soil instead of formwork, as a support for the future foundation. Above ground level, formwork is assembled most often from boards or plywood. It is hammered together or pulled together so that the concrete does not squeeze out the boards and does not spread during its laying. That part of the foundation that protrudes above the ground will be fenced with such a structure.
If the hanging version of the grillage device is chosen, then it is necessary to provide a high-quality foundation in the formwork. It must be calculated based on the load that it must withstand. The load is determined by the mass of concrete and reinforcement. It is also necessary to take into account the mechanical effects on the structure from the vibration of concrete during its pouring.
The side walls of the formwork must be firmly assembled. For this, cross ties, spacers, tubes with studs and other materials can be used to ensure the reliability of the structure.
Poor-quality formwork can lead to disruption of the concrete laying process. This is unacceptable in construction, but often due to negligence in this part of the work.
Reinforcement grillage
Structural reinforcement Reinforcement of a pile grillage or column foundation is one of the most important stages in the construction of the foundation for the building.
Periodic metal reinforcement is used as the main material for reinforcing foundations. IN Lately it began to be replaced with composite fiberglass. It should be noted that fiberglass reinforcement is not suitable for hanging structures. It is good where there is ground support.
Rebar welded into beams The fittings are connected or welded in some cases into frames, the so-called beams. There are several types of beams. The type of reinforcement, and hence the type of beams, is determined at the design stage.
With independent construction, when there is no project, and there is no way to turn to specialists, there is an option to use online calculator reinforcement. It is advisable to find several of these on the Internet. online programs and make calculations in each, in order to compare the data, determine the error in the calculations. Having calculated the reinforcement according to the parameters of the foundation, you can start work.
Reinforcement of a monolithic grillage in the most common form consists of straight longitudinal and transverse rods, which are interconnected by knitting wire or welding. In order to properly connect the structure, clamps and U-shaped products are made from reinforcement. They are connecting elements in the nodes of the reinforcing cage.
To find out how reinforcing cages and their assemblies are made correctly, you need to read the manual for the design of concrete and reinforced concrete structures from heavy concrete (without prestressing).
Reinforcement of pile-grillage foundations is impossible without connecting the pile reinforcement with the grillage frame. When constructing a pile field at the reinforcement stage, vertical rods are made with height allowances. When installing the reinforcing cage of the strip foundation, the rods released from the piles are bent at the desired horizontal level and connected to the main frame. Thus, the integrity of the structure is achieved. For all the details on pouring the pile-grillage foundation, see this video:
Do not heat metal fittings in order to bend them. For bending, use special devices or pipe bender.
Tape concreting
It is necessary to pour concrete into the formwork without interruption to get a high-quality monolith The grillage foundation is poured with concrete at a time without interruption in the work until they are completely completed. It is strictly forbidden to make breaks along the length of the foundation. The only permitted action is a gap along the height of the grillage. After pouring 150-200 mm of the layer over the entire volume of the tape, a break is made in the work.
Before continuing construction works it is necessary to wait until the concrete gains the minimum allowable strength. Then it is required to clean off the top layer, the so-called concrete milk, and only after that continue concreting the tape.
It is important to work in such a way that there are no pores in the concrete mass. It is required that the concrete fills the entire space in the formwork. There should not be a single air pocket inside the grillage.
Stripping
It is important not to remove the formwork ahead of time You can neglect this process once and do it ahead of time in order to incur losses that will significantly affect the construction budget.
With premature demoulding, the foundation may crack, which will leave practically no options other than its dismantling. In this case, a new foundation will be required, respectively, construction costs will increase significantly.
Concrete gains strength depending on its grade and temperature. environment. The ideal temperature is 20 ° C, in such conditions, concrete grades M200-300 will gain 100% strength in 28 days.
Data on concrete strength gain are presented in the table.
| Percentage of concrete strength depending on temperature | |||||||
|---|---|---|---|---|---|---|---|
| Concrete brand | Curing time, days | -3°С | 0°С | +5°C | +10°C | +20°С | +30°С |
| 1 | 3 | 5 | 9 | 12 | 23 | 35 | |
| 2 | 6 | 12 | 19 | 25 | 40 | 55 | |
| M200-300 on Portland cement M-400 and M-500 | 3 | 8 | 18 | 27 | 37 | 50 | 65 |
| 5 | 12 | 28 | 38 | 50 | 65 | 80 | |
| 7 | 15 | 35 | 48 | 58 | 75 | 90 | |
| 14 | 20 | 50 | 62 | 72 | 90 | 100 | |
| 28 | 25 | 65 | 77 | 85 | 100 | - |
The table shows that at low temperatures it is advisable to use concrete with additives for rapid strength development. This slightly increases its cost, but also significantly speeds up the construction process.
It is allowed to strip the formwork when the concrete strength is at least 50%.
Waterproofing Tape
With a hanging grillage, you can use coating waterproofing. In the recessed version, it is possible to lay the rolled waterproofing into the ground before pouring concrete and, after stripping the upper part, completely close the foundation to it. For more information about the waterproofing of the grillage structure, see this video:
It is important to protect the base from moisture. If the foundation absorbs water, then winter time at sub-zero temperatures, during the expansion of freezing water, microcracks will form in it. This must be avoided.
Reinforcement mistakes and how to avoid them
Do not reinforce corners by crossing reinforcement There are a number of reinforcement-related mistakes that inexperienced builders make to save money or simply out of ignorance of building codes and regulations. Below are the most frequently repeated ones.
- Diameter reduction bored pile, according to some builders, should be accompanied by a decrease in the number of vertical reinforcement bars, to which the grillage frame should subsequently be attached. Decreasing the allowance of vertical bars.
- Reinforcement of corner sections by crossing straight bars of reinforcement. Many do this in order not to complicate the knitting of the frame.
- Non-observance of the jumper installation step when reinforcing the grillage. Skipping necessary connections. This is often done to save money.
- Deviation of the reinforcing cage from the central axis. This will lead to an uneven bearing capacity of the base. Such things often happen due to banal negligence. All the subtleties of reinforcing the pile foundation, see this video:
Solutions to the above errors are given below.
- The pile diameter should not be less than 300 mm, and the number of vertical rods should not be less than 4, the reinforcement allowance for the grillage should be at least 0.5 m.
- For the correct connection of the nodes of the beams, bent U- and L-shaped parts should be made, with which it is necessary to connect the corner elements.
- When constructing a reinforcing cage, a step of 200 to 400 mm between the jumpers must be observed. The exact step size is determined at the design stage.
- It is required to make all measurements using building levels so that the frame is set relative to the central axis.
Reinforcement is a significant part of the construction process. Everything is important and the quality of materials, and the experience of builders, and the availability of working documentation. 
Failure to comply with the rules of reinforcement can lead to the most serious consequences. This stage of construction is one of the most responsible.
In the course of construction works, any mistake leads to a decrease in the life of the building without the need for repair. This is at best. At worst, even at the stage of construction of the building, it undergoes restructuring.
To achieve maximum service life, it is required to comply with building codes and rules, avoiding deviations from the project. Construction combines a set of measures that must be observed in order to achieve the desired result. If possible, it is better to entrust such work to professionals.
The pile foundation is a universal basis for the construction of brick (we read about it separately), wooden, aerated concrete (we read about it separately) and foam concrete low-rise buildings in any soil conditions. Such bases are also used for other structures (for example, fences,). The strength and reliability of the pile foundation directly depends on the grillage, the reinforcement technology of which we will discuss in this article.
You will learn why a pile-grillage foundation is needed, what materials are used for this and how the process itself is performed. Schemes and drawings will be given explaining all the nuances of reinforcing a monolithic grillage.
1 What functions does the grillage perform and why is it necessary to reinforce it?
A grillage is a tape structure (we read about how a regular one is reinforced), connecting free-standing piles to each other. Due to the strapping of the support, additional spatial rigidity and resistance to overturning loads are obtained. Also, the grillage acts as a supporting surface on which the walls of the building are erected.
1.1 What and how to reinforce?
Reinforcement of the strip grillage is carried out by means of a spatial reinforcement cage, consisting of two longitudinal reinforcement belts (upper and lower), interconnected by horizontal and vertical jumpers.
Longitudinal chords are made of class A3 rebar (hot-rolled corrugated profile), the diameter of which is 13-16 mm. You can use it, which is confirmed by reviews of the successful operation of such pile-grillage foundations in specialized forums.
Connecting vertical and horizontal jumpers can be made in two versions - in the form of individual bars of reinforcement welded to the longitudinal chords (the diagram shows the configuration). In this case, it is necessary to use rods of the same size as in the arrangement of the longitudinal belt.
Also, the frame can be connected by jumpers from a rectangular reinforcement curved into clamps (diagram below). With this approach, class A2 smooth rods (diameter 8-10 mm) are used. Bent clamps are laborious to install, however, due to the smaller number of welds, they are more reliable and durable. Fiberglass reinforcement, not subject to bending, is not used to create clamps.
According to the provisions SNiP No. 2.03.01 "Manual for the design and arrangement of pile-grillage foundations", when installing the reinforcement cage, it is necessary to observe the following step between the constituent elements:
- the number of rods in the longitudinal belts is at least 4, the distance between them is up to 10 cm;
- the step between the transverse bridges of the longitudinal belt is 20-30 cm;
- step between vertical connecting jumpers - up to 40 cm;
- protective layer of concrete - at least 5 cm.
The protective layer is the distance between the extreme contours of the reinforcement cage and the walls of the concrete body of the monolithic grillage. If the protective layer does not have the required thickness, two problems will arise - the frame will not be able to correctly redistribute the loads acting on the grillage and the reinforcement will be excessively susceptible to corrosion under the influence of moisture penetrating into the concrete micropores.
To make a protective layer along the lower edge of the grillage, special plastic mushroom stands are used, which raise the reinforcement above the formwork. The use of pieces of brick for these purposes is not allowed.
1.2 How to calculate the amount of reinforcement?
As an example, we give for a monolithic grillage with a perimeter of 8 * 6 m. We use the conditional dimensions of the strapping 40 * 40 cm. cm on each side eats a protective layer of concrete). The belts are connected by jumpers made of A1 reinforcement with a diameter of 11 mm, located in increments of 20 cm.
The calculation is performed according to the following algorithm:
- We determine the total length of the rods in the upper longitudinal belt. To do this: a) determine the perimeter of the grillage: 8+8+6+6 = 30 m; b) we calculate the length of 3 rods: 3 * 30 = 90 m; c) calculate the length of reinforcement A3 for both belts: 90 * 2 = 180 m.
- To connect the rods of the longitudinal belt, we need jumpers 30 cm long, which will be located in increments of 20 cm. We calculate their number for both grillage contours: 2*(30/0.2) = 300 pcs, after which we calculate the total length of the transverse jumpers: 300* 0.3 = 100 m.
- It remains to calculate the length of the vertical jumpers connecting the upper and lower contours of the frame to each other. But since a rectangular grillage is calculated in the example, their number and length will be identical to the transverse jumpers. If a grillage of a rectangular configuration is used, the calculation is performed according to the formula specified in paragraph No. 2.
As a result, the calculation showed us that the reinforcement of the grillage requires 180 m of A3 class reinforcement and 200 m (100 + 100) A2 rods with a diameter of 11 mm. Calculation may also be required if you do not plan to use butt welding. It is carried out taking into account the fact that one connection takes about 40 cm of material: we determine the number of connections: 4 * (30 / 0.2) = 600 pcs; and calculate the material consumption - 600 * 0.4 = 240 m.
1.3 Features of grillage reinforcement (video)
2 Technology of reinforcement of a monolithic grillage
Amination of the grillage begins after all the previous stages of arranging the pile foundation have been completed - the installation of piles, their trimming and arrangement of the formwork. You must have a ready-made formwork, inside which the reinforcement cages of the piles protrude to a height equal to the cross section of the strapping.
When assembling the frame, the reinforcement can be knitted together with a wire or the rods can be connected by welding. There is no significant difference in the method of docking - it is often argued that a welded frame, due to lack of elasticity, resists deformations worse than a viscous structure connected, however, in industrial multi-storey construction, frames of pile-grillage foundations are always welded, so these fears are groundless. In addition, welding is a more practical and faster way to implement.
Reinforcement grillage - step by step instructions:
The assembly of the reinforcement cage on straight sections of the grillage is quite simple to perform. Difficulties arise when reinforcing the corners, which must be further strengthened, since this part of the frame experiences maximum loads.
Corners and junctions internal walls bindings to the outer cannot be reinforced with overlapping reinforcement. In these areas, it is necessary to lay solid rods, curved in a L or U-shaped configuration. The diagram of the correct reinforcement of the corners of the pile grillage is shown in the image.
