Reinforced concrete farm: description, types, sizing, installation features

In the article we will talk about reinforced concrete trusses of various lengths. The final moment of building a building or structure is the installation of the roof. This element is basic, it is essential to ensure the safety of the building. In addition, the roof has a direct impact on the comfortable stay in the building of tenants or a person (if we are talking about an industrial building). Bearing elements of the roof quite often are reinforced concrete and rafter trusses. With their help, it is possible to redistribute the main and additional weight on the walls of the structure.

Why is it important to make calculations?

If we take into account the fact that the functions of subrafter and truss reinforced concrete trusses of 18 m length are very important in the construction of the building, then it is necessary to approach design, installation and installation with the utmost seriousness and thoroughness.

A slight inaccuracy may affect the strength of the entire building. And its operation is unlikely to be possible.

When calculating the following data should be taken into account:

Maximum reliability and strength of elements that are made of reinforced concrete. But there is one drawback - the installation of reinforced concrete trusses 18 m long is very complicated, and the total mass of the structure is very large. The complexity of installation work is the moment that limits the use of rafters of this design. As a rule, farms of this type can be found in not very ordinary cases. For example, if you need to build a one-story building with a large area.

What to rely on when calculating?

Do not think that the calculations are simple and there are no "pitfalls". Have to acquire a considerable amount of knowledge to carry out the design. When working, you need to rely on GOST 20213-89, which applies to reinforced concrete trusses of 12 m and other lengths.

Please note that you can not miss even the most minor points. Because in the end, you will indirectly or directly affect what strength characteristics the finished product will have. For this reason, all settlement work must be carried out at the time of design. Moreover, it is recommended to entrust this to professionals, because even the smallest details should not be missed. It is important to consider not only the choice of a specific option for rafters, but also small elements for joining.

What factors need to be considered?

When calculating rafter and sub-rafter reinforced concrete trusses, you need to rely on such factors:

1. The total mass of the entire structure. It includes the mass of the rafter system and coating.
2. A mass of periodic loads. These include climatic phenomena, as well as random (for example, the possible circulation of a person).
3. The mass of additional loads that may arise during the operation of the building (for example, snow, wind, etc.).

Accuracy in the calculations will significantly save on construction. But you will also make the most protected object, which can not be affected by various negative factors.

In order to make a farm, you need to use exclusively high-precision equipment. It is important that it is able to perform the necessary work with minimal error. During the installation of the rafter system, it is important to securely fasten all elements so as not to lose the stability of the structure.

Rafter reinforced concrete elements

There is a large number of reinforced concrete truss structures ; they have a different appearance. You can also find differences in the materials used for manufacturing, methods of bearing on the walls. With the help of such structures it is possible to easily build buildings in which sufficiently large spans - more than 24 m. The type of roof can be steadily or pitched. On the surface you can use lights. It should be noted that such reinforced concrete structures are best used in the construction of industrial premises, warehouses, hangars.

The advantages of such structures are as follows:

1. Very high strength of the building as a whole and individual elements.
2. Low temperatures do not affect the material.
3. Fire safety.
4. High degree of rigidity.
5. High resistance to the effects of aggressive environment of any type.

But it is possible to highlight a drawback - it is difficult to mount, since the design has a lot of weight. But this is a minor minus, since it is overshadowed by all the advantages listed above.

How farms are made

For the manufacture of heavy or lightweight concrete (structural type). Typically, claydite concrete and agloporito concrete are used for the manufacture of farms. Production takes place in special booths, which have several (sometimes only one) tiers. On these tiers, steel molds are mounted with a steam jacket. It is imperative to carry out the correct calculation of reinforced concrete trusses. This will affect all characteristics of the structure.

In order to create struts and braces that are laid directly during reinforcement, you need to use a vibrating table. It must have special cassette forms. The upper reinforcement belt is simple rods, there is nothing complicated in the design. But the lower belt is a high-strength wire with a diameter of 5 mm, assembled in special string packages.

To carry out the tension of these string packages, you need to use hydraulic jacks. As soon as the bags are pulled, you can start pouring concrete. After 2-3 hours, you can heat the farm. Please note that at each stage you need to control the quality of the tension of the string packages.

Product Labeling Procedure

In order to mark the finished product, use numbers and letters. Write them with a hyphen. Letters are the type and size of the workpiece, the numbers can reflect various characteristics, for example:

1. The bearing capacity of the structure.
2. Additional data.
3. The brand of concrete used in the manufacture.

The letters may also indicate the permeability of concrete. This is a characteristic that shows the suitability of the structure for operation under various aggressive conditions, for example:

1. The letter “P” in the marking indicates that the product has reduced fitness.
2. The letter “H” is displayed if fitness is normal.
3. Products withstanding seismic activity up to 8 points will have the letter “C” in the marking.

Design Features

The farm is, in fact, the "skeleton" of the roof. It is she who allows to fulfill the outlines of the future design. To give rigidity, strength, stability to the frame, it is necessary to manufacture farms using a large number of reinforced materials and steel. As a result of this, the scheme of the entire product is significantly complicated. Only such structures can ensure the safety of the entire structure, even when exposed to extreme weather events.

But, despite this, most manufacturers are striving to reduce the weight of the finished product. At the same time, strength, as you know, does not suffer, because concrete of light grades is used. As a result, it is possible to reduce the mass of the farm, but not to lose strength.

Design features of farms

The traditional component of any truss made of reinforced concrete is reinforcing steel. It resists corrosion quite easily. Therefore, high humidity and low temperature can not even slightly affect the strength of the roof structure. A farm contour is two belts that work in bending. The lattice is the braces and struts that are responsible for the force acting along the axis. The following types of farms can be distinguished:

1. Segment reinforced concrete farms. A characteristic feature for them is the presence of a diagonal lattice and a contouring belt.
2. Polygonal - belts are parallel or arranged in the form of a trapezoid.
3. Armless arched - distinguished by the presence of rigid nodes.
4. Diagonal arched - have a curved upper belt and crate.

Quite often you can find such that reinforced concrete trusses with a polygonal type coating and even elements in the upper belt are replaced by segment ones. This option is more profitable from an economic point of view. You can also carry out such a classification of farms:

1. Typical.
2. Slanting.
3. Berezkosy.

Where farms are applied

There are several areas of application of different types of reinforced concrete trusses of 24 m and a different length for the manufacture of the rafter system of the structure:

1. In the manufacture of a steep roof, it is best to use dowel-free farms. In the upper zone, it is recommended to install additional racks. Typically, such buildings have a large number of communication systems. The distance between two neighboring farms is 6 or 12 meters.
2. When constructing a single-span building (in the absence of heating), it is best to use downdraft designs.
3. Pitched roofs are best equipped with bevelless segmented or slanted frames.

If it is planned to cover single-story buildings with several spans with rolled material, it is better to use typical reinforced concrete products.

There are a large number of options, but let's talk more about how they are denoted:

1. FBS - diving farms used for the manufacture of pitched roofs.
2. FS - products of a diagonal type, which are also used on pitched roofs.
3. FP - products that are used as a slab coating. The length of the material is the same as that of the span.
4. FPN - for a roof structure in which a small angle of inclination and racks are prestressed.
5. FPM - is applied on roofs with a low angle of inclination without prestressing.
6. FBM - products of the damp-free type, which are used on pitched roofs with a small slope.
7. FT - bezkarazny types of farms of a triangular outline.
8. FPS - they can often be found on pitched roofs.

What to consider during installation?

Before installing such structures, you need to accurately calculate what the building's bearing capacity is. Fasteners should be made to embedded elements on load-bearing walls or columns. Consider the fact that you can not start installation until you are sure that the quality and dimensions of all elements are in accordance with the norm.

When working, you need to use welding - with its help, the connection of supports and embedded elements is carried out. Metal supports also need to be welded to the supports, with their help you will achieve the optimal value of the frame stiffness. The farm can be of this type:

1. Arched (diagonal and bezkrasno).
2. Segmented.
3. Polygonal.

The entire manufacturing procedure must be carried out in full accordance with GOST. In this case, you need to rely on the main characteristics of the products:

1. The strength of the concrete used in the manufacture.
2. Density of concrete.
3. Low temperature response.
4. Steel grade and reinforcement elements.
5. Reaction to corrosion.
6. The diameter of the layer that envelops the reinforcement.

Despite the fact that the structures have high strength characteristics, they are unlikely to be found in private construction. The reason is that the installation is very complicated and the total mass is too large. Very often reinforced concrete products can be found on structures that have a length of more than 18 meters. The step between the farms is 6..12 m.

In the event that the span is not more than 18 meters, it is more reasonable to use beams. But if it is planned to lay a large number of elements of communication systems that will be located in the frame, it is still worth giving preference to products made of reinforced concrete.

If you plan to build a building with a span of more than 30 m, you need to take into account the total mass of the roof. But this parameter will be very large. It would be more rational to break the entire farm structure into blocks. But there is a drawback of this method - the cost of the work will increase significantly. Even construction using reinforced concrete trusses of 24 m in length will be less costly.

If you look at everything from the perspective of quality-price ratio, the best option would be to use arched or segmented structures. There is almost no change in effort on the belts. But it should be noted that the height of the support is not very large. As a result, a significant reduction in the mass of the structure can be achieved.

Farm Construction

The simplest construction option is the installation of a diving arched farm. She has a fairly simple reinforcement of nodes. All the space that is obtained inside can be easily filled with bends for various communication systems. Very often this is done in the construction of flat, low-sloping and pitched structures.

For the manufacture of farms, it is necessary to use the concrete grade B30-B60. It has high strength, and the mass is quite low. In the lower zone, ropes made of reinforcement, rods, and durable wire are used.

In the manufacture of reinforcement, it is allowed to use a frame of light wire. It will avoid cracking during operation of the structure. For convenient crimping of the lower belt, it is best to use frames no more than 3 m.

In order to reinforce the components of the upper belt and lattice, it is necessary to use frames made of welded reinforcement. They must be installed in the support nodes. At the same time, the strength of the entire frame in inclined sections will increase. To strengthen the intermediate nodes on the belts, sets of rods with a thickness of 6..10 mm in increments of 100 mm are used. It is they who make up the welded frame.

For transportation of the finished construction, special equipment is used, for example, the FKP-16 farm truck. As there is an increase in the growth of demand for lightweight steel structures, the demand for reinforced concrete products inevitably falls. But, according to fire safety requirements, reinforced concrete farms are in their way the best.