Dimensions of beams. Weight and designation of beams
There are many kinds of beams. They are divided by purpose: foundation, for overlapping, supporting; on material: steel, wooden, reinforced concrete. In most cases, all information lies in the designation of the element, but it is clear only to specialists. To find out what is behind the abbreviations in the titles, how to know the size of the beams, determine the weight, the desired type, consider the main categories of construction products.
The beam is a horizontal carrierA structural system having from one to several points of support. It can overlap as one (split), and several spans (continuous). According to the material, the beams are divided into:
- Metal (steel).
- Reinforced concrete.
They are used in construction as load-bearing structures that work on bending, and in mechanical engineering (for example, as an element of a bridge crane).
The largest group. Classification, from which you can get a general idea of the metal beams:
1. According to the working scheme:
1.1. Single-span (split).
1.2. Multiple-span (continuous).
1.3. Cantilever (with one support in the form of pinching).
Fluted is the most convenient formanufacture and installation in comparison with multi-span. Unshielded beams are advisable to be installed on reliable supports, where there is no danger of uneven subsidence.
2. By type of section:
2.1. Rolling (one-T, I, through).
2.2. Composite: welded, bolted, riveted.
The most common in application are I-beam beams - they are simple in production and universal in use. Further, we will consider them.
Parameters of the I-beam
Metal products are differentreliability and high technical indicators. I-beams are no exception. They are referred to the category of long products, production is carried out according to technical specifications. In turn, the specifications are based on the requirements that the beam must meet: GOST 535-2005 "Graded and shaped carbon steel of ordinary quality" they are regulated.
By the form of the beam profile can be:
1) With parallel shelves:
1.1) Normal (B).
1.2) With a wide shelf (W).
1.3) Colonies (K).
In the product name, the profile type is always encrypted. For example, the beam of 20b1 dimensions implies the following: height 20 cm, B - normal, width of shelf - 100 mm (10 cm).
2) With a slope of internal faces:
2.1) Ordinary - 6-12% of the slope.
2.2) Special: M - for hanging ways of cranes and other equipment (≤12%).
2.3) C - for reinforcement of shafts (≤ 16%)
I-beam: dimensions and weight
These values depend on each other, as well as on the type of steel used for production. To determine them, you need to use the lookup tables. Where can I get them?
There are grades based on GOST 8239-89,19425-74, 26020-83. By type of profile, select the appropriate table, find in it the necessary dimensions of the beams, for each specific case, the weight of the product per 1 running meter is given. This value is considered to be a reference, used in calculations, but in practice it may slightly differ from the actual (if the production is conducted according to the specification).
For example: beam 20b1. Dimensions according to the assortment: height - 200 mm, width - 100 mm, wall thickness - 5.6 mm, shelf size - 8.5 mm, radius of curvature of the inner edge - 12 mm.
I-beam, the dimensions and weight of which are indicatedin the table, is the standard for this species. When buying products, the manufacturer must provide information about the actual parameters of the elements to the customer.
Most often used in the construction of housesas elements of overlapping floors, floors, a finishing layer of a ceiling, as a part of a design of trusses, rafters for the device of roofs. The element is a bar of rectangular section with parameters for height - 140-250 mm, width - 50-160 mm. The length can be from 2 to 5 meters (without taking into account the amount of support).
The composition of the bar can be either whole orglued (multi-layered). For production, coniferous trees are used because they have good elasticity and work on bending, which is important for horizontal bearing elements.
Dimensions of wooden beams depend on the sizeload on the future overlap, on the type of filling the volume of the structural element (heaters, rolls), from the size of the span. All these parameters are regulated by GOST 4981-87 "Wooden beams wooden beams".
Features of the installation
Before use, wooden elements are mandatorytreated with antiseptic compounds that prevent rotting, damage by microorganisms and rodents, as well as increasing the fire resistance of the beams.
Elements of floors are installed in a specialarranged nests in the management of masonry, or by cutting into the upper crown the construction of walls made of various wooden materials. Installation is made from the extreme to the central bars. The support end should not be shorter than 15 cm.
- When laying the timber on the outside walls, the free ends are cut down under 600, treated with antiseptics and protected with ruberoid or roofing felt.
- When embedding the beams in the masonry, the end of the bar must be dried and treated with bitumen to prevent its rotting.
- Fill the space niche in the wall with a heater. You can arrange a wooden box.
- In thick walls, it is necessary to leave a ventilation duct, through which moisture will be removed from the free end.
- With thin walls (up to two bricks) the space in the niches can be filled with cement mortar.
- On the inner walls of the beams are laid on the roofing layer.
The beam can be replaced by a log, the diameterwhich corresponds to the height of the rectangular cross-section of the element. This is economical from the point of view of purchasing material, but it is worth remembering that the fixation should be done in a special way using anchors with sealing in the walls.
Reinforced concrete beams
Widely used in large-scale construction of residential and public buildings.
Classify the beam by several parameters, the main one can be considered the separation according to purpose and the type of section simultaneously:
- Foundation. They are used for the device of the foundations of industrial objects and apartment houses in zones of increased seismic activity. They can have a T-shaped profile or a trapezoidal section.
- Rigid gable or single-pitchedsystems serve for the device of overlapping roofs in production and farming complexes. They have ledges for fastening rails.
- Rectangular beams with different configurations(I-beams, I-beams, L-shaped and T-shaped profiles) serve to cover spans of facades, floors up to 18 meters long.
Dimensions of beams depend on their purpose and havedifferent parameters. For example, rafters have a length of up to 24 m, and ordinary floor elements can be supported on a span of up to 18 m. The remaining parameters are determined individually for each product.
The dimensions of the floor beams can be found in the catalogsGosstandart or specific manufacturers, as they may vary. GOST 20372-90 "Trusses and rafters reinforced concrete" defines the basic requirements for products, materials and reinforcement of the structure, on this basis, the enterprises create a technical specification.
All building structures in Soviet timeswere divided into series. There are unified catalogs of concrete products, in which all types and sizes of blocks, beams, plates produced in factories of different regions are given. In the tabular reports, the dimensions of all parts of the elements, their calculated mass, are presented. This literature can still be used as a reference in the design of buildings, but engineers necessarily compare the data of concrete products with the availability of such products from modern suppliers.
There are several principles for calculating reinforced concrete beams. The dimensions must correspond to the following parameters:
- The height is not less than 5% of the length of the span to be overlapped.
- The width of the beam is determined by the ratio 5: 7 (width to height).
- Reinforcement of the product is carried out according to the scheme: 2 bars from below and from above (resistance to deflection). For the frame take the steel rods with a diameter of 12-14 mm.
In this way, you can determine the required beam dimensions for a particular section.