Don’t know how to make a light and rigid floor in building structures with a large span? In such cases, it is best to use flat metal roof trusses. I will tell you what a farm is and how you can make it yourself in a home workshop.
What does a farm consist of?
By definition, a truss is a building structure made of rigid rods that are interconnected at nodes and form a geometrically unchangeable system. The only unchangeable geometric figure in the coordinate system is a triangle, therefore any truss structure consists of many interconnected triangles.
The technical parameters of the farms are characterized by the following values:
- Span length- the distance between the two closest reference points;
- Bottom chord panel- the distance between two adjacent nodes on the lower longitudinal beam;
- Top chord panel- the distance between the nearest two nodes on the upper longitudinal beam;
- Height - overall size trusses with parallel chords vertically.
If the beam of the upper chord is not parallel to the beam of the lower chord, then two height values H1 and H2 are indicated. Measured from the bottom chord beam to the lowest and highest point of the top chord beam.
- Bottom belt- a longitudinal horizontal beam that connects all connecting nodes in the lower part of the truss structure;
- Upper belt- longitudinal, inclined or radius beam connecting all connecting nodes in the upper part of the truss;
- Racks- vertical transverse links that connect all nodes of the lower and upper chords. They absorb and distribute the main compression load throughout the truss;
- Braces- diagonal cross braces connecting all nodes of the upper and lower chords. Resists compressive and tensile loads. The optimal angle of inclination of the braces is 45°;
- Nodes- connection points of vertical posts and diagonal braces with horizontal beams of the lower and upper chords of the truss. In structural mechanics they are conventionally accepted as a hinge joint;
- Nodal connections. In the manufacture of truss structures, two methods are used to connect all elements in nodes:
- Welded connection with direct adjacency of all elements to each other;
- Bolted or riveted connection - all the belts and cross-bracing bars are connected to each other using a gusset made of thick sheet metal.
When manufacturing a welded truss from thin-walled steel pipe or corner, gussets are also sometimes used to weld elements together.
Types of truss structures
The main advantage of trusses over solid beams is their high load-bearing capacity with low specific gravity and low consumption of materials. According to their structure and the nature of load distribution, truss structures are divided into two types:
- Flat trusses- these are structures in which all the rods are located in the same plane:
- The direction of the applied load vector must coincide with the plane of the truss:
- To resist lateral and shear loads flat trusses need to be fastened with additional longitudinal and diagonal ties.
- Spatial trusses- assembled from a set of rods that are oriented in all three planes:
- They are a little more difficult to manufacture, but at the same time they are able to withstand the simultaneous impact of vertical, horizontal and lateral loads;
- Due to this, spatial metal constructions can be installed without connections with other structures, so they are often used for the manufacture of single beams, support pillars, mast, etc.
In private housing construction, flat trusses are usually used, which in turn are also divided into several types:
- Polygonal farms:
- To make the lower chord, one continuous beam is used, and the upper radius belt is assembled from several straight sections;
- Polygonal steel trusses are used for construction arched hangars or semicircular canopies and canopies with a large span.
- Trapezoidal trusses:
- The lower belt is made of one solid beam, and the upper one is made of two inclined ones;
- A trapezoidal metal truss is most often used in industrial construction for large spans, since it can withstand significant weight and wind loads. Main disadvantage- high altitude.
- Parallel or rectangular trusses:
- From the name it is clear that the upper and lower chords are made of two parallel beams, and the outline of the structure is rectangular;
- This is the most common type of farm. They are easy to make with your own hands and have virtually no restrictions on use.
- Segmental farms:
- They are made by analogy with a polygonal design, only for the upper chord, not straight beams are used, but a solid segment of a circle;
- To make the segments, I recommend using a steel pipe rolling machine;
- Symmetrical triangular truss:
- They are made in the form of an isosceles triangle with vertical posts and diagonal braces;
- Used in construction gable roof, and the inclined beams of the upper chord are used as rafters.
- Asymmetrical triangular trusses:
- They have a similar design, but are made in the form of a right triangle;
- They are used as load-bearing trusses for single-pitched sloping roofs.
How to make a roof truss
Below are instructions for making a flat parallel truss. If you need a truss structure of a different shape, you can make it in the same way.
Stage 1: preparing tools and materials
To make trusses and spans you will need a garage or a spacious home workshop, a set of plumbing tools and welding equipment:
| Illustration | Description of work |
|
Locksmith tools:
|
|
Power tools:
|
|
Materials:
|
Stage 2: making a flat truss
In most cases building construction assembled from several flat trusses of one or two identical sizes. Below I will give an example of making one of them:
- Cut the rolled metal into the required sections in accordance with the drawings;
- After sawing, remove burrs from the ends of the pipes and wipe them from factory grease with white spirit and acetone;
- If there are traces of corrosion on the pipes, they must be removed with a grinder with a cleaning disk;
- Mark and drill all necessary holes in the pipes;
- For convenience, connect each group of segments masking tape and mark with a marker.
- Place the beams of the upper and lower chords on the welding table, and weld the outer side posts to them;
- After that, boil everything inside vertical racks and diagonal braces;
- Support heels, brackets and mounting plates welded last;
- First, all the parts must be assembled using spot tacks;
- When you are sure that everything is done correctly, you need to weld the joints with a continuous seam;
- Clean weld seams from slag and scale;
- Finished awnings made from profile pipes should be painted with anti-corrosion primer and metal enamel.
If you need to weld many parts of the same type, I recommend first making a template on a sheet of thick cardboard, hardboard or plywood.
Conclusion
Now you know what metal trusses are used for and how you can make them in your garage or home workshop. I also advise you to watch the video in this article, and leave all your questions and suggestions below in the comments.
(support brace).
Classification
Farms are classified according to the following criteria:
- The nature of the outline of the external contour
- Parallel belts
- Broken belts
- Polygonal belts
- Triangular belts
- Grate type
- Triangular
- Diagonal
- Semi-diagonal
- Rhombic
- Type of support
- Beam
- Arched
- Cantilevered
- Beam-cantilever
- Purpose
- Rafters
- Pratt truss (with compressed posts and stretched braces)
- Warren truss (with triangle lattice)
- Belgian (triangular) truss
- cross-braced truss
- overhead light truss
- Rafters
- Pavements
- Crane
- Tower
- Material of execution
- Wooden
- Metal (steel and aluminum)
- Reinforced concrete
- Made from polymer materials
Application area
Trusses are widely used in modern construction, mainly for covering large spans: bridges, rafter systems industrial buildings, sports facilities. This design can also be used by specialists in production various types pavilions, stage structures, tents and podiums.
Operating principle
If you arbitrarily fasten several rods on hinges, they will randomly spin around each other, and such a structure will be, as they say in structural mechanics, “changeable,” that is, if you put pressure on it, it will fold, just like walls fold matchbox. It’s a completely different matter if you make a regular triangle from the rods. Now, no matter how much you press, the structure will only be able to fold if you break one of the rods or tear it away from the others. This design is already “unchangeable”. The truss design contains these triangles. Both the tower crane boom and the complex supports are all made up of small and large triangles.
It is important to know that since any rods work better in compression-tension than in fracture, the load on the truss should be applied at the points of connection of the rods.
In fact, the truss rods are usually connected to each other not through hinges, but rigidly. That is, if you take any two rods and cut them off from the rest of the structure, they will not rotate relative to each other. However, in the simplest calculations this is neglected and it is assumed that there is a hinge.
The principle of calculating trusses by cutting out nodes
There are a huge number of ways to calculate trusses, both simple and complex. One of the simplest is calculation by cutting out knots. This method Suitable for the simplest flat farms and used for teaching students of technical colleges.
To calculate a truss, all forces acting on the truss are reduced to its nodes. After the forces acting on the truss are determined, the reactions of the truss supports are calculated. After the reactions are determined, take any node in which only 2 rods meet and any forces are applied. Mentally we cut off the rest of the truss and get a node in which several known forces (for example, the reaction of the supports) and two unknown forces meet - those forces that act in the truss rods that we have not cut. Find unknown forces in the rods by composing equations for the equality of forces along any two axes. Next, knowing these forces, the next node is cut out, etc., until the forces are found in all the rods.
Examples
- Metal power line support (power line).
see also
Notes
Links
Wikimedia Foundation. 2010.
See what “truss (structure)” is in other dictionaries:
Truss: A truss is a structure, the main elements of which work in tension and compression. A farm is an agricultural enterprise owned by a farmer. A farm is a livestock-raising agricultural enterprise. A farm in the USA is everyday ... ... Wikipedia
A flat structure consisting of individual rods or disks interconnected, covering the hole between the supports and transferring the load it perceives to the latter. Arched truss Made of metal, wood or reinforced concrete.… … Technical railway dictionary
Farm- – flat rod supporting structure. [Terminological dictionary of concrete and reinforced concrete. FSUE "Research Center "Construction" NIIZHB named after. A. A. Gvozdeva, Moscow, 2007, 110 pp.] Truss is a load-bearing rod structure, as a rule... ...
Rafter truss- (from French) - a building load-bearing structure for covering, as a rule, large spans, is a flat structure of rod elements connected in hinged and/or rigid units, consisting of elements of the upper compressed ... Encyclopedia of terms, definitions and explanations building materials
Truss without diagonals- – Truss without braces [TRUSS FRAME] – rod beam structure, consisting of parallel belts and racks rigidly connected to them, by analogy called a truss. [Terminological dictionary of construction in 12 languages (VNIIIS... ... Encyclopedia of terms, definitions and explanations of building materials
- [FRAME TRUSS] a rod beam structure consisting of parallel chords and racks rigidly connected to them, by analogy called a truss ( Bulgarian language; Bulgarian) virendelova greda; frame farm (Czech; Čeština) rámový… … Construction dictionary
truss (in structural mechanics)- truss A rod system that remains geometrically unchanged if all rigid nodes in it are replaced by hinged ones. [Collection of recommended terms. Issue 82. Structural mechanics. Academy of Sciences of the USSR. Committee of Scientific and Technical Terminology. 1970...
truss without braces- A rod beam structure consisting of parallel chords and racks rigidly connected to them, by analogy called a truss [Terminological dictionary of construction in 12 languages (VNIIIS Gosstroy USSR)] Topics: structural mechanics, ... ... Technical Translator's Guide
- (from the Latin firmus strong) (construction), a rod-bearing structure in which the connections of the rods in the nodes are assumed to be hinged during the calculation. Metal, reinforced concrete, wooden and combined trusses are used in coatings... ... Modern encyclopedia
Truss (French ferme, from Latin firmus √ strong, durable), a supporting structure consisting of straight rods, the nodal connections of which are conventionally assumed to be hinged in the calculations. F. is used mainly in construction (coatings... ... Great Soviet Encyclopedia
A building truss is a metal structure consisting of individual inclined braces or vertical posts, which are interconnected into separate units located on the lower and upper chords of the truss using welded joints; their totality forms a rigid structure. The connected posts distribute the load evenly throughout the truss structure, which transfers it through the support columns to the foundation. In this case, the upper belt works in axial compression, and the lower belt in tension.
Types and varieties
The braces connected to each other form a triangle, which is considered the most durable geometric figure. Therefore, almost any structural diagram of a farm, regardless of its type, consists of a set of a certain number of non-changing geometric shapes in the form of triangles.
Farms consist of the following elements:
Nodal connections can be:
- Welded - all structural elements are connected to each other by welding.
- Bolted or riveted joints - elements are connected to each other using bolts or rivets on a common steel embed (gusset) made of thick rolled sheet.
A steel truss, compared to solid beams, is lighter in weight, less metal is required for its manufacture, and it is characterized by high bearing capacity. And by its design and distribution of vertical loads farms are divided into two types:
Structural devices are much more complex to assemble, but due to their design, are able to carry both vertical and lateral loads. At the same time, they do not require the installation of additional purlins for connection with other metal structures, so they are often used for one solid covering of large and fairly wide spans with a minimum number of support columns.
Design features
Any metal devices, regardless of their design, contour and shape, have their own characteristics and certain parameters. But still, according to the installation method, in addition to the classical one, when the structural device rests on supports at both ends, sometimes there are structural structures in which one edge turns out to be hanging, that is, without support. They are usually installed for the floors of buildings in which the roof slope extends far beyond the outer walls.
Depending on the design, trusses can be straight, single or double slope. According to the contour they differ into several types:
Types of gratings
The following types of gratings exist:
- Triangular lattice. Is the toughest and effective system in designs with parallel, triangular and trapezoidal outlines.
- Diagonal grille. It consists of the longest braces that work simultaneously in compression and tension, but the vertical struts only work in compression.
There are also special cross, truss and other grilles.
An important parameter of truss design is their angle of inclination, and depending on it, designs are divided into 3 groups:
Almost all construction trusses have considerable advantages in front of all-metal beams, among which the main ones are:
Manufacturing of structures
As a rule, the designs of trusses made of metal are selected depending on the designed angle of inclination of their upper chord, the width of the overlapped span and purpose. If we take into account the floors of industrial buildings, bridges and overpasses, where they are most often used, then for this purpose construction trusses are manufactured with a standard length of 12, 18, and 24 m/p.
General requirements
For heavier and more critical structures (bridges and overpasses) they are used I-beams and channels. All hydraulic structures are assembled from elements round section or profile pipes.
Most often, a reinforced rolled angle is used to assemble standard construction trusses. In this case, for the manufacture of all its elements, a paired corner is used, the blanks of which are connected to each other by welding with special metal plates (fishes) inserted between them. The corners are paired in such a way that they cross section resembled a T-section.
However, recently metal structures of this configuration have begun to be in less demand due to the complexity of assembly, welding and painting. Steel profile or round pipes are increasingly becoming an alternative to such structures.
Correct calculation
You need to understand that making a quality calculation carrier device possible only with availability special knowledge taking into account the requirements of SNiP and many other numerous factors. In order to correctly make calculations, designers use special programs.
Calculating the project engineering device, all obtained values must be included in the design drawing, without which assembly of the structure will be almost impossible.
Initially, before drawing up a drawing project, a truss diagram is prepared indicating the main dependence of the slope of the upper chord and the total length of the future product. Factors such as:
Once the main parameters have been calculated, you should decide on the design diagram. It is best to use special programs for this, which can be freely found on the Internet. For example, you can use the Truss Calculation program.
Assembly of the structure
All elements of trusses for covering long spans are manufactured and adjusted in the factory, and part of the assembly of the structure is also carried out there . Its complete installation is carried out directly on the construction site strictly according to detailed drawings that come with the product. The drawing shows individual markings of all structural parts and provides instructions explaining the entire assembly process.
Typically, product blanks have special mounting holes, with the help of which you can assemble and temporarily secure, without the use of clamps and special fastening clamps, all parts of the structure when preparing it for welding work.
If there are no such holes, temporary fixation of the workpieces is carried out using clamps and short welds.
Most metal device parts are electrically welded or connected using bolted connections. The degree of reliability of such connections depends on the force with which the bolts were tightened. This work is usually carried out by two installers who tighten the nuts using long-handled wrenches or pneumatic impact wrenches.
Complete connection of truss structural elements by electric welding are produced in cases where it is required to obtain the most durable connection. Particularly important fastenings of parts can be made using thick steel rivets.
Installation of assembled structures is carried out using a crane, and heavy structural structures can be installed with two cranes. After installation completely assembled structure on columns, it is welded to a mounting plate rigidly fixed to the column head.
Currently farms have become widespread in structural mechanics during the construction of various buildings and structures.
The definition of what a truss is comes from the very meaning of the word from the Latin “firmus”, which means “strong”. Metal trusses have a high degree of rigidity and reliability.
The truss is a load-bearing lattice structure of inclined arms (slope angle of about 20°) in the form of a triangle, which is geometrically unchanged. The main purpose of trusses is to carry loads from the floor. Such structures are used for constructing roofs, roofs, ceilings and coverings of industrial and civil buildings and structures, for example, factories, hangars, warehouses, public facilities, stadiums, swimming pools, and are used for constructing utility networks, electrical wiring or ventilation shafts of buildings.
Manufacturing and installation of metal structures for trusses
The material, manufacturing method, joining of elements and the design of the trusses are selected depending on the operational requirements for the final structure.
Traditionally, load-bearing trusses are made from steel or aluminum alloys pair profile. The basis of the truss are rods, which are connected at the points of fastening with gussets. Metal rods arranged in a triangle, thereby achieving high rigidity non-thrust design.
The structural elements of the trusses are the belt, i.e. the outline of the truss, and a lattice of braces and posts.
Drawing of structural elements of a metal truss
1 - upper belt; 2 - lower belt; 3 - braces; 4 - racks
The length between the nodes of the belt is called panel. The distance between supports is span, and the distance between the outer edges of the belts is truss height. The truss belt carries longitudinal loads, the truss lattice - transverse loads.
The upper chords of the truss are made from two angles with a T-section, having unequal side lengths. The corners are joined on the smaller sides. Equal angles are used for the production of lower belts. Angles with T-shaped or cross-shaped angles are used for the manufacture of braces or racks.
There are welded trusses that are made from brands.
The truss is a geometrically unchanged structure, because its elements are connected rigidly and not hinged. The steel rods of the truss absorb tension-compression loads.
For private construction use roof trusses from profile bent or hot-woven pipes that are welded on site.
The Saratov Reservoir Plant produces trusses in rigid conductors. High manufacturing precision is achieved by milling the ribs of the mounting flanges.
The SARRZ plant produces metal trusses in accordance with GOST 23118-99. This standard regulates the requirements for materials, connections of elements, and marking of structures.
Types of metal structures of trusses
The main types of metal trusses are flat and spatial: flat trusses, the rods of which lie in the same plane, perceive loads only in one plane, while spatial trusses form a spatial beam and absorb loads in any direction. A spatial truss consists of faces in the form of flat trusses.
Flat trusses are attached to other elements of the building frame using ties.
Drawing of a flat and spatial metal structure of a truss
a) flat trusses, b) spatial trusses
According to their intended purpose, trusses are mainly used as trusses and sub-trusses: sub-trusses connect the support columns and are the basis for fastening the trusses.
There are also classifications:
by magnitude of maximum effort (heavy, light);
according to the outline of the belts (segmental, with parallel belts, with broken belts, triangular, trapezoidal, polygonal);
Classification of truss metal structures according to the outline of the chords
a - with parallel belts; b - polygonal; c - triangular; g - with nodes on a parabola or arc of a circle for one belt; d - the same for both belts
according to the lattice system (cross, triangular, rhombic, diagonal);
according to the static scheme/type of support (beams cut/uncut, beams cantilever, frame, arched, combined, cable-stayed);
Classification of trusses by lattice types and types of support
a - beam diagonal; b - beam with a triangular lattice; c - beam-cantilever with a triangular lattice and additional racks; g - cantilever semi-diagonal; d - cantilever two-diagonal; e - double-lattice beam; 1 - upper belt; 2 - lower belt; 3 - brace; 4 - stand
by the method of connecting elements (bolted, riveted, welded);
according to the purpose of the truss (rafter, Pratt truss with compressed racks and stretched braces, Warren truss with a triangle lattice, Belgian triangular truss, cross-braced truss, overhead truss, truss, bridge, crane, tower).
Buildings, bridges and transport galleries are constructed from beam cut trusses, since their installation is quite simple, there is no need for complex support units. Beam uncut trusses are used in the construction of structures of two or more spans. This choice is due to the fact that continuous trusses have greater rigidity compared to uncut ones and are smaller in height. For the construction of canopies, towers and structures such as supports air lines power transmission, use cantilever trusses. Frame trusses are less metal intensive, so they are used for the construction of long-span buildings and structures. The use of arched trusses increases the volume of the structure. The use of this truss design is due to architectural requirements. Cable-stayed trusses only carry tensile loads, which is why they are chosen for the construction of long-span structures and bridges.
The outline of the truss chords is dictated by efficiency and is selected in accordance with the schedule for calculating the loads on the object.
The number of gratings and other elements affects energy and labor costs, the cost of the structure and the complexity of installation. The most cost-effective truss is the triangular lattice truss. Diagonal lattice is used for the construction of buildings and structures of low height with large acting nodal loads. Cross lattice is used in trusses that carry loads in all directions. The rhombic lattice of the truss has the greatest rigidity, therefore similar design used in the construction of bridges, towers, masts.
The most common method of fastening truss elements is mechanical welding. High-strength bolted connections are used when connecting assembly units.
Thus, the use of trusses in the frame of a building or structure is due to the need to construct structures with large spans and high operating loads.
The Saratov Reservoir Plant produces farms of various structural forms in accordance with the requirements for operating conditions, the purpose of the building and structure and other wishes of the Customer. All truss structures produced by our Plant are characterized by high strength and rigidity. At all stages of production of truss metal structures, our specialists are guided by existing standards and rules governing production, installation and construction processes. All work performed meets the requirements of regulatory authorities.
How to order the production of metal trusses at the Saratov Reservoir Plant?
To calculate the cost of producing metal trusses, you can:
- contact us by phone 8-800-555-9480
- write to email technical requirements to metal structures
- use the form " ", provide contact information, and our specialist will contact you
The Plant’s specialists offer comprehensive services:
- engineering surveys at the operation site
- facility design oil and gas complex
- production and installation of various industrial metal structures
Sooner or later, the owners of a private house need to build a carport or a summer holiday on their property, a gazebo, a small fence with a roof for pets, or a canopy over a woodpile. In order for the roof over such a structure to be securely fastened, it is necessary to correctly design and install metal supporting structures.
We welcome our dear reader and offer him an article about what profile pipe trusses are, how to correctly calculate and install them.
A truss is a structure of rectilinear elements connected to each other at nodes into a durable system of unchangeable geometric shape. Most common flat designs, but in large loaded structures, volumetric (spatial) trusses are used. Almost in private houses, farms are made of wood and metal. Small structures of rafters, canopies, and gazebos are made from 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 welding, therefore, for manor buildings, a profile pipe is most often used.
Structural features of trusses
Components of the truss structure:
- Belt.
- The stand is a vertical element connecting the upper and lower belts.
- Brace (brace).
- Sprengel - support brace.
- Grills, overlays, gussets, rivets, bolts - all kinds of auxiliary and fastening materials.
The height of the truss is calculated from the lowest point of the lower chord to the highest point. Span - the distance between supports. Rise is the ratio of the height of the truss to the span. The panel is the distance between the nodes of the belt.
Types of trusses from professional pipes
Farms are divided according to the outline of the belts. There are two-band and three-band 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 outlines of the chords: beams with parallel chords (rectangular), triangular (gable and single-pitch), trapezoidal (gable and single-pitch), segmental (parabolic), polygonal (polygonal), cantilever; with a broken raised or concave lower belt and a varied shape of the upper belt; arched with horizontal and arched lower belt; complex combined forms.
Trusses are also distinguished by types of gratings - see in the figure. In private buildings, triangular and diagonal grilles are most often found - simpler and less metal-intensive. Triangular gratings are usually used in rectangular and trapezoidal structures, while diagonal gratings are used in triangular ones.
Before erecting any structure, you should decide on the choice of material. At the time of buying metal profile or pipes, you should carefully inspect the workpieces to see if there are any cracks, cavities, sagging, inconsistencies along the seam, or a large number of dented and bent workpieces. When purchasing galvanized materials, it is advisable to check the quality of the coating - whether there are any peelings or sagging.
When purchasing, you must request a copy of the certificate and a receipt. It is imperative to ensure that the pipe wall thickness corresponds to that stated in the documents. You can’t make pipes in a garage on your knees, 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, usually in purchased products (awnings, rocking chairs). For the construction of metal structures, you can use pipes of hollow section and solid section profiles (circle, strip, square, channel, I-beam).
A huge advantage of rectangular and square pipes compared to a profile of the same weight is their high resistance to crushing and other deformations. Therefore, solid profiles can be replaced with much lighter corrugated pipes - this greatly simplifies (2 times or more) and reduces the cost of a tubular type design.
The cross-sectional dimensions of the pipes are selected depending on the span length and the distance between the 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, profiles of 40x20x2 mm are suitable, for spans of up to 5 m - 40x40x3, 60x30x3 mm; spans longer than 5 m – 60×40x3, 60×60x3 mm. If you are planning a carport for two cars with a width of 8-10 m, then a profile will be required from 60x60 to 100x100 with a wall thickness of 3-4 mm. The profile dimensions depend on the distance between the trusses.
Corrugated pipes are sold in lengths of 6 and 12 m. With a length of 12 m, metal is consumed more economically, but transporting such pipes requires a long length. Before purchasing materials, you should think about 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 corrugated pipe you will need.
You cannot rely on the nominal weight - the weight is 1 m.p. in a particular batch will differ from the nominal one, and most likely upward (it is more profitable for sellers to produce products with a thicker wall - the price is per ton). When purchasing by weight, the material will have to be purchased and transported - and this is an extra expense.
Advantages and disadvantages of different metals
In practice, steel is used for structural profile pipes the following types: carbon of ordinary quality and high-quality, structural, alloyed. Pipes come with a protective zinc coating. Aluminum is also used - but rarely, for small, often seasonal structures. Aluminum profiles are used for small structures.
Traditionally, for small structures in a private estate, carbon steel St3sp, St3ps, and sometimes galvanized, is used for the construction of steel structures with trusses. This steel has sufficient strength to ensure the reliability of the structure; there is practically no difference in corrosion resistance between all three types of steel.
If structures are exposed to precipitation, 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, 38KhA 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 and tempering can warp pipes, and usually such heat treatment does not finished products no one does. Annealing can be carried out on seamless pipes - after annealing, residual stresses in the metal are removed (hardening), but it becomes softer.
Structural steels (20A, 45, 40, 30A) are of higher quality and more high price. Alloy steels are even more expensive (and there is a chance that they will sell you pipes made from steel 3 instead of alloy steel). Therefore, when installing structures less than 20 m wide, it does not make sense to buy professional pipes made of alloy or structural steel. It definitely makes sense to use galvanized corrugated pipe if the installation will be carried out using crab systems.
If installation is carried out by welding, the welds will rust as quickly as ordinary uncoated metal. But if you carefully monitor the seams and 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 - especially don’t bother, buy ordinary pipes from carbon steel without cover.
If you plan to build on a plot of very large canopy or a hangar with a long span, it is worth contacting professional builders and make a project - they will determine which steel you should choose.
Make it yourself or order it
Trusses for a carport or gazebo roof are small in size and simple design– most often triangular with several struts and racks. You can complete such a design yourself if you have at least basic welding skills and are not afraid to learn new jobs.
But the manufacture of trusses requires accuracy, the presence of an assistant, a very flat area on the estate - for laying out and welding structures, the presence welding machine and time. Can be ordered ready-made designs at the factory or construction company, and install it yourself.
Requirements for calculating 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:
- Dimensions of the metal structure, and in particular, length, support spacing - the distance between supports.
- Height of supports and trusses.
- Farm shape.
- Possible features of geological conditions (seismic activity, possibility of landslides).
- Coating weight.
What happens if you calculate incorrectly
If the calculations are incorrect, the following consequences are possible:
- Farm structures will deform under the weight of snow and wet leaves.
- In the worst case, the structures will deform under their own weight.
- The entire structure may collapse in strong winds.
- Deformation will sooner or later lead to the destruction of the truss and the entire structure, which is dangerous for humans and can damage objects located under the canopy - a car, for example.
- A fragile and movable structure will lead to the destruction of the roof laid on the truss.
- When using a profile that is too powerful and heavy, the costs of materials and work during the construction of metal structures increase unjustifiably.
We design a farm and its elements
A complete and accurate calculation of the load on a truss along with diagrams is complex, and to perform it you should contact specialists.
When designing large canopies, hangars, and garages made of metal structures, an accurate calculation of the required profile is necessary, but for the construction of not too large canopies or gazebos in a private estate, you can use the well-known recommendations of experts.
For very small structures (a canopy in an animal enclosure, a canopy over a firewood store), it is enough to use pipes measuring 40x20 mm with a wall thickness of 2 mm; for gazebos and canopies over tables, barbecues or recreation areas - 40x40 mm with a wall thickness of 3 mm; canopy over a place for a car - from 60x40 to 100x100 mm with a wall thickness of 3-4 mm.
If the canopy has several trusses and supports and the support spacing is less than 2 m, you can take a thinner pipe; if there are only 4 supports and two trusses and the span length is 6-8 m or more, you can take a thicker one.
Permissible loads on trusses are given in the table:
| Span width, m Pipe size per wall thickness, mm | 1 | 2 | 3 | 4 | 5 | 6 |
| For profile pipe | ||||||
| 40×40x2 | 709 | 173 | 72 | 35 | 16 | 5 |
| 40×40x3 | 949 | 231 | 96 | 46 | 21 | 6 |
| 50×50x2 | 1165 | 286 | 120 | 61 | 31 | 14 |
| 50×60x3 | 1615 | 396 | 167 | 84 | 43 | 19 |
| 60×60x2 | 1714 | 422 | 180 | 93 | 50 | 26 |
| 60×60x3 | 2393 | 589 | 250 | 129 | 69 | 35 |
| 80×80x3 | 4492 | 1110 | 478 | 252 | 144 | 82 |
| 100×100x3 | 7473 | 1851 | 803 | 430 | 253 | 152 |
| 100×100x4 | 9217 | 2283 | 990 | 529 | 310 | 185 |
| 120×120x4 | 113726 | 3339 | 1484 | 801 | 478 | 296 |
| 140×140x4 | 19062 | 4736 | 2069 | 1125 | 679 | 429 |
| For rectangular pipe(with the larger side vertical) | ||||||
| 50×25x2 | 684 | 167 | 69 | 34 | 16 | 6 |
| 60×40x2 | 1255 | 308 | 130 | 66 | 35 | 17 |
| 80×40x2 | 1911 | 471 | 202 | 105 | 58 | 31 |
| 80×40x3 | 2672 | 658 | 281 | 146 | 81 | 43 |
| 80×60x3 | 3583 | 884 | 380 | 199 | 112 | 62 |
| 100×50x4 | 5489 | 1357 | 585 | 309 | 176 | 101 |
| 120×80x3 | 7854 | 1947 | 846 | 455 | 269 | 164 |
Drawings and diagrams
When manufacturing metal structures, drawing with exact dimensions is mandatory! This will allow you to purchase the required amount of material, save time when assembling and preparing workpieces, and allow you to easily control the dimensions of the metal structure during installation and the finished structure. IN in this case The safety of you and your household depends on the accuracy of the assembly - a structure that collapses due to snow or wind can bring a lot of trouble.
Truss Calculation Basics
The types of trusses depend on the shape of the roof, and the shape of the roof of a structure on an estate is chosen depending on the purpose and location of the metal structures. Cantilever trusses and farms adjacent to the house are usually made with single-pitched triangular ones, free-standing canopies - with polygonal, triangular, segmental structures and arches. Gazebos can have a six- or eight-slope roof or a fantasy roof with trusses of a non-standard design.
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 snow cover, roofing, sheathing, and the weight of the structures themselves. Accurate calculations- a task for a professional builder. The basis for the calculation is SP 20.13330.2016 “Loads and impacts. Updated edition of SNiP 2.01.07-85" and SP 16.13330.2011 "Steel structures. Updated edition of SNiP II-23-81".
For calculations, the cutting method is used: cutting out nodes (areas where the rods are hingedly connected); Ritter method; Henneberg rod replacement method. In modern computer programs The method of cutting out knots is more often used.
It's better to use a ready-made one standard project or our recommendations for choosing profiles. Assembling a truss of a simple trapezoidal or triangular structure is not too difficult, and if you have experience in welding and installing metal structures self-installation awnings and gazebos are quite possible. If you want to build a large shed with a truss length of 10 m or more, you need to complete the project with specialists.
Influence of inclination angle
The design of the truss is primarily affected by the angle of inclination of the ramps (ramp). The angle of inclination is selected primarily depending on the shape of the roof and the placement of the metal structure. Sheds adjacent to buildings should have a larger roof angle to allow snow sliding off the roof to roll off more quickly and flowing water to drain away.
For single structures, the roof slope may be less. The angle of inclination also depends on the amount of precipitation that falls in your region - the more precipitation, the greater the angle of inclination of the roof should be. The steeper the roof, the less precipitation it retains.
A slight slope of the slope - up to 15° - is used on small free-standing sheds. The height of the slope is approximately equal to 1/7-1/9 of the span length. Trapezoidal trusses are used.
Slope from 15° to 22° - the height of the slope is 1/7 of the span length.
Slope from 22° to 30°-35° - the height of the slope is equal to 1/5 of the span length; with this slope, triangular structures are usually used, sometimes with a broken lower chord to make the structure lighter.
Base Angle Options
For correct calculation quantities and lengths individual elements for a truss made of corrugated pipe, it is necessary to determine the base angles between the elements. In general, the lower chord is perpendicular to the supports, the upper chord is inclined to the horizontal depending on the angle of the roof. The optimal angle of inclination of the braces to the horizontal/vertical is 45°, the racks must be strictly vertical.
The exact angle of inclination of the roof is either specified by the project, or is found according to the relationships given above ( for a slope of up to 15° - the height of the slope is approximately equal to 1/7-1/9 of the span length; for a slope from 15° to 22° - 1/7 of the span length; for a slope from 22° to 30° - 35° - the height of the slope is equal to 1/5 of the span length).
Having determined the exact angle of inclination of the roof, the lengths of the blanks for making the truss are determined - this information will be required when performing the work.
Significant factors for site selection
If you have a choice, you should choose a flat area for installing metal structures that is not prone to landslides and waterlogging. But in small personal plots Most often there is no choice - a carport is placed right behind the gate, a veranda near the house, a gazebo in the depths of the site. The area may need to be leveled and sometimes drained.
If there is a danger of soil layers sliding, or you live in an earthquake-prone area, the design of any structure above a dog kennel should be left to professionals to ensure your safety.
How to calculate the load
Snow load per 1 m² of roof is calculated according to SP 20.13330.2017 “Loads and impacts. Updated version of SNiP 2.01.07-85" depending on the region. When calculating, it is not the roof area that is taken, but the area of the roof projection onto the horizontal. The weight of the sheathing and roofing is calculated in the same way. According to the drawing, the weight of one truss is calculated and multiplied by their number.
The load on one truss is calculated by dividing the sum total load on the roof of snow, the weight of the sheathing and covering, the weight of the structures themselves, and the number of trusses.
Entrance door and canopy
The canopies above the front door are small in size and cantilevered.
The width of the canopy should be equal to the width of the porch + 300 mm on each side. The depth of the canopy should cover the steps. The length of the canopy is equal to the sum of the length of the platform and steps. The length of the upper platform should be one and a half times wider than the door, that is, 0.9 × 1.5 = 1.35 m. Plus 250 mm for each step.
For example:
for a porch with two steps and a width of 1200 mm, the dimensions of the covered area ( horizontal projection visor) are equal:
length (visor depth) = 1.35 + 2×0.25 = 1.85 m;
width = 1.2 + 0.3×2 = 1.8 m.
Free calculation programs
- On the site http://sopromatguru.ru/raschet-balki.php.
- On the site http://rama.sopromat.org/2009/?gmini=off.
Calculation example
An example of calculating the truss of a free-standing carport for a middle-class car (D):
The width of the car is 1.73 m, length 4.6 m.
Minimum truss width between supports:
1.73 + 1 = 2.73 m, for ease of opening doors we take a width of 3.5 m.
Truss width including roof overhangs:
3.5 + 2×0.3 = 4.1 m.
Canopy length:
4.6 + 1 = 5.6 m, take a length of 6 m.
With this length it is possible to install supports every 2 m or less. For relax load-bearing structures We assume the distance between supports is 1.5 m.
We adopt a triangular gable roof shape - it is the easiest to manufacture and at the same time economical in terms of material consumption. We take the roof inclination angle to be 30° - at this inclination angle, snow and fallen leaves will not linger on the roof.
The height of the truss in the center (central post) will be equal to:
Total: the length of the lower chord of the truss is 4.1 m; the upper belt - two halves of 2.355 m each, total length 4.71 m, the stand in the center has a height of 1.16 m.
For such short trusses it is quite enough to use square pipe 40×40 mm with a wall thickness of 3 mm.
The main stages of work on the manufacture and installation of trusses with your own hands
Before installing the trusses, work is carried out on site planning, installation of supports, concreting of support foundations, welding of side braces or side trusses. Then the transverse trusses are installed.
The procedure for performing work on the manufacture and installation of trusses:
- Trusses are welded on a flat surface.
- The trusses are treated with an anti-corrosion primer and painted twice. Do not paint areas where trusses are welded to supports. This work can be done after the trusses are installed, but painting at height is inconvenient.
- They lift the trusses, install them on supports, check the angles and horizontality, and weld them to the supports. This work is performed by a team of several people.
- Paint over the welding areas.
- The sheathing is installed and the roofing is laid.
How to weld trusses
The trusses are assembled on a level area. Before assembly, the workpieces are cut, cleaned of rust, and burrs on the cuts are sanded off. The truss elements are fastened with clamps, the dimensions, angles, and flatness are checked. Weld the structure on one side, let it cool, and turn it over to the other side. Remove the clamps and boil the other side. Then the bead on the seam is sanded off. You can see the features of welding trusses in our video:
If you have limited skills as a welder and installer, you can order the manufacture of a truss from a specialized organization or team.
Conclusion
Construction of a canopy and installation of trusses is complex, skilled work. Small canopies and gazebos can be made independently with the help of family members.
It is better to entrust the installation of large metal structures to a team of professionals. But professionals also need supervision. We say goodbye to our dear reader and hope that our article will help you understand the types of trusses, the choice of design, material and the procedure for constructing canopies and gazebos on your site. Subscribe to our website's newsletter, bring friends, share interesting information with your interlocutors on social networks.