Houses made of natural wood are now gaining popularity again. But wood is far from a homogeneous material, therefore, during the shrinkage process, a slight deformation occurs, different parts of the house take on their final appearance unevenly.
This implies the problem of attaching the timber to each other, which will ensure reliability, on the one hand, and uniform shrinkage, on the other. The solution was found a very long time ago - pins. The element differs in size, section shape (circle or square), material of manufacture.
Types of dowels
There are many types of fasteners, but conventionally they are divided into groups according to material and shape. Let's consider this question in more detail.
Production material
Two types are actively used:
- Wooden. Most experts strongly recommend using a wooden spike when building wooden structures. The main advantages of choosing such fasteners are given:
- Even drying. The beam and dowel should be approximately the same humidity. This will allow the shrinkage process to go through with virtually no visible changes;
- Unaffected by temperature fluctuations. The tree practically does not change linear dimensions at different temperatures, so the fastener will always be in its place;
- No rust. Metal rusts over time, which leads to rotting of wooden surfaces in contact with it;
- There is no condensate. On steel, with a sharp change in temperature, moisture forms, which is completely useless inside the load-bearing wall.
- The dowel fuses with the wall. After a certain time, the house will become monolithic, wooden surfaces are soldered.
- Metal. This option also applies to the budgetary method of fastening; waste (pipes, fittings) is often used. Although experts prefer the previous method, metal dowel has its advantages:
- The top layers of wood are protected from torsion;
- Structural durability.
The form
There are also several main forms:
- Round 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 is also cheaper. But that's where the positives end. When entering the hole, the edges of the stud are deformed, and the total contact area remains minimal. It is dangerous to build a house in this way;
- narrow rectangle. The easiest option to make. A board of a certain thickness is taken, dissolved into rectangles. The only advantage is the very small thickness. Suitable for narrow timber, but installation is extremely difficult.
We make dowels with our own hands
This type of fastener is sold in stores, but you can easily make it at home. The wooden element is made as follows:
- scraps of boards are taken, from which bars of 25 by 25 centimeters are cut;
- stakes are made, 1.5 times the thickness of the construction timber, with a diameter of 2.5 centimeters;
- corners are cut with an ax to give a rounded shape.
But the following must be taken into account:
- wood for fasteners should be harder than 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 chosen fastening technology, it is possible to determine the number of dowels with sufficient accuracy and calculate their correct characteristics.
Deciding on sizes
There are many scientific works that will help determine the diameter of the dowel. But in the professional environment of carpenters-builders, certain rules have already been formed:
- for a beam with a thickness of 20 centimeters or less, a dowel with a diameter of 25 millimeters is used;
- a thicker beam is fastened with a spike measuring 3 centimeters;
- a beam thicker than 0.2 meters can be fastened with a dowel of 2.5 cm, but subject to a decrease in step to a meter.
The length is determined even more simply - the most common and recommended method is to fasten two logs with a dowel one and a half beams long.
We count the number
Even a small bath will require a fairly large number of spikes to be purchased or made, which can be time consuming. Therefore, it is better to know the number of fasteners in advance.
There are fastening 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 building, the diameter of the beam, you can easily calculate the number of dowels needed 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 tool 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 care, accurate 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 must match, and for the upper tiers of the timber, the hole should even be two millimeters larger. So get rid of 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 comfortably during shrinkage.
hammering
A sledgehammer weighing several kilograms is usually used. The dowel is driven inward below the edge of the beam to the end of the hole; nozzles (usually made of brass) are used for this.
Correct location
The ideal option is when the dowels are staggered. But a strictly vertical direction along parallel lines is also allowed and does not significantly affect strength.
A gap before the beginning of the opening is recommended at least thirty centimeters. 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 grades require a smaller step).
Advantages and disadvantages
Like any other fastener, the dowel has a number of positive aspects, as well as a liability from the disadvantages.
Advantages:
- The spike gives reliable grip, prevents the crown from sagging;
- Provides long-term reliability under bending loads, which nails and bolts cannot boast of;
- Promotes uniform shrinkage of the house. The fastener moves freely along the vertical plane, preventing horizontal deformations;
- The wooden product is not exposed to the formation of moisture and corrosion, excluding the process of decay;
- Ultimate cheapness. Even buying ready-made pins will not hit your pocket too hard, allowing you to minimize the budget.
But there are also disadvantages:
- Difficulty of installation. Absolute vertical position, ideal diameter selection, implies decent building skills;
- Serious quality requirements. The presence of knots or heterogeneity of the material can lead to disastrous consequences;
- Excessive application of force when driving often results in cracks in the cant. After that it needs to be changed.
There is a set of installation tricks that allow you to build your dream home that will last for many years:
- Chess order. The condition is not mandatory, but highly recommended by carpenters of all stripes;
- To avoid sagging, it is necessary to use rounded wooden dowels. Square items are mostly promoted by manufacturers as they are easier to make;
- When clogging, friction can and should be reduced. To do this, it is enough to use a soap solution;
- It is recommended to use birch fasteners. This guarantees the reliability of the structure, gives a certain charm, while not increasing the cost of construction;
- Similar humidity between tenon and timber- a fundamental condition for the durability of the structure. Close attention must be paid to this;
- Feel free to use additional fasteners. Science does not stand still, modern devices can greatly facilitate the task.
The basis of any house is the foundation and its walls. This also applies to the construction of wooden houses. Their walls must be strong, logs or beams are well fixed. It’s not possible to lay even a small frame just like that; over time, the crowns will deform, shift, 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 log crowns are firmly fastened to each other. The easiest to use, affordable and popular are nagels. But they exist in several types and different forms, so when choosing them, you need to know which pins it is better to give your preference to.
What are fasteners - dowels?
Nagel - these are rods of square, triangular or cylindrical section, designed to fasten two logs or beams in a log house to each other (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 beams, and then it is already necessary to hammer the dowels 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 prevent the logs or beams from sliding down. If the dowel is difficult to drive, then you should not be zealous, it is better to drill this hole with a slightly larger diameter.
These fasteners provide the log walls with stability and strength. Nagel during the shrinkage of the log house prevent the deformation of logs, the likelihood of formation of cracks of impressive size on them is reduced. Also, after drying, the dowel logs provide them with a smooth sliding down, which reduces the gaps between the crowns of the log house. They are made in various sizes. Most often they are found 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 wooden. Metal dowels are durable, made of steel, have a ribbed surface. They are rarely used in wooden housing construction, because. even after being treated with protective compounds, being in the structure of a tree, they corrode over time, and rust, in turn, negatively affects the log crowns themselves. Yes, and condensation forms on metal dowels, which will sooner or later lead to the development of rotting of the wooden material. In addition, the ribbed surface of the metal dowels injures the wood during its movement.
Wooden dowels are not inferior in strength to metal dowels, because. they are made from solid wood. They have a smooth surface, which does not injure the moving crowns of the log house during their drying and shrinkage. Wooden dowels are well combined with log crowns, they do not cause their decay and other negative reactions.
How to choose the right dowel for assembling a log house?
When buying dowels for assembling a wooden house, you must consider the following:
- It is still desirable to acquire wooden dowels. The most durable are dowels made of birch. You can also buy dowels made of oak, but they are too expensive for their cost.
- It is advisable to buy dowels of exactly circular cross section, it will be easier to prepare a hole in the crowns for them.
- Both short and long dowels can be found on sale. It is recommended to stop at long ones, they can be cut to the required length already on the spot.
- Be sure to pay attention to the existing defects when buying. They should be at a minimum, it is desirable to acquire dowels perfectly smooth and without knots.
It is believed that dowels need to be purchased only for rounded logs, in fact, they will be of great benefit to timber 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: scheme for installing dowels in a bar of a wooden house.
These fasteners prevent the crowns from moving relative to each other. The main thing is to purchase dowels that meet the recommendations of these experienced builders.
Photo: scheme for installing dowels in the logs of a wooden log house or bath.
Photo: scheme of the device of the log wall of a wooden frame. The correct installation of a dowel (nagel) in a chopped log is shown. It is clearly seen that the main diameter of the round dowel made of birch is 25 mm. and the allowance for the draft of logs is clearly visible, which should be approximately 50 mm.
Photo: when drilling holes in the timber for the installation of dowels, the presence of two workers is required. So it is best to do this work correctly and without errors - distortions of drilling and control of the margin for shrinkage of the timber.
Photo: in the places of installation of door and window blocks, the so-called "cutouts" for windows and door frames, it is best to put planed bars 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, the so-called "casing", to such bars. But, at the junction of logs and timber - in the "castles" wooden round dowels made of hardwood - oak, beech or birch - are necessarily placed.
Photo: to improve sedimentary deformations in a log house made of logs and timber, according to new technologies, it is recommended to install compression devices, the so-called spring units "Strength". The installation of such structural parts - "floating in the tree" wood grouses "" with a powerful compression spring allows you to properly press the timber and logs to each other when building the walls of wooden log and block log cabins.
Thematic video about "spring knots":
How much do nails cost? Price?
Cost - the prices of pins in 2016 in a warehouse in Moscow are as follows:
A universal dowel d.25 mm., 1.25 m long (for cutting) costs 17 rubles per 1 pc. for grade 1. Prices for dowels of the 2nd grade 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 listed in the contacts section.
Thematic Video:
Pickup from the warehouse and delivery
Our online store - a warehouse for issuing goods is located in Balashikha, Moscow Region.
There is a preferential delivery to the nearest cities of the Moscow region: Schelkovo, Reutovo, Lyubertsy, Zheleznodorozhny, Elektrougli, Noginsk, Pavlovo-Posad, Orekhovo-Zuyevo, Chernogolovka, Pushkino, Korolev, Ivanteevka, Mytishchi, Sergiev Posad.
We have inexpensive (80 percent of the commercial value) delivery to the following 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, Yeysk, Armavir, Kropotkin, Anapa, Tuapse, Gelendzhik, Slavyansk in the Kuban, Tikhoretsk, Timashevsk, Belorechensk, Ust-Labinsk, Apsheronsk, Korenevsk, Goryachiy 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 built, the shape and grade of the timber, and the layout. At the same time, such a detail as connecting materials is missed, while it is this factor that affects the further operational characteristics of the structure. Wooden and metal dowels are used as fasteners for a wooden house. Which of these options is preferable in terms of ensuring the optimal qualities of the object?
Timber fastening technology in a wooden house
In order to avoid displacement of logs relative to each other, in addition to fastening "into a bowl" and a shrinkage groove, dowels are used. Their use allows you to provide the necessary verticality of the walls. The detail is a wooden or metal rod that keeps adjacent logs from shifting. The element is installed in a checkerboard pattern, with a step of approximately 2m, 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 small tightness.
The assembly of the beam using dowels is carried out in the following order:
- holes of a given diameter are drilled in the laid timber;
- dowels are driven into the prepared holes to a depth of at least 2 cm;
- the next log is added with holes corresponding to the layout of the dowels in the previous row.
Metal dowels: pros and cons
Products are pieces of reinforcement of a given length and diameter. They can be smooth and grooved. In some cases, metal clusters are used as pins. The benefits 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:
- Heterogeneity of structures. Wood will dry out and deform over time, metal will not. With rigid fixing, the beams forming the wall can “hang” on the reinforcement, or vice versa, begin to dangle.
- Susceptibility to corrosion. Temperature fluctuations, changes in humidity levels lead to rusting of the element and damage to 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 item was made of wood with high strength - oak, birch, beech. It is recommended to give preference to this fastener option for the following reasons:
- prevention of timber deformation during further operation;
- uniform shrinkage of the walls of the house;
- resistance to warping, temperature extremes.
When buying a part, you should pay attention to its quality. The wood of the dowel must be well dried, free of mold. Hammer the product 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 impact 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, the purchase of pins of the “spring assembly” type, a fastener consisting of a bolt with a spring, will help.
In all other cases, a wooden joint is preferred. It will ensure uniform shrinkage of the whole house, good thermal insulation of the building.
Concrete due to its high strength and durability is one of the best materials for walls, partitions and ceilings. However, he has some shortcomings. For example, the inconvenience of mounting any attachments on such enclosing structures - chandeliers, shelves or a conventional cornice.
To help solve this problem, a special fastener called a dowel for concrete will help. Inexpensive in price and easy to install, these items will save you a lot of time spent trying other methods of fixing to concrete.
Features and purpose
Screws or dowels for concrete are rods with variable threads and sharp tips. As a rule, the product is equipped with a countersunk head with internal notches, to work with which you will need a special bit, made in the form of a six-pointed star. Notches also allow the screws to hold on to the base even more tightly.
Basically, pins are designed to fasten various structures to bases such as concrete. Among them are cabinets, frames, door jambs, 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 dowel screw in any suitable surface, including concrete.
Pin classification
The main classification according to which different types of dowels are distinguished depends on the shape of their head. There are several more options for separating products, although they are all of lesser importance when installing hinged products - the type of fastener coating, dimensions and price.
According to the shape of the head, pins for concrete are:
- secret, i.e. conical and having cross-shaped slots;
- rectangular or in the form of a hook (loop), sometimes rounded;
- hexagonal with internal thread and cross slot, designed for cap and open-end wrenches;
- in the form of a stud having a threaded drive for a nut.
To some extent, the features of their installation also depend on the shape of the heads. So, for example, a dowel ending in a hook or stud can only be installed in pre-drilled holes with a dowel installed. The rest of the options can be screwed in without pre-drilling.
Countersunk or hex head screws do not require hole preparation, although this may not be possible for every concrete.
Coating type
According to the type of coating, dowels can be:
- galvanized;
- copper-plated;
- blackened.
The choice of type of dowel coating 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 dowel screw has a variable thread (which differs from other fastener options) and the same diameter of 7.5 mm, there are differences in the length of the products.
It varies from 70mm to 200mm (72mm to 202mm with head dimensions) in 20mm increments, except for a 30mm gap between 150mm and 180mm. The length 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 dowels for concrete depends mainly on their length and coating parameters. For example, copper-plated products will cost more than blackened ones, and 150 mm ones will have to pay more than 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 the construction work of these products you usually need a little.
There are only three main stages of installing dowels. These are preparatory work, calculation of the quantity and dimensions of the product, and direct installation.
For each of them, you should know some features.
Preparatory work
When installing a dowel screw, it will not be possible to do without drilling additional holes. The diameters of such passages in concrete should be approximately 15–20 percent smaller than the threaded area of the fastener. After the holes are drilled, they must be cleaned of dust.
Size and Quantity Calculations
The dimensions of the pins for concrete are most often selected 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 dowels, the length of which does not exceed 70 millimeters. Do not hang a new design on dowels designed to hang a lighter object.
The number of pins is determined by the distance between them. Usually it is taken equal to 70–100 mm in each of the directions. That is, for example, for a cabinet with a size of 60 × 90 mm, you will need to install 4 screws in the corners, and for a design 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 of 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. For screwing, use a special screwdriver, the parameters of which depend on the shape of the dowel head.
Proper screwing of the self-tapping screw will prevent it from breaking off. Therefore, this should be done carefully, without overtightening. It is also worth avoiding too fast screwing, which leads to overheating of the screw head and its destruction.
Nagels are called liners that prevent the mutual shift of the connected elements and work mainly in bending. The shape of the pins are cylindrical and lamellar. Cylindrical dowels include: bolts, pins, nails and screws. Plate dowels include oak plates (laid into the nest) and steel plates (embedded and driven).Scope of dowels: bolts and pins - at 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 dowels - for rallying beams in composite beams; capercaillie and screws - in joints with steel plates.
Depending on the type of deformation of the pins (relative to the middle of their length), there are: symmetrical connections (Fig. 59) and asymmetric (Fig. 60). According to the number of shear planes between the connected elements, the connections 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.
The work of the dowel connection
In a properly designed dowel joint, the nest wood is crushed (joint viscosity) and the dowel bends (Fig. 61, a), with a rigid dowel, wood splitting between nests (brittle fracture) can occur (Fig. 61, b). Therefore, the use of rigid dowels is not recommended. Nagelny connections differ in density. On fig. 62 shows the operation of various types of single-cut dowel joints and the scheme of the action of shear forces on them in the form of distributed crushing stresses σ cm, diagrams of bending moments M and shear forces Q. Dowel joints (non-expansion) - 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 gradation of 2 mm, oak - with a diameter of 12 ... 30 mm with a gradation of 4 mm (turned from bars). The pins are inserted into holes of the same diameter as them.
Pins and bolts can also be made from other materials. Metal pins are unacceptable when structures operate in a chemically aggressive environment and for these conditions the pins are made entirely of wood or wood-plastic, for example, from oriented press material AG-4S and from chipboard-B. Bolts, dowels, nuts and washers are made from these materials by pressing.
Screws and screws with a diameter of up to 10 mm and capercaillie with a diameter of up to 20 mm are screwed into holes pre-drilled with a drill of a smaller diameter.
Nails up to 6 mm in diameter are driven into solid wood; with a larger diameter of nails, nests are pre-drilled with a drill of a smaller diameter (not recommended connection).
Connection calculation. Due to the density of the dowel joint, the deformations of the dowel and wood are closely related. Therefore, the bearing capacity of the dowel connection is determined by the type of resistance (i.e., the bending of the dowel or the collapse of the wood of the nest walls), which reaches the limit state earlier and is found for one cut of the dowel using the formulas:
By crushing the nest
along the bend of the dowel
In these formulas with and a- the thickness of the connected elements, k- coefficients taken according to the table. 11. The minimum of the obtained values is taken as the calculated bearing capacity for one section.
Formulas (65) and (66) are used to calculate joints operating 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 calculated bearing capacity is found by the indicated formulas multiplied by the coefficient kα (Table 12) when calculating by crushing the wood of the nest and by √k α when calculating by bending the dowel. The angle is taken equal to the largest of the angles of crushing by the dowel of the elements adjacent to the seam in question.
In connection with dowels made of plastic, in addition to crushing the nest wood and bending the dowel, shearing of the dowel may occur. The bearing capacity of the dowel per one cut with this type of resistance is found by the formula
where R cp is the design shear resistance of the dowel material.
In this case, the minimum value obtained by formulas (65), (66) and (67) is taken as the design bearing capacity of the dowel per one cut.
When designing connections of elements operating at high humidity or temperature, when testing connections for the effects of only permanent and temporary long-term loads or calculated for the effects of short-term loads, the load-bearing capacity per one section should be determined by formulas (65) ... (67) with multiplication to the corresponding correction factors according to table. 1, 2, 3, 4 when calculating from the condition of the collapse of the wood and to the square root of their coefficients when calculating from the condition of the bending of the dowel.
The number of pins in the connection is determined by the formula
where N is the design force in the joint;
T min - calculated bearing capacity of one section;
n cp - number of dowel cuts.
Connection design. The pins in the connection are placed taking into account the prevention of the destruction of wood from splitting as a result of an unacceptable weakening of the connected elements. The standard distances between the rows of pins s 2, between the pins in a row s 1 depend on the type of pin, on the thickness of the package being connected and on the arrangement method (Fig. 63 and Table 13). The thicker the package, the greater the risk of distorting the correct spacing of the dowels on the back of the package (due to the withdrawal of the drill when drilling). Therefore, in thick packages with b>10d, increased distances between pins are accepted.
Nagels should be placed, as a rule, in two, less often - in four longitudinal rows. Placement of dowels 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.
Placing pins in a checkerboard pattern is not recommended. The time-consuming markup process makes it easy to apply templates. Drilling holes with guide frame electric drills also makes the job easier and improves hole quality. Reaming is carried out through the entire package of boards, temporarily connected with clamps or nails.
Pins are hammered into holes of equal diameter with light blows of a hammer. Driving dowels into holes of smaller diameter can cause the wood to split into rows of holes.
Coupling bolts must be supplied in dowel joints: in tensioned joints with wooden slips 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 nodal connections put at least one coupling bolt in the center of the node.
The connected elements are checked for strength, taking into account the weakening by holes.
The use of dowel joints with thin gaskets, steel or plastic slips (Fig. 59, b, d and Fig. 60, d) is permissible if the dowels are tightly placed in the holes. This is achieved by through-drilling the package. Gaskets and linings are checked for tension along a weakened section, for buckling, for collapse of the walls of the holes according to the formulas:
here N is the design force in the gasket or one lining;
F nt - the estimated area of the section weakened by holes;
Fbr - gross area of the section of the lining;
φ - coefficient of buckling at the flexibility of the lining, determined on the estimated length between the fixing points;
d - hole diameter;
δ n - thickness of the lining (gasket);
n n is the number of holes;
R p , R c , R cm - calculated resistance of the material of the lining (gasket) to tension, compression, crushing.
Nail connections
The normal thickness of the punched element should be considered c = 10 gv, at which s 1 ≥15d gv, the minimum thickness is c = 4d gv, at which s 1 = 25d gv. For intermediate values with the smallest distance s 1 is determined by interpolation. For elements that are not pierced through by a nail, regardless of their thickness, s 1 ≥15d guards is accepted. The distance along the fibers from the nail to the end of the element in all cases must be at least 15d guards. When arranging nails in oblique rows in a checkerboard pattern, the distance s 2 can be reduced to 3d guards.Counter nailing 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 wood fibers in the elements made of aspen, alder and poplar should be increased up to 50% compared to those indicated above.
Round steel pins in connections with sheet hinges
Connections with sheet hinges are used mainly for fastening massive tensioned elements in 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 drill for metal through wood and a steel strip previously inserted into the slot of the wooden element.
In joints with leaf hinges, double-cut symmetrical dowels are used. The bearing capacity of one cut of the dowel, kN, is determined by the formula
where d- dowel diameter, cm;
α = h / 2d - coefficient equal to the ratio of half the thickness of the connected element to the diameter of the dowel d.
The bearing capacity of one double-cut dowel T n \u003d 2T 1.
To ensure the equal strength of the dowel in terms of crushing and bending, it is recommended to take the values of the coefficient α in the range of 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 pins.
Dowels are placed in joints with a sheet hinge according to the general rules for placing dowels made of round steel, and the distances between the dowels along the fibers and from the extreme dowel to the end of the element are taken s 1 ≥7.5d.