Triangular truss with a span of 12 meters. Wooden trusses are strong and lightweight structures for spanning large spans. Creation of a computer model in SCAD

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:

1. The main secret is in savings due to the rational shape of the profile and the connection of all elements of the lattice.
2. 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.
3. 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 elements of the metal truss 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.

All photos from the article

Despite the fact that in addition to wood, builders have many other building materials (concrete, metal) in their arsenal, wood continues to be popular. The reasons for this lie in its availability, ease of processing and sufficiently high strength. Moreover, with the help of wood, even fairly large spans can be blocked - wooden trusses for the roof make it possible to block a span of about 30 m without any problems.

Types of wooden farms

Such structures can be used not only in the construction of roofs, earlier, for example, they were used in the construction of bridges. But, given the susceptibility of wood to moisture and insects (despite all the protective impregnations), recently they have been used mainly for roofing, or as floors between floors in private construction.

As for the classification, according to the purpose, we can distinguish:

• wooden roof trusses- they can be assembled on the ground, and then simply lifted and fixed on an almost finished house. It is very convenient and reduces construction time;
• floor trusses- in this case, they are used as an overlap between floors.

There are certain differences in the form of construction, such types can be distinguished as:

• with parallel belts - used for overlapping between floors;

Note! This type can also be used when constructing a roof with a slight slope.

• triangular - in the construction of private houses, the roof frame consists of several triangular trusses connected on top with a wooden beam;
• rectangular trusses can be used for a roof with a slight slope;
• options with a trapezoidal shape are possible, as well as with a curved upper belt.

As a rule, a wooden truss is made either from a wooden beam or from sufficiently wide boards (if the load is mainly vertical).

But other options are also possible:

• if it is necessary to perceive large loads, combined structures can be used. In them, for example, the lower belt can be made of steel, and the remaining elements can be made of wood. This will reduce the weight as much as possible, and the metal will withstand the operational load without problems;
• there are also farms made of plywood pipes. The main advantage of this type can be considered low weight (even in comparison with an analogue from a bar or board). A small price can also be considered an advantage. Of course, the strength of such structures is somewhat less than that of analogues made of thick beams, which is why they are used mainly not as load-bearing structures;

• farms that combine fiberglass and wood may be considered exotic, but they exist. Fiberglass is quite durable, besides it is lightweight, so the design is quite strong and light;
• but most often there are conventional structures made of solid or glued timber, as well as boards.

More about wooden trusses

To a person far from construction, the use of wooden trusses may seem illogical - why waste time assembling such a structure if you can simply block the span with a wooden beam ().

In fact, this is nothing more than a delusion, and in some cases these designs are simply irreplaceable. For example, a beam with a span of 12 m only under the action of its own weight will give a considerable deflection and cannot be used without additional supports.

Advantages and disadvantages of using lumber trusses

The use of such structures has several advantages:

• large spans can be easily bridged without installing additional supports. No beam can compete with them with a span of several tens of meters;

The video in this article shows the assembly and installation of roof trusses.

Explanatory note
Equivalent uniformly distributed design loads on the truss from snow cover, hanging weights and a lantern
Equivalent uniformly distributed design loads on the truss from crane beams. Estimated loads on truss suspensions
Basic parameters and suspension schemes for crane beams. Loads from hanging loads
Roof truss diagrams with node markings. Marking of truss support nodes on columns and truss trusses
Connection schemes for the upper chords of truss trusses. Farms with a lantern and without a lantern. Connection diagrams of the 2nd type along the lower chords of truss trusses. Truss spacing 6 m
Connection schemes for the upper chords of truss trusses. Farms with a lantern and without a lantern. Connection diagrams of the 2nd type along the lower chords of truss trusses. Truss spacing 12 m
An example of solving the type 1 connection scheme along the lower chords of roof trusses with the number of spans in the temperature compartment up to 3 inclusive. Schemes of the location of stretch marks along the lower chords of the trusses. Truss spacing 6 m
An example of solving the type 1 connection scheme along the lower chords of roof trusses with the number of spans in the temperature compartment up to 3 inclusive. Schemes of the location of stretch marks along the lower chords of the trusses. Truss spacing 12 m
An example of solving the type 1 connection scheme along the lower chords of truss trusses with more than 3 spans in the temperature compartment. Truss spacing 6 m
An example of solving the type 1 connection scheme along the lower chords of truss trusses with more than 3 spans in the temperature compartment. Truss step 6 m. Column step along the extreme rows 6 m, along the middle rows 12 m
An example of solving the type 1 connection scheme along the lower chords of truss trusses with more than 3 spans in the temperature compartment. Step of trusses and columns 12 m
Marking of truss truss nodes and connection schemes along the lower chords of truss trusses in the presence of suspended crane beams. Truss spacing 6 m
Marking of nodes of truss trusses and diagrams of connections along the lower chords of truss trusses in the presence of overhead crane-beams. Truss spacing 12 m
Marking of truss truss nodes and connection diagrams along the lower chords of truss trusses in the presence of overhead crane-beams or overhead loads (hoists). Truss spacing 6 and 12 m
Assortment of trussless trusses
Assortment of truss trusses
Roof truss knots. Knots 74-76. Marking holes on the upper and lower chords of roof trusses
Link attachment points. Knots 77-81
Roof truss nodes in the presence of overhead crane beams or overhead loads (hoists). Knots 65,83-86
Connection nodes in the presence of overhead crane beams or overhead loads (hoists). Knots 64.87-90
Weight indicators of roof trusses. Forces in the rods of roof trusses from single loads
Truss steel specification

Farms 12 meters from a profile pipe

Farm steel span 12 mis a finished or assembled structure at the installation site. It finds application in the installation of prefabricated hangars, industrial and residential buildings, and is also used as a support for load-bearing floors and structures, minimizing labor costs. With steel truss 12 m always in stock in our warehouse!

Farm from a profile pipe span of 12 meters:

Material for the manufacture of metal trusses

Metal trusses are most often made of rough or galvanized steel, while there can be several types of rolled products:

Taurine rental. Basically, farms from it are used in the construction of industrial buildings.

profile pipe.

Corner. Farms from a corner are ideal for the construction of outbuildings or temporary buildings.

Also, in the construction of a lightweight roof, construction trusses made of aluminum profiles are sometimes used. Their light weight greatly simplifies installation work.

Advantages of metal trusses:

F metal staves 12 metersare widely used in modern construction due to a number of undeniable advantages, in particular:

Low manufacturing cost. The production of trusses requires many times less metal than the production of solid beams, while the strength of the structure remains quite high.

The bar grating with a belt can be dismantled and transported to another place, which is especially important for industrial enterprises operating in a time cycle.

12 meter truss installation:

Installation of farms does not take much time.Building trusses differ in shape and design features, therefore they are suitable for the construction of a wide variety of buildings and structures. FThe floor length of 12 meters is a reliable and optimal solution.

The determining factors in choosing a truss are the width of the spans and the angle of inclination of the structure for the construction of which is usedtypical truss 12 meters. Depending on these parameters, the type of metal structure and the cross section of its supporting pipes are selected.The choice of one or another option directly depends on the features of the project of the future structure.Provided that the calculations are made correctly, the high-quality welding work, the construction of trusses requires minimal labor and time costs: after the pipe assemblies rise to the upper piping, they are installed according to the markup.

We are ready to offer youready-made sets of arched hangars by price 1800 rub.m2 on the floor, which are always available onour warehouse. The kit includes: trusses, profiled sheet, gates, fasteners.Deliveries are made to any region of the Russian Federation. The cost of delivery according to the current tariffs of the carrier, orpickup.

Farms 12 meters buy:

We also sellarch trusses,which are always in stock in our warehouse, at the price:

Width 12 - 29 000 rub.per piece (consists of 4 parts, height 6 m in the ridge);

Width 15 - 36 000 rub. a piece (consists of 5 parts, height 7.5 m in the ridge);

Width 18 - 39 000 rub. a piece (consists of 6 parts, height 9 m in the ridge).

Ready for special orderarched trusses:

Width 20 - 55 000 rub.per piece (consists of 6 parts, height 10 m in the ridge);

We start designing by compiling the initial data for design

Initial data

Construction area - Ufa;

The temperature of the coldest day with a probability of 0.98 - minus 41 ° С;

The temperature of the coldest five-day period with a probability of 0.92 - minus 33 ° С;

Truss span length - 12 m;

Truss installation step - 6 m;

Farm ramp slope - 10%;

Snow load - 320 kg / m² (V snow region);

Coating design - girders, profiled sheet, insulation, PVC membrane (see figure below);

Load from suspended equipment and communications - 150 kg / m² (cables, ventilation, false ceiling);

Collection of loads

It is necessary to find the constant load on the floor

The thickness of the insulation is determined in accordance with SNiP 23-02-2003 or SP 50.13330.2012 (Thermal protection of buildings) according to the climatic conditions of construction. Because this is a topic for a separate article, we will assume that we have calculated it and accept the min. cotton wool with a density of 150 kg / m³ with a total thickness of 250 mm. Total mass of insulation 150*0.25=37.5

PVC membrane is laid in 1 layer, its weight is 2.5 kg/m²;

According to SNiP 2.01.07-85* or SP 20.13330.2011, we determine the estimated snow load according to formula 5 of SNiP 2.01.07-85*

where Sg is the weight of the snow cover, taken in accordance with Table 4 of SNiP 2.01.07-85* and map 1 of the annex to SNiP 2.01.07-85*. In SP 20.13330.2011, the formula looks a little different, but the final value should not differ much from the value obtained according to SNiP 2.01.07-85*.

μ = 1, taken according to Annex 3, a slope of 10% equals an angle of 6 degrees.

S=320 kg/m²;

The load on the profiled sheet is 320+37.5+2.5=360 kg/m².

Profiled sheet selection

According to the table on the bearing capacity, we accept the necessary profiled sheet

* in the table means that it is necessary to reinforce the overbearing sections with inserts from profile sections of the same type.

If we take profiled flooring 6 m long, then the loading scheme will be 3-span, but a 2-span loading scheme can be taken as a reserve. The professional flooring H57-750-0.6 mm suits us. For reliability, I recommend taking a thicker corrugated board. in places of damage, corrosion will reduce the bearing capacity and it is better not to choose such materials on the verge. I accepted the profiled H57-750-0.8 mm. The weight of corrugated board is 10 kg/m².

Calculation of the roof run

The slope is not large, so we will not use strands. The load on runs from 1 m² is 370 kg.

We choose the steel grade according to SNiP II-23-81 (see article). Runs, as a rule, use one-piece, without welded joints, so the group of structures for them will be the third. We assign steel C235 for runs. The design resistance of steel, see table 51 of SNiP II-23-81. Ry=230 MPa.

It is necessary to use a purlin with profile 22P according to GOST 8240-97. The critical factor in this case is the deflection - it should not be more than 1/200 of the span, i.e. 30 mm.

Run weight 21 kg/m.p.

Farm design

The optimal height from the point of view of saving metal is the height of the truss 1/4 - 1/5 of the span length. However, the height of the trusses should not be set higher than 3.85 m. at high altitudes, it may be a problem to transport the truss from the factory. In addition, heating costs increase in heated buildings. Therefore, the height of the truss for heated buildings is assigned 1/7-1/12 of the length of the truss span. In addition, you need to know the production technology in order to choose the optimal height (perhaps the farm space is necessary for laying communications).

For a truss with a span of 12 m, the height of the truss in a heated building should be set in the range from 1 to 1.7 m.

Because I need the truss space for laying communications, I decided to assign a truss height of 1.5 m.

The design scheme is as follows:

The truss support nodes on the columns are hinged.

Collection of loads on the farm

The weight of the farm elements is calculated automatically in the program, so we will set it in the program itself.

The weight of the coating structures is transmitted through the truss nodes, the run spacing is 2 m, the span is 6 m. N=(50*2+21)*6=726 kg.

On the extreme run, the load from the weight of the overlap is collected from 1 m, but the run will be from the same section, so the load on the edge will be: N=(50*1+21)*6=426 kg. Although this load will not affect the calculation of the farm, because. in an idealized model, the load is transferred to the support node, but in the case of a frame calculation, a spatial model, or a support reaction calculation, it must not be forgotten.

The final load from the weight of the coating will look like this:

The snow load will be transferred through the girders to the truss nodes, the spacing of the girders is 2 m, the span is 6 m. N=320*2*6=3840 kg. At the edges of the truss, it will be equal to half of this load (although in reality there will be more roof overhangs and they also need to be taken into account, but in this case this does not affect the calculation of the truss, since the load is transferred to the support node).

The resulting snow load will look like this:

Load from suspended equipment (for simplicity, we will take a concentrated load in knots) - N \u003d 150 * 2 * 6 \u003d 1800 kg

The resulting load from suspended equipment is as follows:

I want to draw your attention to the fact that it is necessary to take into account the design loads, and not the normative ones (see SNiP "Loads and Impacts"). In addition, it is not necessary to combine loads of different types, for example, snow and floor weights. they have different safety factors and they must be specified separately in the program.

Creation of a computer model in SCAD

Now about the choice of the type of scheme.

For farm calculations, you can use:

type 1 - Flat articulated-rod system (in this scheme, loads are taken into account only in 2 planes, and all nodes are assumed to be articulated), in the truss, all nodes are assumed to be articulated, so this type of design scheme can be selected;

type 2 - Flat frame (in this scheme, loads can also be only in 2 planes, but in addition to hinge joints, rigid ones can be used), in the truss, the upper and lower chords are usually made in one piece, so the knot between them cannot to be articulated and by installing the hinges in the right places, you can create a scheme that is closer to reality, although this will not greatly affect the result;

type 4 - Spatial hinge-rod system (differs from a flat one in that movement along the axis is allowed Y and rotation around the X and Z axes) can be used, but it is necessary to fix the truss in the support node and attachment points to the connections that will be in the real structure, from displacement along the Y axis and rotation around the X and Z axes;

type 5 - General view system (models are designed here in 3-dimensional format and, accordingly, the load can be applied in all planes and have both hinged and rigid nodes), I usually design in this type of scheme. using this scheme, you can create a 3-dimensional building frame and create a model that is closest to reality, however, when calculating the farm, it is necessary to fix the nodes from rotation and displacement along the axis Y where in reality there will be points of support and connection.

Even for flat tasks, I prefer to use type 5 (General view system) and fix in the necessary nodes from rotation and movement along the axis Y because this allows you to create a circuit that is closest to real conditions.

We choose the CIS design standards.

Units of measurement initially:

Linear dimensions - m (meters);

Section sizes - cm (centimeters);

Forces - t (tons).

You can change some parameters if they are more convenient for you to read and save for default.

The numbers after the selection of units indicate the accuracy of the units, i.e. 1.12 means up to 1/100, 1.123 up to 1/1000. Changing these parameters does not mean that the accuracy of the calculation will change, just numbers will be displayed on the screen rounded up to the specified value, for example, if you want the load accuracy to be up to kg, you must click on the right arrow so that opposite the force inscription is 1.123.

After creating the file, we get into the project tree and the next step will be the construction of the calculation scheme. We go to Design scheme(click on this tab in the project tree).

You can create a design model in SCAD in many ways: generating standard structures and modifying them, creating points in space and connecting them to a design model, importing them from AutoCad. We will make a farm based on standard schemes used in SCAD.

On the Scheme tab, click the button Farm Prototype Generation(2nd button from the left on the top bar)

In the window that appears, there are several standard farm schemes that you can create, the choice is not too large, but we can create a farm roughly resembling ours and adjust it. Choose a tab double farm, We are looking for the most similar scheme. In my version, this is the 3rd scheme from the bottom (depending on the version of the program, the standard schemes may differ). We fill in the initial data for farm design:

Truss span - 12 m;

Truss height - 1.5 m (meaning the height at the base, see picture);

Number of panels - 12 pcs. (in this scheme there are also intermediate racks, but they are not in our scheme, we will remove them later);

Tilt angle is 5.71° (10% angle is 5.71°).

Please note that in SCAD you need to put a period between numbers, not a comma - he does not understand a comma.

Our schema looks like this:

If you didn’t manage to set the parameters correctly the first time, then press the button again Farm Prototype Generation, we will be asked whether to delete this scheme, we answer yes and re-generate the scheme.

Next, you need to edit the resulting scheme, for this we first remove the extra racks, for this we go to the tab "Knots and elements", button "Elements" and in the drop down list button "Removing Items", then select the extra rods (they are highlighted in red):

Now our circuit looks like we intended, but that's not all. In panel "Display Filter" press the button "Knots"

If we look at the diagram, we will see that nodes remained in the place where the remote posts connected to the upper chord of the farm:

In order to avoid these nodes, it is necessary to connect the rods; for this, on the tab "Nodes and elements" -> "Elements", press the button "Combining Rods"

Next, select the rods in pairs and press Enter (you cannot select all the rods at once, because in this case you will get a single rod and the scheme will not be correct). Nothing has changed in appearance, the nodes remain, in fact the elements are connected, and the extra nodes need to be deleted, for this we go to the panel "Nodes and elements" -> "Knots", press the button "Data Packing" a window appears in which we are told that the nodes that do not belong to the elements will be deleted, we agree.

It is very important that these nodes are removed. if in the program this node is hinged, then the solution will not be correct.

Installing hinges in nodes

Next, we need to set the hinges at the nodes (if during the creation of the project the type of scheme 1 - Flat hinged rod system or 4 - Spatial hinged rod system was selected, then the hinges will already be in the nodes).

In the tab "Destinations" press the button "Hinge Installation" click on the button "Hinge Installation", allow rotation at node 1 and 2 around the Y axis

select all the braces of the truss and press Enter. It is also necessary to add a hinge assembly between the 2 upper belts, for this we again press the button "Hinge Installation" and allow rotation around the Y axis for node 2, select the 3rd, upper segment of the upper left chord and press Enter.

To understand which node will be number 1 and which node number 2, you need to know the rules for constructing elements in SCAD - elements are drawn from left to right and top to bottom, so the first node is the lowest left node, the second node is the top right.

To check the location of the hinges on "Display Filter" turn on the button "Hinges".

We get the following diagram:

The small circles near the nodes indicate the hinges. To make sure that the hinges are installed correctly or edit them, you can use the panel "Display Filter" click on the button "Element Information", then select the element of interest and press the button "Hinges" in the window that appears. In this window, you can see which hinges the selected element has, add new ones or remove them.

I did not add hinges in the upper and lower chords because. these belts are made from a single element and there will definitely be a rigid knot, although we know that in order to simplify the manual calculation, these knots were taken to be hinged, but this was done only to simplify the calculations. By and large, the nodes between the braces and chords can also hardly be called articulated, because. they are rather rigidly welded to the belt, but after selecting the profiles, we will remove the hinges and compare the results.

Change the type of finite elements

What it is? There are several types of elements in the SCAD program. Let's click on the button Element Types» on the panel "Display Filters" and we will see that the number 1 has appeared under each element.

Depending on the element type, the bar has several degrees of freedom for deformation. Let's press the button "Assignment of Finite Element Types" tab "Destinations". If we select bar type #1 in the list, then in the description we will see that for this type of bar, movements along the X and Z axes are allowed.

For an element of type 2, it is possible to move along the X, Z axis and rotate around the Y axis.

We are interested in element type 5 - Spatial rod, there are no restrictions on movement for it, so I choose it in order to make the picture more realistic. Although the farm can be calculated and leaving the element type No. 1.

Select element type 5, click OK, select all elements of the farm and press Enter.

Now we have all elements of rod type #5.

Fixing the farm in space

Next, we need to fix the farm in space. For this, in the tab "Destinations" press the button "Establishing connections in nodes". We have articulated nodes, so we must prohibit movement in all directions and rotation around the X and Z axes in one node, and prohibit movement in all directions except the X axis in the other and also secure it from rotation around the X and Z axes. To make it easier to navigate in the location of the axes in the panel "Display Filters" press the button "Displaying a shared coordinate system", the directions of the axes will appear on the bottom left of the screen.

After pressing the button "Establishing connections in nodes" menu appears "Connections" in it we mark all the buttons except Uy (i.e. we fix the node in all directions except for rotation around the Y axis), the type of operation "Total Replacement", click OK, select the leftmost node (we have it number 7), the node should highlight in red and press Enter.

To display the node number on the panel "Display Filter" Click on the Node Numbers button.

To make sure the anchor is set in "Display Filter" press the button "Connections", you should see a yellow rectangle in the pinned node.

To view in which directions movements are prohibited in a node on the panel "Display Filter" press the button "Node Information" and select the node of interest, in the same place you can change the fixings if necessary.

Next, we fix the right corner (in our case, No. 13) from moving along the Y and Z axes, and turning around the X and Z axes (button "Establishing connections in nodes"), press OK, select the rightmost corner. It turns out the following picture:

Next, it is necessary to secure the truss from moving along the Y axis at the nodes, where in reality runs and connections will be attached, which will ensure the rigidity of the structure in the horizontal plane. From above, there will be runs in any case; at the bottom, with a given truss design, they may not be.

The girders from above are fixed at the nodes, so we fix the nodes from 8 to 12 from moving along the Y axis. If we had a 3D model of the entire building frame, then this is not necessary, but in this case we fix the truss at the nodes simulating the location of the girders . Also, we don’t need to fix it from moving along the Y axis if we have a scheme type 1 or 2 (Flat hinged rod system or a flat frame), but in my example, scheme type 5 is a General view system (see above if you have already forgotten) .

Initial assignment of truss sections

The program can independently select a section, but first we must assign any section at your discretion. In the future, the program will check it, and then, if necessary, select the optimal section from the same assortment that you have chosen, so you don’t have to bother much about choosing a section, most importantly, if you are designing a farm from paired corners, then these should be paired corners, if you are designing a pipe farm, it must be pipes. the program selects sections from the same assortment that you selected initially.

We are designing a truss from paired corners with a T-shaped section, it is necessary to set the thickness of the gussets. The thickness of the gussets is set based on the maximum stresses that occur in the truss. You can choose the desired thickness of the gussets according to the following table:

Because we do not yet know what loads we will have in the farm, therefore, as a first approximation, we assign 6 mm, in the future we will be able to change this value if necessary.

It is also worth noting that the thickness of the gussets should be the same everywhere, but if necessary, a difference in the thickness of the gussets of no more than 2 mm is allowed.

On the tab "Destinations" press the button "Assigning Stiffnesses to Bars", ways of setting - "Rolled metal profiles", a tab appears "Rolled metal profiles", go to this tab, assign the material "Ordinary steel"(we will assign the steel grade later), at the bottom we tick the tab "Composite section", then select 2 corners (leftmost button), parameter g assign 0.6 cm (remember that you need to write a dot between the numbers, SCAD does not understand the comma), in the right window select "Full catalog of GOST profiles" — >"Equal-shelf corner according to GOST 8509-93", initially we can choose any corner, for example 30x5, it should be like this:

Next, click OK, and select all the elements of the farm and press Enter. To make it easier to select all the elements, press the right mouse button, set "Cursor Type" - "Rectangle" and select all the elements. If you select from left to right, then only those elements that completely fall into the contour are selected, if from right to left, then all elements that at least partially fall into the contour.

Now we can see how our farm looks like, for this we click on the button "Presentation Graphics" on the panel "Display Filters".

In the window, you can view the structure from all sides. If the scheme is displayed as lines, but the section type is not visible, then you must enable the button "Show bar elements"(on the panel above). After viewing, just close the window and we will again get into the program interface.

If we pay attention to the diagram, we will see that the lower belt is drawn with the shelves up, but in reality the shelves will be at the bottom. To rotate a profile 180 degrees in a tab "Destinations" press the button "Setting the orientation of the local coordinate axes of elements". Set the rotation angle in degrees, the value is 180, click OK, select the entire lower belt (you can right-click in the workspace and select the rectangle as in AutoCAD to select the entire lower belt), press Enter.

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