Wood construction materials. Wood is a natural construction material. Marking is the application of contour lines of the future product to the workpiece.
Lesson No. _____ Date:_________________
Subject: Wood is a natural construction material.
Goals : create conditions for students to develop: the concepts of “wood”, “wood structure” to develop the ability to distinguish tree species by their characteristics; create conditions for the development of memory in students, logical thinking, imagination; create conditions for the formation of self- and mutual control.
Lesson type: combined.
Forms of work: independent, individual, group.
DURING THE CLASSES.
I. Organizational moment.
II. Updating basic knowledge.
Conversation
Remember what material is called structural.
What raw materials are paper and cardboard made from?
Name it construction materials, which are used for the production of cars, aircraft, construction of houses, manufacturing home furniture. Where are these materials made and what raw materials are used for this?
III. Learning new material.
The development of modern equipment and technologies depends on the production and use of various structural materials: wood, metal, plastics, glass, etc.
The use of wood has become widespread. Products made from it are used in almost all areas of our lives. Paper, cardboard, artificial silk, plastic, furniture, building elements, musical instruments and souvenirs and many other necessary things are made from this material.
All tree species are divided into two groups: coniferous and deciduous (Fig. 13).
Conifers have needle-shaped leaves. These include: spruce, pine, cedar, larch, fir, etc. Deciduous species are alder, linden, oak, beech, hornbeam and others (Fig. 14). Trees are used to make structural wood products.
Wood materials can easily be processed with various cutting tools: saws, knives, chisels, drills, files and others. Structural elements made of wood materials are reliably and firmly connected with nails, screws, and gluing.
Trees are the tallest of all plants, although there are also dwarfs among them, up to several centimeters in height.
Wood as a natural structural material is obtained from tree trunks by sawing them into pieces.
The tree trunk has a thicker (butt) part at the base and a thinner part at the top. The surface of the trunk is covered with bark. The bark is like clothing for a tree and consists of an outer cork layer and an inner bast layer. The cork layer of bark is dead. The bast layer serves as a conductor for the juices that nourish the tree. Main inner part The tree trunk is made of wood. In turn, the wood of the trunk consists of many layers, which are visible in the section as growth rings. The age of the tree is determined by the number of growth rings.
Loose and soft center the tree is called the core. The medullary rays extend from the core to the bark in the form of light shiny lines. They have different colors and serve to conduct water, air and nutrients inside the tree. The core rays create the pattern (texture) of wood.
Cambium is a thin layer of living cells located between the bark and wood. Only from the cambium does the formation of new cells and the annual increase in thickness of the tree occur. “Cambium” comes from the Latin “exchange” (of nutrients).
Main sections of the trunk.
1 - end section;
2 - radial section;
3 - tangential section
To study the structure of wood, three main sections of the trunk are distinguished. A cut that runs perpendicular to the core of the trunk is called an end cut. It is perpendicular to the grain. Cut 2 passing through the core of the trunk is called radial. It is parallel to the fibers. Tangential cut 3 runs parallel to the core of the trunk and is some distance away from it. These sections reveal various properties and wood drawings.
Wood species are determined by their characteristic features: texture, smell, hardness, color.
Tree /species/Hardness
Color
Application
Pine /coniferous/
Wood of light red color with a pronounced texture
Used for the manufacture of windows and doors, floors and ceilings, furniture, in the construction of ships, carriages, bridges
Spruce /coniferous/
Soft. Impregnated with resinous substances
Color white with a yellowish tint
Used for making musical instruments, furniture, windows and doors
Birch /hardwood/
Solid
Color white with a brownish tint
Used for making plywood, furniture, dishes, gun stocks, tool handles, skis
Aspen /hardwood/
Soft. Prone to rotting.
The color is white with a greenish tint.
Used for making matches, dishes, toys, paper.
Linden /hardwood/
Soft.
The color is white with a soft pink tint.
It is used for making dishes, drawing boards, pencils, and products with artistic carvings.
Alder /hardwood/
Soft.
The color is white, turns red in the air.
Serves as a raw material for the manufacture of plywood, hollowed-out dishes, and packing boxes.
Oak /hardwood/
Solid. On a radial section, the medullary rays in the form of shiny stripes are clearly visible.
The color is light yellow with a brown-gray tint and a pronounced texture
It is used for the manufacture of furniture, parquet, cladding of valuable products, as well as in the construction of bridges and carriages.
The pattern on the surface of wood formed as a result of cutting growth rings and fibers is called wood texture. The beautiful surface of wood is said to have a rich texture. For example, wood walnut has brown and gray colors a wide variety of shades, it is highly valued for making furniture and hunting rifle stocks from it. Beautiful textures have oak, ash, as well as mahogany species growing in Africa, America and Australia, which produce red wood of various shades. Such valuable species wood is planed into thin sheets (veneer), which are glued onto valuable products.
To make useful things, a variety of construction materials are used: metal, plastic, plexiglass, silk, textile and other materials. The use of wood and materials made from it has become widespread. All structural materials have certain properties that must be taken into account when manufacturing products. These include the color and texture of wood that you already know. In addition, you also need to know how easily a certain type of wood and materials made from it can be processed, what tool needs to be used for this, whether nails, screws and other fastening parts will be held in it, how humidity and temperature changes will affect wood materials environment and so on. It is also necessary to consider what type of wood or materials made from it must be used so that the structure, for example a bridge or multi-story building, will not collapse if it is used under heavy loads, etc.
Knowledge will help answer these questionsmechanical properties construction materials. The main ones primarily include:strength, hardness, elasticity .
Strength – a property that characterizes the resistance of wood against external mechanical forces, that is, its ability to withstand heavy loads and not collapse. It is worth making structural elements from high-strength wood, that is, those that are subject to significant loads. The most durable wood is oak, followed by ash, hornbeam, maple, birch, pine, spruce, alder, aspen, and linden.
Hardness - the ability of a material to resist the penetration of another solid body into it, for example, processing tools (knives, files, chisels, drills and other cutting tools). Knowing the hardness of wood has great importance. Cutting tools for wood processing are used taking this property into account. The harder the wood, the harder it is to process and the more larger angle exacerbations must have a tool.
Based on hardness, wood can be arranged in the following order: hornbeam, oak, ash, maple, birch, pine, alder, spruce, linden. That is, hornbeam has the greatest hardness. Therefore, it is difficult to process cutting tool. Linden is the easiest to process of all wood materials. Therefore, it is used mainly for making souvenirs, household items, etc.
Elasticity – the property of a material to change its shape (and not collapse) under the influence of a load and resume it after the cessation of this action. Wood bends (deforms) under the influence of force and straightens out again, or springs back, after the load is removed. The wood of ash, oak, larch, pine and other species has high elasticity.
IV. Consolidation of the studied material.
PRACTICAL WORK
Determination of wood species from samples.
Study the table of tree species.
Write down in your notebook the main characteristics by which wood species are determined.
Identify the types of wood using the samples given by the teacher.
V. Summing up.
Conversation:
1. What types of wood are classified as coniferous? To deciduous?
2. What wood materials are produced at woodworking enterprises?
3. What is wood texture called?
4. What is the structure of a tree?
5. What types of lumber do you know?
6. Describe the role of forests in human life.
7. How do green spaces affect the improvement of the natural environment?
VI. Homework.
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Learn the notes.
Lecture No. 1
Properties of wood as a structural material.
Types and properties of construction plywood.
Protection wooden structures from rotting and fire.
Our country is the first in the world in terms of the number of forest areas, which occupy almost half of the territory of Russia - approximately 12.3 million km2. The main part of Russia's forests, about 3/4, is located in the regions of Siberia, the Far East, and in the northern regions of the European part of the country. The predominant species are conifers: 37% of the forests are larch, 19% - pine, 20% - spruce and fir, 8% - cedar. Deciduous trees occupy about ¼ of our forest area. The most common species is birch, occupying about 1/6 of the total forest area.
Wood reserves in our forests amount to about 80 billion m3. About 280 million m3 are harvested annually. industrial wood, i.e. suitable for the manufacture of structures and products. However, this amount does not exhaust the natural annual growth of wood in remote areas of Siberia and the Far East.
Harvested timber in the form of sections of trunks of standard length is delivered by road, rail and water transport or by rafting along rivers and lakes to wood processing enterprises. There, sawn materials, plywood, wood boards, structures and building parts are made from it. During logging and wood processing, a large amount of waste is generated, efficient use which are of great national economic importance. The production of insulating fiberboards and particle boards from wood waste, which are widely used in construction, allows saving a large amount of industrial wood.
Coniferous wood is used for the manufacture of basic elements of wooden structures and building parts. Straight tall trunks coniferous trees dream big amount knots make it possible to obtain straight lumber with a limited number of defects. Coniferous wood contains resins, which makes it more resistant to moisture and decay than deciduous wood.
Most hardwood species are less straight, have more knots, and are more susceptible to rot than softwood. It is almost never used for the manufacture of basic wooden elements building structures.
Oak wood stands out among hardwoods for its increased strength and resistance to decay. However, due to its scarcity and high cost, it is used only for small connecting parts.
Birch wood is also a hard wood deciduous trees. It is used mainly for the production of construction plywood. Needs protection from decay.
Wood structure
As a result of plant origin, wood has a tubular layered fibrous structure. The bulk of wood consists of wood fibers located along the trunk. They consist of elongated hollow shells of dead cells (tracheids, about 3 mm long) of organic substances (cellulose and legnin).
Wood fibers are arranged in concentric layers around the axis of the trunk, which are called annual layers, because each layer grows throughout the year. They are clearly visible in the form of a series of rings on transverse sections of the trunk, especially of coniferous trees. By their number you can determine the age of the tree.
Each annual layer consists of two parts. The inner layer (wider and lighter) consists of soft early wood, formed in the spring when the tree grows quickly. Earlywood cells have thinner walls and wider cavities. Latewood cells have thicker walls and narrow cavities. The strength and density of wood depends on the relative content of late wood in it.
The middle part of coniferous wood trunks has more dark color, contains more resin and is called the core. Then comes the sapwood and finally the bark.
In addition, the wood contains horizontal core rays, a soft core, resin ducts, and knots.
Assortment, defects and quality of wood
Timber obtained during construction is divided into round And sawn.
Round timber, also called logs, are parts of tree trunks with smoothly sawn ends - ends. The logs have a natural truncated conical shape. Reducing their thickness along the length is called running. On average, the runoff is 0.8 cm per 1 m of length (for larch 1 cm per 1 m of length) of the log. Medium logs have a thickness of 14 to 24 cm; large logs are up to 26 cm. Logs with a thickness of 13 cm or less are used for temporary construction structures.
Lumber obtained as a result of longitudinal sawing of logs on sawmill frames or circular saws. They have a rectangular or square section. The wider sides of lumber are called facets, and the narrower sides are called edges. Lumber has standard length 1 – 6.5 m with gradation every 0.25 m. The width of lumber ranges from 75 to 275 mm, thickness – from 16 to 250 mm.
The quality of timber is determined mainly by the degree of homogeneity of the wood structure, on which its strength depends. The degree of homogeneity of wood is determined by the size and number of areas where the homogeneity of its structure is disrupted and strength is reduced. Such areas are called vices.
The main unacceptable defects of wood are: rot, wormholes and cracks in chipping zones in joints.
The most common and inevitable defects of wood are knots - overgrown remains of former tree branches. Knots are acceptable with limited defects.
The inclination of the fibers (oblique) relative to the axis of the element is also acceptable with the limitation of a defect. It is formed as a result of the natural helical arrangement of fibers in the trunk, as well as when sawing logs as a result of their running.
Cracks that occur when wood dries are also one of the limited permissible defects.
Defects also include a soft core, falling knots and other, less common violations of the uniformity of the wood structure.
The quality of timber is determined by the grade (selected, I, II, III, IV), established depending on the type, size, location and number of defects. Wood for load-bearing elements of wooden structures must meet the requirements of grades I, II and III.
WoodIvarieties used in the most critical stressed tensile elements. These are individual stretched rods and boards of stretched zones of laminated beams with a section height of more than 50 cm
Cross-layer ≤ 7%.
d ≤ 1/4 b .
WoodIIvarieties used in compression and bending elements. These are individual compressed rods, boards of the extreme zones of glued beams with a height of less than 50 cm; boards of the extreme compressed zone and stretched zone located above boards of the 1st grade in laminated beams with a height of more than 50 cm, boards of the extreme zones of working glued compressed, bent and compressed-curved rods.
Cross-layer ≤10%.
Total diameter of knots over a length of 20 cm d ≤ 1/3 b .
WoodIIIvarieties used in less stressed medium laminated compressed, flexural and compressed-flexural elements, as well as in lightly critical elements of decking and sheathing.
Cross-layer ≤12%.
Total diameter of knots over a length of 20 cm d ≤ 1/2 b .
Properties of wood
Physical properties
Density. Wood belongs to the class of lightweight structural materials. Its density depends on the relative volume of the pores and their moisture content. The standard density of wood should be determined at a moisture content of 12%. Freshly cut wood has a density of 850 kg/m3. The calculated density of coniferous wood as part of structures in rooms with a standard air humidity of 12% is taken equal to 500 kg/m3, in rooms with an air humidity of more than 75% and at outdoors– 600 kg/m3.
Temperature expansion. Linear expansion upon heating, characterized by the coefficient of linear expansion, in wood varies along and at angles to the fibers. Linear expansion coefficient α along the fibers is (3 ÷ 5) ∙ 10-6, which allows you to build wooden buildings without expansion joints. Across the wood fibers, this coefficient is 7–10 times less.
Thermal conductivity Due to its tubular structure, the thickness of wood is very small, especially across the grain. Thermal conductivity coefficient of dry wood across the grain λ ≈ 0.14 W/m∙ºС. A 15 cm thick beam is equivalent in thermal conductivity brick wall 2.5 bricks thick (51 cm) will, as well as when sawing logs as a result of their runaway.
fins, sawing machines. .- ends. than pine needles.
Heat capacity wood is significant, the heat capacity coefficient of dry wood is C = 1.6 KJ/kg∙ºС.
Another valuable property of wood is its resistance to many chemical and biological aggressive environments. She is chemically more resistant material than metal and reinforced concrete. At ordinary temperatures, hydrofluoric, phosphoric and hydrochloric (low concentration) acids do not destroy wood. Most organic acids do not weaken wood at ordinary temperatures, so it is often used for structures in chemically aggressive environments.
Mechanical properties of wood
Strength. Wood is a medium-strength material, however, its relative strength, taking into account its low density, allows it to be compared with steel.
Wood is an anisotropic material, so its strength depends on the direction of the forces applied to the fibers. When forces act along the fibers, cell membranes work in the most favorable conditions and wood shows the greatest strength.
The average tensile strength of pine wood without defects along the grain is:
Tensile – 100 MPa.
When bending – 80 MPa.
Under compression – 44 MPa.
When stretched, compressed and sheared across the fibers, this value does not exceed 6.5 MPa. The presence of defects significantly (by ~30%) reduces the strength of wood in compression and bending, and especially (by ~70%) in tension. The duration of the load significantly affects the strength of wood. Under unlimited long-term loading, its strength is characterized by a long-term resistance limit, which is only 0.5 of the strength limit under standard loading. Wood exhibits the greatest strength, 1.5 times higher than short-term strength, under the shortest shock and explosive loads. Vibration loads, causing stress to change in sign, reduce its strength.
Wood hardness(its degree of deformability under load) significantly depends on the direction of action of the loads in relation to the fibers, their duration and the moisture content of the wood. Stiffness is determined by the elastic modulus E.
For conifers along the fibers E = 15000 MPa.
In SNiP II-25-80, the modulus of elasticity for any type of wood is Eo = 10,000 MPa. E90 = 400 MPa.
At high humidity, temperature, as well as under the combined action of permanent and temporary loads, the value of E is reduced by the operating condition coefficients mв, mт, mд< 1.
Effect of humidity. A change in humidity ranging from 0% to 30% leads to a decrease in wood strength by 30% of the maximum. Further changes in humidity do not reduce the strength of the wood.
Transverse changes in humidity (shrinkage and swelling) lead to warping of wood. The greatest shrinkage occurs across the fibers, perpendicular to the annual layers. Shrinkage deformations develop unevenly from the surface to the center. During drying, not only warping appears, but also shrinkage cracks.
To compare the strength and stiffness of wood, the standard moisture content is set to 12%
B12=BW,
where α is the correction factor, for compression and bending α = 0.04.
Effect of temperature. As the temperature rises, the tensile strength and modulus of elasticity decrease, and the fragility of wood increases. The tensile strength of wood Gt at a temperature t ranging from 10 to 30 °C can be determined based on its initial strength - G20 at a temperature of 20 °C, taking into account the correction factor β = 3.5 MPa.
Gt = G20 – β(t-20).
Construction plywood
Construction plywood is a sheet wood material factory made. It consists, as a rule, of an odd number of thin layers - veneers. The fibers of adjacent veneers are located in mutually perpendicular directions.
SNiP II-25-80 for the design of wooden structures recommends the following types waterproof plywood as construction:
1. FSF brand plywood glued with phenol-formaldehyde adhesives. This plywood is produced:
Made from birch wood (5- and 7-layer, 5–8 mm thick or more).
Made from larch wood (7-layer, 8 mm thick or more).
Sheets of plywood with a thickness of more than 15 mm are called plywood boards. The shear strength of plywood in a plane perpendicular to the sheet is approximately 3 times higher than the strength of wood when chipped along the grain, which is its important advantage.
The modulus of elasticity of birch plywood along the grain is 90%, and across it is 60% of the modulus of elasticity of wood along the grain. The elastic moduli of larch plywood are 70% and 50% of the Eo of wood, respectively.
1. Banelized plywood (FBS) differs from FSF brand plywood in that its outer layers are impregnated with waterproof, alcohol-soluble resins. It has a thickness of 7 - 18 m. Its strength along the grain is 2.5 times, and across it is 2 times greater than the strength of coniferous wood along the grain. Used in particularly unfavorable humidity conditions.
Rotting and protection of wooden structures from rotting
Rotting- This is the destruction of wood by the simplest plant organisms - wood-destroying fungi. Some fungi infect still growing and drying trees in the forest. Warehouse mushrooms destroy timber during storage in warehouses. House mushrooms - (merilius, poria, etc.) destroy the wood of building structures during operation.
Fungi develop from cells called spores that are easily transported by air movement. Growing, the spores form a fruiting body and a mycelium of the fungus - a source of new spores.
Rot protection
1. Wood sterilization in the process of high temperature drying. Warming up wood at t > 80°C, which leads to the death of fungal spores, myceliums and fungal fruiting bodies.
2. Constructive protection assumes an operating mode when the wood moisture content is W<20% (наименьшая влажность при которой могут расти грибы).
2.1. Protecting wood from atmospheric moisture– waterproofing of coatings, required roof slope.
2.2. Protection against condensation moisture– vapor barrier, ventilation of structures (drying vents).
2.3. Protection against moisture from capillary moisture (from the ground)– waterproofing device. Wooden structures must rest on a foundation (with bitumen or roofing felt insulation) above the ground or floor level by at least 15 cm.
3. Chemical protection against rotting necessary when wood moisture is unavoidable. Chemical protection consists of impregnation with substances poisonous to mushrooms - antiseptics.
Water-soluble antiseptics(sodium fluoride, sodium fluoride) are colorless, odorless substances that are harmless to humans. Used indoors.
Oily antiseptics– these are mineral oils (coal oil, anthroscene oil, shale oil, wood creosote, etc.). They do not dissolve in water, but are harmful to humans, therefore they are used for structures in the open air, in the ground, above water.
Impregnation is carried out in autoclaves under high pressure (up to 14 MPa).
Protection against grinder beetles– heating to t>80oC or fumigation poisonous gases type hexachlorane.
Combustion and protection of wooden structures from fire
It is characterized by a fire resistance limit (about 40 minutes for a beam 17 x 17 cm, loaded to a stress of 10 MPa).
Protection
1. Constructive. Elimination of conditions favorable for fires.
2. Chemical(fireproof impregnation or painting). Impregnated with substances called flame retardants(for example, ammonium salt, phosphoric and sulfuric acid). Impregnation is carried out in autoclaves simultaneously with antiseptic treatment. When heated, fire retardants melt, forming a fire retardant film. Protective painting is carried out with compositions based on liquid glass, superfluoride, etc.
IN Lately Products made from laminated wood are becoming increasingly popular in the building materials market. The production technology of these products has been quite well studied and has been widely covered in special publications. The article describes the classification of laminated wood in Germany, since these products are most widespread in Europe.
Structural wood- what it is?
Engineered wood is the simplest type of construction lumber, made primarily from spruce or pine. This type of product is high-tech and is gradually gaining wide application in modern construction.
The manufacturing process begins with careful technical drying of softwood boards, separated by core, to the required moisture level, which, however, should not exceed 15%. In this case, it is necessary to ensure that the wood does not deform during the drying process. The dried boards pass through a planing line and are then manually or automatically sorted by strength. At the same time, defects are marked and cut out. First of all, sorting is carried out to ensure the required level of quality (standard DIN 4074 - sorting by strength). The sorting process can also take into account aesthetic requirements, which is sometimes necessary in the production of glued products for interior decoration premises. Then the blanks are spliced onto a toothed tenon. This is the process of producing a theoretically endless laminated board.
After the glue has dried, the workpieces pass through the planing line and are trimmed to length. Structural wood is widely used in modern production wooden structures thanks to high level quality.
Application:
– frame structures;
– formwork - superstructures, extensions;
– ceilings;
– interior decoration.
Sorting classes: S10. (The figure indicates the permissible bending stress in newtons per mm 2).
Product Dimensions (mm): Standard Sections
| Width | ||||||
| Thickness | 120 | 140 | 160 | 180 | 200 | 240 |
| 60 | X | X | X | X | X | X |
| 80 | X | X | X | X | X | |
| 100 | X | X | ||||
| 120 | X | X | X | |||
Two-layer and three-layer glued beams
Name of this product helps to imagine their method of production, namely: two boards glued to each other. In this case, it is necessary that one of the boards be glued with the core facing out. And this is no coincidence, since it is precisely this gluing technology that makes it possible to significantly minimize cracks in wood. In addition, in the core area, which is the face of the glued two-layer beam, there are the fewest defects, which gives an undeniable advantage for the product in an aesthetic sense.
The process of manufacturing three-layer beams repeats the process of manufacturing two-layer beams, the only difference is that in this case not two, but three boards are glued together. The manufacturing process proceeds in the same way as in the case of the production of structural wood, with the addition of the operation of gluing the lamellas along the face and planing the beams.
Acceptable cross-sectional dimensions of individual lamellas:
– max. width: 240 mm;
– max. thickness: 80 mm;
– max. cross-sectional area of the board: 150 sq. cm;
– depending on the cross-section, the length reaches 18 m.
Sorting classes: S10, S13.
Application area:
– frame structures;
– frame structures;
– rafters;
– supports.
Product dimensions for two-layer and three-layer beams (mm):
| Double-layer beams | Three-layer beams | |||||||
| Width | ||||||||
| Height | 80 | 100 | 120 | 140 | 160 | 180 | 200 | 240 |
| 100 | X | X | ||||||
| 120 | X | X | X | |||||
| 140 | X | X | X | |||||
| 160 | X | X | X | X | X | X | ||
| 180 | X | X | X | X | X | |||
| 200 | X | X | X | X | X | X | ||
| 220 | X | X | X | X | ||||
| 240 | X | X | X | |||||
Multilayer laminated wood
Multilayer laminated wood just by its name determines the production method. Individual blanks (boards) are glued together in length and thickness. In Germany, the main share of production of multi-layer laminated wood comes from pine or spruce.
Application area:
– awnings;
– winter gardens;
– rafters;
– beam structures;
– bridges;
– warehouse, sports and production facilities;
– supports;
– racks;
– railings;
- gazebos and galleries.
The permissible thickness of lamellas for straight building elements without special climatic requirements is from 6 to 42 mm.
Straight building elements with climatic requirements - from 6 mm to 33 mm.
Strength classes: BS11, BS14, BS16, BS18.
Product dimensions (mm): Standard sections with length: 12-18 (24 m).
Product dimensions (mm): Standard sections at length: 12-18 (24 m)
| Width | |||||||
| Height | 60 | 80 | 100 | 120 | 140 | 160 | 180 |
| 100 | X | ||||||
| 120 | X | X | X | X | |||
| 140 | X | ||||||
| 160 | X | X | X | X | X | X | |
| 200 | X | X | X | X | X | X | |
| 240 | X | X | X | ||||
| 280 | X | X | X | ||||
| 320 | X | X | X | X | |||
| 360 | X | X | X | ||||
| 400 | X | X | |||||
Advantages of using multi-layer laminated wood:
– high level of strength and rigidity, and at the same time – low weight;
– high dimensional stability and conformity the right sizes;
– the formation of cracks is practically eliminated;
– absence of distortions and curvatures in the design of workpieces large section and length;
– the ability to manufacture products of any length and cross-section;
– high quality surfaces;
– chemical preservation of wood is not required (depending on the design) due to the low level of moisture in the wood (- especially well suited for chemically aggressive environments (for example, warehouses for storing fertilizers);
– product quality is guaranteed by constant monitoring of the production process.
Admission standards for the sale of laminated wood products in Germany
Production of glued and load-bearing wooden elements requires not only special technical knowledge, but also specially equipped production areas, specialized machines and installations, as well as measures to control product quality, i.e. Only high-quality products can be exported and used in construction.
Companies that set themselves the task of producing laminated wood elements for export must obtain the appropriate approval in accordance with DIN 1052 - 1 (EN 338) "Wood Processing Plants", Chapter 12.1. When obtaining a production permit, the manufacturing company receives a corresponding certificate of approval, which is divided into the following 4 groups:
Tolerance "A" (multi-layer laminated timber, two- and three-layer laminated beams)- confirmation of professional suitability for the production of laminated wood elements load-bearing structures all kinds. Basically, the production covers the production of wooden parts and multi-layer laminated wood in lengths specified by the manufacturer himself.
Tolerance "B" (multi-layer laminated timber, two- and three-layer laminated beams)- confirmation of professional suitability for the production of laminated timber elements of load-bearing structures (for example, beams, supports and racks with a supporting width of up to 12 m). As a rule, this tolerance category involves the production of straight structural elements from multi-layer laminated wood.
Tolerance "C" (structural wood)- confirmation of professional suitability for the production of glued special building elements in accordance with the conclusion of admission from the Institute construction technologies, Berlin (e.g. triangular support construction methods, scaffolding boards, timber block elements, formwork, end-glued edged lumber), especially for tenon joints.
Tolerance "D"- confirmation of professional suitability for the production of glued materials for walls and roofs, for panel structures of wooden houses.
In the approval standards of categories A, B, C (special structural elements) it is in any case stated that companies must prove the level of quality of finger jointing of multi-layer laminated timber elements in accordance with DIN 68140-1 standards.
In addition, the approvals "A" and "B" indicate that, in accordance with DIN 68140-1, special building elements and tenon joints are made from boards of the corresponding class.
P. A. Vypov
Commercial Director "EMITIMASH"
The manufacturing process begins with careful technical drying of softwood boards, separated by core, to the required moisture level, which, however, should not exceed 15%. In this case, it is necessary to ensure that it does not become deformed in the process.
Structural wood protection
Chemical methods of protecting wood are certainly effective, but they cannot always be used for a number of reasons. For example, restrictions in their use arise due to technological, organizational and production difficulties in processing timber, products and structures.
The probability and rate of biodegradation of wood in structures depend mainly on the temperature and humidity conditions in which it is operated. As a rule, in the field of construction, simple and affordable measures are sought to install either heat, vapor barrier, or ventilation, as well as provide reliable joints, protection from atmospheric influences, etc., aimed at maintaining a “dry” mode.
The importance of structural prevention can hardly be overestimated, given that in some cases it is the only and sufficient measure to protect wooden structures from adverse operational influences. Structural anti-rot prevention of wooden structures should be carried out in all buildings and structures, regardless of service life.
Basic requirements for structural anti-rot prevention:
1) protection of wood structures from direct moisture from precipitation, ground and surface waters, as well as from freezing and condensation moisture;
2) systematic drying of wood structures by ensuring drying temperature and humidity conditions (room ventilation);
3) use for structures of wood that has undergone atmospheric or chamber drying (if the humidity is less than 18%, fungi do not develop).
Glued laminated wood has been used for many years not only for installation wall structures, but also as a material for the manufacture of trusses, frame and arch systems. However, in fairness, we note that previously a complex roof made of structural timber did not always have the required strength. The reason is simple: builders were unable to take full advantage of the material due to shortcomings in its production. Most difficult place there were stitches. 
In the wall, such wood performed excellently, since here it was mainly subjected to only compression. Here's the montage rafter systems required greater strength due to complex loads in different directions (tension, torsion and, of course, compression). Insufficient shear strength led to partial destruction of the load-bearing roof system already in the first year of operation. Weaknesses in structural wood made installation and operation particularly difficult complex roofs.
In a few recent years The quality of laminated timber in Russia has improved significantly. This has made it possible for laminated wood to displace steel and concrete from many areas of construction, the roof trusses of which are now significantly inferior to wooden ones in many respects. But most importantly, it is now possible to successfully build long-span systems from structural timber and install complex roofs.
From numerous innovations in production wooden trusses Perhaps the most important thing was their reinforcement. Reinforcement has had a significant impact on strengthening all kinds of compressively bendable and simply bendable systems, eliminating the lack of their shear strength.
To give high reliability to the trusses, rods with a periodic profile of class A300-400, 14-25 mm, are glued inside the composite wood. in diameter. For standard loads on roof systems, it is also permissible to use reinforcement class A240. It is pre-degreased, treated with an anti-corrosion substance, in some cases, threads are cut on the rods along the gluing length.
Complex adhesives are used as adhesives. epoxy resins, which contain marshalite (ground sand) or ED-20 type resins. With their help, steel rods are inserted at an angle of 30-40o towards the fibers. The joints and assemblies of rafter system modules are secured with bolts or even welding, if the heat resistance of the adhesive used allows this. Thus, with the help of embedded elements, super-strength anchoring of the nodal connections of the roof trusses was ensured.
The next step in improving the installation of rafter systems was the use of V-shaped anchors. They are used to secure embedded parts in laminated veneer lumber. The reliability of truss truss connections using this method exceeds the strength of the connections concrete structures. Tests have shown that under extreme loads the truss itself is destroyed, but the connection remains intact.
With the described technology, the installation of complex roofs has become much easier, and their service life has increased several times. Reinforcement has opened up wide opportunities for the installation of rafter systems for stadiums, ice palaces and other large-scale objects. Now builders have a material that is sometimes not inferior to steel in strength, but at the same time much lighter, which is very important in the installation of complex roofs. In addition, many manufacturers are now capable of producing laminated roof trusses up to half a meter thick and over two meters high.
Antiseptic for structural wood Vidaron (Vidaron)
The product is ready for use.
Properties:
- does not wash out;
- from fungus;
- from insects;
- penetrates deeply;
- for use outdoors and indoors.
Description:
Ready to use, water impregnation to protect wood from the action of insects and house fungus, which cause deep decay of wood. Impregnation does not cause corrosion metal elements. Effectively protects against atmospheric conditions - does not wash out. Can be coated with any finishing product.
Application:
For general and industrial protection of wooden elements, construction and structural wood installed in open spaces exposed to atmospheric conditions, as well as in closed spaces. The product is approved in safety classes I, II, III.
Compound:
- triazoles, amines, propiconazole.
Mode of application:
Preparing the base:
- wood intended for impregnation must be cleaned and dry, with a moisture content not exceeding 25%. 
Impregnation:
- mix the preparation thoroughly before use and during painting;
- application and drying of the product cannot occur under poor atmospheric conditions;
- apply at substrate and ambient temperatures from +5 to +30°C;
- apply twice by brush, by spraying, at intervals of at least 2 hours, by immersion with whole elements - for at least 30 minutes or in pressurized chambers;
- after impregnation, keep the wood for min. 72 hours under, on pads;
- you can stay in the rooms in which the wood has been impregnated after intensive ventilation for 3 days.
Attention - the dye is only an indicator of the place of painting, does not have any biocidal properties and can wash out.
Color spectrum:
colorless, brown, green.
Packing method:
packaging from synthetic materials– 5 kg, 20 kg.
Consumption and performance:
− 140 kg/m3 of wood, safety class 3 – wood affected by leaching factors;
− 800 g of impregnation/m2 of wood area - double painting, safety class 2, wood that is not affected by leaching factors (packaging 5 kg up to 6.25 m2);
− 600 g of impregnation/m2 of wood area – double painting, 1st safety class, wood that is not affected by leaching factors (packaging 5 kg up to 8 m2).
Warranty period:
36 months from production date.
Storage and transportation:
Protect the drug from freezing. Store in dry, ventilated areas, away from food products and feed, in places inaccessible to children. During transportation, protect from movement, damage or deterioration. Prevent penetration into soil and water. Dispose of drug waste in accordance with waste regulations or use it in accordance with its intended purpose. Packaging waste should be recycled.
Health and Safety:
Contains propicanazole. May cause an allergic reaction. Keep away from children. Do not inhale vapor/spray liquid. In case of contact with eyes, rinse immediately with plenty of water and consult a doctor. Wear suitable protective clothing and suitable protective gloves. Use only in well-ventilated areas. In case of poisoning or allergic reaction See a doctor immediately. If any alarming symptoms occur, immediately call a doctor or take the victim to the hospital, show the drug packaging or label.
ATTENTION! Place the unconscious patient in a standard lateral position, ensure he is calm, protect him from heat loss, and control his breathing and pulse. Never induce vomiting or give anything to an unconscious or fainting person to swallow. Detailed information is contained in the drug characteristics sheet. The product is biocidal and should be used with special precautions. Please read the label and information insert before use.
Wood in construction
Monolithic wood Monolithic structural wood is obtained as a result of double sawing of a log. Thanks to this, the side and front parts of the elements are flat and rectangular in shape. The most common are: boards, beams, slats and four-edged logs - hewn on four sides.
Glulam is produced by gluing together several layers of longitudinal wooden planks or strips of plywood. In this way, structural elements are created, the length of which even reaches 40 m. They are leveled on four sides and, if the need arises, they are milled and impregnated. Elements are created from laminated wood non-standard forms(arc, trapezoid).
The most commonly used materials for its production are pine, spruce or Scandinavian spruce. Laminated timber is intended primarily for large structures, but is sometimes also used in single-family construction. It surpasses traditional lumber in strength, so it can be used to make elements of very large widths. 
Easy to process. It has low humidity - 10-12%. Structures made from it are not deformed. Many structural elements are factory-varnished or specially impregnated and wrapped in film for the duration of transportation. I-beams Made from OSB boards, plywood or laminated wood.
They are characterized by very high strength, low weight, not prone to deformation, and high dimensional accuracy. Due to their low weight, installation of such beams is very simple and does not require the use of complex instruments. Mainly used as floor beams, rafters or posts. During transportation, the beams are placed on special pallets. Coniferous trees are most suitable...
For construction structural elements First of all, coniferous wood - pine, spruce - should be used. These varieties have great strength, and due to the fairly high resin content, they are resistant to changing atmospheric conditions. In addition, they are widely available and relatively cheap.
The lightest and most durable structural wood is larch. But larch, as a species, is protected, its felling is limited, so it is sold at very high prices. Sometimes structural wood is made from deciduous trees such as poplar or alder. Wooden parts are used to make the most different designs– walls, rafters, stairs, canopies, ceilings: Wood is an excellent construction material. It is durable, easy to process, relatively inexpensive and, importantly, lightweight.
Most often used in construction:
Boards. Typically they have a width of 75 to 250 mm and a thickness of 19-45 mm. They are mainly used as elements that strengthen the structure. Also used for making roofing sheathing. Sometimes rafters in the form of lattice are made from boards (usually in houses where the attic is not a living space);
The beams have a width from 100 to 250 mm and a thickness from 50 to 100 mm. They are mainly used for the manufacture of rafters and floor beams;
The bars usually have a square cross-section with sides 100x100 mm, 175x175 mm. Most often, they are used to make mauerlats (lower horizontal rafter supports);
Reiki (slats).
Their width is usually about 38-75 mm. Used for making various types frames (for slabs, for wood cladding). They are also used as counter-battens in the manufacture of rafters.
Structural wood in Ukraine is the simplest type of construction lumber, made mainly from spruce or pine. This type of product is high-tech and gradually 
o is widely used in modern construction.
The manufacturing process begins with careful technical processing of softwood, separated according to the core, to the required moisture level, which, however, should not exceed 15%. In this case, it is necessary to ensure that it does not become deformed in the process. The dried boards pass through a planing line and are then manually or automatically sorted by strength. At the same time, defects are marked and cut out. First of all, sorting is carried out to ensure the required level of quality (standard DIN 4074 - sorting by strength). During the sorting process, aesthetic requirements can also be taken into account, which is sometimes necessary in the production of glued products for interior decoration. Then the blanks are spliced onto a toothed tenon. This is the process of producing a theoretically endless laminated board.
After the glue has dried, the workpieces pass through the planing line and are trimmed to length. Structural timber is widely used in modern timber construction due to its high level of quality.
The first main advantage of wood compared to other construction materials is the constant renewal of its reserves. This is typical for our Motherland, a significant part of which is covered with forests. Soviet Union has a vast green factory, on the territory of which, every day, every hour, the beneficial forces of nature create wonderful materials needed in various industries National economy. When creating other structural materials (steel, concrete, plastic, etc.), a large amount of raw materials is consumed, the reserves of which are not renewed, but are constantly running out. In addition, the creation of most structural materials requires large amounts of energy, a shortage of which is already felt in many countries. The process of creating wood uses solar energy, the reserves of which are colossal.
The second advantage of wood is its low density and relatively high specific strength and rigidity. The corresponding table describes these indicators for wood and basic structural materials.
This table gives the maximum (numerator) and minimum (denominator) strength limits and elastic moduli of pine ( conifers), ash (deciduous ring-vascular) and birch (deciduous disseminated vascular) at a humidity of 12%. From the given data it is clear that the maximum specific strength of wood of all species is approximately equal to the specific strength the best varieties steel and is 4 times higher than the specific strength of steel. The maximum specific stiffness of wood of all species is approximately equal to the specific stiffness
steel and significantly exceeds the specific rigidity of duralumin and fiberglass.
The third advantage of wood compared to other structural materials is its easier workability.
A decisive role when choosing wood for the manufacture of many products and structures is also played by its low thermal and electrical conductivity, high sound insulation, biological compatibility, high acoustic properties, aesthetics, chemical resistance, etc.
Long-term observations indicate that wooden houses equipped with objects made of natural wood, a person feels much better than in stone and reinforced concrete ones interiors made of plastic. Replacement of reinforced concrete and stone buildings wooden in agriculture helps to increase livestock productivity. Studies of the acoustic properties of materials have shown that wood is the best and so far indispensable for the manufacture of soundboards of musical instruments. The presence of aggressive environments in chemical production shops dictates the need to replace metal and reinforced concrete structures wooden ones as more resistant to chemical influences.
However, defects that significantly reduce the quality of wood products are low strength and rigidity and in directions perpendicular to the fibers, a significant reduction mechanical characteristics with increasing humidity, creep even at normal temperatures gives rise in some cases to mistrust of wood as a structural material. This mistrust is largely a consequence of the relatively little knowledge of the strength and rigidity of wood products. Thorough theoretical and experimental studies of these issues are necessary to develop recommendations rational use wood and products and determining their reliability and durability.
The use of wood in combination with other structural materials deserves special attention. In this case you can use positive properties wood and compensate for its shortcomings. The use of various materials (wood, metal, plastics, reinforced concrete) in combination ensures the most effective use of the properties inherent in each of them. Thus, the role of wood as a structural material should constantly increase.
