Houses made of natural wood are now popular again.But wood is far from a homogeneous material, therefore, in the process of shrinkage, a slight deformation occurs, different parts of the house take on the final appearance unevenly.
Hence the problem of fixing the timber to each other, which will ensure reliability, on the one hand, and uniform shrinkage, on the other. The solution was found a long time ago - nagels. The element differs in size, sectional shape (circle or square), material of manufacture.
Types of dowels
There are many types of fasteners, but they are conventionally divided into groups according to material and shape. Let's consider this issue in more detail.
Manufacturing material
Two types are actively used:
- Wood. Most experts strongly recommend using a wooden spike in the construction of wooden structures. The main advantages when choosing such a fastener are given:
- Uniform drying. The bar and the dowel should be approximately the same moisture content. This will allow the shrinkage process to go through with practically no visible changes;
- Not subject to temperature extremes... The tree practically does not change its linear dimensions at different temperatures, so the fastener will always be in place;
- No rust... The metal rusts over time, which leads to rotting of wooden surfaces in contact with it;
- There is no condensation. On steel, with a sharp change in temperature, moisture is formed, which is completely useless inside the load-bearing wall.
- The dowel grows together with the wall. After a certain time, the house will become monolithic, wooden surfaces are soldered.
- Metal. This option also refers to the budgetary method of fastening, waste is often used (pipes, fittings). Although experts prefer the previous method, the metal nail has its advantages:
- The upper layers of wood are protected from torsion;
- Durability of the structure.
The form
There are also several main forms:
- Rounded section. Taking into account the fact that the holes for fastening in the log are made with a drill, the round dowel will provide the maximum contact area, guaranteeing the reliability and durability of the structure;
- Square. It is easier to make such an element, it also costs less. But this is where the positives end. When entering the hole, the edges of the spike are deformed, and the total contact area remains minimal. Building a house in this way is dangerous;
- Narrow rectangle... The easiest option to manufacture. A board of a certain thickness is taken, dissolved into rectangles. The only advantage is the very low thickness. Suitable for narrow beams, but installation is extremely difficult.
We make a dowel with our own hands
This type of fastener is sold in stores, but you can easily make it at home. The wooden element is manufactured as follows:
- trim boards are taken, from which beams are cut 25 by 25 centimeters in size;
- stakes are made, length 1.5 times the thickness of a building bar, a diameter of 2.5 centimeters;
- the corners are cut off with an ax to give a rounded shape.
But the following must be taken into account:
- the wood for fasteners must be harder than the timber. Now birch is most often used for these purposes;
- the dowel should not differ significantly in humidity from the main structural element;
- it is strictly forbidden to use a dowel with a knot.
We carry out calculations
Depending on the selected fastening technology, it is possible to determine the number of pins with sufficient accuracy, to calculate their correct characteristics.
Determining the size
There are many scientific papers that will help determine the diameter of the dowel. But in the professional environment of carpenters-builders, certain rules have already formed:
- for a bar with a thickness of 20 centimeters or less, a dowel with a diameter of 25 millimeters is used;
- a thicker bar is attached with a spike measuring 3 centimeters;
- a bar thicker than 0.2 meters can be fastened with a dowel of 2.5 cm, but subject to a step reduction to a meter.
The length is determined even easier - the most common and recommended method is to fasten two logs with a dowel one and a half long.
We count the number
Even a small bath will require a fairly large number of thorns to be purchased or made, which can be time-consuming. Therefore, it is better to know the number of fasteners in advance.
There are fixing rules:
- the first dowel is inserted at a distance of 20 to 70 centimeters to the corner;
- the step is from one and a half to 2 meters;
- two logs adjacent in height are necessarily fastened.
Knowing these tricks, the height of the structure, the diameter of the timber, you can easily calculate the number of dowels required for the construction.
Fastening technology
Drilling
A powerful drill is used if it is necessary to make holes directly on the construction site or a machine if the timber is prepared in advance.
The second method is common in the West and allows you to assemble the structure of almost any house in a few days. But attentiveness, precise drawing, professionalism are required.
In the first and second cases, the rule remains unshakable - the hole must be strictly vertical.
The diameter of the drill and the thickness of the dowel should be the same, and for the upper tiers of the timber, the hole should even be two millimeters larger. This eliminates the sagging of the supporting structure due to a small vertical load. The hole is made 2 centimeters longer than necessary so that the spike can walk safely during shrinkage.
Clogging
A sledgehammer weighing several kilograms is usually used. The dowel is driven inward below the edge of the bar to the end of the hole; for this, nozzles (usually made of brass) are used.
Correct location
The option is considered ideal when the pins are staggered. But a strictly vertical direction along parallel lines is also allowed and does not significantly affect the strength.
It is recommended that a gap of at least thirty centimeters before the beginning of the opening. The distance of the fastener to the corner should not exceed 70 centimeters. The step can vary from a meter to 3, depending on the material from which the timber is made (hard varieties require a smaller step).
Advantages and disadvantages
Like any other fastener, the dowel has a number of positive sides, as well as a liability of the disadvantages.
Benefits:
- The spike gives a reliable grip, prevents the crown from sagging;
- Provides long-term reliability under bending loads, which nails and bolts cannot boast of;
- Promotes even shrinkage at home. The fastener moves freely along the vertical plane, preventing horizontal deformations;
- The wooden product is not subject to the formation of moisture and corrosion, excluding the decay process;
- Extreme cheapness. Even buying ready-made dowels will not hit your pocket too much, allowing you to minimize your budget.
But there are also disadvantages:
- Complexity of installation. Absolute vertical position, perfect selection of the diameter, implies the presence of decent construction skills;
- Serious quality requirements. The presence of knots or heterogeneity of the material can lead to disastrous consequences;
- Excessive driving force often leads to cracks in the timber. After which it must be changed.
There are a number of installation tricks to build your dream home that will last for years:
- Chess order. The condition is optional, but highly recommended by carpenters of all stripes;
- To avoid sagging, it is necessary to use round wooden dowels. Square products are mainly promoted by manufacturers, as they are easier to manufacture;
- When hammering, friction can and should be reduced. To do this, it is enough to use a soapy solution;
- Birch fasteners are recommended. This guarantees the reliability of the structure, gives a certain charm, while not increasing the cost of construction;
- Similar moisture between the spike and the bar - a fundamental condition for the durability of the structure. You need to pay close attention to this;
- Feel free to use additional fasteners. Science does not stand still, modern devices can greatly facilitate the task.
The foundation of any house is the foundation and its walls. This also applies to the construction of wooden houses. Their walls should be solid, logs or beams well fixed. It is impossible to lay even a small log house just like that, over time the crowns will be deformed, displaced, which will lead to the curvature of the walls or even to their complete destruction. That is why a wide variety of fasteners are made, with the help of which the crowns of the log house are firmly fastened to each other. The most easy to use, affordable and popular are the dowels. But they exist of several types and different forms, therefore, when choosing them, you need to know which kind of dowels it is better to give your preference to.
What are the fasteners - dowels?
Nagel are rods of square, triangular or cylindrical cross-section, designed to secure two logs or beams in a log house (lower and upper). Dowels are installed in a log house in a checkerboard pattern, the distance between them should be at least 1 meter. To begin with, a hole is drilled in the logs or bars, and then it is already necessary to drive the dowel into them. In this case, you need to use only wooden hammers so as not to damage the end of the dowel. The dowels are installed strictly vertically, so they will not interfere with the sliding of the logs or beams down. If the dowel does not lend itself well to driving, then you should not be zealous, it is better to drill this hole with a slightly larger diameter.
These fasteners provide stability and strength to the walls of the log house. The dowels during the shrinkage of the log house prevent deformation of the logs, the likelihood of the formation of cracks of impressive sizes on them decreases. Also, after drying, the dowel logs provide them with a smooth slide down, thereby reducing the gaps between the crowns of the frame. They are made in various sizes. Most often they are made with a diameter of 25-30 mm. Differences in pins are not only in their size, but also in varieties.
Types of dowels
There are several types of these fasteners: metal and wood. Metal pins are durable, made of steel, and have a ribbed surface. They are rarely used in wooden housing construction, because even after treatment with protective compounds, being in the structure of the tree, they corrode over time, and rust, in turn, negatively affects the crowns of the log house. And condensation forms on the metal dowels, which will lead sooner or later to the development of decay of wooden material. In addition, the ribbed surface of metal pins injures the wood during its movement.
Wooden dowels are not inferior in strength to metal ones, because they are made from hard wood. They have a smooth surface, which does not injure the moving crown of the log house during their drying and shrinkage. Wooden dowels go well with the crowns of a log house, they do not cause rotting and other negative reactions.
How to choose the right dowel for assembling a log house?
When buying a dowel for assembling a wooden house, consider the following:
- It is still desirable to acquire wooden dowels. The most durable dowels are made of birch. You can also buy dowels made of oak, but they are too expensive for their cost.
- It is advisable to buy a dowel of a circular section, it will be easier for them to prepare a hole in the crowns.
- Both short and long dowels can be found on sale. It is recommended to stay on long ones, they can be cut on the spot to the required length.
- Be sure to pay attention to the existing defects when buying. There should be a minimum of them, it is advisable to acquire a dowel perfectly smooth and without the presence of knots.
It is believed that dowels need to be purchased only for rounded logs, in fact, they will be of great benefit to squared and even chopped log cabins. They will give the walls strength, stability, reduce the risk of deformation of the crowns, their torsion, and the appearance of cracks on them.
Photo: a diagram of the installation of pins in the timber of a wooden house.
These fasteners prevent the movement of the rims relative to each other. The main thing is to purchase a dowel that meets the recommendations of these experienced builders.
Photo: a diagram of the installation of dowels in the logs of a wooden log house or bath.
Photo: a diagram of the device of a log wall of a wooden frame. Shown is the correct installation of the dowel (dowel) in the chopped log. It is clearly seen that the main diameter of a round birch nail is 25 mm. and the tolerance for the draft of the logs is clearly visible, which should be approximately 50 mm.
Photo: when drilling holes in a bar for installing dowels, two workers must be present. So it is best to do this work correctly and without errors - drilling distortions and control of the stock for shrinkage of the bar.
Photo: in places where door and window units are installed, the so-called "cutouts" for windows and door frames, it is best to put planed bars of 40x40 mm instead of dowels. in typical wooden log cabins and bars 50x50mm in log cabins of large diameter logs. This is due to the fact that it is best to attach window and door casing to such bars. But, at the junction of logs and beams - in the "locks", round wooden pins made of hard wood - oak, beech or birch - are necessarily placed.
Photo: to improve sedimentary deformations in a log house made of logs and beams, it is recommended to install compression devices, so-called “Force” spring units, using new technologies. The installation of such structural parts - "wood grouse floating in the tree" with a powerful compression spring allows you to properly press the timber and logs to each other when building the walls of wooden log cabins and block log cabins.
Thematic video about "spring assemblies":
How much do the dowels cost? Price?
Cost - the prices of dowels in 2016 at a warehouse in Moscow are as follows:
A universal dowel 25 mm in length, 1.25 m long (for cutting) costs 17 rubles per 1 piece. for 1 grade. Prices for 2nd grade pins are 5-10 percent lower than this price. But they are not always available. For wholesale lots from 1000 pcs. there are discounts. It is best to find out more about the availability of goods in stock and prices by calling the numbers indicated in the contacts section.
Thematic Video:
Pickup from the warehouse and delivery
Our online store - a warehouse for issuing goods is located in the city of Balashikha, Moscow region.
There is a preferential delivery in the nearest cities of the Moscow region: Shchelkovo, Reutovo, Lyubertsy, Zheleznodorozhny, Elektrougli, Noginsk, Pavlovo-Posad, Orekhovo-Zuevo, Chernogolovka, Pushkino, Korolev, Ivanteevka, Mytishchi, Sergiev-Posad.
We have inexpensive (80 percent of the commercial value) shipping to cities:
1. Tver region: Tver, Konakovo, Kimry, Kalyazin, Kashin, Myshkin, Uglich, Torzhok, Ostashkov, Nelidovo
2. Vladimir region: Vladimir, Kovrov, Petushki, Kirzhach, Pokrov, Gus-Khrustalny, Murom, Suzdal, Yuryev-Polsky, Kolchugino, Lakinsk and Strunino.
3. Yaroslavl Region: the cities of Yaroslavl, Pereslavl-Zalessky, Rostov, Rybinsk, Tutaev, Uglich, Myshkin.
4. Ryazan region: the city of Ryazan, Kasimov, Skopin, Sasovo, Ryazhsk.
5. Krasnodar Territory: Krasnodar, Novorossiysk, Sochi, Yeisk, Armavir, Kropotkin, Anapa, Tuapse, Gelendzhik, Slavyansk in the Kuban, Tikhoretsk, Timashevsk, Belorechensk, Ust-Labinsk, Apsheronsk, Korenevsk, Goryachy Klyuch, Temryuk and Krymsk.
6. Kaluga region: the cities of Kaluga, Obninsk, Lyudinovo, Maloyaroslavets, Balabanovo and Kozelsk.
When ordering a log house made of natural wood, buyers first of all pay attention to the forest from which the building is being erected, the shape and type of timber, and the layout. At the same time, such a detail as connecting materials is overlooked, while it is this factor that affects the further operational characteristics of the structure. Wooden and metal pins are used as fasteners for a wooden house. Which of these options is preferable from the point of view of ensuring the optimal qualities of the object?
Timber fastening technology in a wooden house
In order to avoid displacement of the logs relative to each other, in addition to fastening "in the bowl" and the shrinkage groove, pins are used. Their use allows you to provide the necessary verticality of the walls. The part is a wooden or metal rod that keeps adjacent logs from shifting. The element is installed in a staggered manner, with a step of about 2 m, in pre-drilled holes. The length of the part should be 2-3 cm less than the seat, the thickness should be such as to provide a slight interference.
The assembly of a bar using pins is carried out in the following order:
- holes of a given diameter are drilled in the laid timber;
- pins are driven into the prepared holes to a depth of at least 2 cm;
- the next log is added with holes corresponding to the arrangement of the dowels in the previous row.
Metal pins: pros and cons
Products are pieces of reinforcement of a given length and diameter. They can be smooth or grooved. In some cases, bunches of metal are used as dowels. The advantages of this type of product include:
- simplicity and speed of installation and, as a result, cheaper construction;
- strength and durability;
- low price.
The reasons why you should abandon the use of metal fasteners are:
- The heterogeneity of structures. Wood will dry out over time, deform, metal will not. When rigidly fixed, the beams forming the wall can "hang" on the reinforcement, or vice versa, start to dangle.
- Corrosion susceptibility. Changes in temperature, changes in humidity levels lead to rusting of the element and deterioration of the material around it. In the future, brown spots may form on the surface of the log house.
Wooden pins: time-tested
Traditionally, wooden dowels were used in the construction of log cabins. The part was made of wood with high strength - oak, birch, beech. It is recommended to give preference to this type of fastener for the following reasons:
- prevention of deformation of the timber during further operation;
- uniform shrinkage of the walls of the house;
- resistance to warpage, temperature extremes.
When buying a part, you should pay attention to its quality. The wood of the dowel should be well dried and free from mold. The product should be hammered into the holes with a mallet.
Which option to choose
Metal pins are best suited in situations where special attention is paid to the reliability of the beam screed. To minimize the negative effect of the part on the structure as a whole, it is recommended to use dowels made of corrosion-resistant steels. To compensate for the inability of the product to cope with the “bending” load, purchase of “spring assembly” type pins - a fastener consisting of a bolt with a spring will help.
In all other cases, a wooden connection is preferred. It will provide uniform shrinkage of the whole house, good thermal insulation of the building.
Due to its high strength and durability, concrete is one of the best materials for walls, partitions and ceilings. However, it has some disadvantages. For example, the inconvenience of mounting any hinged parts on such enclosing structures - chandeliers, shelves or an ordinary cornice.
A special fastener called a concrete dowel will help solve this problem. Inexpensive and easy to install, these items will save you a lot of time wasted trying other methods of fastening to concrete.
Features and purpose
Screws or pins for concrete are rods with variable threads and sharp tips. As a rule, the product is equipped with a countersunk head with internal notches, for work with which you will need a special bit made in the form of a six-pointed star. The notches allow the screws to stick to the base even more tightly.
Basically, pins are designed to fasten various structures to substrates such as concrete. Among them are cabinets, frames, door frames, heating radiators and various communications. However, the same fasteners are also suitable for bricks (solid or hollow). And the reliability of fastening with the help of the product is explained by the unevenness of its thread, which reliably fixes the screw-dowel in any suitable surface, including concrete.
Classification of pins
The main classification, according to which different types of pins are distinguished, depends on the shape of their head. There are several more options for dividing products, although all of them are of less importance when installing attached products - the type of fastener coating, size and price.
According to the shape of the head, concrete pins are:
- secret, i.e. tapered and cross-slotted;
- rectangular or in the form of a hook (loop), sometimes rounded;
- hexagonal with internal thread and cross-slot, designed for box and open-end wrenches;
- in the form of a stud with a threaded squeegee for the nut.
The features of their installation also depend to some extent on the shape of the heads. So, for example, a dowel ending with a hook or hairpin can only be installed in pre-drilled holes with an installed dowel. The rest of the options can be screwed in without preliminary drilling.
For screws with a countersunk head or hex head, preparation of the bore holes is not required, although this is not possible for every concrete.
Cover type
By the type of coating, pins can be:
- galvanized;
- copper-plated;
- blackened.
The choice of the type of coating of the dowel for concrete depends on how it will be used. The first option has a silver color and is suitable for installation in any place, both outside and inside. Copper-plated screws are used for interior work only. And the blackened dowel is suitable for conditions with a low level of humidity and, of course, cannot be installed either on the street or in basements.
Despite the fact that each nail screw has a variable thread (which differs from other fasteners) and the same diameter of 7.5 mm, there are differences in the length of the products.
It ranges from 70 to 200 mm (72 to 202 mm based on head dimensions) in 20 mm increments, except for a 30 mm gap between 150 and 180 mm. The length of time depends on the time of screwing the screw into the wall, and, accordingly, the strength of the product mounted on it.
Cost of materials
The cost of concrete pins depends mainly on their length and coating parameters. For example, copper-plated products will cost more than blackened ones, and you will have to pay more for 150-mm products than for 70-mm ones. In any case, the purchase of screws will not cause much damage to your budget, since the dowel is inexpensive, and for construction work these products usually do not need much.
There are only three main stages of installation of dowels. These are preparatory work, calculation of the quantity and size of the product and installation itself.
For each of them, you should know some features.
Preparatory work
When installing a screw-head, it will not be possible to do without drilling additional holes. The diameters of these passages in concrete should be about 15 to 20 percent smaller than the threaded area of \u200b\u200bthe fastener. After the holes are drilled, they must be cleaned of dust.
Size and quantity calculations
The dimensions of the concrete pins are most often chosen based on the load that they need to withstand. For example, a weight of 100 kg will require the installation of self-tapping screws about 150 mm long. And a small shelf weighing up to 10 kg can be easily held by small pins, the length of which does not exceed 70 millimeters. Do not hang the new structure on pins designed to hang a lighter object.
Determination of the number of pins is carried out by the distance between them. Usually it is taken equal to 70-100 mm in each direction. That is, for example, for a cabinet measuring 60 × 90 mm, you will need to install 4 screws in the corners, and for a structure with sides of 120 × 150 mm - already eight pieces.
Mounting
A dowel of the appropriate size is inserted into the hole intended for installing the dowel on concrete. The material for its manufacture can be both plastic and wood, and the main characteristic is the ability to withstand fasteners and secure fastening in the ceiling or wall. To screw in, you should use a special screwdriver, the parameters of which depend on the shape of the head of the nail.
Screwing in the self-tapping screw correctly will avoid breaking it off. Therefore, this should be done carefully, without overtightening. It is also worth avoiding screwing in too quickly, which leads to overheating of the screw head and its destruction.
Dowels are liners that prevent mutual displacement of the connected elements and work mainly in bending. In shape, pins are cylindrical and plate-like. Cylindrical pins include bolts, pins, nails, and screws. Lamellar dowels include oak plates (laid in the nest) and steel plates (embedded and driven).Scope of pins: bolts and pins - in the joints of elements for rallying composite compressed elements, in nodal joints; nails - for rallying composite compressed elements from boards, less often - in nodal joints; lamellar pins - for rallying the beams in split beams; wood grouses and screws - in connections with steel plates.
Depending on the type of deformation of the pins (relative to the middle of their length), there are symmetrical joints (Fig. 59) and asymmetric (Fig. 60). By the number of shear planes between the connected elements, the joints are divided into single-shear, double-shear and multi-shear. Here the concept of "cut" does not refer to the nature of the work and destruction of the dowel, but only means the place where it intersects the shear plane.
Work of the nail connection
In a properly designed dowel joint, the wood of the nest collapses (the viscosity of the joint) and the bending of the dowel (Fig. 61, a), with a hard dowel, splitting of the wood between the nests (brittle fracture) occurs (Fig. 61, b). Therefore, it is not recommended to use hard pins. The bolt connections differ in density. In fig. 62 shows the operation of various types of single-shear dowel joints and the scheme of action on them of shear forces in the form of distributed shear stresses σ cm, diagrams of bending moments M and shear forces Q. Nagged connections (non-thrust) - T 1 e 1 \u003d T 2 e 2.Connections on cylindrical pins. Steel cylindrical pins are made with a diameter of 12 ... 24 mm with a graduation every 2 mm, oak - with a diameter of 12 ... 30 mm with a graduation every 4 mm (they are turned from bars). The pins are inserted into holes of the same diameter.
Dowels and bolts can also be made of other materials. Metal pins are unacceptable when structures operate in a chemically aggressive environment, and for these conditions pins are made entirely of wood or wood-plastic, for example, from oriented press material AG-4S and from particle board-B. Bolts, pins, nuts and washers are made of these materials by pressing.
Screws and screws up to 10 mm in diameter and wood grouses up to 20 mm in diameter are screwed into holes pre-bored with a drill of a smaller diameter.
Nails up to 6 mm in diameter are driven into solid wood; for larger nails, pre-drill the sockets with a smaller drill (not recommended connection).
Connection calculation... Due to the density of the nail connection, the deformations of the nail and wood are closely related. Therefore, the bearing capacity of the dowel joint is determined by the type of resistance (i.e., bending of the dowel or crushing of wood of the walls of the nest), which earlier reaches the limiting state and is found for one cut of the dowel by the formulas:
By crushing the nest
on the bend of the dowel
In these formulas with and and - the thickness of the connected elements, k - the coefficients taken according to the table. 11. The minimum of the obtained values \u200b\u200bis taken as the calculated bearing capacity per shear.
Formulas (65) and (66) are used to calculate the joints working along the fibers. In cases where the force transmitted by the dowel is directed at an angle a to the fibers of the elements, the design bearing capacity is found according to the indicated formulas multiplied by the coefficient k α (Table 12) when calculating by crushing the wood of the nest and by √k α when calculating by bending of the dowel. The angle is taken to be equal to the larger of the crushing angles with the dowel of the elements adjacent to the seam under consideration.
In the joint on plastic dowels, in addition to crushing the wood of the socket and bending the dowel, the dowel shear can occur. The bearing capacity of the dowel per cut with this type of resistance is found by the formula
where R cp is the design shear resistance of the nail material.
In this case, the minimum value obtained by formulas (65), (66) and (67) is taken as the calculated bearing capacity of the dowel per cut.
When designing connections of elements operating at high humidity or temperature, when checking connections for the effect of only constant and temporary long-term loads or calculated for the effect of short-term loads, the bearing capacity per shear should be determined by formulas (65) ... (67) with multiplication on the corresponding correction factors according to table. 1, 2, 3, 4 when calculating from the condition of crushing wood and by the square root of their coefficients when calculating from the condition of bending of the dowel.
The number of pins in the joint is determined by the formula
where N is the design force in the joint;
T min - design bearing capacity of one cut;
n Wed is the number of dowel cuts.
Connection design... The pins in the joint are placed taking into account the prevention of the destruction of wood from splitting as a result of unacceptable weakening of the connected elements. The standard distances between the rows of dowels s 2, between the dowels in the row s 1 depend on the type of dowel, on the thickness of the connected package and on the method of placement (Fig. 63 and Table 13). The thicker the package, the greater the risk of distortion of the correct breakdown of the pins on the back of the package (due to drift of the drill during drilling). Therefore, in thick packages with b\u003e 10d, increased distances between the pins are accepted.
Pins should be placed, as a rule, in two, less often - four longitudinal rows. The placement of pins in one or three longitudinal rows is not allowed in order to avoid coincidence of the middle row with the core plane of the element, where a shrinkage crack appears.
Staggered pins are not recommended. The cumbersome markup process makes it easy to apply templates. Reaming holes with electric drills with a guide frame also makes work easier and improves hole quality. Drilling is carried out through the entire package of boards, temporarily connected with clamps or nails.
The pins are driven into holes of equal diameter with light hammer blows. Driving dowels into smaller holes can cause the wood to split along the rows of holes.
In the dowel joints, tie bolts must be supplied: in stretched joints with wooden lining in the amount of 25 ... 40% of the total number of dowels; in stretched joints with steel plates in the amount of 50% of the total number of dowels; in the nodal joints, at least one tie bolt is placed in the center of the node.
The connected elements are checked for strength taking into account the weakening of the holes.
The use of dowel joints with thin gaskets, steel or plastic pads (Fig. 59, b, d and Fig. 60, d) is permissible if the dowels are placed tightly into the holes. This is achieved by through-drilling the package. Gaskets and linings are checked for tension along the weakened section, for longitudinal bending, for crushing of the walls of the holes according to the formulas:
here N is the design force in the pad or one pad;
F nt - the calculated area of \u200b\u200bthe section weakened by the holes;
F br - gross cross-sectional area of \u200b\u200bthe lining;
φ is the coefficient of buckling with the flexibility of the lining, determined at the calculated length between the fixing points;
d - hole diameter;
δ n is the thickness of the lining (gasket);
n n is the number of holes;
R p, R c, R cm - design resistance of the material of the linings (gaskets) to tension, compression, crushing.
Nail connections
The normal thickness of the pierced element should be considered c \u003d 10 gv, at which s 1 ≥15d gv, the minimum thickness is c \u003d 4d gv, at which s 1 \u003d 25d gv. For intermediate values \u200b\u200bwith the smallest distance s 1 is determined by interpolation. For elements that cannot be pierced by a nail through, regardless of their thickness, s 1 ≥15d gv is taken. The distance along the fibers from the nail to the end of the element in all cases should be at least 15d gv. When arranging nails in oblique rows in a checkerboard pattern, the distance s 2 can be reduced to 3d gv.Opposite hammering of nails from opposite sides of the package is allowed only if their ends are deepened into the middle element of the package by no more than 2/3 of its thickness.
Driving nails into hardwood and larch is not allowed due to the risk of cracking.
The distance between the nails along the grain of the wood in elements made of aspen, alder and poplar should be increased by up to 50% compared to those indicated above.
Round steel pins in connections with sheet hinges
Connections with sheet hinges are mainly used for fastening massive stretched elements at nodes and joints (Fig. 64).The steel strip is attached to the element with bolts and pins. The number of bolts should be 25 ... 50% of the total number of dowels. To ensure the required tightness of the connection, the holes for the dowels are drilled with a metal drill through the wood and a steel strip previously inserted into the slot of the wooden element.
In joints with sheet hinges, double-shear symmetrical pins are used. The bearing capacity of one cut of the dowel, kN, is determined by the formula
Where d - diameter of the dowel, cm;
α \u003d h / 2d - coefficient equal to the ratio of half the thickness of the element to be connected to the diameter of the dowel d.
Bearing capacity of one double-shear dowel T n \u003d 2T 1.
To ensure uniform strength of the pin in terms of crushing and bending, the values \u200b\u200bof the coefficient α are recommended to be taken within 4 ... 5. The dimensions of the cross-section of the strip are determined from the condition of its tensile strength along the section weakened by the pins.
Pins are placed in joints with a sheet hinge according to the general rules for placing pins made of round steel, and the distances between the pins along the fibers and from the extreme dowel to the end of the element are taken as s 1 ≥7.5d.