Reinforcement of a high grillage. Rostwerk: what it is, its types and purpose. Pile with grillage
In the field of individual construction, when using a pile foundation, a monolithic reinforced concrete grillage is the most popular option, since even with significant sizes it can always be made on its own.
The materials used for this can be delivered to the construction site by conventional trucks or even light vehicles without the use of special platforms or cranes.
However, the installation of a monolithic grillage is more complicated than a precast one, and the main difficulty lies in the correct reinforcement. pile grillage.
You can often hear about the similarity of the grillage device and the usual strip foundation, but this statement is only partly true. Indeed, in its appearance and function, the grillage is very similar to a tape base, however, the operating conditions of these structures are significantly different:
- if for a strip foundation the occurrence of a bending moment in a vertical plane is more likely a phenomenon out of the ordinary, then for grillages, which are beams laid on piles, this is the norm. The span located between the supports takes the weight of parts of the building and other loads, while being, as it were, suspended in the air, which causes deflection;
- another difference is that the load on the strip foundation is less predictable. The underlying soil under various parts of the base may "float" or swell. This causes multidirectional deflections, in which both the upper and lower parts of the cross section can be stretched. And the stretched zone that occurs when a reinforced concrete element is deflected is, as you know, exactly the zone in which the reinforcement should be located. Thus, a conventional strip foundation has to be reinforced in the same way both at the top and at the bottom.
In the case of the grillage, the impact from the soil is completely excluded, therefore, the stresses that arise in it are quite predictable: in the spans between the piles, the lower part of the cross section is always stretched, in the areas supported by the piles - the upper one.
This also determines the scheme of reinforcement of the pile foundation grillage. The lower belt of the reinforcing cage in the areas between the piles is made more powerful, and at the points of support on the piles, the upper belt is strengthened.
Selection of materials for the reinforcing cage and determination of its parameters
The diameter of the reinforcement used and the parameters of the frame are selected on the basis of a calculation that takes into account permanent and temporary loads.
The calculation of the reinforcement of the pile foundation grillage should be performed by an experienced civil engineer who is well versed in the topic of reinforced concrete structures.
Typical solutions
In practice, in individual construction, the following rules are followed:
- in the stretched zones of the grillage, several longitudinal reinforcement bars of class AIII with a diameter of 20 mm or more are laid;
- reinforcement with a diameter of 8 - 15 mm is placed in the compressed belt. The pitch between the bars of the longitudinal reinforcement, also called working, is 80 - 100 mm.
- For the perception of transverse tensile forces, as well as for combining longitudinal reinforcement into a single frame, transverse bars are attached to it - smooth reinforcement of class AI with a diameter of 6 to 8 mm. The distance between them should not be less than 250 mm, but usually it is taken equal to 3/8 of the height of the grillage section.
If the height of the grillage exceeds 150 mm, vertical rods are installed in the reinforcement cage, the step of which corresponds to the step of the transverse reinforcement.
Most often, instead of individual longitudinal and transverse rods, clamps are used - reinforcement parts in the form of a closed rectangle or an inverted letter "P".
Reinforcement of the abutment zones of the grillage tapes
Where the grillage ribbons form an L-shaped or T-shaped intersection, it is not enough to simply fasten the intersecting rods of the working reinforcement.
Here, rods bent at right angles are placed, each part of which fits into one of the adjoining tapes and enters into it at least 40 diameters.
Clamps in these areas are installed twice as often.
Manufacturing jobs
Reinforcement of the pile foundation grillage is performed immediately after the construction of the formwork. An obligatory element of the latter should be transverse jumpers in the upper part, to which, in the end, the reinforcing cage will be suspended.
Work on the installation of reinforcement in the future grillage can be divided into several operations.
The device of the lower belt of the reinforcing cage
At the bottom of the formwork, special plastic bosses are laid on top of the waterproofing, on which the lower belt of the reinforcing cage will then be located.
If the bosses are not available, they can be replaced with brick fragments or wooden blocks 40 - 50 mm high:
- the height of all shims must be the same so that the reinforcement rods take a strictly horizontal position;
- the spacing between the bosses or elements used as an alternative depends on the diameter of the working reinforcement: it must be such that the bars do not bend;
- on the bosses with an equal pitch, it is necessary to lay the working reinforcement of the lower chord. The distance from the outer rods to the side surfaces of the formwork should be 30 - 40 mm.
When constructing the frame, the contractor must be guided by the requirements of the documents describing the reinforcement of the grillage of the pile foundation: a design drawing with all the necessary instructions is given in the construction project.
If the grillage tape has a considerable length, each thread of the working belt is recruited from several reinforcing rods connected with an overlap of 1 m.
Bars of transverse reinforcement or clamps are attached to the lower chord, combining transverse and vertical reinforcement.
Upper belt device
The working reinforcement of the upper chord is suspended from the lintels of the formwork, which were mentioned at the beginning of the section. The length of the suspensions should be such that after the grillage is poured over the reinforcement, a protective layer of concrete 30 to 40 mm thick is formed.
The rods of the upper chord are connected with transverse and vertical reinforcement or with clamps, if any.
Then both working chords should be tied to the reinforcement protruding from the piles. The reinforcing frame can be considered ready.
Reinforcement knitting methods
The most common fastening method is tying the reinforcement with a special wire. Electric welding is used very rarely and only for fittings marked with the letter "C".
It is not allowed to weld ordinary fittings, since due to exposure to high temperatures, it becomes weaker.
For knitting of reinforcement, only annealed round wire with a diameter of 1 mm is used. Unbaked wire is less ductile, therefore it bends poorly and breaks easily.
The fastest way to knit fittings is with a special pistol equipped with a battery. But its acquisition is advisable only for large volumes of work, moreover, it is not very convenient when knitting reinforcement in hard-to-reach places.
Reinforcement of the pile - grillage foundation for a private house is mainly carried out using another tool - a special hook. Professionals prefer homemade crochet hooks, but purchased hooks are also suitable for one-time work.
On the market you can find both conventional and screw hooks, also called semi-automatic.
The latter make it possible to knit reinforcement a little faster, but due to their design, after tightening the knot, they leave too long free ends of the wire, which often protrude from the concrete and begin to rust.
The simplest and most common types of knots are the so-called "loop" and "two loops". The first is used for overlapping reinforcement, the second for butt joints. In practice, the loop is often used not only for overlap joints, but also for corner joints.
At the final stage of the installation of the reinforcing cage, you should remove the bosses on which the working reinforcement of the lower belt was installed. After that, the entire frame will be suspended on a wire twisted around the upper formwork lintels. Now you can start pouring concrete.
Video about the reinforcement of the pile foundation grillage
Pile foundation - a universal foundation for the construction of brick (about reinforcement brickwork - read separately), wooden, aerated concrete (about the reinforcement of aerated concrete - read separately) and foam concrete low-rise buildings in any soil conditions. Such bases are also used for other structures (for example, fences, columns). The strength and reliability of the pile foundation directly depends on the grillage, the reinforcement technology of which we will talk about in this article.
Grillage reinforcement
You will learn why it is necessary to reinforce the pile-grillage foundation, what materials are used for this, and how the process itself is performed. Diagrams and drawings will be given explaining all the nuances of reinforcing a monolithic grillage.
What functions does the grillage perform and why do you need its reinforcement?
The grillage is a strip structure (we read separately about how a conventional strip foundation is reinforced), connecting the free-standing piles to each other. Due to the strapping of the supports, additional spatial rigidity and resistance to tipping loads are obtained. Also, the grillage acts as a supporting surface on which the walls of the building are erected.
See also: What is reinforcement anchoring and why is it necessary?
There are several types of strapping according to the material of manufacture - steel (from a channel or I-beam), wooden (from a bar) and reinforced concrete. It is in the case of the installation of a monolithic pile grillage, which is used in the arrangement of houses made of heavy materials, that it is necessary to reinforce the strapping.
The need to strengthen the monolithic grillage with reinforcement is due to the fact that concrete as a material has a high resistance to compressive loads, but at the same time it has a weak resistance to bending and tensile loads, which can cause its deformation.
Diagram of the pile-grillage foundation
The reinforced frame placed inside the monolithic grillage absorbs the above loads, preventing the risk of its destruction, which significantly increases the reliability and durability of the structure. Reinforcement is necessary not only when installing a pile-grillage foundation, but also in a columnar base, which has a similar configuration.
See also: what kind of mesh is the reinforcement of the floor screed?
Note that the foundations are subject to reinforcement, in which two types of piles are used - driven and bored. Driven piles are prefabricated structures that, upon completion of installation, are cut with a special hydraulic pile cutter using a pile driver.
After trimming, the reinforcement is exposed on the end part of the pile, which is subsequently connected to the frame of the monolithic grillage. When installing bored supports, their reinforcement cage is made so that reinforcement protrusions with a height of 30-40 cm are above the concrete body of the pile.
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What and how to reinforce?
The reinforcement of the tape grillage is carried out by means of a spatial reinforcement cage, consisting of two longitudinal reinforcement belts (upper and lower), connected by horizontal and vertical bridges.
Longitudinal belts are made of rods of A3 class (hot-rolled corrugated profile), the diameter of which is 13-16 mm. It is possible to use fiberglass reinforcement, which is confirmed by reviews on 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 separate bars welded to the longitudinal belts of the reinforcement (the diagram shows the configuration). In this case, it is necessary to use rods of the same standard size as when arranging a longitudinal belt.
Drawing of the connection of belts with separate jumpers
Also, the frame can be connected with jumpers from the reinforcement curved into the clamps (the diagram below). This approach uses smooth rods of class A2 (diameter 8-10 mm). Bent clamps are laborious to install, but due to the smaller number of welded seams they are more reliable and durable. Fiberglass reinforcement, which cannot be bent, is not used to create clamps.
Drawing of the connection of belts with 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, the following step must be observed 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 crosspieces of the longitudinal belt is 20-30 cm;
- the step between the vertical connecting jumpers - up to 40 cm;
- protective concrete layer - at least 5 cm.
The protective layer is the distance between the outer 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.
Plastic stand for fittings
To make a protective layer along the bottom 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.
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As an example, we give the calculation of the amount of reinforcement for a monolithic grillage with a perimeter of 8 * 6 m.We use the conditional dimensions of the strapping 40 * 40 cm.The reinforcement frame for such a strapping will consist of two longitudinal belts of 3 rods A3 with a diameter of 14 mm each (the pitch between the rods is 10 cm , 5 cm on each side eats away the protective layer of concrete). The belts are connected by jumpers made of reinforcement A1 with a diameter of 11 mm, located in 20 cm increments.
The calculation is performed according to the following algorithm:
- 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 \u003d 30 m; b) we calculate the length of 3 rods: 3 * 30 \u003d 90 m; c) we calculate the length of reinforcement A3 for both belts: 90 * 2 \u003d 180 m.
- To connect the rods of the longitudinal belt, we need jumpers 30 cm long, which will be located with a step of 20 cm.Calculate their number for both grillage contours: 2 * (30 / 0.2) \u003d 300 pieces, after which we calculate the total length of the transverse jumpers: 300 * 0.3 \u003d 100 m.
- It remains to calculate the length of the vertical bridges connecting the upper and lower contours of the frame to each other. But since in the example a rectangular grillage is calculated, their number and length will be identical to the transverse lintels. If a grillage of a rectangular configuration is used, the calculation is performed according to the formula specified in paragraph 2.
As a result, the calculation showed us that the grillage reinforcement requires 180 m of A3 class reinforcement and 200 m (100 + 100) of A2 rods with a diameter of 11 mm. You may also need to calculate the tying wire if you do not plan to use a weld splice. 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) \u003d 600 pcs; and calculate the material consumption - 600 * 0.4 \u003d 240 m.
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Features of grillage reinforcement (video)
Monolithic grillage reinforcement technology
Reinforcement of the grillage begins after the completion of all the previous stages of the arrangement of the pile foundation - the installation of piles, their trimming and the arrangement of the formwork. You must have a ready-made formwork, inside of which the reinforced frames of the piles protrude to a height equal to the cross-section of the strapping.
Formwork and piles before starting reinforcement
When assembling the frame, the reinforcement can be knitted with each other using a wire, or the rods can be connected by welding. There is no significant difference in the method of joining - it is often argued that the welded frame, due to the lack of elasticity, is less resistant to deformations than a connected viscous structure, however, in industrial multi-storey construction, the frames of pile-grillage foundations are always welded, so these fears are groundless. In addition, welding is a more practical and quicker way to implement.
See also: how stairs are reinforced, and should it be done?
Reinforcement of the grillage - step by step instructions:
The assembly of the reinforcement cage in straight sections of the grillage is quite simple to perform. Difficulties arise when reinforcing the corners, which must be additionally reinforced, since this part of the frame experiences maximum loads.
Scheme of the correct reinforcement of the corners and abutments of the grillage
The corners and places of abutment of the inner walls of the strapping to the outer cannot be reinforced with overlapping reinforcement... In these areas, it is necessary to lay solid rods bent in a L or U-shaped configuration. A diagram of the correct reinforcement of the corners of the pile grillage is shown in the image.
Related articles:
Reinforced concrete monolithic structures are one of the prerequisites for the strength, reliability and durability of an object. Reinforced concrete means that the concrete is reinforced with a special frame, tied or welded from reinforcing bars. You should learn how to properly knit reinforcement for the foundation before reinforcing concrete in your personal plot, building a house, garage or other durable objects.
Rebar knitting options
The basics of properly tying reinforcement
Basically, in individual construction, a reinforcing frame is used when laying a strip foundation. The strip base is a monolithic structure made of concrete and a reinforced cage inside, in which the frame takes on tensile loads and lateral shifts of the soil. Due to the multidirectional loads on the reinforcing cage, it is important to correctly make its calculations, as well as find out the parameters of a house or other building that uses reinforcement in the structure, the number of building materials and their characteristics.
In order to tie a reinforcing belt with your own hands for any type of foundation in which it can be used, you need to be able to tie the transverse and longitudinal joints of the rods in the correct way. Welding is very often not recommended for assembling a reinforcing cage due to a too rigid connection, which, under sufficiently strong loads, can burst and weaken the entire structure. Therefore, you should use a special factory or homemade hook, plus know the basic layouts of reinforcing bars in concrete.
Reinforcement parameters when calculating the frame for a strip foundation
Knitting steel wire must be soft or annealed, and in order to correctly crochet the reinforcement, it is necessary to study the requirements for knitting wire, which are regulated in GOST 3282.
Professional builders categorically deny knitting of metal reinforcement with plastic clamps, which are allowed to knit fiberglass reinforcement, since the mass of concrete pouring into the formwork displaces the knitting points along with the mortar. Slab concrete foundations are a separate topic, and reinforcing frames are allowed to be welded in them. There are ready-made industrial reinforcement mesh welded from rods. But such a frame is much more expensive than a home-made one, in addition, the end joints need to be additionally reinforced with U-shaped clamps in place, which makes the welded frame even more expensive. Therefore, for the foundation of a private or country house, it is easier to knit the reinforcement cage by hand using a coil of soft wire, a special crochet hook, and instructions for use.
Rebar Tying Hook
When knitting a frame for a foundation, operations are performed in the following order:
- A piece of knitting wire 20-25 cm long is used for tying reinforcing rods Ø 8-16 mm. A segment of this length must be cut off from the bay;
- The segment is bent in half in the center, brought under the intersection of the rods diagonally;
- The sharp end of the crochet hook needs to be threaded into the loop, which turned out when the piece of wire was folded;
- The clamp, which turned out from a piece of wire, should be pulled tight;
- the free end of the clamp is applied to the working end of the crochet hook;
- now we knit two intersections together: when you rotate the hook 3-5 turns, you get a strong, but flexible twist;
- After removing the knitting hook from the loop, the remaining free ends of the wire clamp must be bent inside the reinforcement cage.
Important: If reinforcement Ø 25 mm or more is used for the aromatic cage, the intersections of the rods must be welded, not tied. Connected joints can break during operation of the finished reinforced foundation under the weight of concrete and building.
Ready reinforcement cage
Common mistakes when knitting a reinforcing frame that do not need to be repeated:
- Straight bar segments at the corners of the frame are connected by the overlap method;
- The reinforcing frame is installed not on pads, but on the vertical rods of the frame;
- In the context of a concrete tape, the reinforcing binder and reinforcing material is less than 0.1% of the total volume of concrete;
- There is no protective layer on the sides of the formwork, due to which the rods can come into contact with the formwork material.
The corner intersections of the frame rods in the strip foundation cannot be simply tied and left in the form of an overlap of the rods. The connection of the rods is done according to specially designed anchoring schemes for such cases, one of which is presented below:
Anchorage schemes for frame corners
Reinforcement of the concrete foundation must take into account some of the features of the strip structure:
- The reinforced frame for the concrete tape can be tied both in the ground and in the finished formwork. For this, reinforcing bars, metal clamps and anchors are used;
- The deep-seated foundation is reinforced before installing the panel formwork - this option is preferable due to the fact that the heavy frame does not have to be lowered into the trench and deform it;
- The reinforced frame must be reinforced with U-shaped or L-shaped anchors at the corners of the structure;
- To ensure the protection of the frame from below with concrete, props 5-7 cm in size are used, which are called glasses;
- Elongation of short longitudinal bars occurs with an overlap, the overlap should be ≥ 20 bar diameters, or ≤ 25 cm;
- It is impossible to place the reinforcement cage on stones, bricks or pieces of reinforcing rods - only iron, plastic or concrete linings should be used;
- Overlapping reinforcement joints must be spaced apart - in one section, more than half of the total section of the longitudinal rods should not be connected.
Important! Clamps in the reinforcement cage are used to create and hold the geometry of the structure. Therefore, the diameter of the long horizontal rods should be 6 for a length ≤ 0.8 m and 8 mm for a rod length ≥ 80 cm.
Reinforcement of a tape with L-shaped and U-shaped reinforcements
Reinforcement of a slab floating foundation should take into account some design features and not repeat common mistakes:
- The rods at the corners of the upper and lower levels should be connected with U-shaped clamps;
- You cannot use one reinforcing mesh instead of two frames - the lower frame takes on tensile loads from the weight of the house, and loads from heaving forces are applied to the upper layer of the frame. One reinforcement mesh is allowed with a concrete slab thickness ≤ 15 cm;
- Non-compliance with the provision of concrete protective layers for the frame from above and below. Concrete layers should be ≥ 5-7 cm thick;
- The mesh size of the reinforcing mesh should be ≤ 40 cm, the optimal mesh size is taken at 20 cm.
To assemble the concrete slab reinforcing frame, the upper belt of the mesh is fixed using such bracket-bending devices as "tables", "conductors", "pawns", "frogs", "clubs", "spiders", and other supporting elements with extended rods, which rest against the design of the lower belt.
Brackets for reinforcing frames and meshes
Bending of reinforcing bars should not be carried out using gas welding. The rods are bent on special bending mills or clips, in which you can set the required radius.
Near the bearing walls, the foundation should be reinforced with additional rods, since the dimensions of the mesh cells near the walls are half the size of the others. If slabs with stiffeners are used for the base, then the reinforcement cage is used the same as for the strip foundation or grillage.
Bending machine
Grillage reinforcement
Due to the fact that the grillage is like a foundation strip, many craftsmen make mistakes in reinforcing it. Tensile loads from the weight of the house are applied to the concrete tape in the area of \u200b\u200bthe sole, top part the foundation is experiencing loads from seasonal soil heaving. The grillage never experiences loads from heaving forces, since it rises above the soil and has an air gap or a layer of expanded polystyrene, which crumples during deformations. Only vertical bending forces are applied to the grillage in the areas where the supports are pinched.
Important: In the grillage, the reinforcing frame is necessarily reinforced with longitudinal reinforcement connected with steel clamps. Strengthening is carried out for the upper columns, piles or pillars, as well as for the lower armored belt.
Reinforcement of grillage for piles
The section of the reinforcing frame is of different types:
- If the formwork is tubular, then the frame can be tied round or square;
- For columnar foundation in the formwork from prefabricated panels, round or square clamps are used, which are used to knit vertical reinforcement rods;
- One support must contain at least four longitudinal bars.
Pile reinforcement
The bottom of the piles does not need to be reinforced. The pile head at a distance of 1 meter from the bottom must be reinforced and poured with concrete. The vertical bars of the reinforcement are bent at an angle of 900 with subsequent tying to the grillage.
Pile reinforcement
Homemade reinforcing frame is made only on twists of soft knitting wire. Ready-made reinforcing cages for floating, slab, pile and columnar foundations are fastened using electric welding. It is forbidden to use gas welding, as the reinforcement rods become soft in the heating places.
Using the recommendations above, you can tie the reinforcement cage or mesh yourself - on the ground or in the formwork. Each type of foundation has its own design differences that affect the thickness of the protective concrete layer, and the most difficult operation during reinforcement is anchoring the corners of the base, strengthening the stretching and squeezing areas.
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 foundations in strict accordance with the design documentation.
For monolithic structures, a rather important part of the work is the reinforcement of the grillage. The strength of the entire structure largely depends on the quality of the connected reinforcement. You can make the reinforcement yourself, having previously familiarized yourself with the technology of this type of work.
What is grillage
A grillage is a monolithic element of the base of a building that connects free-standing pillars or piles into a single system. It is manufactured 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.
Grillage device diagram
The grillage can be made not only in the form of a monolithic strip foundation. It is also made of wood, metal and reinforced concrete products, located between the columnar support structures. Such a device in the form of beams is used much less often 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. When building a buried grillage, a monolithic version is selected. If a hanging one is made, then the base of the grillage can be arranged from horizontal beams.
The monolithic grillage is based on concrete and reinforcement. Reinforcement takes most 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 regulations 52-01-2003.
The grillage must 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.
Monolithic grillage device
To make a monolithic grillage foundation, you will need to complete several stages of work.
- Installation of formwork.
- Reinforcement of the grillage.
- Concreting.
- Stripping.
- Waterproofing tape.
Formwork installation
The formwork must be installed strictly at an angle of 90 degrees
The grillage foundation is made hanging or buried in the ground. The formwork design 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 angles must correspond to 90 °, unless the project provides for another design.
When making a tape in the ground, you can use the soil instead of formwork, as a support for the future foundation. Above ground level, formwork is usually assembled from boards or plywood. It is knocked together or pulled together in such a way that the concrete does not squeeze out the boards and does not spread during the laying process. The 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 base in the formwork. It needs to 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 vibration of concrete in the process of pouring it.
The side walls of the formwork must be firmly assembled. For this, transverse ties, spacers, tubes with pins and other materials can be used to ensure the reliability of the structure.
Poor-quality formwork can lead to disruption of the concrete placement process. This is unacceptable in construction, but often happens due to negligence in this part of the work.
Grillage reinforcement
Reinforcement of the structure
Reinforcement of the grillage of a pile or columnar foundation is one of the most critical stages of the foundation for a building.
Periodic metal reinforcement is used as the main material for the reinforcement of foundations. IN recent times they began to replace it with composite fiberglass. It should be noted that fiberglass reinforcement is not suitable for hanging structures. It is good where there is support on the ground.
Reinforcement is welded into beams
The reinforcement is bonded 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.
For self-construction, when there is no project, and there is no way to contact specialists, there is an option to use the online reinforcement calculator. It is advisable to find several such online programs and make calculations in each, so that, by comparing the data, determine the error in the calculations. Having calculated the reinforcement according to the entered 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 correctly make the connection of the structure, clamps and U-shaped products are made from reinforcement. They are the connecting elements in the reinforcement cage nodes.
To find out how to correctly manufacture reinforcing cages and their assemblies, you need to familiarize yourself with the guidelines for designing concrete and reinforced concrete structures from heavy concrete (without prestressing).
Reinforcement of pile-grillage foundations is impossible without connecting the reinforcement of the piles to the grillage frame. When arranging a pile field at the stage of reinforcement, vertical rods are made with allowances in height. 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, structural integrity 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, you must use special devices or a pipe bending machine.
Concreting tape
It is necessary to pour concrete into the formwork without interruption in order to get a high-quality monolith
The grillage foundation is poured with concrete at a time without interruption in the work until their complete completion. It is strictly forbidden to make gaps along the length of the foundation. The only permitted action is to break the height of the grillage. After pouring a 150-200 mm layer over the entire volume of the tape, a break is made in the work.
Before continuing construction work, you must wait until the concrete has reached the minimum permissible strength. Then it is required to clean off the top layer, the so-called concrete milk, and only then continue concreting the tape.
It is important to carry out work so that there are no pores in the concrete mass. The concrete is required to fill 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 make it ahead of time in order to incur losses that will significantly affect the construction budget.
If the formwork is prematurely removed, the foundation may crack, which will leave almost no options other than dismantling it. In this case, a new foundation will be required, respectively, construction costs will increase significantly.
Concrete gains strength depending on its grade and ambient temperature. The ideal temperature is 20 ° C, in such conditions concrete of the M200-300 grades will gain 100% strength in 28 days.
Data on concrete strength gain are presented in the table.
| Concrete grade | Curing time, days | -3 ° C | 0 ° C | + 5 ° C | + 10 ° C | + 20 ° C | + 30 ° C |
| 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 a quick set of strength. This slightly increases its cost, but also significantly speeds up the construction process.
It is allowed to make stripping when concrete gains strength of at least 50%.
Waterproofing tape
With a hanging grillage, you can use a coating waterproofing. In the recessed version, it is possible to lay the roll waterproofing into the ground before pouring the concrete and, after stripping the upper part, completely close the foundation with it. For more information on waterproofing grillage structures, see this video:
It is important to protect the substrate from moisture. If the foundation absorbs water, then in winter at subzero temperatures during the expansion of the freezing water, microcracks will form in it. This must be avoided.
Reinforcement errors and how to avoid them
Do not reinforce the corners by crossing the reinforcement
There are a number of mistakes associated with reinforcement that inexperienced builders make in order to save money or simply because of ignorance of building codes and regulations. Below are the most frequently recurring ones.
- A decrease in the diameter of a bored pile, according to some builders, should be accompanied by a decrease in the number of vertical reinforcement rods, to which the grillage frame should subsequently be attached. Reducing the allowance for vertical bars.
- Reinforcement of corner sections by crossing straight reinforcement rods. Many do this so as not to complicate the knitting of the frame.
- Failure to comply with the step of installing jumpers when reinforcing the grillage. Skipping required connections. This often happens in order to save money.
- Deviation of the reinforcement cage from the central axis. This will lead to uneven bearing capacity of the base, which often happens due to trivial negligence. All the intricacies of reinforcing the pile foundation, see this video:
The 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 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, it is necessary to make bent U- and L-shaped parts with which you want to connect the corner elements.
- When installing the reinforcing cage, a pitch 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 aligned with respect 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 critical.
During construction work, any mistake leads to a decrease in the life of the building without the need for repair. This is at its best. At worst, even at the stage of construction of the building, it undergoes reconstruction.
To achieve the maximum service life, it is required to comply with building codes and regulations, avoiding deviations from the project. Construction combines a set of measures that must be followed to achieve the desired result. If possible, it is better to entrust such work to professionals.
The reliability and strength of a columnar foundation with a grillage largely depends on its correct reinforcement. The features of the reinforcement of a columnar foundation, the sequence of work during reinforcement, requirements for reinforcement, the location of reinforcement in the corners of the building and at the intersection with load-bearing walls are considered. Also shown are the regulatory documents according to which the construction is being carried out and the errors that should not be made during the work are listed.
Features of the reinforcement of the columnar foundation
An increase in the strength and reliability of the foundation is achieved by reinforcing it. Concrete can withstand high compressive loads. Bending or tensile forces, even small ones, tear it apart.
The following loads act on the foundation pillar:
- compression - the weight of the building;
- to break - in winter, the heaving of soil compresses the walls of the pillar and tears it up from the sole;
- on a break / shift, in winter - horizontal ground movements during freezing or in summer - a shift of a dense layer over a water-saturated or weak ground.
For compressive loads, they are not reinforced, and the effect of heaving of the soil is completely eliminated by wrapping the post with three layers of polyethylene or roofing material. Shear loading is rarely possible, but it is protected from it by reinforcement.
The second zone of reinforcement in columnar foundations is the grillage. Reinforcement of the pile foundation grillage is carried out only along its lower and upper surfaces, taking into account the thickness of the protective concrete layer.
Requirements for reinforcement of foundation pillars and grillage
For horizontal longitudinal reinforcement of the grillage, rods with a regular profile and a diameter of 10 - 16 mm are taken. Vertical and horizontal transverse sections of the frame are made of smooth reinforcement with a diameter of 6 - 8 mm.
For posts, vertical reinforcement is profiled, horizontal reinforcement is smooth. The diameters are the same.
Usually, rods of grades A I and A III (A 400 C) are used.
You can use a new type of reinforcement - composite. The practice is not great yet, but its characteristics are good.
The sequence of reinforcement of pillars and grillage
The pillars are reinforced with vertical rods. They are boiled or knitted with wire into frames.
Sand is poured at the bottom of the pit, 200-250 mm thick, and on top of the same layer of sand with crushed stone. Lay at least 50 - 100 mm of concrete to protect the metal from soil moisture and corrosion.
The finished frames are lowered into the wells of bored piles or pits under the pillars.
The dimensions of the frame in the section should be 35 - 50 mm less than the borehole diameter on each side. This layer of concrete is called protective. With an alkaline reaction, it protects the metal from corrosion.
The outlets of the reinforcement of the posts in the manufacture of the frame are bent horizontally to a length of 30 - 40 rod diameters. If a certified welder knows how to correctly, and without overheating to cook fittings, bends are not done.
The rods are laid in the grillage in two layers:
- the upper layer is below the upper cut by the thickness of the protective layer;
- in the lower layer, the same thickness above the sole.
The middle is not reinforced, there are almost no loads here.
The layout of the reinforcement rods is determined by the requirements for the parts of the foundation:
- for bored piles or reinforced concrete pile posts - the shear strength requirements are determined by the load from the horizontal displacement of soil massifs;
- for a horizontal, usually monolithic grillage, the load will be bending, since the grillage beam is located with its ends on the supports, and there is almost no support under its middle part.
How are the reinforcement in the corners of the grillage positioned?
Reinforcement of the corners of the pile foundation grillage and the intersection with the load-bearing internal walls should be carried out with bending of the rods to a length of at least 0.4 - 0.8 m. The bent parts of the horizontal rods of one side of the grillage should go to the other side perpendicular to it and vice versa.
It is not always possible to cook - some steel grades are not cooked with ordinary electrodes, overheating of the rods, metal leakage and weakening of joints, seams, etc. are possible.
Regulatory documents for columnar foundations
The number of bars, grades of reinforcement, the value of the diameters are obtained as a result of the calculation of the columnar foundation by a professional civil engineer. As well as the drawings for its reinforcement.
To do this, use the following regulatory documents:
- SP 20.13330.2011 (SNiP 2.01.07-85 *) "Loads and Impacts" - terminology and loads on a columnar foundation;
- SP 50-101-2004 (updating SNiPs 2.02.01-83 and 3.02.01-87) - Code of Rules for the foundations of buildings and structures, clauses 12.1 - 12.8 - general requirements to the calculation, calculation of columnar foundations - p. 12.3;
- SP 22.13330.2011 (updated SNiP 2.02.01-83) "Foundations of buildings and structures" - loads, depth of placement, groundwater accounting, features of design stages;
- SP 63.13330.2012 (SNiP 52-01-2003 update) "Concrete and reinforced concrete structures", design requirements in clauses 5, 7, 10.
The calculation according to the documents allows you to more accurately determine the price for reinforcing a columnar foundation.
Reinforcement errors
The most common errors:
- The reinforcement cage is installed on the ground. The metal corrodes, expands in volume and tears concrete in the most important place - the soles of the posts.
- When installed in a well, the frame is not centered. The reinforcement can protrude outside the post or a thin protective layer can remain.
- Reinforcement for connections with the grillage frame is not produced. A monolithic grillage will not be able to withstand horizontal ground movements, and the foundation may collapse.
- When welding rods, the joints should not be at the corners and at the intersections of the walls.
- When bending the rods, the bend is not heated - the rod gives microcracks.
- Reinforcement in the middle part of any reinforced concrete product is a gross mistake - a concrete beam or slab is stretched either from above when loaded on the edges and support in the middle, or from below - when the supports are at the edges, and the load is in the middle. These tensile forces and the reinforcement must withstand. In the middle part of the product, there are almost no loads, and the fittings are there - wasted money, time and labor.
- When pouring concrete, use the deep vibrator only in the inner area of \u200b\u200bthe frame and be careful not to disturb its configuration.
Questions and answers on the topic
No questions have been asked about the material yet, you have the opportunity to do it firstIn contrast to the strip foundation, it is easier to calculate the reinforcement of the grillage. Without exception, all arising stresses are absolutely predictable, since the heaving forces are completely absent. The upper belt is strengthened above the piles, and more powerful reinforcement is laid between them in the lower belt.
The advantage of the pile foundation is the support on layers with a guaranteed high bearing capacity. For example, if for a strip foundation on bulk, undermined, swampy soils, a huge budget is required to go through them, piles will cost 10 to 15 times cheaper. However, it is difficult to support small-format wall materials on them, therefore, the heads are connected with monolithic beams, on which masonry or crowns of a log house are erected without problems.
Common to the strip foundation and the grillage is only a drawing, the operational characteristics are different:
- the vertical bending moment in tapes resting on the ground with the entire sole is an extremely rare phenomenon, with a grillage it is the norm;
- the soils, when swelling, try to break, push the MZLF tape to the surface, the beams on the piles are separated from the ground by 15 - 20 cm with an air layer or expanded polystyrene, which takes the indicated loads on itself;
- therefore, the tape is reinforced in both belts in the same way, in the grillage the lower layer of reinforcement is strengthened, the upper layer above them (only in tension zones, which concrete cannot cope with without cracking).
The reinforcing frame in any reinforced concrete product is just designed to compensate for stretching. Composite reinforcement, popular among individual developers, has poor adhesion to concrete, is highly stretched, which leads to the opening of cracks.
Therefore, experts recommend creating a reinforcement 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).
Reinforcement cage technology for tape grillage
Despite the name of the strip grillage of the pile foundation, monolithic beams have a lattice structure. Therefore, the frame has several nodes of mating walls (external / internal), corners in which overlapping is not allowed. The rods in these places are bent, run on the adjacent side, and overlap with the frame.
Longitudinal reinforcement is similar to strip foundations; rectangular clamps are also used to give the frameworks a 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 special programs it is difficult for an individual developer to correctly calculate the cross-section and the number of longitudinal bars. The simplest option is to use the ARBAT tool of the Scad Office computing complex with the simplest interface:
- unlike piles, grillage is calculated by bending moments, punching, cutting forces;
- the reinforcing cage is made of longitudinal bars of 8 - 16 mm;
- unlike the strip foundation, in addition to the clamps, vertical rods are added near each longitudinal bar.
The laying technology is standard, longitudinal rods are tied with clamps or welded to them. Then the reinforcing cage is placed in the formwork on the lower gaskets made of concrete, plastic (providing a protective layer), reinforcement elements (vertical rods) are added to it in place.
In cottage projects with concrete or brick walls, a two-row pile arrangement can be used. Therefore, for the strip part of the pile foundation, a calculation in the transverse direction can be added, since the torques occur there too, sometimes exceeding the value of the longitudinal ones. In some cases, the reinforcement cage is reinforced with rods of 14 - 16 mm with a step of 20 cm.
Transverse reinforcement
Without clamps, it is impossible to give the frames the required spatial geometry. At the same time, these elements strengthen the armored belt. All joints are scalded or tied with wire twists. Additional vertical rods are mounted with a calculated pitch (usually 20 - 40 cm). The above photo contains almost all possible errors:
- the 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 curved rods;
- there are no concrete, plastic gaskets;
- the armored belt is displaced relative to the center of the pile;
- instead of the middle belt, which does not perceive any loads, the upper / lower levels should be strengthened with a thicker reinforcement of the pile foundation or by adding additional rods (this option is preferable);
- incorrect connection of the reinforcement 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 connections with schemes
In the majority of Soviet literature (for example, V.S.Sazhin's manual), incorrect layouts of reinforcement at the interface are given. According to the correct reinforcement of such L-shaped, T-shaped joints, you need to as follows:
- launching a U-shaped element onto an adjoining wall, counter bending of the bar from the side tape at a right angle;
- two U-shaped elements on top of the crosshairs of the longitudinal bars from the corner of the structure outward;
Drawing of the correct reinforcement of the corners and abutments of the grillage.
The pile foundation is a universal foundation for the construction of brick (read separately), wooden, aerated concrete (read 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 talk about in this article.
You will find out why a pile-grillage foundation is needed, what materials are used for this and how the process itself is performed. Diagrams and drawings will be given explaining all the nuances of the reinforcement of a monolithic grillage.
1 What functions does the grillage perform and why do you need its reinforcement?
The grillage is a tape structure (we read about how the usual one is reinforced - read separately), connecting the free-standing piles to each other. Due to the strapping of the supports, additional spatial rigidity and resistance to tipping 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?
The reinforcement of the tape grillage is carried out by means of a spatial reinforcement cage, consisting of two longitudinal reinforcement belts (upper and lower), connected by horizontal and vertical bridges.
Longitudinal belts are made of rods of A3 class reinforcement (hot-rolled corrugated profile), the diameter of which is 13-16 mm. You can use it, which is confirmed by reviews on the successful operation of such pile-grillage foundations on specialized forums.
Connecting vertical and horizontal bridges can be made in two versions - in the form of separate bars welded to the longitudinal belts of the reinforcement (the diagram shows the configuration). In this case, it is necessary to use rods of the same standard size as when arranging a longitudinal belt.
Also, the frame can be connected with jumpers from the reinforcement curved into the clamps (the diagram below). This approach uses smooth rods of class A2 (diameter 8-10 mm). Bent clamps are laborious to install, but due to the smaller number of welded seams they are more reliable and durable. Fiberglass reinforcement, which cannot be bent, 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, the following step must be observed 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 crosspieces of the longitudinal belt is 20-30 cm;
- step between vertical connecting jumpers - up to 40 cm;
- protective concrete layer - at least 5 cm.
The protective layer is the distance between the outer 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 bottom 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.The reinforcement frame for such a strapping will consist of two longitudinal belts of 3 A3 rods with a diameter of 14 mm in each (the pitch between the rods is 10 cm, 5 cm on each side eats away the protective layer of concrete). The belts are connected by jumpers made of reinforcement A1 with a diameter of 11 mm, located with a step of 20 cm.
The calculation is performed according to the following algorithm:
- 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 \u003d 30 m; b) we calculate the length of 3 rods: 3 * 30 \u003d 90 m; c) we calculate the length of reinforcement A3 for both belts: 90 * 2 \u003d 180 m.
- To connect the rods of the longitudinal belt, we need jumpers 30 cm long, which will be located with a step of 20 cm.Calculate their number for both grillage contours: 2 * (30 / 0.2) \u003d 300 pieces, after which we calculate the total length of the transverse jumpers: 300 * 0.3 \u003d 100 m.
- It remains to calculate the length of the vertical bridges connecting the upper and lower contours of the frame to each other. But since in the example a rectangular grillage is calculated, their number and length will be identical to the transverse lintels. If a grillage of a rectangular configuration is used, the calculation is performed according to the formula specified in paragraph 2.
As a result, the calculation showed us that the grillage reinforcement requires 180 m of A3 class reinforcement and 200 m (100 + 100) of A2 rods with a diameter of 11 mm. Calculation may also be required if you do not plan to use butt weld. 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) \u003d 600 pcs; and calculate the material consumption - 600 * 0.4 \u003d 240 m.
1.3 Features of grillage reinforcement (video)
2 Technology of reinforcement of monolithic grillage
Reinforcement of the grillage begins after the completion of all the previous stages of the arrangement of the pile foundation - the installation of piles, their trimming and the arrangement of the formwork. You must have a ready-made formwork, inside of which the reinforced frames of the piles protrude to a height equal to the cross-section of the strapping.
When assembling the frame, the reinforcement can be knitted with each other using a wire, or the rods can be connected by welding. There is no significant difference in the method of joining - it is often argued that the welded frame, due to the lack of elasticity, is less resistant to deformations than a connected viscous structure, however, in industrial multi-storey construction, the frames of pile-grillage foundations are always welded, so these fears are groundless. In addition, welding is a more practical and quicker method to implement.
Reinforcement of the grillage - step by step instructions:
The assembly of the reinforcement cage in straight sections of the grillage is quite simple to perform. Difficulties arise when reinforcing the corners, which must be additionally reinforced, since this part of the frame experiences maximum loads.
The corners and places of abutment of the inner walls of the strapping to the outer cannot be reinforced with overlapping reinforcement... In these areas, it is necessary to lay solid rods bent in a L or U-shaped configuration. A diagram of the correct reinforcement of the corners of the pile grillage is shown in the image.
A pile-type foundation is used as a reliable foundation for the construction of buildings. The base on the supporting elements is necessary for the construction of facilities on problem soils. The pile foundation is the optimal solution in many situations, including if the structure is being erected on permafrost or weak soil with closely located aquifers, as well as in the presence of significant height differences at the construction site. Reinforcement of the grillage of the pile foundation allows to ensure the strength of the base, to form a reliable base for the building being erected.
The grillage is a critical, horizontally located part of the load-bearing frame, connecting the supporting columns into a single contour. It ensures the verticality of the posts, 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 estimated forces acting on the base during the operation of the structure are required.
Pile foundation - a universal foundation for the construction of brick, wood, aerated concrete and foam concrete low-rise buildings
Let's 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 base being built.
What is a grillage?
For those who do not know the 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 different types of grillages used in pile foundations:
- tape type, representing a monolithic concrete tape. It is located along the perimeter of the supports sequentially located under the load-bearing capital walls;
- slab structure, in the form of a monolithic slab, the dimensions of which correspond to the contour of the base of the structure and cover all the supports.
The grillage is a strip structure that connects freestanding piles to each other
Depending on the features of the grillage foundation, it can be manufactured in the following versions:
- One-piece version. Manufacturing is carried out by pouring concrete mortar into a previously prepared formwork. The formation of a monolithic base occurs after the concrete mixture has hardened.
- Composite. The base is a prefabricated surface of industrially produced reinforced concrete products, connected during installation with support columns, as well as with each other.
Regardless of the design features, the grillage forms a supporting surface intended for the construction of the walls of the building. The strapping of the columns located in the ground ensures high rigidity of the spatial system and resistance to the effect of acting 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 the piles, grillages are made at different heights in relation 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. Constructed for light buildings located on all types of soil. On problem soils, its device is especially important. The structure needs serious reinforcement 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 installing a monolithic pile grillage, which is used when arranging houses made of heavy materials, that it is necessary to reinforce the strapping
- ground version, made on gravel-sand bedding without burying into the soil. Its peculiarity is the lack of free space between the concrete monolith and the ground. Installation is carried out on non-problematic grounds. If the soil is susceptible to frost heaving, cracks may form and the hardened concrete mass may separate from the support columns;
- shallow-buried type, formed by burying the lower part into the soil on a previously prepared sand and gravel bed. The design of such a base resembles the device of a strip foundation, the base of which rests on piles. The formation of a buried foundation is associated with significant costs and is used for the construction of massive buildings located on soils characterized by a low bearing capacity.
Pile-type foundations are mainly formed for light structures. That is why the 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.
About the expediency of reinforcement
The need to strengthen the base of the building with steel reinforcement is associated with the characteristics of the concrete. The material has increased resistance to compressive forces, but is susceptible to bending moments and stretching, which cause 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 allows you to prevent the likelihood of destruction, increase the stability, service life of the building being built. The reinforcement cage located inside the concrete mass absorbs tensile loads and bending forces, ensuring the stability of the base being erected.
Regardless of the design of the piles used, located inside the soil, the support columns are also reinforced with reinforcement. The steel bars located in the piles are connected to a common structure with the reinforcement cage of the supporting surface.
Reinforcement of the pile foundation grillage allows:
- Prevent the destruction of the monolithic mass as a result of soil reaction.
- Significantly increase the strength of the base, taking the load from the mass of the structure.
- To prevent shrinkage of the structure caused by the low strength characteristics of the base.
Strengthening the grillage foundation avoids negative phenomena.
Reinforcement specifics
Reinforcement of the grillage of the pile foundation is carried out with a pre-fabricated volumetric 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 reinforcement belts