Publication date: 03/03/2018 00:00
What loads can the beam withstand?
Beam and logs have long been used in Russia for the construction of houses. wooden buildings have a number of advantages:
- Ease of construction.
- High construction speed;
- Low cost.
- Unique microclimate. Wooden house“breathes”, the air in it is much lighter and more pleasant;
- Excellent operational characteristics;
- A wooden house holds heat well. It is 6 times warmer than brick buildings, and 1.5 times warmer than foam concrete buildings;
- Various types and sizes of this lumber allow you to realize a wide variety of projects and design ideas.
This type of building material is a log rectangular section. It is considered the cheapest lumber and at the same time very convenient for construction.
A beam is made from saw logs, conifers.
- Double-edged - processed (cut off at the log) only two opposite sides, while the other two are left rounded.
- Three-edged. There are three sides cut off.
- Four-edged - cut 4-sides.
Dimensions:
The standard length of the beam is 6 meters. Glued laminated timber is a prefabricated structure, so here the length can reach 18 meters.
Section dimensions
- Thickness from 100 to 250 mm. The section step size is 25 mm, that is, the thickness is 100, 125.
- Width from 100 mm to 275 mm.
The choice of cross-section of the beam must be approached with particular care. After all, the safety of the building will depend on what load this building material can withstand.
For the correct calculation of the load, there are special formulas and programs.
1. Permanent. These are the loads on the beam that the entire structure of the building exerts, the weight of the insulation, finishing materials and roofs.
2. Temporary. These loads can be short-term, rare and long-term. These include soil movements and erosion, wind and snow loads, the weight of people at construction works Oh. Snow loads are different, they depend on the region where the building was erected. In the north, the snow cover is greater, so the load on the timber will be higher.
In order for the calculation of the load to be correct in the formula (it can be found on the Internet), both types of loads, the characteristics of the building material, its quality, and humidity must be entered. Especially carefully you need to calculate the load on the timber during the construction of the rafters.
What load can a beam 150x150 withstand A bar with a section of 15 by 15 cm is widely used in the construction of buildings. It is used for the manufacture of supports, formwork and for the construction of walls, as it can withstand heavy loads. But the size of 15 by 15 is better to use for building houses in the southern regions, in the north you need additional insulation walls, since this lumber stores heat only at an air temperature of -15 degrees. But if you use a glued beam of this size, then in terms of its heat-saving properties it will be equal to a beam with a section of 25 by 20 cm.
What load can a beam 100 by 100 mm withstand
This beam is no longer so reliable, it can withstand less load, so its main application - manufacturing rafters and ceilings between floors. It is also necessary in the construction of stairs, the manufacture of props, arches, the design of attics, the ceiling of the house. You can also make a frame of a panel one-story house out of it.
What load can a beam 50 by 50 mm withstand
A beam of 50x50 mm is in great demand. You can’t do without this size when, the way it is auxiliary material. Of course, it is not suitable for building walls, since it can withstand a small load, but for building battens for exterior finish walls, frames, partitions, this size is needed. A wall frame is made from a 50 by 50 timber, onto which drywall is then attached. Here you can use the most various mounts from nails to staples or wire.
Wooden floor beams are often the most economical option in the construction of a private country house. At the same time, it should be noted that wooden beams are easy to manufacture and easy to install, have low thermal conductivity compared to steel or reinforced concrete structures. Main disadvantage wooden beams- low mechanical strength, requiring large sections, as well as low resistance to damage by microorganisms and wood-boring insects and combustibility. Therefore, wooden floor beams must be carefully calculated for the required load and treated with antiseptic and fire protective equipment.
Beams are led into the wall by at least 120 mm and waterproofing is arranged around the perimeter, except for the end. In addition, it is desirable to fix the beam with an anchor embedded in the wall.
The cross section of the beam and the step of laying the beams is calculated when designing the house, depending on the width of the overlapped span. If there is no such project, then the beam section is chosen larger, and the step of laying the beams is smaller. Best section for a wooden beam - rectangular with a ratio of width to height 1: 1.4. So with a beam width of 150 mm, its height should be about 210 mm. It should be noted that the optimal span for wooden beams is in the range of 2.5-4.0 meters. Floor beams are laid along a short section of the span. Installation step of wooden beams frame structure it is recommended to choose equal to the installation step of the frame racks.
When choosing a section of a wooden beam, take into account the load of the self-weight of the floor, which for beams floors, as a rule, is 190-220 kg / m 2, and the load is temporary (operational), the value of which is taken equal to 200 kg / m 2. Therefore, it is recommended to calculate the cross section of wooden beams for a floor load of 400 kg / m 2.
You can determine the cross section of wooden floor beams at a load of 400 kg / m 2, depending on the span length and installation step, according to table 1.
Table 1. Optimum sections of wooden floor beams at a load of 400 kg / m 2.
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installation step, |
Span length, m |
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If during the construction of an interfloor or attic floor it is not planned heat, sound insulation, and also if this is a floor with an unused attic, then for lower load values it is possible to determine from table 2 minimum dimensions sections of wooden floor beams.
Table 2. Minimum sections of wooden floor beams for loads from 150 to 350 kg / m 2.
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Cross-section of beams with span length, m |
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In conclusion, it can be noted that the installation step of the floor beams for this structure is optimal, and the cross section must be determined from the tables.
If the section of the wooden floor beams is not enough, it is not enough time for the floor to walk, additional supports should be installed under the floor beams. This can be done in the form cross beam supported by walls or columns.
If the installation of an additional support under the floor beams on the lower floor is not desirable, then you can install a transverse beam on top of the floor beams and fasten it to them, and if possible, to the central run of the truss system. This will redistribute the load between the beams.
There is another option to eliminate the deflection of the beams - to reduce the step of their laying.
Added: 05/25/2012 09:14
Forum discussion:
At my dacha, they made the overlap of the 2nd floor. The logs were laid (beam 150 * 150mm, step 500mm), plywood nailed on top = 10mm thick. In some places, the overlap walks: up and down. Tell me, please, did I take the step of the beam correctly and how can I strengthen the structure?Today, a variety of materials are used for construction, but wooden beams are most often in demand. They are used for the construction of the truss system, for the organization of floors of attics, basements and between floors. It is wooden structures that are used in the construction of the floor along the logs. This material is durable, able to withstand numerous loads, environmentally friendly and relatively low cost. If a wooden beam is used, it is necessary to first carry out calculations regarding their length. If there is no experience, then it is better to entrust the work to specialists.
Loads on wooden structures
If floor beams are used, it should be taken into account what load will be in general. This takes into account:
- own weight of a wooden beam;
- weight from inter-beam filling, i.e. insulation, waterproofing and other things;
- sheathing.
The calculation is carried out taking into account what kind of insulation is used, what step of the beams is taken (the amount of material depends on this). The issue of insulation should be taken seriously. Cold attic will lead to an increase in heating costs, this is approximately 15% of additional costs. To insulate the attic, you can purchase fiberglass or basalt slabs. They are relatively lightweight and install quickly.
The weight from furniture, equipment and people is taken into account. Usually the value is taken as an average of 50 kg / m² for hemming and inter-beam filler. The operational load according to SNiP 2.01.07-85 for overlapping in this case will be equal to:
70 * 1.3 = 90 kg / m², while
"70" is the standard, and 1.3 is the so-called safety factor.
The total value is:
50 + 90 = 130 kg/m².
The value should be rounded up, the figure is 150. If heavy material is purchased for insulation, then general meaning will be different. It will be 245 or 250 kg / m².
50 + 1.3 * 150, where 150 kg / m² is normative value.
If the attic is used as living space, then the calculated load level rises to 350 kg / m².
This should not be forgotten, otherwise the design will not turn out as strong as it is necessary. For ordinary interfloor, a standard value of 350-400 kg / m² is used.
Cross section and other parameters
To measure the cross section of timber beams, data such as:
Table 1. Section selection truss systems.
- product length for the overlapping device - L;
- product height - h;
- beam width - s.
For construction work, it is recommended to use products of rectangular section, while the height and width should be in a ratio of 1.4: 1. Optimal Height should be 100-300 mm, and the width - 40-200 mm (depending on the purpose of laying the material). When choosing a height, it is necessary to focus on what kind of heat insulator will be bought, since after laying it should go flush with the surface, not form cavities and gaps after sewing.
If logs are used for work, then it is best to take the diameter equal to 110-300 mm - this is the most optimal size. When constructing a floor made of wooden beams, attention should be paid to what the laying step will be. It can be equal to 30-120 cm, it all depends on the features of the future structure and the expected loads. Often the step is chosen based on what the insulation will be. For building a house frame technology it must be equal to the pitch of the racks used. For example, if vertical racks walls are mounted in increments of 60 cm, then the distance between the lags is made equal to 60 cm.
How is the data calculated? There are specially developed standards, according to which any calculation is carried out. Using them, it must be remembered that the deflection for an interfloor ceiling can be 1/350, and for an attic - 1/200 of the length of the product.
Table 2 attic floors depending on the span at a load of 400 kg per 1 m2.
For example, when a calculation is carried out taking into account the beam section, the following steps and span lengths are observed:
- section of a wooden beam 75 * 100 mm, step - 60 cm, span - 200 cm;
- 75*150 mm, step - 100 cm, span - 200 cm;
- 75*200 mm, span - 200 cm, etc.
Such data are used when an interfloor floor is being constructed with a planned load of 400 kg / m². If it is at the level of 150-350 kg / m² for the attic (less often interfloor) floor, then you need to take the following data:
- load 150 kg/m², span 300 cm, beam section 50*140 mm;
- 200 kg / m², span - 300 cm, beam section 50 * 160 mm, etc.
These data are shown in table 1.
If logs will be used for the construction of the floor, then the data indicated in table 2 (with a weight of 400 kg / m²) are used for the calculation. When using the given data for calculation, it must be remembered that the products should be taken whole, without defects, including cracks, rot, falling knots.
When using wooden beams for construction, utmost attention should be paid to calculations. This concerns the calculation of the section and the step of the overlap, corresponding to its length of the span. It is necessary to immediately carry out all the calculations, do not forget that for attic, basement and interfloor structures, the loads will be completely different.
The main condition for any construction is the simplicity and reliability of the design, but in order to achieve this, it is necessary to produce correct calculations strength of the material. Since for the construction wooden houses, attic or attic space used wooden frame its choice must be approached with all responsibility, because the durability, reliability and stability of the built house will directly depend on what load the beam can withstand (100x100, 50x50, 150x150, etc.).
For the correct calculation of the load withstood by the beam, special programs or formulas can be used, but in this case, additional loads will have to be introduced into the calculations, which directly affect the strength of the structure. In order to calculate the load on the beam correctly, you will have to indicate the snow and wind effects that are present directly in the building region, as well as the characteristics of the materials used (heat isover, beam, etc.).
In this article, we will consider what kind of load a beam with a size of 50x50, 100x100, 150x150 can withstand. various designs, such as a log house, wooden floor and the truss system, and as an example, we will analyze the latter, because this is the most responsible and difficult work.
In the photo you can see the varieties of timber, which differ not only in shape, but also in the load capacity.
What will be discussed:
How does the cross-section of a log house affect its reliability?
When building a roof prerequisite its reliability is the cross-section of the timber used and the type of wood, which affects the durability.
Performing the calculation with your own hands, you will need to take into account such indicators as:
- what is the mass of all roofing building materials;
- the weight of the attic or attic finish;
- for truss supports and beams, the calculated value is taken into account;
- the thermal and sedimentary effects of nature are taken into account.
In addition, you will need to specify:
- distance between beams;
- the length of the gap between the rafter supports;
- the principle of fastening the rafters and the configuration of its truss;
- the severity of precipitation and the effect of winds on the structure;
- other factors that may affect the reliability of the design.
All these calculations can be done manually using special formulas. But it will be simpler both in time and in quality to calculate the load of the beam using special programs, and even better when these calculations are performed by a professional.
What requirements must the beam meet?
So that the entire truss system is strong and reliable in quality building materials will have to take full responsibility. For example, there should be no defects on the beam (cracks, knots, etc.), and its moisture content should not exceed 20%. In addition, a log house of any size (50x50, 100x100, 150x150, etc.) must be treated with protective agents against shashel and other insects, rotting and fire.
Also, when choosing a material, you will have to take into account that additional loads may be applied to the timber, such as:
- Continuous load beam. These include directly the weight of the entire truss system, which includes: facing and roofing materials, heaters, etc. The data obtained for each material are summarized.
- Short-term loads can be of several types: especially rare, short-term and long-term effects. The first type includes incidents that happen very rarely (earthquakes, floods, etc.). Wind and snow impacts, the movement of people repairing the roof, etc. are short-lived. All other impacts that occur within a certain period of time are long-term loads.
We determine the wind and snow load on the beam
To determine what load the beam can withstand (100x100, 150x150.50x50, etc.) under wind and snow exposure, you can use certain tables.
To determine the effect of snow on the rafters different section apply the formula S=Sg*µ.
- Sg - is the calculated weight of snow lying on the ground, which affects 1 m².
Important! This value cannot be compared with the roof load.
- µ is the value of the load on the roof surface, which varies from horizontal to sloping. This coefficient can be various meanings, it all depends on the slope of the roof.
With a surface slope of up to 25 degrees, µ takes on the value 1.
When the slope of the roof is in the range of 25-60 degrees, µ is 0.7.
With a slope of 60 degrees or more, the coefficient µ is not taken into account because it practically does not affect the truss system.
In addition to the snow load, before construction, the rafter system is calculated wind load on the wooden beam 50 to 50, 100x100, etc. If these indicators are not taken into account, as a result, everything can end in failure. Table values and the formula W=Wo*k are used for the calculation.
Wo - is a tabular value of the wind load for each individual region.
k is the wind pressure, which has different meanings as altitude changes. These indicators are also tabular.
The table of beam loads shown in the photo when exposed to the elements is easy to use, you just need to remember that the 1st column shows the values \u200b\u200bfor the steppe, desert regions, rivers, lakes, forest-steppe, tundra, seashores and reservoirs. The next column contains data related to urban areas and areas with 10 meter obstacles.
Important! In calculations, it is desirable to use information on the direction of wind movement, because this can make an important correction to the results.
By what rules is the desired cross section of the beam calculated?
Several parameters influence the selection of the log section for the truss system:
- what is the length of the rafter construction;
- the distance between each subsequent beam;
- the results of load calculations for the corresponding area.
Today, for each specific area, there are special tables with data already entered on the load values \u200b\u200bfor truss systems. An example is the Moscow region:
- in order to install a Mauerlat, you can use a bar with a section of at least 100x100, 150x100 and 150x150;
- timber 200x100 can be used for diagonal valleys and rafter supports (legs);
- runs can be created from wood 100x100, 150x100 or 200x100;
- log house 150x50 will become optimal solution for tightening;
- it is best to use a log house 150x150 or 100x100 as racks;
- a 150x50 rafter is suitable for a cornice, struts or filly;
- crossbars are best installed from rafters 150x100 or 200x100;
- As a sheathing or frontal, you can use a board of at least 22x100.
The above data are optimal, that is, less than this value, the material cannot be used. Also, all dimensions are in millimeters.
Summarize
To create a reliable and durable wooden structure you need to carefully calculate all possible loads, after which only acquire a beam. If you have doubts about the correctness of the calculations, it is best to use the services of a professional or use a special program that will calculate the allowable load on the timber (150x150, 100x100, etc.).
One of the most popular device solutions floors in private homes is to use load-bearing structure from wooden beams. It must withstand the design loads without bending and, moreover, without collapsing. Before proceeding with the construction of the ceiling, we recommend using our online calculator and calculating the main parameters beam structure.
