Metal structures truss calculation. An example of calculating a triangular truss

In various sectors of construction, trusses from a profile pipe are often used. Structurally, such trusses are metal structures consisting of individual rods and having a lattice shape. Trusses differ from structures made of solid beams by lower cost and greater labor intensity. To connect profile pipes, both the welded method and rivets can be used.

Metal profile trusses are suitable for creating any span, regardless of their length - but in order to be able to do this, the structure must be calculated with the utmost accuracy before assembly. If the calculation of the metal truss was correct, and all the assembly work of the metal structures was carried out correctly, then the finished truss will only have to be lifted and installed on the prepared harness.

Benefits of using metal rafters

Trusses from a profile pipe have many advantages, including:

Light weight design;
Long service life;
Excellent strength indicators;
Ability to create structures of complex configuration;
Acceptable cost of metal elements.

Classification of trusses from a profile pipe

All metal truss structures have several common parameters, which ensure the division of trusses into types.

These options include:

The number of belts. Metal trusses can have only one belt, and then the whole structure will lie in one plane, or two belts. In the latter case, the farm will be called hanging. The design of the hanging truss includes two belts - upper and lower.
The form. There is an arched truss, straight, single-slope and double-slope.
Circuit.
Tilt angle.

Depending on the contours, the following types of metal structures are distinguished:

Parallel belt trusses. Such structures are most often used as a support for arranging a roof made of soft roofing materials. A truss with a parallel belt is created from the same parts with identical dimensions.
Shed trusses. Single-slope designs are inexpensive because few materials are required to make them. The finished structure is quite durable, which is ensured by the rigidity of the nodes.
Polygon farms. These structures have a very good bearing capacity, but you have to pay for it - polygonal metal structures are very inconvenient to install.
triangular trusses. As a rule, trusses with a triangular contour are used for the installation of roofs located at a large slope. Among the disadvantages of such farms, it is worth noting the large number of unnecessary costs associated with the mass of waste during production.

How to calculate the angle of inclination

Depending on the angle of inclination, farms are divided into three categories:

22-30 degrees. In this case, the ratio of the length and height of the finished structure is 5:1. Trusses with such a slope, being light in weight, are great for arranging short spans in private construction. As a rule, trusses with such a slope have a triangular contour.
15-22 degrees. In a design with such a slope, the length exceeds the height by seven times. Farms of this type cannot be more than 20 m long. If it is necessary to increase the height of the finished structure, the lower belt is given a broken shape.
15 or less. The best option in this case would be metal rafters from a profile pipe, connected in the form of a trapezoid - short racks will reduce the effect of longitudinal bending on the structure.

In the case of spans whose length exceeds 14 m, it is necessary to use braces. The upper belt must be equipped with a panel about 150-250 cm long. With an even number of panels, a structure consisting of two belts will be obtained. For spans longer than 20 m, the metal structure has to be reinforced with additional support elements connected by support columns.

If you need to reduce the weight of the finished metal structure, you should pay attention to the Polonso farm. It includes two triangular-shaped systems that are connected by tightening. Using this scheme, you can do without large-sized braces in the middle panels.

When creating trusses with a slope of about 6-10 degrees for shed roofs, you need to remember that the finished structure should not be symmetrical in shape.

Calculation of a metal truss

When calculating, it is necessary to take into account all the requirements for metal structures by state standards. In order to create the most efficient and reliable design, it is necessary at the design stage to prepare a high-quality drawing, which will display all the elements of the truss, their dimensions and features of the connection with the supporting structure.

Before you calculate a truss for a canopy, you should decide on the requirements for a finished truss, and then start from savings, avoiding unnecessary costs. The height of the truss is determined by the type of floor, the total weight of the structure and the possibility of its further displacement. The length of the metal structure depends on the expected slope (for structures longer than 36 m, a calculation of the building lift will also be required).

Panels must be selected in such a way that they can withstand the loads that will fall on the farm. Braces can have different angles, so this parameter must also be taken into account when choosing panels. In the case of triangular gratings, the angle is 45 degrees, and with slanted gratings - 35 degrees.

The calculation of a roof from a profile pipe ends with determining the distance at which nodes will be created relative to each other. As a rule, this indicator is equal to the width of the selected panels. The optimal indicator of the pitch of the supports of the entire structure is 1.7 m.

When calculating a single-slope truss, you need to understand that with an increase in the height of the structure, its bearing capacity will also increase. In addition, if necessary, it is worth supplementing the truss scheme with several stiffeners that can strengthen the structure.

Calculation examples

When choosing pipes for metal trusses, it is worth starting from the following recommendations:

For the arrangement of structures with a width of less than 4.5 m, pipes with a section of 40x20 mm with a wall thickness of 2 mm are suitable;
With a construction width of 4.5 to 5.5 m, 40 mm square profile pipes with a 2 mm wall are suitable;
For larger metal structures, the same pipes are suitable as in the previous case, but with a 3 mm wall, or pipes with a section of 60x30 mm with a 2 mm wall.

The last parameter, which should also be paid attention to when calculating, is the cost of materials. First, you need to consider the cost of pipes (remembering that the price of pipes is determined by their weight, not length). Secondly, it is worth asking about the cost of complex work on the manufacture of metal structures.

Recommendations for the selection of pipes and the manufacture of metal structures

Before you cook farms and select the best materials for future construction, you should familiarize yourself with the following recommendations:

When studying the range of pipes available on the market, it is worth giving preference to rectangular or square products - the presence of stiffeners significantly increases their strength;
When choosing pipes for the truss system, it would be best to opt for stainless products made of high-quality steel (pipe sizes are determined by the project);
When installing the main elements of the farm, tacks and double corners are used;
In the upper chords, I-beams with different sides are usually used to connect the frame, the smaller of which is necessary for docking;
For mounting the lower belt, corners with equal sides are quite suitable;
The main elements of large-sized structures are attached to each other with overhead plates;
The braces are mounted at an angle of 45 degrees, and the racks are mounted at a 90-degree inclination.
When a metal truss for a canopy is welded, it is worth making sure that each weld is sufficiently reliable (read also: "");
After welding, the metal structural elements remain coated with protective compounds and paint.

Conclusion

Profile pipe trusses are quite versatile and suitable for solving a wide range of tasks. The manufacture of trusses cannot be called simple, but if you approach all stages of work with all responsibility, then the result will be a reliable and high-quality design.

Canopies on a metal frame make life easier. They will protect the car from the weather, cover the summer veranda, gazebo. They will replace the roof of the workshop or the canopy over the entrance. Turning to professionals, you will get any kind of canopy. But many will cope with the installation work themselves. True, you will need an accurate calculation of the farm from the profile pipe. You can not do without the appropriate equipment and materials. Of course, welding and cutting skills are also needed.

frame material

The basis of the canopies is steel, polymers, wood, aluminum, reinforced concrete. But, more often, the frame is made up of metal trusses from a profile pipe. This material is hollow, relatively light, but durable. In section it looks like:

rectangle;
square;
oval (as well as semi- and flat-oval figure);
polyhedron.

When welding from a truss profile pipe, a square or rectangular section is often chosen. These profiles are easier to process.

Variety of pipe profiles

Permissible loads depend on the wall thickness, metal grade, manufacturing method. The material is often high-quality structural steel (1-3ps/sp, 1-2ps(sp)). For special needs, low-alloy alloys and galvanizing are used.

The length of profile pipes usually ranges from 6 m for small sections to 12 m for large ones. Minimum parameters from 10×10×1 mm and 15×15×1.5 mm. With an increase in the wall thickness, the strength of the profiles increases. For example, on sections 50 × 50 × 1.5 mm, 100 × 100 × 3 mm and more. Products of maximum dimensions (300 × 300 × 12 mm or more) are more suitable for industrial buildings.

As for the parameters of the frame elements, there are the following recommendations:

for small-sized canopies (up to 4.5 m wide), pipe material with a section of 40 × 20 × 2 mm is used;
if the width is up to 5.5 m, parameters 40 × 40 × 2 mm are recommended;
for canopies of larger sizes, it is advised to take pipes 40 × 40 × 3 mm, 60 × 30 × 2 mm.

What is a farm

The farm is called the core system, the basis of the building structure. It consists of rectilinear elements connected at nodes. For example, we consider the design of a truss from a profile pipe, in which there is no misalignment of the rods and there are no off-nodal loads. Then only tensile and compressive forces will arise in its constituent parts. The mechanics of this system allows it to remain geometrically unchanged when replacing rigidly attached nodes with articulated ones.

The farm consists of the following elements:

upper belt;
lower belt;
stand perpendicular to the axis;
brace (or brace), inclined to the axis;
auxiliary support brace (sprengel).

Lattice system can be triangular, diagonal, semi-diagonal, cross. For connection, scarves, paired materials, rivets, welds are used.

Mounting options in knots

The manufacture of trusses from a profile pipe involves the assembly of a belt with certain outlines. By type they are:

segment;
polygonal;
gable (or trapezoidal);
with parallel belts;
triangular (d-i);
with a raised broken lower belt;
lean-to;
console.

Some systems are easier to install, others are more economical in terms of material consumption, and others are easier in terms of supporting nodes.

Fundamentals of Farm Calculation

Influence of tilt angle

The choice of the design of canopy trusses from a profile pipe is associated with the slope of the designed structure. There are three possible options:

from 6° to 15°;
from 15° to 22°;
from 22° to 35°.

With a minimum angle (6°-15°), trapezoidal outlines of the belts are recommended. To reduce weight, a height of 1/7 or 1/9 of the total span length is allowed. When designing a sloping canopy of complex geometric shape, it is necessary to raise it in the middle part above the supports. Take advantage of the Polonso farms recommended by many experts. They are a system of two triangles connected by a puff. If you need a tall structure, it is better to choose a polygonal structure with a raised lower chord.

When the slope angle exceeds 20°, the height should be 1/7 of the total span length. The latter reaches 20 m. To increase the structure, the lower belt is made broken. Then the increase will be up to 0.23 span length. Tabular data is used to calculate the required parameters.

Table for determining the slope of the truss system

With a slope of more than 22 °, calculations are carried out according to special programs. Canopies of this kind are more often used for roofing made of slate, metal and similar materials. Here, triangular trusses from a profile pipe are used with their height of 1/5 of the entire length of the span.

The greater the angle of inclination, the less precipitation and heavy snow will accumulate on the canopy. The bearing capacity of the system increases with its height. Additional stiffening ribs are provided for additional strength.

Base Angle Options

To understand how to calculate a truss from a profile pipe, it is imperative to find out the parameters of the base nodes. For example, the dimensions of the span should usually be specified in the terms of reference. The number of panels, their dimensions are pre-assigned. Calculate the optimal height (H) in the middle of the span.

If the belts are parallel, polygonal, trapezoidal, H=1/8×L, where L is the length of the truss. The top belt should have a slope of about 1/8xL or 1/12xL.
For triangular type, on average, H=1/4×L or H=1/5×L.

Lattice braces should have a slope of approximately 45° (within 35°-50°).

Use a ready-made standard project, then you don’t have to do the calculation

In order for the canopy to be reliable and last for a long time, its project requires accurate calculations. After the calculation, materials are purchased, and then the frame is mounted. There is a more costly way - to purchase ready-made modules and assemble the structure on site. Another option is more difficult - to do the calculations yourself. Then you will need data from special reference books on SNiP 2.01.07-85 (impacts, loads), as well as SNiP P-23-81 (data on steel structures). You need to do the following.

Decide on the block diagram in accordance with the functions of the canopy, the angle of inclination, the material of the rods.
Select options. Take into account the relationship between the height and minimum weight of the roof, its material and type, slope.
Calculate the panel dimensions of the structure according to the distance of the individual parts responsible for the transfer of loads. The distance between adjacent nodes is determined, usually equal to the width of the panel. If the span is more than 36 m, the building lift is calculated - the reverse extinguishing bend, which acts due to the loads on the structure.

Among the methods for calculating statically determinate trusses, one of the simplest is cutting out nodes (areas where the rods are hinged). Other options are the Ritter method, the Henneberg rod replacement method. As well as a graphical solution by drawing up a Maxwell-Cremona diagram. In modern computer programs, the method of cutting nodes is more often used.

For a person who has knowledge of mechanics and strength of materials, it is not so difficult to calculate all this. The rest should take into account that the service life and safety of the canopy depend on the accuracy of the calculations and the magnitude of the errors. It might be better to contact the experts. Or choose an option from ready-made design solutions, where you can simply substitute your values. When it is clear what kind of truss truss is needed from a profile pipe, a drawing for it will surely be found on the Internet.

Significant Site Selection Factors

If the canopy belongs to a house or other building, it will require official permission, which will also have to be taken care of.

First, a site is selected where the structure will be located. What is taken into account?

Constant loads (fixed weight of lathing, roofing and other materials).
Variable loads (impact of climatic factors: wind, precipitation, including snow).
A special type of load (is there seismic activity in the region, storms, hurricanes, etc.).

Also important are the characteristics of the soil, the influence of nearby buildings. The designer must take into account all significant factors and clarifying coefficients that are included in the calculation algorithm. If you plan to do the calculations on your own, use 3D Max, Arkon, AutoCAD or similar programs. There is a calculation option in online versions of building calculators. Be sure to find out for the intended project the recommended step between the bearing supports, the crate. As well as the parameters of materials and their quantity.

An example of a software calculation for a canopy covered with polycarbonate

Sequence of work

The assembly of the frame from metal profiles should be carried out only by a specialist in welding work. This responsible business requires knowledge and skillful handling of the tool. It is necessary not only to understand how to weld a truss from a profile pipe. It is important which nodes are more correct to assemble on the ground, and only then raise them to the supports. If the structure is heavy, equipment will be required for installation.

Usually the installation process takes place in the following sequence:

Area marking is in progress. Embedded parts, vertical supports are installed. Often, metal pipes are immediately placed in the pits, and then concreted. The verticality of the installation is checked by a plumb line. To control parallelism, a cord or thread is stretched between the extreme racks, the rest are set along the resulting line.
Longitudinal pipes are fixed to the supports by welding.
On the ground, nodes and elements of trusses are welded. With the help of braces and jumpers, the belts of the structure are connected. Then the blocks should be raised to the desired height. They are welded to the longitudinal pipes in the areas where the vertical supports are placed. Longitudinal lintels are welded between the trusses along the slope for further fastening of the roofing material. They make holes for fasteners.
All connecting areas are carefully cleaned. Especially the upper edges of the frame, where the roof will lie in the future. The surface of the profiles is cleaned, degreased, treated with a primer and painted.

Using the finished project, you will quickly start assembling the canopy

Experts advise to perform such responsible work only with relevant experience. It is not enough to know in theory how to properly weld a truss from a profile pipe. Having done something wrong, ignoring the nuances, the home master risks. The canopy will collapse and collapse. Everything that will be under it will suffer - cars or people. So take your knowledge to heart!

Video: how to weld a truss from a profile pipe

Today, profile pipe trusses are considered to be the ideal solution for building a garage, a residential building and outbuildings. Robust and durable, these designs are inexpensive, quick to build, and anyone with a modicum of math and cutting and welding skills can handle them.

And how to choose the right profile, calculate the farm, make jumpers in it and install, we will now tell you in detail. To do this, we have prepared for you detailed workshops for making such farms, video tutorials and valuable tips from our experts!

So what is a farm? This is a structure that ties the supports together into one single whole. In other words, the farm belongs to simple architectural structures, among the valuable advantages of which we highlight the following: high strength, excellent performance, low cost and good resistance to deformations and external loads.

Due to the fact that such trusses have a high bearing capacity, they are placed under any roofing materials, regardless of their weight.

The use in the construction of metal trusses from new or rectangular closed profiles is considered one of the most rational and constructive solutions. And for good reason:

The main secret is in savings due to the rational shape of the profile and the connection of all elements of the lattice.
Another valuable advantage of profile pipes for use in their manufacture of trusses is equal stability in two planes, excellent streamlining and ease of use.
With all their low weight, such trusses can withstand serious loads!

Roof trusses differ in the shape of the belts, the type of section of the rods and the types of lattice. And with the right approach, you can independently weld and install a truss from a profile pipe of any complexity! Even this one:

Stage II. We acquire a quality profile

So, before drafting future farms, you first need to decide on such important points:

contours, size and shape of the future roof;
material for the manufacture of the upper and lower chords of the truss, as well as its lattice;

Remember one simple thing: the profile pipe frame has so-called balance points, which are important to determine for the stability of the entire truss. And it is very important to choose high-quality material for this load:

Farms are built from a profile pipe of such types of sections: rectangular or square. These are available in different section sizes and diameters, with different wall thicknesses:

We recommend those that are specially sold for small buildings: these go up to 4.5 meters long and have a section of 40x20x2 mm.
If you will make farms longer than 5 meters, then choose a profile with parameters 40x40x2 mm.
For a full-scale construction of the roof of a residential building, you will need profile pipes with the following parameters: 40x60x3 mm.

The stability of the entire structure is directly proportional to the thickness of the profile, so do not use pipes for the manufacture of trusses, which are intended only for welding racks and frames - here are other characteristics. Also pay attention to which method the product was manufactured: by electric welding, hot-formed or cold-formed.

If you undertake to make such trusses on your own, then take square-section blanks - it is easiest to work with them. Get a square profile 3-5 mm thick, which will be strong enough and close in its characteristics to metal bars. But if you will make a farm just for a visor, then you can give preference to a more budget option.

Be sure to consider snow and wind loads in your area when designing. After all, when choosing a profile (in terms of the load on it), the angle of inclination of the trusses is of great importance:

You can more accurately design a truss from a profile pipe using online calculators.

We only note that the simplest design of a profile pipe truss consists of several vertical posts and horizontal levels on which roof rafters can be attached. You can buy such a frame ready-made on your own, even on order in any city in Russia.

Stage III. We calculate the internal stress of the trusses

The most important and responsible task is to correctly calculate the truss from the profile pipe and select the desired format of the internal lattice. To do this, we need a calculator or other software similar to it, as well as some tabular data of SNiPs, which for this:

SNiP 2.01.07-85 (impacts, loads).
SNiP p-23-81 (data on steel structures).

Please review these documents if possible.

Roof shape and slope

The farm is needed for which specific roof? Shed, gable, domed, arched or hipped? The easiest option, of course, is the manufacture of a standard shed canopy. But you can also calculate and manufacture quite complex farms yourself:

A standard truss consists of such important elements as the upper and lower chords, racks, braces and auxiliary struts, which are also called sprengels. Inside the trusses there is a grid system; welds, rivets, special paired materials and scarves are used to connect pipes.

And, if you are going to make a roof with a complex shape, then such trusses will be an ideal option for it. It is very convenient to make them according to a template right on the ground, and only then lift them up.

Most often, in the construction of a small country house, garage or change house, the so-called Polonso trusses are used - a special design of triangular trusses connected by puffs, and the lower belt here comes out raised.

In fact, in this case, in order to increase the height of the structure, the lower chord is made broken, and then it is 0.23 of the flight length. For the interior space of the room is very convenient.

So, in total there are three main options for making a truss, depending on the slope of the roof:

from 6 to 15°;
from 15 to 20°;
from 22 to 35°.

What is the difference you ask? For example, if the angle of the structure is small, only up to 15 °, then it is rational to make the trusses in a trapezoidal shape. And at the same time, it is quite possible to reduce the weight of the structure itself, taking in height from 1/7 to 1/9 of the total flight length.

Those. follow this rule: the lower the weight, the greater the height of the truss. But if we already have a complex geometric shape, then you need to choose a different type of truss and gratings.

Types of trusses and roof shapes

Here is an example of specific trusses for each type of roof (single, double, complex):

Let's look at the types of farms:

triangular trusses are a classic for making the base for steep roof slopes or sheds. The cross section of pipes for such farms must be selected taking into account the weight of the roofing materials, as well as the operation of the building itself. Triangular trusses are good because they have simple shapes, are easy to calculate and execute. They are valued for under-roofing providing natural light. But we also note the disadvantages: these are additional profiles and long rods in the central segments of the lattice. And also here you will have to face some difficulties when welding sharp reference corners.
The next view is polygonal farms from a profile pipe. They are indispensable for the construction of large areas. Their welding is already of a more complex shape, and therefore they are not designed for lightweight structures. But such trusses are distinguished by greater metal savings and strength, which is especially good for hangars with large spans.
It is also considered strong truss with parallel belts. Such a farm differs from others in that it has all the details - repeating, with the same length of rods, belts and gratings. That is, there are a minimum of joints, and therefore it is easiest to calculate and cook one from a profile pipe.
A separate species is single slope trapezoidal truss supported by columns. Such a farm is ideal when a rigid fixation of the structure is necessary. She has slopes (braces) on the sides and there are no long rods of the upper crate. Suitable for roofs where reliability is especially important.

Here is an example of making trusses from a profile pipe as a universal option that is suitable for any garden buildings. We are talking about triangular farms, and you have probably already seen them many times:

A triangular truss with a crossbar is also quite simple, and is quite suitable for building gazebos and change houses:

And here arched farms are already much more difficult to manufacture, although they have a number of valuable advantages:

Your main task is to center the metal truss elements from the center of gravity in all directions, in simple terms, to minimize the load and correctly distribute it.

Therefore, choose the type of farm that is more suitable for this purpose. In addition to those listed above, a scissor truss, asymmetric, U-shaped, two-hinged, a truss with parallel belts and an attic truss with and without supports are also popular. As well as the attic view of the farm:

Grating types and point load

You will be interested to know that a certain design of the internal lattices of trusses is selected not at all for aesthetic reasons, but for quite practical ones: for the shape of the roof, the geometry of the ceiling and the calculation of loads.

You need to design your farm in such a way that all forces are concentrated specifically in the nodes. Then there will be no bending moments in the belts, braces and trusses - they will only work in compression and tension. And then the cross section of such elements is reduced to the required minimum, while significantly saving on the material. And the farm itself, to everything, you can easily make articulated.

Otherwise, the force distributed over the rods will constantly act on the truss, and a bending moment will appear, in addition to the total stress. And here then it is important to correctly calculate the maximum bending values for each individual rod.

Then the cross section of such rods should be larger than if the truss itself was loaded with point forces. To summarize: trusses, on which the distributed load acts evenly, are made of short elements with hinged nodes.

Let's see what is the advantage of one or another type of lattice in terms of load distribution:

triangular Lattice systems are always used in trusses with parallel chords and trapezoidal truss. Its main advantage is that it gives the smallest total grating length.
Diagonal the system is good at low truss heights. But the consumption of material for it is considerable, because here the entire path of effort goes through the nodes and rods of the lattice. And therefore, when designing, it is important to lay a maximum of rods so that the long elements are stretched and the racks are compressed.
Another view - trussed lattice. It is made in case of loads of the upper belt, as well as when it is necessary to reduce the length of the lattice itself. Here, the advantage is to maintain the optimal distance between the elements of all transverse structures, which, in turn, allows you to maintain a normal distance between the runs, which will be a practical moment for the installation of roof elements. But creating such a lattice with your own hands is a rather laborious task with additional metal costs.
cruciform the lattice allows you to distribute the load on the farm in both directions at once.
Another type of grid cross where the braces are attached directly to the truss wall.
And finally semi-diagonal And rhombic lattices, the most rigid of the listed. Here two systems of braces interact at once.

We have prepared an illustration for you, where we have collected all types of trusses and their lattices together:

Here is an example of how a triangular lattice truss is made:

Making a truss with a diagonal lattice looks like this:

This is not to say that one type of truss is definitely better or worse than the other - each of them is valuable for less material consumption, lighter weight, bearing capacity and method of fastening. The figure is responsible for which load scheme will act on it. And the type of lattice chosen will directly depend on the weight of the truss, the appearance and the complexity of its manufacture.

We also note such an unusual version of the manufacture of a farm, when it itself becomes a part or support for another, wooden one:

Stage IV. We manufacture and install farms

We will give you some valuable tips on how to weld such farms on your own without much difficulty right on your site:

Option one: you can contact the factory, and they will make to order all the necessary individual elements according to your drawing, which you will only have to weld on the spot.
The second option: purchase a ready-made profile. Then you will only have to sheathe the trusses from the inside with boards or plywood, and in between lay insulation if necessary. But this method will cost, of course, more expensive.

Here, for example, is a good video tutorial on how to lengthen a pipe by welding and achieve the perfect geometry:

Here is also a very helpful video on how to cut a pipe at a 45° angle:

So, now we come directly to the assembly of the farms themselves. The following step-by-step instructions will help you deal with this:

Step 1: Prepare the trusses first. It is better to weld them in advance directly on the ground.
Step 2. Install vertical supports for future farms. It is imperative that they are truly vertical, so test them with a plumb line.
Step 3. Now take the longitudinal pipes and weld them to the support posts.
Step 4 Raise the trusses and weld them to the longitudinal pipes. After that, it is important to clean all junctions.
Step 5. Paint the finished frame with special paint, having previously cleaned and degreased it. In this case, pay special attention to the junctions of the profile pipes.

What else do those who make such farms at home face? First, consider in advance the support tables on which you will lay the truss. It is far from the best option to throw it on the ground - it will be very inconvenient to work.

Therefore, it is better to put small support bridges that will be slightly wider than the lower and upper chords of the truss. After all, you will manually measure and insert jumpers between the belts, and it is important that they do not fall to the ground.

The next important point: profile pipe trusses are heavy in weight, and therefore you will need the help of at least one more person. In addition, help will not hurt in such tedious and painstaking work as sanding metal before cooking. Also keep in mind that you will need to cut a lot of farms for all elements, and therefore we advise you to either purchase or build a home-made machine like that in our master class. Here is how it works:

In this way, step by step, you will draw up a drawing, calculate the truss lattice, make blanks and weld the structure already in place. Moreover, you will also have the remains of profile pipes in your consumption, therefore, you will not need to throw anything away - all this will be needed for the secondary parts of the canopy or hangar!

Stage V. We clean and paint finished trusses

After you install the trusses in their permanent place, be sure to treat them with anti-corrosion compounds and paint with polymer paints. Ideal for this purpose paint, which is durable and resistant to ultraviolet radiation:

That's all, the profile pipe farm is ready! All that remains is the finishing work on sheathing the trusses from the inside with finishing and from the outside with roofing material:

Believe me, making a metal truss from a profile pipe is really not difficult for you. A well-designed drawing, high-quality welding of a truss from a profile pipe and the desire to do everything correctly and accurately play a huge role.

Sooner or later, the owners of a private house need to build a shed for a car or a summer holiday, a gazebo, a small fence with a roof for pets, a canopy over a woodpile on the site. In order for the roof over such a structure to be securely fixed, it is necessary to correctly design and install metal supporting structures.

We welcome our esteemed reader and offer him an article about what trusses from a profile pipe are, how to calculate and mount them correctly.

A truss is a structure of rectilinear elements interconnected at nodes into a solid system of an unchanging geometric shape. Most often there are flat structures, but in large loaded structures, volumetric (spatial) trusses are used. Practically in private houses, farms are made of wood and metal. Small structures of rafters, canopies, arbors are made of wood. But durable and high-tech metal is an almost ideal material for load-bearing metal structures.

For the manufacture of complex structures, rolled solid sections and pipes are used. Profile pipes (square, rectangle) have greater resistance to crushing and bending, small structures for the house are mounted without the use of welding, therefore, a profile pipe is most often used for estate buildings.

Structural features of trusses

The constituent elements of the farm structure:

Belt.
Rack - a vertical element connecting the upper and lower chords.
Brace (strut).
Sprengel - support brace.
Cut-outs, overlays, scarves, rivets, bolts - all kinds of auxiliary and fastening materials.

The height of the farm is considered from the lowest point of the lower belt to the highest point. Span - the distance between the supports. Rise - the ratio of the height of the truss to the span. The panel is the distance between the nodes of the belt.

Types of farms from a professional pipe

Farms are subdivided according to the outline of the belts. There are two-layer and three-layer varieties. In small structures, simpler two-belt trusses are used. Each variety has a certain slope and height depending on the length of the span and the shape of the truss.

Types of trusses according to the contours of the chords: beams with parallel chords (rectangular), triangular (double and single pitch), trapezoidal (double and single pitch), segmental (parabolic), polygonal (polygonal), cantilever; with a broken raised or concave lower chord and a varied shape of the upper chord; arched with a horizontal and arched lower belt; complex combined forms.

Farms are also distinguished by the types of lattices - see the figure. In private buildings, triangular and diagonal gratings are most often found - simpler and less metal-intensive. Triangular gratings are usually used in rectangular and trapezoidal structures, diagonal gratings - in triangular ones.

Before building any structure, you should decide on the choice of material. When buying a metal profile or pipes, you should carefully examine the workpieces - for cracks, shells, sagging, inconsistencies along the seam, a large number of dented and bent workpieces. When buying galvanized materials - it is advisable to make sure the quality of the coating - whether there are any delaminations and sagging.

When buying, you must require a copy of the certificate and a receipt. Be sure to make sure that the wall thickness of the pipe is stated in the documents. You can’t make pipes in a garage on your knee, and there are no fakes, but you can come across poor quality material, so it’s better to buy in fairly large stores.

What material to choose for the frame

In most cases, steel is chosen for the frame of manor buildings or the roof of a house. For very small structures, aluminum is sometimes used and - usually in purchased products (awnings, rocking chairs). For the erection of metal structures, pipes of a hollow section and a profile of a solid section (circle, strip, square, channel, I-beam) can be used.

A huge advantage of rectangular and square pipes compared to a profile of the same weight is the high resistance to crushing and other deformations. Therefore, solid profiles can be replaced with much lighter corrugated pipes - this greatly facilitates (2 times or more) and reduces the cost of tubular-type construction.

The dimensions of the pipe section are selected depending on the span length and the distance between supports and trusses. In private estates, sheds and other structures are not very large, and you can take the advice of experts or find ready-made drawings on the Internet.

With a distance between supports of up to 2 m, for small canopies with spans up to 4 m long, a profile of 40 × 20x2 mm is suitable, with spans of up to 5 m - 40 × 40x3, 60 × 30x3 mm; spans longer than 5 m - 60 × 40x3, 60 × 60x3 mm. If a carport for two cars with a width of 8-10 m is planned, then the profile will be required from 60 × 60 to 100 × 100 with a wall thickness of 3-4 mm. The dimensions of the profile depend on the distance between the trusses.

Professional pipes go on sale in lengths of 6 and 12 m. With a length of 12 m, metal is consumed more economically, but a length gauge is needed to transport such pipes. Before buying materials, you should consider how you will cut the blanks and how many of them will fit in a pipe 6 m or 12 m long, and calculate how many sections of the professional pipe you will need.

It is impossible to focus on the nominal weight - the weight is 1 r.m. in a particular batch will differ from the nominal, and most likely upwards (it is more profitable for sellers to manufacture products with a thicker wall - the price is per ton). When buying by weight, the material will have to be bought and transported - and these are extra costs.

Advantages and disadvantages of different metals

In practice, for structural profile pipes, the following types of steel are used: carbon ordinary quality and high-quality, structural, alloyed. Pipes come with a protective zinc coating. Aluminum is also used - but rarely, for small, more often seasonal structures. Aluminum profiles are used for small structures.

Traditionally, for small structures in a private estate, for the construction of steel structures with trusses, carbon steel St3sp, St3ps, sometimes galvanized, is used. Such steel has sufficient strength to ensure the reliability of the structure, there is practically no difference in corrosion resistance for all three types of steel.

If precipitation falls on structures, sooner or later both structural and alloy steel products will rust. A small amount of alloying elements does not protect against corrosion (for structures, low-alloy steels such as 30KhGSA, 30KhGSN, 38XA can be used - the content of alloying elements in them is 2-4%, and this amount does not affect corrosion resistance).

In terms of strength, structural and alloy steels should be slightly more durable than carbon steels - they are more resistant to cyclic loads. But this quality in steels manifests itself after heat treatment - and quenching with tempering can warp pipes, and usually no one does such heat treatment on finished products. Annealing can be carried out on seamless pipes - after annealing, residual stresses (hardening) are removed in the metal, but it becomes softer.

Structural steels (20A, 45, 40, 30A) are of higher quality and higher price. Alloyed steels are even more expensive (and there is a chance that you will be sold pipes made of steel 3 instead of alloyed). Therefore, when installing structures with a width of less than 20 m, it makes no sense to buy professional pipes made of alloyed or structural steel. It definitely makes sense to use a galvanized professional pipe if the installation will be carried out using crab systems.

If the assembly is to be carried out by welding, the welds will rust as quickly as normal uncoated metal.. But if you carefully monitor the seams, regularly carry out anti-corrosion treatment (cleaning, priming, painting), then a galvanized pipe is preferable. If you need a temporary shed for 10 years for building materials, and then you will demolish the shed - all the more so do not bother, buy ordinary carbon steel pipes without coating.

If you plan to build a very large shed or a hangar with a long span on the site, you should contact professional builders and make a project - they will determine which steel you choose.

Do it yourself or order

Trusses for a canopy over a car or a gazebo roof are small in size and have a simple design - most often triangular with several struts and racks. You can also complete such a design yourself if you have at least the initial skills of a welder and you are not afraid to learn new jobs.

But the manufacture of farms requires accuracy, the presence of an assistant, a very flat area in the estate - for laying out and welding structures, the presence of a welding machine and time. You can order ready-made structures at a factory or a construction company, and mount it yourself.

Requirements for the calculation of a profile pipe for the construction of a farm

When calculating the dimensions and wall thickness of profile pipes required for the construction of your metal structures; the following conditions are taken into account:

The dimensions of the metal structure, and in particular, the length, the pitch of the supports - the distance between the supports.
The height of supports and trusses.
Farm shape.
Possible features of geological conditions (seismic activity, the possibility of landslides).
Coating weight.

What happens if you calculate incorrectly

In case of incorrect calculations, the following consequences are possible:

Farm structures will deform under the weight of snow, wet foliage.
In the most unfortunate case, the structures will deform under their own weight.
The entire structure can collapse in strong winds.
Deformation sooner or later will lead to the destruction of the farm and the entire structure, which is dangerous for humans and can damage objects under a canopy - a car, for example.
A fragile and movable structure will lead to the destruction of the roof laid on the farm.
When using a profile that is too powerful and heavy, the cost of materials and work during the construction of a metal structure unreasonably increases.

We design a farm and its elements

A complete and accurate calculation of the load on the farm, along with diagrams, is complex, and for its implementation, you should contact the experts.

When designing large sheds, hangars, garages made of metal structures, an accurate calculation of the required profile is necessary, but for the construction of not too large sheds or gazebos in a private estate, you can use the well-known recommendations of specialists.

For very small structures (shed in an animal enclosure, shed over a store of firewood), it is sufficient to use pipes measuring 40 × 20 mm with a wall thickness of 2 mm; for gazebos and canopies over tables, barbecues or places of rest - 40 × 40 mm with a wall thickness of 3 mm; canopy over a place for a car - from 60 × 40 to 100 × 100 mm with a wall thickness of 3-4 mm.

If there are several trusses and supports at the canopy and the step of the supports is less than 2 m, you can take a thinner pipe, if there are only 4 supports and two trusses and a span of 6-8 m or more - a thicker one.

Permissible loads on trusses are shown in the table:

Span width, m Pipe size per wall thickness, mm	1	2	3	4	5	6
For profile pipe
40x40x2	709	173	72	35	16	5
40x40x3	949	231	96	46	21	6
50x50x2	1165	286	120	61	31	14
50x60x3	1615	396	167	84	43	19
60x60x2	1714	422	180	93	50	26
60x60x3	2393	589	250	129	69	35
80x80x3	4492	1110	478	252	144	82
100x100x3	7473	1851	803	430	253	152
100x100x4	9217	2283	990	529	310	185
120x120x4	113726	3339	1484	801	478	296
140x140x4	19062	4736	2069	1125	679	429
For a rectangular pipe (when the larger side is vertical)
50x25x2	684	167	69	34	16	6
60x40x2	1255	308	130	66	35	17
80x40x2	1911	471	202	105	58	31
80x40x3	2672	658	281	146	81	43
80x60x3	3583	884	380	199	112	62
100x50x4	5489	1357	585	309	176	101
120x80x3	7854	1947	846	455	269	164

Drawings and diagrams

In the manufacture of metal structures, a drawing with exact dimensions is mandatory! This will allow you to purchase the right amount of material, save time when assembling and preparing blanks, and allow you to easily control the dimensions of the metal structure during installation and the finished structure. In this case, the safety of you and your household depends on the accuracy of the assembly - a building that collapsed from snow or wind can bring a lot of trouble.

Fundamentals of Farm Calculation

The types of trusses depend on the shape of the roof, and the shape of the roof of the building in the estate is chosen depending on the purpose and location of the metal structures. Cantilever and adjoining trusses are usually made with single-sided triangular, free-standing canopies - with polygonal, triangular, segmental structures and arches. Arbors can have a six- and eight-slope roof or a fantasy roof with custom-design trusses.

To calculate the trusses, it is necessary to calculate the load on the roof and on one truss. The calculations take into account the load of the snow cover, roofing, battens, the weight of the structures themselves. Accurate calculations are a task for a professional builder. The basis for the calculation is SP 20.13330.2016 “Loads and impacts. Updated version of SNiP 2.01.07-85” and SP 16.13330.2011 “Steel structures. Updated version of SNiP II-23-81".

For calculations, the cutting method is used - cutting out nodes (sections where the rods are hinged); Ritter method; Henneberg rod replacement method. In modern computer programs, the method of cutting nodes is more often used.

It is better to use a ready-made standard project or our recommendations for choosing profiles. It is not too difficult to assemble a farm of a simple trapezoidal or triangular design, and if you have experience in welding and installing metal structures, self-assembly of sheds and arbors is quite possible. If you want to build a large canopy with a truss length of 10 m or more, you need to complete the project with specialists.