Beautiful and reliable.
And what is the basis of any roof?
From how correctly the calculation of the parameters of the elements will be carried out rafter systemwill depend on how much the roof is durable and reliable.
Therefore, at the stage of compiling the project of the building, a separate calculation of the rafter system is performed.
It is impossible to calculate correctly if you do not take into account the intensity of various loads that will affect the roof of the house in different periods.
Factors affecting the roof is customary to classify on:
And the newcomer is difficult to do it, as there are a lot of factors that affect the roof must be considered.
After all, besides the above factors, it is also necessary to take into account the weight of all elements of the rafter system and fasteners.
Therefore, special programs for calculation come to help calculators.
To learn the load on the rafters of our house, one should first calculate the weight of the roofing pie.
This calculation is easy, if you know the total area of \u200b\u200bthe roof and materials that are used when creating this cake itself.
At first, they consider the weight of one square meter of the cake.
The mass of each layer is summed up and multiplied by the correction coefficient.
This coefficient 1.1 is equal.
Here is a typical example of calculating the weight of the roofing cake.
Suppose you have decided to use Ondulin as roofing material.
And that's right!
After all, Ondulin is a reliable and inexpensive material. It is for these reasons that it is so popular among developers.
So:
We summarize the obtained data: 3 + 5 + 10 + 15 \u003d 33 kg.
Now the result obtained must be multiplied by 1.1.
Our correction coefficient.
The final figure is 34.1 kg.
This is the weight of one square meter of roofing cake.
The total area of \u200b\u200bthe roof, for example, 100 square meters. meters.
So, it will be weighing 341 kg.
This is very small.
Here in this and there is one of the advantages of Ondulin.
Moment is very important.
Because in many areas our winter drops a fairly decent amount of snow.
And this is a very large weight that is necessarily taken into account!
To calculate the snow load, a snow load card is used.
Determine your region and perform the calculation of snow load by the formula
In this formula:
- S is the desired snow load;
- SG - a lot of snow cover.
The weight of snow per 1 square is taken into account. meter.
This indicator is in each region.
It all depends on the location of the house.
To determine the mass and the map is used.
- μ is a correction coefficient.
The indicator of this coefficient on the roof angle depends.
If the angle of the slope is less than 25 degrees, the coefficient is equal to 1.
At the angle of inclination 25 - 60 degrees, the coefficient is 0.7.
If the angle of inclination is greater than 60 degrees, then the coefficient is not taken into account.
For example, the house is built in the Moscow region.
Skates have an angle of inclination of 30 degrees.
The map shows us that the house is located in the 3 district.
Snow mass per 1 square. The meter is 180 kg.
We carry out the calculation, not forgetting about the correction ratio:
180 x 0.7 \u003d 126 kilograms per 1 kV. meter roof.
To calculate the loads from the wind also use a special card with a breakdown by zones.
Use such a formula:
Wo is a regulatory indicator defined by the table.
Each region has its own wind tables.
And the indicator K is a correction coefficient that depends on the height of the house and the type of terrain.
The calculation of the length of the rafting leg belongs to the simplest geometric calculations.
Since you will need only two sizes: width and height, as well as Pythagore's theorem.
In order for the calculation to be more understandable, look at the drawing below.
We know two distances:
- And is a height from the bottom to the upper point of the inner part of the rafted.
First catat;
- B is a value equal to half of the width of the roof.
Second catat.
- C is a triangle hypotenuse.
c² \u003d (2 x 2) + (3 x 3).
TOTAL C² \u003d 4 + 9 \u003d 13.
Now it is necessary to get a square root out of 13.
You can, of course, take the brady's tables, but it is more convenient to the calculator.
We get 3.6 meters.
To this number now need to add the length of the removal d to get the desired length of the rafted.
The cross-section of the planks that we will use for the manufacture of rafters and other elements of the rafter system depends on how long it has a rafter, with which step they will be installed and from the magnitude of snow and wind load that exist in a particular region.
For simple designs Use the table of typical sizes and sections of the board.
If the design is very complicated, it is better to use special programs.
The distance between their bases is called.
Experts believe that the minimum distance should be 60 cm.
And the optimal distance is 1 meter.
We carry out the calculation distance between the rafters:
For example, the bottom of the roof of the roof is 12 meters.
Pre-select a step of rafted 0.8 meters.
12 / 0.8 \u003d 15 meters.
We add unit 15 + 1 \u003d 16 rafters.
If a fractional number turned out, then we would round it in the biggest.
Now from 12 meters should be divided into 16.
As a result, 1216 \u003d 0.75 meters.
Here is the optimal distance between the rafters on one slope.
A table, which was mentioned earlier can also be used.
For wooden beams The optimal value of the span is from 2.5 to 4 meters.
The optimal cross section is rectangular.
The ratio of height and width 1.4: 1.
The beam should enter at least 12 cm.
Ideally, the beams are fixed to anchors, which is installed in advance in the wall.
Waterproofing beams is performed "in a circle".
When calculating the beam section, the load is taken into account (as a rule, 200 kg / sq. Meter), and operational temporary load.
Its value is equal to the load constant - 200 kg / sq. meter.
Knowing the magnitude of the span and the beam installation step, the table is calculated by their cross section:
| Span (m) / installation pitch (m) | 2.0 | 2.5 | 3.0 | 4.0 | 4.5 | 5.0 | 6.0 |
| 0.6 | 75x100. | 75x150 | 75x200 | 100x200 | 100x200 | 125x200. | 150x225 |
| 1 | 75x150 | 100x150. | 100x175 | 125x200. | 150x200. | 150x200. | 175x250. |
If a more accurate calculation is required, then use the Romanov calculator.
Single roof - the easiest option of the roof.
But this option is not suitable for each construction.
And the calculation of the rafter is required in any case.
Calculations single Roof Start from determining the angle of inclination.
And it depends on that, first of all, what material you plan to use for the roof.
For example, for a professional flooring, the minimum angle is 8 degrees.
And the optimal - 20 degrees.
If online calculators perform simple calculations, then special software Capably Calculate everything you need.
And there are quite a lot of such programs!
The most famous of them are 3D MAX and autocadus.
These programs have only two drawbacks:
There are a number of free programs.
Most programs can be downloaded to your computer.
Or use them online.
Video on the calculation of rafters.
Slinge system. Calculation of rafters and overlap beams. Before embarking on the construction of the roof, of course it is desirable that its rafter system is designed for strength. Immediately after the publication of the past article " Double roof At home with their own hands, "I will have questions about the choice of the cross section of the rafters and beams of overlapping. Yes, to understand this issue on the expanses of our entire favorite Internet is really quite simple. There are a lot of information on this topic, but it is as always so scattered and sometimes even contradictory that inexperienced person, who in his life may not even come across such a subject as "conversion" (lucky someone), it is easy to confuse in these DeBries. I, in turn, try to now make up step by step algorithmwhich will help you independently calculate the rafter system of your future roof and finally get rid of permanent doubts - and suddenly it will not stand, but suddenly fall apart. Immediately I will say that I will not go deep into terms and various formulas. Well, why? In the light of so many useful and interesting things that you can score yourself. We need to just build a roof and forget about it. The entire calculation will be described on the example of the two-tie roof, which I wrote about in the last article. So, step number 1: Determine the snow load on the roof. For this we need a map of the snow loads of the Russian Federation. To enlarge the picture, click on it with the mouse. Below I will give a link for which it can be downloaded to my computer. On this map, we define the number of the snow region in which we build a house and from the table below, choose the corresponding snow load (S, kg / m²) corresponding to this region: if your city is on the border of the regions, choose a larger load value. You do not need to adjust the resulting digit depending on the angle of slope of our roof. The program we will use will do this itself. Suppose in our example we are building a house in the suburbs. Moscow is located in 3 snowdrows. The load for it is 180 kg / m². Step # 2: Determine the wind load on the roof. To do this, we will need a map of the wind loads of the Russian Federation. It can also be downloaded by reference below. On this map, we also select the corresponding number of the region and determine the value of the wind load (values \u200b\u200bare shown in the lower left corner): Next, the resulting digit must be multiplied by the correction coefficient "k", which in turn is determined by the table: here the column A is the open coast seas, lakes and reservoirs, deserts, steppes, forest-steppe and tundra; Column in - urban areas, forest arrays and other areas are uniformly covered with obstacles. Need to consider that in some cases the type of terrain may vary in different areas (For example, the house stands on the outskirts of the settlement). Then choose the values \u200b\u200bfrom the column "A". Return to our example again. Moscow is located in the I-M Windbine. The height of our house is 6.5 meters. Suppose it is built in the settlement. Thus, we take the value of the correction coefficient k \u003d 0.65. That is, the wind load in this case will be equal to: 32x0.65 \u003d 21 kg / m². Step # 3: You need to download myself on the computer, the calculation program made in the form of the Exel table. Next, we will work in it. Here is a link to download: "Calculation of the rafting system". Also here are the roads of snow and wind loads of the Russian Federation. So, download and unpack the archive. Open the "Calculation of the Slinge System" file, while we fall into the first window - "loads": here we need to change some values \u200b\u200bin cells flooded with blue. The entire calculation is performed automatically. Let's continue to consider our example: - in the "Source Data" plate, change the angle of inclination by 36 ° (what angle will be, so write, well, I think everyone is understandable); - Change the step of rafters, to the one we chose. In our case, it is 0.6 meters; - Narr. The roof (load from the own weight of the roofing material) is the value of this value from the table: for our example, we choose metal tile with a weight of 5 kg / m². - Snow. District - here we enter the amount of snow and wind load values, which we have earlier, that is, 180 + 21 \u003d 201 kg / m²; - insulation (mans.) - This value is left unchanged if we put the insulation between the rafters. If we make a cold attic without insulation - change the value to 0; - In the "Disease" table, enter the necessary sizes of the root. In our case, for metal tile, we change the pitch of the root of 0.35 m and the width is 10 cm. Leave the height without changes. All other loads (from their own weight of rafters and dohes) are taken into account by the program automatically. Now we look at what we did: we see the inscription "The carrying ability of the doomle is provided!" We do not touch anything else in this window, even to understand what the numbers are in other cells. If, for example, we will choose another step of rafters (more), it may turn out that the carrying ability of the doom will not be provided. Then it will be necessary to pick up other sizes of the root, for example, to increase its width, etc. In general, I think you will figure it out. Step number 4: Press the bottom of the working screen to the "Slop.1" tab and go to the Calculation window with two support points. Here, all the earlier incoming data made by us are already substituted by the program automatically (so it will be in all other windows). In our example, from the article "Double roof at home with your own hands" rafters have three points of support. But let's imagine that there are no intermediate racks and make a calculation: - Change the length of its horizontal projection on the line of its horizontal projection (cell flooded with blue). In our example, it is 4.4 meters. - In the "Calculation of the Slinge" plate, we change the value of the thickness of the rafted in (specified) to the selected one by us. We set 5 cm. This value must be more specified in the CTR cell (stable); - Now in the "Accepted H" string, we need to make the chosen width of the rafted in centimeters. It must be more values \u200b\u200bspecified in the Rows "HTR., (MUST.)" And "HTR., (Deflection)". If this condition is met, all the inscriptions at the bottom under the Scheme of the rafter will be of the form "condition performed". In the line "H, (by variety)" is indicated that the program itself offers to choose the program itself. We can take this figure, and we can take another. Usually choose the sections are available in the store. So, what happened to us shown in Figure: In our example, to comply with all strength conditions, it is necessary to choose rafters with a cross section of 5x20 cm. But the roof scheme shown by me in the last article has a rafted with three points of support. Therefore, for its calculation, go to the next step. Step number 5: Press the bottom of the working screen to the "Lock.2" tab or "Sling. 3 ". This opens a window of calculating rafters having 3 points of support. Selection of the tabs we need to produce depending on the location of the middle support (rack). If it is rightly the middle of the rafted, i.e. L / L1<2, то пользуемся вкладкой «Строп.2″. Если стойка расположена левее середины стропила, т. е. L/L1> 2, we use the "Lock.3" tab. If the rack is exactly around the middle, you can use any tab, the results will be the same. - on the rafter scheme I reconcile the sizes in the cells of bold blue (except RU); - In the same principle, which was described above, we choose the dimensions of the cross section of the rafter. For our example, I accepted 5x15 cm. Although it was possible and 5x10 cm. Just got used to work with such boards, and the safety margin will be more. Now IMPORTANT: From the figure obtained when calculating the figure we will need to write the value of the vertical load acting on the rack (in our example (see Fig. Above) it is equal to 343.40 kg) and the bending moment kghm). These figures will be needed to us further when calculating the racks and beams of overlapping. Further, if you go to the "Arch" tab, a window of calculating the rafter system is a skate arch (two rafters and tightening). I will not consider it, for our roof it will not suit. Too we have a big span between the supports and the small angle of slope. There will be raftered with a cross section of about 10x25 cm, which is certainly irreversible for us. For smaller spans, you can use this scheme. I am sure who I understand what I wrote above, he himself will figure it out with this calculation. If any questions appear, write in the comments. And we go to the next step. Step number 6: Go to the "Rack" tab. Well, everything is simple. - We defined previously values \u200b\u200bof the vertical load on the rack and the bending moment we introduce in the figure, respectively, in the cell "n \u003d" and "m \u003d". They were recorded in us in kilograms, we enter them in tons, while the values \u200b\u200bare automatically rounded; - Also in the figure change the height of the rack (in our example it is 167 cm) and put the size of the sections we have chosen. I chose a 5x15 cm board. Below in the center we see the inscription "Central provided!" and "Etcenter. Provided. " So everything is fine. The reserve coefficients "KZ" are very large, so you can safely reduce the cross section of the racks. But we will leave as it is. The result of the calculation in Figure: Step # 7: Go to the "Beam" tab. On the ceiling beams, the distributed load and focused ones. We need to take into account both. In our example, the beams of the same cross section overlap the spills of different widths. We, of course, make a calculation for a wider span: - in the "Distributed load" plate indicate the step and the breakage of the beams (we take 0.6 m and 4 m from the example); - We accept nation. (norms.) \u003d 350 kg / m² and nation. (calcul.) \u003d 450 kg / m². The values \u200b\u200bof these loads in accordance with the SNiP are averaged and taken with a good safety margin. They include load from its own overlap weight and operational load (furniture, people, etc.); - in the string "in the specified" enter the beam section selected width (in our example it is 10 cm); - In the lines "H, durability" and "H, Progibe", the minimum possible heights of the section of the beams under which it will not break and the deflection will be permissible. We are interested in a large of these numbers. The height of the section of the beam we take on the basis of it. In our example, the beam is suitable with a cross section of 10x20 cm: So, if we had no racks resting on the beams of overlapping, the calculation of this would be completed. But there are racks in our example. They create a concentrated load, so we continue to fill the signs "concentrated load" and "distribution + focus.": - In both plates we introduce the sizes of our flights (here I think everything is clear); - in the table "Concentrated load" change the values \u200b\u200bof the nation. (norms.) and nurts. (q.) On the figure that we got higher when calculating a rafted with three points of the support - this is a vertical load on the rack (in our example 343.40 kg) ; - in both plates enter the accepted width of the section of the beam (10 cm); - The height of the section of the beams is determined by the "Campering + focus" tablet. ". We again focus more. For our roof, we take 20 cm (see Fig. Above). This calculates the solving system is completed. I almost forgot to say: the estimated program used by us is applicable to the rafter systems made of pine (except Waemutov), \u200b\u200bspruce, European and Japanese larch. All used wood 2nd grade. When using another wood, the program will need to make some changes. Since other wood breeds in our country are rarely used, I will now not paint what you need to change. Read more.
-\u003e calculation of the rafter systemThe main element of the roof, perceiving and opposing all types of loads, is Slinge system. Therefore, in order for your roof to reliably oppose all environmental impacts, it is very important to do right calculations rafter system.
For independent calculation Characteristics of materials required for mounting the rafter system, I cite Simplified formulas calculation. Simplifications are made in the direction of increasing the strength of the structure. This will cause some increase in lumber consumption, but on small roofs of individual buildings it will be insignificant. This formulas can be used when calculating two-tie attic and attic, as well as single-sided roofs.
On the basis of the calculation methods below, the programmer Andrei Mutovkin (Andrei-Mutovkin's business card - Mutovkin.rf) has developed a program for calculating the solo system. At my request, he generously allowed to place it on the site. You can download the program.
The calculation technique was prepared on the basis of SNiP 2.01.07-85 "load and impact", taking into account the "change ..." from 2008, as well as on the basis of the formulas given in other sources. I developed this technique many years ago, and time confirmed its correctness.
To calculate the rafting system, first of all, it is necessary to calculate all loads acting on the roof.
1. Snow loads.
2. Wind load.
On the rapid system, except the above, the load from the elements of the roof is also available:
3. The weight of the roof.
4. The weight of the draft flooring and doom.
5. The weight of the insulation (in the case of a warmed attic).
6. The weight of the solo system itself.
Consider all these loads.
1. Snow loads.
To calculate snow load, we use the formula:
Where,
S - the desired snow load, kg / m²
μ - coefficient depending on the roof slope.
SG - Regulatory Snow Load, kg / m².
μ is a coefficient depending on the roof slope α. Dimensional value.
It is possible to approximately determine the angle of the liner of the roof α as follows the resulting of the height of H on half of the span - l.
The results are reduced to the table:
Then, if α is less than or equal to 30 °, μ \u003d 1;
if α is greater than or equal to 60 °, μ \u003d 0;
if a 30 ° calculate the formula:
μ \u003d 0.033 · (60-α);
SG - Regulatory Snow Load, kg / m².
For Russia, it is accepted on a card 1 of the mandatory application 5 SNiP 2.01.07-85 "Loads and Impact"
For Belarus, the regulatory SG light load is determined
The technical code of the established practice of Eurocode 1. Impact on the design part 1-3. General impacts. Snow loads. TKP EN1991-1-3-2009 (02250).
For example,
Brest (I) - 120 kg / m²,
Grodno (II) - 140 kg / m²,
Minsk (III) - 160 kg / m²,
Vitebsk (IV) - 180 kg / m².
Find the maximum possible snow load on the roof of 2.5 m high and a long span 7m.
The structure is in the der. Babenki Ivanovo region RF.
On the card 1 of the mandatory application 5 SNiP 2.01.07-85 "load and exposure" define SG - regulatory snow load for the city of Ivanovo (IV district):
SG \u003d 240 kg / m²
Determine the angle of the liner of the roof α.
For this, the height of the roof (H) is divided by half of the span (L): 2.5 / 3,5 \u003d 0.714
And on the table we will find the angle of the slope α \u003d 36 °.
Since 30 °, calculation μ We produce according to the formula μ \u003d 0.033 · (60-α).
Substituting the value α \u003d 36 °, we find: μ \u003d 0.033 · (60-36) \u003d 0.79
Then S \u003d SG · μ \u003d 240 · 0.79 \u003d 189kg / m²;
the maximum possible snow load on our roof will be 189kg / m².
2. Wind load.
If the roof is cool (α\u003e 30 °), then due to its sail, the wind presses one of the rods and strives to overturn it.
If the roof is common (α, then the lifting aerodynamic force arising when it is driving with its wind, as well as turbulence under the sips tend to raise this roof.
According to SNiP 2.01.07-85 "Loads and Impact" (in Belarus - Eurocode 1 Exposure on structures Part 1-4. General impact. Wind exposure), regulatory value The medium component of the wind load WM at the height Z above the ground should be determined by the formula:
Where,
Wo is the regulatory value of wind pressure.
K is a coefficient that takes into account the change in wind pressure in height.
C is an aerodynamic coefficient.
K is a coefficient that takes into account the change in wind pressure in height. Its values, depending on the height of the building and the nature of the terrain, are reduced to Table 3.
C - aerodynamic coefficient,
which, depending on the configuration of the building and the roof, can take values \u200b\u200bfrom minus 1.8 (the roof rises) to plus 0.8 (the wind presses on the roof). Since our calculation is simplified in the direction of increasing strength, the value C is taken equal to 0.8.
When building the roof, it is necessary to remember that the wind forces seeking to lift or disrupt the roof can reach significant values, and therefore, the bottom of each rapid leg must be carefully attached to the walls or to the matzam.
This is done by any means, for example, with the help of annealed (for softness) with a steel wire with a diameter of 5 - 6mm. With this wire, each rafter foot is screwed to the matsam or to the ears of the slab overlap. It's obvious that than the roof is harder, the better!
Determine the middle wind load on the roof one-storey house With the height of the skate from the ground - 6m. , an angle of slope α \u003d 36 ° in the village of Babenki Ivanovo region. RF.
3 applications 5 in "SNiP 2.01.07-85" find that Ivanovo region refers to the second wind area Wo \u003d 30 kg / m²
Since all buildings in the village are below 10m., The coefficient K \u003d 1.0
The value of the aerodynamic coefficient C is taken equal to 0.8
the regulatory value of the average component of the wind load WM \u003d 30 · 1.0 · 0.8 \u003d 24kg / m².
For information: If the wind blows into the end of this roof, it acts on its edge (breaking) force to 33.6 kg / m²
3. The weight of the roof.
Different types of roof have the following weight:
1. Slate 10 - 15 kg / m²;
2. Ondulin (Bituminous Slate) 4 - 6 kg / m²;
3. Ceramic tile 35 - 50kg / m²;
4. Cement-sand tiling 40 - 50 kg / m²;
5. Bituminous tile 8 - 12 kg / m²;
6. Metal tile 4 - 5 kg / m²;
7. Professional flooring 4 - 5 kg / m²;
4. The weight of the draft flooring, the root and the rafter system.
The weight of the black flooring is 18 - 20 kg / m²;
The weight of the lamb 8 is 10 kg / m²;
The weight of the actual stage system 15 is 20 kg / m²;
When calculating the final load on the solo system, all the above loads are summed up.
Now I will open you little secret. Sellers of some species roofing materials As one of the positive properties, their eases are noted, which, according to their assurances, will lead to a significant savings of lumber in the manufacture of a rafter system.
As a refutation of this statement, I will give the following example.
Calculation of the load on the rapid system when using various roofing materials.
Calculate the load on the rafter system when using the heavyweight (cement-sand tile
50 kg / m²) and the easiest (metal tile 5 kg / m²) of the roofing material for our house in the village of Babenka Ivanovo region. RF.
Cement-sand tile:
Wind Loads - 24kg / m²
Roof Weight - 50 kg / m²
Grub weight weight - 20 kg / m²
TOTAL - 303 kg / m²
Metal tile:
Snow Loads - 189kg / m²
Wind Loads - 24kg / m²
Roof Weight - 5 kg / m²
Grub weight weight - 20 kg / m²
The weight of the solo system itself - 20 kg / m²
TOTAL - 258 kg / m²
It is obvious that the existing difference in settlement loads (only about 15%) will not be able to lead to any tangible savings of lumber.
So, with the calculation of the total load q, acting on the square meter of the roof, we figured out!
I especially pay your attention: when calculating, carefully follow the dimension !!!
Slinge system It consists of individual rafters (rafter feet), therefore the calculation is reduced to the definition of the load on each rapid leg separately and the calculation of the cross section of a separate rafting leg.
1. Find a distributed load on the pattern meter of each rapid leg.
Where
QR is a distributed load on a rabbown meter of a rafter foot - kg / m,
A - distance between the rafters (step rafter) - m,
Q is the total load acting on the square meter of the roof - kg / m².
2. Determine the working plot in the rafter leg maximum length LMAX.
3. Calculate the minimum cross section of the material of the rafter.
When choosing a material for rafters, we are guided by the table of standard timber sizes (GOST 24454-80 lumber coniferous rocks. Sizes) that are reduced to Table 4.
| Board thickness - Section Width (B) | Board width - section height (H) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| 16 | 75 | 100 | 125 | 150 | |||||
| 19 | 75 | 100 | 125 | 150 | 175 | ||||
| 22 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | ||
| 25 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 32 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 40 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 44 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 50 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 60 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 75 | 75 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 |
| 100 | 100 | 125 | 150 | 175 | 200 | 225 | 250 | 275 | |
| 125 | 125 | 150 | 175 | 200 | 225 | 250 | |||
| 150 | 150 | 175 | 200 | 225 | 250 | ||||
| 175 | 175 | 200 | 225 | 250 | |||||
| 200 | 200 | 225 | 250 | ||||||
| 250 | 250 |
A. Calculate the cross section of the rafter foot.
We specify an arbitrarily width of the section in accordance with the standard dimensions, and the height of the section is determined by the formula:
H ≥ 8,6 · LMAX · SQRT (QR / (B · RIPS)) if the slope of the roof α
H ≥ 9.5 · LMAX · SQRT (QR / (B · RIPS)) if the slope of the roof α\u003e 30 °.
H - the height of the section cm,
B - the width of the section cm,
RiPridge - wood resistance to bending, kg / cm².
For pine and fir riesg is equal to:
1 grade - 140 kg / cm²;
2 grade - 130 kg / cm²;
3 grades - 85 kg / cm²;
SQRT - Square root
B. We check whether the magnitude of the deflection is stacked.
The normalized material deflection under load for all roof elements should not exceed L / 200. Where, L is the length of the work area.
This condition is performed with the faithfulness of the following inequality:
3,125 · QR · (LMAX) ³ / (b · h³) ≤ 1
Where,
QR is a distributed load on a rabbown meter of a rafter foot - kg / m,
LMAX is a working plot of a rafter foot of the maximum length m,
B - the width of the section cm,
H - the height of the section cm,
If the inequality is not respected, then increase B or h.
Condition:
Roof angle α \u003d 36 °;
Step rafted a \u003d 0.8 m;
Working plot of the rafter foot of the maximum length LMAX \u003d 2.8 m;
Material - pine 1 grade (Rizg \u003d 140 kg / cm²);
The roof is a cement-sand tile (the weight of the roof is 50 kg / m²).
As it was calculated, the total load acting on the square meter of the roof is q \u003d 303 kg / m².
1. Find a distributed load on the pattern meter of each rafter foot QR \u003d A · Q;
QR \u003d 0.8 · 303 \u003d 242 kg / m;
2. Choose the thickness of the chalkboard for rafters - 5cm.
Calculate the cross section of the rafting leg with the width of the section 5cm.
Then, H ≥ 9,5 · LMAX · SQRT (QR / B · RIPS)Since the bias of the roof α\u003e 30 °:
H ≥ 9.5 · 2.8 · SQRT (242/5 · 140)
H ≥15.6 cm;
From the table of standard sizes of sawn timber, choose a board with the nearest cross section:
width - 5 cm, height - 17.5 cm.
3. We check whether the magnitude of the deflection is stacked. For this should be observed inequality:
3,125 · QR · (LMAX) ³ / b · h³ ≤ 1
Substituting values, we have: 3,125 · 242 · (2.8) ³ / 5 · (17,5) ³ \u003d 0.61
Value 0.61, which means the cross section of the rafted material is chosen correctly.
The cross section of the rafted, installed in increments of 0.8m, for the roof of our house will be: width - 5 cm, height - 17.5 cm.
Considering the erected house, you can estimate the design of the roof, pattern and color of the roofing material, the overall design of the building. However, what it provides all this is impossible to see. The rapid system is responsible for all elements associated with the roof of the building, and it is from it that the durability, quality and comfort of the house depends on it. The calculation of the rafter system is the leading stage in the design of the building that determines all parameters carrier design.
Before you start the calculation of the rafter, it is necessary to determine the intensity of the loads that will act on the roof during all seasons of the year. By nature, influencing factors are classified on:
The construction of the roof begins with the installation of the rafter system.
The complexity of calculations is due to the fact that the beginners of the construction case are hard to take into account all the factors of influence simultaneously. After all, besides these indicators, it is necessary to take into account the weight and strength of the rafting boards themselves, the method of their attachment among themselves and other important, but little-known values. It is proposed to help the rafal and farms calculation program, but sometimes it is more logical to use formulas. After all, it is independent analysis that all structural features of the roof erected is helping to "feel".
To understand how to calculate the length of the rafted and what figures to navigate, first it is worth determining the total weight of the "roofing pie". To obtain the final indicator, it is necessary to calculate the weight of one square meter of each layer. The average roof consists of elements:
"Roofing Pie" whose weight must be considered when calculating the load on the truss system
Studying the technical characteristics of any of these layers, it is easy to find information about the required value. After summing up all data, it is recommended to increase the result by 10 percent, that is, multiply to a permanent coefficient of 1.1. It will help to lay safety for the planned rafter system.
Important ! Experienced builders are recommended to choose materials so that the outcome of the load on one square meter does not exceed the number of 50 kg.
Someone calls 50 kg overpriced magnitude, but it is worth understanding that the strength of the strength does not hurt. Determining the weight of roofing pie, it is worth passing to the calculation of the second indicator - snow loads.
This indicator is very important, since most of the regions are experiencing a long-term effect on the side of snow precipitation. For the severity of snow did not break the roof, it is worth worrying about additional strength in advance. For calculation, the formula was derived, in which the coefficients are used from SNiP 2.01.07-85.
Formula: Full Snow Load \u003d Snow Weight per 1 sq.m. x corrective coefficient.
The first value is determined depending on the location of the house. By the intensity of precipitation falls, all regions are divided into snow zones for which the averaged value is derived.
Snow load map indicating regions
The corrective coefficient can also be found in the specified Spepe. It is modified depending on the roof slope angle:
It is worth noting the fact that the snow is distributed over the surface of the roof uneven, forming more intense clusters in the places of breakfast (outputs auditory windows, endanda, etc.). The step of the rafter is recommended to do in these places the minimum - it is better to establish paired elements. In addition, forming a layer of roofing cake, it is worth using a solid crate and double waterproofing in complex zones.
Important ! Any calculation results are desirable to multiply by 1.1, that is, increase the margin of strength by 10%.
This indicator has a high level of criticality, since independent of the corner of the roof the roof is dangerous with strong wind. At low angles of inclination, there is a threat of breakdown and destruction of the roof under the action of aerodynamic load. The big angle of inclination leads to the fact that the roof is experiencing a huge wind pressure over its entire surface.
To calculate the wind load also withdrawn the formula with correction coefficients.
Formula: Wind Load \u003d Indicator of the region x coefficient.
Wind load card allows you to determine the region
The indicator of the region is a tabular value reflected in SNUP, but the coefficient must be selected, given the height of the house and the area in which the building is located. The values \u200b\u200bof the coefficient are changing according to the following scheme:
To understand how to calculate rafters, it is necessary to take into account the fact that almost the entire design is a system of triangles, therefore problems with the definition of the length of the boards usually do not occur. But since when calculating it is necessary to take into account loads, the shaft step, the magnitude of the spans and the features of the configuration of the roof itself, better decision The special program for calculating rafters becomes. It is enough to enter all the necessary data and obtain the final result.
Important ! Few programs can do all the work on design. Most often, they operate with ready-made numbers in the wind and snow load, and also request complete information on the weight of roofing layers.
Making calculations stropile designcan be focused on standards tables. In the construction market, the range of finished rafters is represented by boards with a length of 4.5 to 6.0 meters, but these are not finite values. Depending on the design of the building, the length can be changed to the necessary one.
The selection of the cross section of the rafter timber is determined depending on the following factors:
Table in which collected optimal values, as follows:
Table of settlement values \u200b\u200bof the cross section of the rafter
However, it is worth remembering that depending on the region, recommendations may vary.
The calculation of the rafter foot - its length is the simplest task of all voiced. When searching for meaning, we advise you to contact the Pythagoreo Theorem, where the costs will serve as the width of the house and the difference in height between its walls, then the hypotenneus will be the rafter board, the length of which must be found.
All information provided implies the calculation wooden timingIf it comes to the use of metal, then the numbers will be slightly different. After all, the strength characteristics of these two materials differ significantly, which means that the indicators of the section and the step of the rafter design will change.
The calculation of the rafter system of the house can not be called a light occupation. After all, to obtain correct data, it is necessary not only to be able to operate with formulas and initial values, know the slope, but also be able to draw and enjoy spatial imagination. If there are doubts about our own, but I do not want to pay money for the calculated minimization, you can use professional programs.
Among the high-precision information products, 3D MAX and auto channel can be distinguished. With certain skills to cope with these software, it is not difficult. However, there are even more simple solutions.
In the program for calculating the rafter, it suffices to enter the necessary parameters and get the result
For example, the Arcon program allows you to create simple sketching projects, has a calculator for calculating the length and cross section of the rafter. It is easy to work with an accessible interface and easy to enter information.
It is also worth noting that there are online programs. These are calculators that provide data on the values \u200b\u200bof the rafter system on user entered information.
If the program for calculating the rafter system issued information that the bars are needed greater than that are available, then it is easy to solve this problem. There are certain methods for connecting rafters, usually use one of three:
The "On-Scatch" method implies the exact calculation of the cross section of the rafter, because with this method there will be a compound of the end parts of the bars, cropped strictly at right angles. The joint is closed with overlays, the value of which must be more than half a meter. If wooden elements are used for linings, the fastening is carried out by long screws, placing them in a checker order. But the more durable compound provide metal plates mounted in the joint area using nuts and bolts.
The splicing of the rafters in the construction system is done so that the load has affected the load as little as possible.
"Spit ORBUB" is used when the end parts of the cut spire at an angle of 45 degrees. The compound in this case is carried through bolts, the diameter of which is 12-14 mm.
Wrong extension is the easiest, but most expected way. Its essence is that the ends of the rafting boards are laid on each other with the intersection of at least 1 meter. The connection occurs by any fastening elements in a checker order.
The accurate calculation of the rafter farm will not matter if high-quality will not be selected construction material. Wood can be used almost any, therefore it is worth paying attention to the amount and number of defects, as well as on the accompanying documentation for the bruus.
Among the allowable deviations according to GOST according to the requirements for lumber, are considered:
Choosing the rafting boards, you need to get documents confirming their quality
Documents on high-quality material must contain the following information:
The study of SNiP and GOST on sawn timber and rafter systems will show that when working with wood can not be done without some events. Most often, the action is subdivided into protective and structural.
Protection of the rafter system looks like:
An important role is played by firefare and antiseptic impregnation for a rafter, which has a direct impact on the duration of the service life of the roof
Start the construction of the roof of the house, not knowing the dimensions of the rafter, it is impossible. However, it is not necessary to approach the issue of superficially. It is impossible to limit ourselves to only the calculation of the rafter system, its configuration and test load. The house is a single project in which all parameters are associated together. The foundation, the possibilities of the supporting design, the rafter system, the roof - all this and much more can not be considered isolated.
During construction, special attention is paid to the installation of rafters, because the safety of residents of the residents depends on the correctness of the system assembly
The competent project created at the planning stage will help to consider all questions in the complex. Therefore, if the plans arose an idea of \u200b\u200berecting his own home, then the ideal solution will be the consultation of professional builders and designers. Experts will help in solving all issues and will not allow errors that may damage the construction of the building.
Roof, along with the foundation and walls, is one of the main constructive elements Constructions, providing protection for the inner part of the building from atmospheric precipitation, convergence, temperature drops, wind loads and other effects. At the same time, the roofing system is the most cumbersome hard-scale design in the house, since it consists of a huge number of individual components and compounds. For most beginner masters, construction turns into solid Testwhich is not visible to the end and edges - it is necessary to make a project, carry out a lot of calculations, draw diagrams, manufacture elements and, ultimately, collect everything into a single structure.
Building online calculator Calculation of the roof from service KALK.PRO allows you to facilitate the process of building the roofing design at the stage preparatory work, providing a detailed report with the parameters of individual elements and the number of sawn timber for their manufacture, providing detailed drawings rafter system and crates, as well as visualizing the resulting structure in the form 3D model For subsequent assessment. In addition, our program takes into account all the additional structural elements of the roof, including Maurylalat, vapor barrier, insulation, a counterclaim, OSP sheets. Soon, it is planned to enter a wind and snow load.
3D roof designer is simple, convenient and does not require special skills when used - you need to measure the dimensions of the building, select the type of roof (rigid, soft) and specify the characteristics of the materials used. In the case of input invalid values, the program will stop the calculation and specifies the cell, where it was the error that was performed. Also, on the Each Calculator tab, there is a detailed text instruction with a description of all fields and designations that are duplicated on the appropriate images for clarity.
Save time and money using the professional calculation of the roof on the site of Kalk. Pro - we consider the roof for more than 5 years and helped to implement over 1000 different projects!
Close cooperation with roof manufacturers
Highest detail of drawings and 3D-models
Final report with list essential materials
Finished estimate for the manufacture of the contractor
Technical support helps when working with a calculator
Positive feedback and large number of projects implemented
You can calculate the roof on any site and this is a fact, but you have to realize that, unlike other resources, our project has a long history, positive feedback, prompt technical support and regularly updates the work algorithms, eliminating the occurrence of errors. Feedback with users has been established and works flawlessly, any visitor can ask a question, and Kalkpro will try to answer it.
In addition, we would like to highlight the following:
In the comments to each calculator and on the "Reviews" page, you can read the reports of real people who use our tools. Check personally that users write about us.
Service Kalk. Pro is a universal assistant for a beginner and professional master, with which you can make a truly reliable and safe design. However, it is necessary to understand that the program performs the calculation of the roof on the basis of the entered data and does not take into account their correctness, except for exceptional cases when the design is guaranteed by an unstable. When building the roof (especially for the first time), we recommend paying attention to the following regulatory documents: Snip 2.01.07-85 (SP 20.13330.2010) "Loads and Impact", SNIP II-26-76 (SP 17.13330.2017) " Roofs, TSN 31-308-97 "Roofs. Technical requirements and acceptance rules. Moscow Region, "SP 31-101-97" Design and construction of roofs ".
On this we provide the calculation of the following roofing structures:
Among the main possibilities of the designer must be allocated (- only on Kalk.Pro.):
Many specialists use our professional roof calculators - if you want to use them for commercial purposes, you can remove our watermark and download your logo.
After entering all the initial parameters, you get a comprehensive report, which contains a ready estimate for the manufacture of a design with a detailed calculation of sawn timber and roofs, a set of drawings of all roof elements in various projections and an adaptive 3D model. The roof area is also automatically calculated and an angle of inclination angle will be available, rafted. Unlike other services, we disclose each element of the structure in detail and do not summarize the parameters so that you can use our results as guidelines for action.
Drawings are an integral element project documentation any design because they are a kind of "work card" for mounting work. Many professionals prefer to make a roof plan with their own hands in specialized programs of type AutoCAD, ArchiCAD, etc., but for a beginner master independent development, without proper experience, it is usually ends and without starting, or ends very poorly. It must be remembered that any random error can lead to unforeseen expenses and violation of the structure of the entire structure.
Using the online roof calculator KALK.PRO You exclude errors in the calculations, since the graphics are built on the basis of the actually entered parameters, the correctness of which can be risening on an interactive 3D model. Depending on the roof design, we provide a different amount of drawings - complex systems are described in more detail. For example, when calculating the cumbersome walm roofThe kit contains 12 design drawings with detailed description The rapid system (in different projections), its elements, crates, spice places and laying roofing materials.
When creating a roof calculator, we have made all possible efforts to ensure that the subsequent collection of design and layout of individual elements, in particular, was the most fast and comfortable.
Architectural visualization allows you to clearly appreciate the planned design in real proportions, make sure that the project is performed qualitatively and without errors. Nevertheless, spatial modeling is a painstaking and technically complex process that cannot be performed without special skills, and professional designers have such services worth five more money.
However, by performing the calculation of the roof on our website, you will receive an adaptive 3D model with accurate observance of the dimensions with which you can interact and which can be downloaded in OBJ format to further download it to your edit software.
To perform the calculation of the roof on the online calculator, it is necessary to correctly fill out all the available fields and click the "Calculate" button. We recommend to make measurements as accurately and several times rechecked the imposed values \u200b\u200bto avoid problems when collecting structures, since it is possible to re-produce a large number of items.
Recall that our calculators have built-in functionality to accomplish:
You do not need to look for other tools on the Internet or bother with the calculation manually.
Detailed step-by-step textual instructions with graphic annotations for each tool are presented on the tabs of the corresponding calculator in the Help section. We also offer to watch a brief overview video of the calculation of a bartal structure, which demonstrates the main features of the Calculator of the roofs.
Online calculator calculating the roof from Kalk.PRO is the most effective method obtaining project documentation for the manufacture of a reliable rafting roof system and other structures.
