Recently, to fix any elements into the wall, special wooden plugs were used - dowels, which were driven into previously drilled channels to ensure that the fasteners were held in a solid base.
However, such dowels had many disadvantages, including drying out or swelling. All this led to violations of direct function. The next “evolutionary” stage was plastic dowels, which are compact, inexpensive and have good fixing properties.
But they also have disadvantages - delayed deformation with a significant weakening of the expansion restraint. This was especially evident in monolithic concrete structures, when the plastic burst and the dowels freely came out of the channel.
Taking into account the above disadvantages, an anchor was invented - the most reliable method of fixation today. It clings to solid material like an anchor, preventing various factors from disturbing the fastening.
Let's take a closer look at this latest development in the field of fastening and retaining elements.
Commonly used types of anchors
Products are divided according to type of application into:
- synthetic (chemical)– has a capsule with glue in its design, which collapses when the bolt is screwed in. The glue flows out and bonds the channel walls with the bolt after the composition dries. The disadvantage is the need to wait for the glue to dry, after which you can only “load” the product. The advantages are undeniable - strong fixation and reliable retention in both monolithic and lightweight wall bases;
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- metal- simpler in structure, consists of a metal sleeve and a screwed-in bolt. An untwisted anchor is inserted into the drilled channel, and when the bolt is screwed onto the thread, the sleeve expands (expands) with its walls tightly pressed into the surface of the channel. The main advantages are fastening strength, the ability to create shallow fastenings and the feasibility of reuse. The disadvantage is the high price.
In addition, there is a classification by functional type:
- clamping– operates on the principle of opening the fastening petals and the middle deformation of the sleeve when tightening the bolt. In addition to the main application (thick walls), it is used for thin structures, for example, plasterboard;
- shnipovoy– the design provides an end screw (or wedge) that pushes the walls of the sleeve apart when the core is screwed in. There is a modification with a groove rod that wedges the sleeve. It is then removed from the threaded passage, and a core bolt is screwed into its place. This anchor option requires exact matching of the dimensional parameters of the holes and fasteners;
- spacer (crushed)- the most common variation. When the cone-shaped bushing is twisted, the rear sleeve part expands. The element does not require strict adherence to the dimensions of the channel and sleeve. Used for fixing to concrete and brick walls;
- driven in- the simplest option, used without additional complications. The sleeve is soft and when the core bolt is tightened, it begins to deform with a tight stop against the channel walls, which creates a strong fixation. The anchor is used for natural stone and monolithic walls.
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Method of screwing in an anchor
To perform high-quality anchoring, it is necessary to use metal (steel) elements with an anti-corrosion protective coating, for example, M-30.
In addition, you need to realize that all connections are characterized by certain hole parameters and norms of applied force for tightening.
They depend on the properties of the wall or coating. Thus, for durable concrete, the minimum depth of the establishment is 8.0 cm with a load of less than 7.1 kN, and for thin material these values are half as much.
Let us analyze step by step the correct technology for fixing expansion (crushed) anchors into a concrete wall.
Stage 1. Calculation of the required bolt length
Very often, walls have a layer of finishing material, such as plaster. For good fastening, it is necessary to place the bolt into the base to a depth of more than 5.0 cm. Therefore, the length of the anchor sleeve must have a length of 5 + the thickness of the plaster.
Stage 2. Determining the required diameter (diameter) of the hole and channel depth
It is necessary to carefully monitor the diameter of the channel for the anchor bolt, since the parameter of the applied force for tightening depends on this value. The sleeve must fit tightly and absolutely perpendicularly into the channel. The depth of the drilled hole should exceed the length of the anchor by 2.2–3.8 mm.
Stage 3. Marking and drilling holes
The creation of the hole for the anchor must be optimally precise, since the bolt cannot be moved once installed. Marking must be done very carefully. Then, a hole is made with the necessary drill and the channel is cleared of fragments and dust particles.
Typical anchor bolt is a rod from 45 to 200 mm made of alloy steel (09G2S-6), characterized by strength category 6-8. The bolt has a hex head and a threaded fastening end. The fundamental features of the anchor bolt are provided by a sleeve with longitudinal slots and a conical nut, the movement of which along the rod is carried out by the principle of anchoring. The technical characteristics of anchor bolts are discussed in detail in this.
Anchor attachment method is determined by the nature of the payloads, which ensure its strong connection with a material-specific base. This includes frictional force, counteraction at the stop, and adhesion when using chemicals or transforming the surface under thermal conditions.
The cheapest and most common type of anchor fastening is a connection to the base based on the frictional force experienced by the bolt in the hole of the fastening body. For thin-walled materials, an external stop is more effective, in which the outer element of the fastening end allows the base to be tightened between it and the bolt head. The most promising and versatile in its capabilities is considered to be a chemical anchor that includes synthetic resins or adhesives in the fastening system. In fact, the way the anchor is attached determines its type.
The advantage of anchor fasteners is the ability to effectively combine various connection methods, based on the specific construction task and the characteristics of the material of the structures being connected.
Classification of anchors
The basis for the classification of anchors is determined by:
- technique for inserting the anchor into the base: driving, petal, screw, drilling;
- according to the characteristics of sealing the fastening site: with drilling, with expansion, tubular;
- according to the structural characteristics of the main element: cylindrical, rod, made of wire strands;
- by service life: temporary and permanent.
Mechanical anchors
For the ease of installation of mechanical anchor bolts It is worth calculating internal pressure, stress and loads. An error can result in the bolt being sheared or pulled out, even with part of the base still attached. In addition, it is necessary to anticipate possible bending of the protruding part and chemical reactions to environmental influences.
- Mortgage anchor installed in the frame of a structure before pouring concrete or in a stone wall during its construction. This type of fastener is designed for high loads; installation is associated with certain difficulties and material investments.
- makes the connection due to the frictional force of the conical element (sleeve, nylon bushing, spring ring) expanded by the translational movement of the bolt. Used for fastening a massive structure to a base made of concrete, brick or stone. A double-expansion anchor usually has two sleeves and provides a more reliable connection. Even more information about these anchors.
- involves expansion of the notched metal sleeve when driving the fastening rod into it. Performed manually or using a pneumatic tool. Due to the friction connection, it is very effective when working with dense substrates. Read about drive-in anchors in this
- , original in its design, is installed in a drilled hole by driving and screwing in a bolt with a metal coupling until the maximum level of resistance due to friction is obtained. Has the ability to withstand heavy loads. The features of wedge anchors are discussed in a separate section.
- - a mechanical type of anchor, designed not only to overcome internal loads, but also external ones, considering that it is used for suspended structures, fastening cables, chains and hinge systems. Installed using the hammer or wedge anchor method. Read more about such anchors.
- - a lightweight version of the anchor bolt for fastening plastic and wooden structures of window frames, as well as slotted bricks, concrete, and stone. A special feature is the shape of the head, which allows it to be leveled with the surface of the base. The connection is wedged using a brass or steel collet. We looked at frame anchors in more detail in this article.
- - a fastening element having two fastening ends. The connection is tightened using a nut. Used for mounting load-bearing consoles, heavy structures, cables, antennas, masts, fences to solid bases and partitions. More details about the anchor stud and nut are described.
- Designed to fasten elements of curtain facades. Has a polyamide coupling and a galvanized screw. The screw head, due to the washer, presses the facade cladding. Read more about facade anchors in the article.
- , operates on the wedge principle, has an eyelet. Compact, reliable, used for mounting suspended structures, chandeliers and lamps. Read more about them.
- Spring anchor- lightweight fasteners for thin-walled structures. Fastening is carried out by unwinding a spring passing through the hole. Available with a hook or ring for use in interior design.
Plastic anchors
Plastic anchors- a type of anchors used in land management. Fastening elements are manufactured as solid cast products from polymer-based compositions that are impact-resistant and frost-resistant. They are a rod from 60 to 120 cm long. The kit consists of punches, plastic anchors and ATP clips (for anchoring cells), and a polyamide cord.
The anchor has a T-shape and is driven into the ground with a punch. When installed with an ATP clip, it allows you to stretch a polymer cable to secure the geogrid. Being a load-bearing element, the plastic anchor is installed before the soil is released.
It is not afraid of groundwater, corrosion, or exposure to chemicals. It is used in the construction of pipelines, road embankments, and strengthening the banks of reservoirs.
This giants among anchor connections: the length of the rods reaches 15 -22 meters, which is due to their practical purpose. Ground anchors are used to strengthen the slopes of construction pits and ensure the safety of construction work carried out next to them, as well as for constructing retaining walls and strengthening landslides.
During the work, high-strength screw reinforcement of the anchor is placed in a hole drilled at an angle of 40 degrees, securing its lower end with concrete. The anchor is tensioned to the required strength using a jack and secured with flare nuts over the anchor plates.
Features of ground anchors are discussed in the article.
To increase the adhesion of structures to the foundation, use foundation bolts: removable, blind and embedded. They are made straight, curved, composite or even in connection with an anchor plate, which allows installation directly into liquid concrete. The biggest difficulties with installing blind bolts: their position is precisely verified using steel conductors (posts and connections), since after pouring concrete nothing can be corrected. More information about foundation anchors.
Classification of anchors according to the material of the structures being connected
- For sheet materials: chipboard panels, plasterboard, etc.
- For dense materials: natural stone, concrete, brick.
- For hollow materials: foam concrete, aerated concrete, slotted brick.
Depending on the mass of the structures being connected and the material, the anchor connection method or an integrated approach to its use is selected.
The article describes anchors for drywall, concrete, aerated concrete and brick.
There is no construction project or type of material for which anchor connections cannot be used. Foundation, ceiling, floor, walls, internal partitions, structural elements, plumbing fixtures, communication wiring - places available for a quick and cheap method of fastening using a dowel anchor. Installation of the anchor is available to both a professional and a home craftsman. Everything necessary for this type of work is available in abundance on the construction market. Read more about installing anchor bolts.
The calculation is carried out based on the ratio bolt dimensions, its strength category and destructive forces (dynamic loads) provoked by the mass of the connected structures (static loads):
- tearing force;
- bending moment;
- torque;
- combined loads.
What does the price of anchor bolts consist of?
The range of prices on the building materials market always allows the product to find its buyer. When comparing price lists, it is clear that prices for anchor bolts consist of differences:
- in the size of the product;
- by appointment;
- by material;
- in the size of the purchase lot
- innovative modifications;
- popularity of manufacturers.
More details about calculating the loads of anchor bolts and their prices are described.
If we talk about the reliability of fasteners for brick and concrete, then an anchor is preferable to a dowel. The main “holding force” for it is not friction, but the resistance of the material to destruction. And these forces are activated thanks to a kind of anchor, which is formed due to the section of the sleeve weakened by the slots.
Anchor bolt with nut
Despite the name, in essence this type of fastener is a threaded rod with a wedge in a metal sleeve. In the central part of the sleeve there are sealing beads and four “windows” with slots up to the wedge. And a nut is used as a “propeller” that brings the anchor into working condition.
The dimensions of the wedge are selected in such a way that the diameter of the base of the cone is equal to the outer diameter of the sleeve, and the “narrow part” coincides with the diameter of the pin.
Installation is simple:
- drill a hole (with a diameter slightly larger than that of the sleeve) and clean it;
- drive the anchor bolt until the washer stops at the base;
- turn the nut clockwise;
- the pin moves outward, and the sleeve remains motionless due to the sagging;
- the wedge is pulled inside the sleeve and pushes the cut petals apart.
An anchor with a countersunk head works the same way. The role of the nut and washer is performed by a hollow cylinder with an internal thread, which looks like a corresponding screw for a Phillips screwdriver.
Wedge anchor
To some extent, this type of anchor resembles the previous one, but has a short coupling put on a pin just before the wedge.
Operating principle: the sleeve “sits” tightly in the hole, and when the nut is turned, a pin moves, which retracts the wedge and pushes the blades of the sleeve apart.
Ceiling anchor with ring (eye)
This is a type of wedge anchor. The difference is that the coupling petals move apart not under the influence of rotation of the pin with a wedge, but under the force of pulling the anchor out of the ceiling.
anchor bolt
The metal coupling of this type has the same structure as an anchor bolt with a nut - a hollow cylinder with four windows and slots up to the wedge. But a cone nut is used as a wedge. The wedge slides into the coupling when a conventional hex bolt is turned.
In addition to the hex head for the wrench, the bolt may have a fastening “shank” in the form of a ring or hook.
Double spacer anchor
This is a reinforced version of the anchor bolt.
- two couplings are put on a metal rod (pin) with a slot for a slot;
- the short coupling fits into the long coupling with a cone;
- when screwing the nut, the short coupling is pushed apart by the cone nut;
- the long coupling slides onto the short one, which serves as an expanding wedge for it.
In addition to this option, these anchors can end with a fastening hook or ring.
Expandable anchor
The sleeve of this anchor is made in the form of a hollow cylinder with four wide slots at the end and a locking flat spring that holds the petals in their initial position. Inside the sleeve there is a tetrahedral element, each face of which fits into its own slot. And so that the element does not fall out of the anchor before installation, each petal ends with a small side.
The type and length of the bolt are selected for the sleeve. This could be a regular hex bolt.
A stud with a hook or ring shank and a nut.
When the bolt is screwed in, the tetrahedral element pushes the sleeve segments apart.
Frame anchor
The main purpose is through fastening to the base of window frames and door blocks.
The sleeve has slots on the side of the conical nut and on the side of the screw head. When the screw is screwed in, the anchor is “anchored” on both sides. And special ribs prevent the sleeve from turning along with the screw.
A special type for fastening parts in weak foundations (in building blocks with high voids).
The sleeve has slots weakened at the top and in the middle, and ends with a nut at the end.
When a screw is screwed into a nut, the sleeve is deformed, the lamellas expand as far as the hollowness of the base allows and form a holding “belt”.
An anchor is essentially a fastener that resembles an anchor in shape, for example a steel tie installed in stone walls; there are anchor bolts, anchor ties in connections with guaranteed tension, etc.
The fastening element mates with the base mass not directly, but through an anchor or dowel, which creates the necessary adhesion moment. Strictly speaking, it is difficult to make a clear distinction between an anchor and a dowel. In our opinion, an anchor is an element that in a certain (mechanical or chemical) way increases the adhesion between the main fastener and the base to the required level. In fact, a dowel is a lighter type of anchor.
There are driven, wedge, rod, embedded (anchor bolts) and chemical anchors.
Wedge anchor
Used for fastening heavy structures, cable routes, load-bearing consoles, railings, etc. through the method of through installation to solid concrete, natural building stone, solid brick.
This is a steel rod with a cylindrical movable collar in the form of a belt, a cone-shaped shank and a nut. Does not require precise drilling depth and hole cleaning.
When the nut is tightened, the coupling creeps onto the shank, and expansion occurs, which reliably holds the structure in the supporting base.
Rod anchor
Essentially a wedge anchor, but designed for deep installation through several successive layers of cladding and insulation. An additional advantage of such a product is the ability to install it at an angle.
Drive-in anchor
Used for critical installation (under heavy loads), for fastening heavy structures, cable routes, consoles, gates, etc. to solid concrete, natural building stone, solid brick.
The hammer anchor is a hollow cylinder. On one side there is an internal thread, on the other side there is a spacer zone of four segments. To ensure controlled wedging, a core (cone) is located inside the hollow cylinder.
When the anchor is driven in, the segments in the drilled hole expand. This prevents twisting and securely fixes the anchor. When the bolt is screwed in, additional expansion and fixation occurs.
Embedded anchor or anchor bolt.
Used for fastening heavy structures, cable routes, load-bearing consoles, railings, etc. through the method of through installation to solid concrete, natural building stone, solid brick. Can be used for fastening to thin concrete partitions.
An anchor bolt at the end can have a nut, a ring, a hook or a head, and depending on the use case, one or another type of this anchor is used.
When screwing the bolt, the cone-shaped nut is pulled into the coupling and expansion occurs. Moreover, the fastening runs along the entire coupling due to its additional deformation at the base of the anchor.
Such a fastener should be loaded after the concrete has completely hardened.
The recommended working load on anchors should not exceed 25% of the maximum (pull-out load). Load indicators are given for concrete with a strength of 200-250 kgf/cm2. The recommended load increases in proportion to the increase in concrete strength. When installing anchors in concrete with cracks, the pullout loads must be multiplied by a factor of 0.6.
Chemical anchor
Above we looked at anchors that operate on a mechanical principle. A chemical anchor is a glass ampoule containing an adhesive (polyester resin) combined with a chemical pin.
Used for mounting suspended ceilings, as well as for fastening various materials under water. Withstands exposure to aggressive environments well. Another advantage is the small size of the hole relative to the stud. If necessary, two ampoules can be used in series, which increases the depth and reliability of the attachment.
After preparing the hole, an ampoule is installed into it, which should then be drilled with a pin. Some time must pass for the adhesive to harden, during which time the anchor should not be loaded. The duration of hardening depends on the ambient temperature and can range from 10 minutes at a temperature of more than 20 degrees to 5 hours at a temperature of minus 5 degrees.
For use on vertical surfaces only, not suitable for use on ceilings.
To hit or not to hit? I mean, is it worth driving a nail into a concrete wall? And are there any more effective fastening methods? The answers to these questions are provided by this article, which talks about modern fasteners - anchors. There are a great variety of anchors, for example: drive-in anchor LAH, screw anchor RA, wedge anchor KA, rod anchor TA, embedded anchor SORMAT, anchors MTA, PFG, KVTM, OLA, DRIVA, brass anchor MSA, rod lock RU, etc., etc. ., etc.
When carrying out construction, finishing or repair work, it is impossible to do without fasteners. These can be nails or screws, that is, products that themselves, without additional devices, are capable of fastening the material and bearing the corresponding load. Whether applied to wood, sheets of plasterboard or thin metal elements, the adhesion created between such simple fasteners and the material is sufficient to securely hold and support structural loads.
At the same time, if the base consists of concrete, stone or brick and has greater hardness compared to lightweight building materials, then the use of such fasteners cannot solve the problems that arise. It is enough to try driving a nail into concrete to see the truth of this statement.
Anchor means “anchor” in German, and this name explains the principle of its operation. The fastening element mates with the base mass not directly, but through an anchor or dowel, which creates the necessary adhesion moment. Strictly speaking, it is difficult to make a clear distinction between an anchor and a dowel. In our opinion, an anchor or dowel is an element that in a certain (mechanical or chemical) way increases the adhesion between the main fastener and the base to the required level. In fact, a dowel is a lighter type of anchor.
The area of application of anchors in construction is fastening critical heavy structures. In apartments, anchors are used mainly for installing window and door frames, when making a suspended ceiling, and also for installing chandeliers.
Drive-in anchors
Drive-in anchors LA, LAH. This is the simplest type of anchor with internal thread. Suitable for installation in concrete, stone or brick structures. Mounted in a pre-drilled hole of the required depth and diameter. The hole for this type of anchor (as, indeed, for all others) must first be cleaned. After installation in the hole, the anchor is unclenched using a special device, thereby achieving a reliable degree of fixation. After this, a fastener corresponding to the thread is screwed into the anchor. The same type includes the multifunctional anchor MTA, used for bases with internal cavities.
Wedge anchors
Wedge anchors KA. Available in electro-galvanized KA, hot-dip galvanized KAK and acid-resistant KAH. They are equipped with a special wedge, which expands during installation and is fixed in the socket. Allows through installation through the material installed on the base. Placed in the prepared hole, hammered in and tightened with a wrench. Products of the same type include screw anchors RA - electro-galvanized, or RAR - stainless. Such anchors are equipped with a screw with a recessed head, which allows them to be used when installing window and door frames. As the screw is tightened, the anchor wedge is firmly fixed in the hole.
Rod clamps
The RU rod anchor, operating on the principle of a wedge anchor, is designed for deep installation through several successive layers of cladding and insulation. An additional advantage of such a product is the ability to install it at an angle. The socket fixing mechanism using an expanding wedge is also used in the TA rod anchor. A similar part with an internal thread in combination with a rod, which, if necessary, is cut to the required length, can be used to install several layers of material. After the anchor is driven into the hole, the material to be fastened is secured to the rod using a nut and washer.
PFG anchors
PFG anchors have internal threads and during the process of screwing the insert elements into them, they expand and are securely fixed in the socket. The PFG anchor can be used in combination with VR cone bolt, IR insert bolt, AK hook bolt, SR loop bolt or IH, IHH insert sleeves. Used for hard substrates.
MSA Brass Anchor
MSA Brass Anchor. The structural basis for this anchor is concrete or brick. The brass sleeve of the MSA anchor has a conical (threaded) internal cavity that tapers to a point. Due to this, as the screw is tightened, the sleeve expands in width and is tightly pressed with its rough walls to the inner surface of the hole in the base.