Not a single building object, whatever its purpose, can do without the use of floor beams. Its function as an engineering structure is to successfully redistribute vertical and horizontal loads in the process own work to the bend.

I-beams are a type of structural steel made from high quality steel. Steel can be either low alloy or carbon steel. This type of long products is in the form of a bar oriented horizontally or obliquely. Or, speaking plain language, a steel I-beam structure is a rolled product of a certain shape, made of profile steel of a special design. The shape is determined by it design features. Most often, it looks like the letter "H". This form enhances the strength of the structural elements and gives additional rigidity. Where are I-beams used?

I-beam: application

A metal I-beam made of steel is better known as an element of the ceilings of the frames of industrial buildings with large spans. They are also used in the construction of bridges and other overhead paths, columns and other in all those places where there are increased loads and they need to be resisted. They perceive the load from the vertical transverse impact, which is simultaneously reflected on the walls, columns and other supports.

A wooden analogue of a steel I-beam is used in frame housing construction. It should be noted that recently it has often been used in the design of buildings as a design element.

Their correct calculation provides a greater efficiency of metal consumption than this indicator for a conventional hot-rolled design. When installing an I-beam, the mass of supporting structures is reduced, which reduces construction costs. I-beams are also used in heavy engineering when creating heavy equipment.

Their low weight and extremely high rigidity make them ideal for use as a foundation for heavily loaded structures.

Interesting

Note that I-beams are much stiffer than square profiles and corners.

Types of I-beams

In the designs of I-beams, the inner edges of the shelves can be inclined or parallel. , which has an I-beam, characteristics, dimensions are mainly determined by the distance between parallel (P) or inclined (U) external faces.

Standard sizes and GOSTs:

• I-beam GOST 26020 83 is characterized by parallel edges of the shelves. This standard includes I-beams with a height of 10–100 cm and a shelf width of 5.5–40 cm. According to the latter parameter, they are classified into: narrow-shelf (U), normal (B), medium-shelf (D), wide-shelf (W) and columned (TO). Columned I-beams differ in almost the same profile height and shelf width.

I-beams, characterized by inclined faces, are classified into:

• ordinary (GOST 8239 89) - restrictions on the slope of the inner faces are about 6–12%;

• special (GOST 19425 74) - M: overhead tracks with an inclination angle of not more than 12% and C: for reinforced mine shafts with an inclination angle of up to 16%.

A product made in accordance with GOST fully complies with the parameters of the drawing, that is, it has a given cross section, shelf dimensions (height, width and thickness) and more.

Marking: how to decipher

Let's start with two numbers at the beginning of the marking. They mark the height in centimeters of a particular group of profiles. The following indices are alphabetic, they indicate the type of profile in accordance with the width of the shelves, for example, U, K, etc. If the profiles in the group differ in the dimensions of the walls and shelves, then the size of the profile in the series is indicated in the marking. For example, marking an I-beam with parallel edges may look like: 25B, 100Sh, 35K, 24DB1.

Installation

Metal I-beam is made in stages. First of all, the metal is cut into strips of the required dimensions. To improve the penetration, the edges are cut on a special machine. Prepared strips are mounted on an assembly mill. They are placed on the input conveyor, clamped, positioned and fixed. Finishing the assembly welding work on a special machine. It is welded with two sets of submerged arc welding heads. An I-beam basically consists of three elements. Waist seams are welded with automatic welding machines, and stiffeners are welded across more often manually, in extreme cases - semi-automatically. Welded structures are assembled different ways: using clamps and tacks or in a special jig.

metal I-beam: production process

The finished I-beam is cleaned of rust, grease, dirt and other deposits using a shot blasting machine. After that, the quality of its coating of paint and varnish is noticeably improved.

When constructing a structure, the seams of the belts are sometimes welded along manual technology. Then the assembly sequence completely changes. First, a vertical wall is mounted on the belt in the lower part of the structure, followed by stiffeners. They are captured and the belt is mounted in the upper part. The assembled structure is clamped with clamps and proceed to welding.

on the photo is a metal beam I-beam

The most critical stage of installation is the joining of I-beams. The seams of the belts in both directions from the joint are not welded to a length one and a half times greater than the belt width. The joint of the I-beams is welded in the following order: the joints of the vertical wall, two belts are welded, first the one that works in tension, then the second one that works in compression. The joint is completed by welding the seams on the belts in those areas that remained unwelded.

For welding field joints, it is necessary to use electrodes of the highest quality.

A welded construction has a lot of advantages over a rolled one, and, first of all, these are its higher strength characteristics with a mass that is about a third less than the rolled one.

I-beam metal: assembly on video

Materials for the article.

The construction of any, even the smallest building, is impossible without the use of a number of elements that, during the construction of buildings, have long been referred to as the so-called basic components. One of the so-called basic elements can be called an ordinary metal beam. It is a metal product with an H-shaped section, which is actively used in various construction areas for the creation of bridge structures, overhead tracks, supports, ceilings, as well as various types of metal structures.

If we talk about the function of this element, then its main task is to perform the function of a support for the entire structure. In life, we can meet it as a ceiling and roof. And if, for example, you use the so-called 2-tee beam, then you can quickly make a simple but extremely effective rack crane that will allow you to move large loads. For the same purpose, a rack profile is used, like guides or rails. In addition, its configuration makes it possible to use it for laying railway connections.

What are they like

To date, there are several categories of beams that are manufactured by large enterprises:

• I-beam, made according to GOST;
• welded;
• of steel;
• tee;
• from metal;
• welded double tee.

They can also differ in a number of characteristics: in the thickness of the shelves and walls, in the location of the edges, in the production methodology, and the like. If we talk about the main characteristics, then the beams are:

• hot-rolled steel;
• I-beam steel;
• I-beams made of low-alloy and carbon steel.

• with parallel edges. This includes normal, wide-shelf and column beams;
• with sloped edges. They are ordinary and special;
• special steel;
• hot-rolled steel;
• high density carbon low alloy steel.

It should be said that all beams of the 2-tee category are divided into 2 categories according to the production method. The first is hot-rolled beams, created when heated billets are passed through the rolls of a rolling mill. The second type of products is produced using welded technology, when the metal sheet is cut into pieces, after which the so-called tack is made, and then welding is already performed.

In addition, steel beams with parallel type faces are divided into three groups:

• normal;
• with wide shelves;
• category column.

Beams where there is a slope of the faces are divided into:

• conventional with a slope of 5-11%;
• special.

The latter, in turn, can be classified as:

• M. These are steel products designed to create overhead type tracks. The slope of the inner faces here will be at least 5 percent;
• C. Metal products that are used to strengthen shafts in mines. In this case, the slope will be at least 11 percent.

If you are interested in quality steel beam in Rostov , then it can be purchased cheaply at the "Steel Industrial Company" in a short time.

Where else can you use these devices?

Continuing the theme of the purpose of steel beams, let's say that they are used not only as solid elements in the construction of industrial, public and other types of structures. Also, they often act as structural parts of the roof, can act as parts of floors between floors, and also be the basis for crane-type racks. I-beam options are often used to create columns and ceilings. They are also used in steel floor trusses. The widespread use of just this type of beams is explained by the fact that they are quite simple to make, and in operation they are classified as very reliable.

Also popular are products that are made from low-alloy steel. The chemical composition during their creation must necessarily comply with GOST standards. Separately, it should be said that the number of a metal beam means its conditional size in centimeters. The smallest number is ten and the largest is one hundred. Creation of beams with other characteristics is possible only by special order. The size of the considered steel product is the value between the outer edges of its shelves.

Usually a beam in a horizontal position, takes the transverse vertical load coming from the weight. But quite often one should take into account the influence of a number of hypothetical horizontal forces of the transverse type. An example is the wind load when taking into account a possible earthquake.

Such a product under load also affects the supports, which can be columns, walls, suspensions, or the same beams. After that, the load passes on and in some cases, it is perceived by various structural elements working in compression - supports. We can also say separately about the case of a truss structure, where the rods rest on a beam that is in a horizontal position.

Also, it should be said that the strength characteristics of the product depend on the following physical parameters:

• the material from which it is made;
• length;
• areas, as well as cross-sectional shapes;
• the way it is attached to other elements.

Where can I buy quality steel beams

If we talk about where you can buy high-quality steel beams in Rostov, then this can be done at the Steel Industrial Company. Only high-quality beams made of strong metals with high characteristics, which have been tested for strength and for the presence of defects. Here you can also make a number of beams to order, if you need any non-standard solutions in this matter. In addition, the price of beams in the "Steel Industrial Company" is quite affordable, which is explained by the absence of intermediaries when selling beams to a client.

Despite cost reductions in construction industry, consumed still make a pretty decent revenue for firms that produce building materials. Now many people buy the necessary materials for self construction, the same applies to metal beams, metal is one of the most durable and affordable bases for the foundation and frame of a building.

What are beams and what are they made of

The beam is an important element in the design, it is placed to increase stability and strengthen the structure. Metal beams are most often made of steel, their action is directed to bending. If the structure is too massive, then the beam is made of an I-beam, it looks like two connected letters t. With this section, the load on the material is distributed evenly and resistance increases.
Beams are not only made of metal joints, there are also wooden ones, they are used in simpler construction, they cannot be made with different types sections, therefore, they are an ordinary beam with different lengths and widths.

Types and properties

Beams are distinguished by size, they are assigned numbers by which you can pick up desired characteristics individually for construction:

• Size "10" - the smallest by standards, is used as a ceiling, strengthens moving elements in buildings. It can be installed as a guide structure for lifts, provided that they are small.
• "12" - the beam will be slightly larger, and, accordingly, can withstand more pressure. Most often used as the basis of frames, installed in mechanisms and machines.
• Number "14" is more massive and helps to create more loaded floors, it is subject to installation in reinforced concrete structures, such are often installed in industrial construction.
• The "16" beam is distinguished by its strength and can already be a full-fledged support; it is installed not only to ensure the stability of the gran-beams, but also for the movement of shop transport along rail lines.
• Beam "18" can be used specifically in the construction of buildings, creating a reliable support. If you need to support large mechanisms or ensure the stability of wide areas.
• "20" number is already included in the number of large beams, it can be the basis for columns or frames for engineering.
• "25" - is no longer so often used in the construction of houses, but it will be a reliable time for any lifting mechanisms, even large cranes.
• "30" number is also used as the basis for lifting, but unlike "25" it is made wider and longer, this provides higher resistance under heavy loads.

Aluminum and steel floors, their pros and cons.

Often used in construction aluminum, more precisely its alloys, it quite resistant to environmental influences, but does not know how to be so stable under weight load. Compared to steel, they are lighter and thinner, but most often they have to be thickened for extra strength. In the construction of structures, both materials can be used, depending on the volume of construction, since industrial production is a more voluminous work with strong fortifications, but small buildings can be assembled from aluminum, it is economical and easy to use.

There is one important feature - metal melts when exposed to high temperatures, literally melts, creating a homogeneous mass that cannot be restored, while aluminum, when heated, does not turn into a melted puddle, but, on the contrary, when the temperature decreases, it is restored to its normal form. Of course, not every production environment has a temperature of 80 degrees, so there will be no deterioration with normal heating. From the side of chemical designations, iron has more noble compounds, and aluminum has not received recognition from chemists.

There is such a thing as the modulus of elasticity, it is responsible for the resistance of the material to regeneration after strong pressure, that is, if the action of the beam is directed to bending, then it should not bend, so the greater the pressure, the higher the modulus of elasticity should be. Aluminum alloys have an elastic modulus of 70.000 MPa, which is three times less than the same indicator for iron. It is on the basis of this that a plan for the location of the beams is built, their bearing capacity is calculated.

Shapes, thickness and height

The difference in shape and size is determined in accordance with the numbers of the manufactured beams, they can be either small and narrow with a solid shape, or massive I-beams, which are easily recognized as a support for large working cranes. Individual production allows you to order the basis for movable structures with specific indicators and shapes. The most important thing is that the height must always be increased by 1.5 times, this will shrink and other construction work.

Usage

The main purpose of metal floors - industrial engineering, it is different from civil special requirements. Most often, developers for these buildings already have ready plan, therefore, there will be no problems with sketching the project, but for such an industry, the material must have all the certifications, because the structures will be used for mass gatherings of people or large factories that are tested for strength by government agencies.

At the same time, complex metal structures are affordable for really large customers, their price is quite high, and aluminum is most often used in civil engineering, although it is not so strong, but it is not necessary to spend money on additional anti-corrosion treatment, and the material can withstand the standard load of a residential building.

A beam is, in construction, not only a support for flooring and floors, but also an element that performs the functions of fastening the entire structure of the building, giving it the necessary rigidity. In the list of materials and products used in construction, you can find many options for the manufacture of floor beams. But the main and most commonly used types of load-bearing beams include metal, reinforced concrete and wood.

Wooden floor beams must meet such requirements as strength, rigidity, fire safety. The calculation of the beam is made depending on the selected material.

The beam is a key fragment of the floor, the purpose of which is to separate the floors in the house, as well as to carry and distribute the load from the components located at the top - walls, roofs, communications, furniture, interior details.

Advantages of wood beams:

low labor intensity during installation in comparison with metal or reinforced concrete counterparts;

affordability of prices for wood materials;

quick installation without the use of expensive mechanisms and tools;

aesthetic appearance;

light weight;

maintainability.

Disadvantages of wood beams:

without special protective impregnation combustible;

low strength compared to reinforced concrete or metal beams;

exposed to moisture, fungus and living organisms;

can be deformed by temperature changes.

Types of wooden floor beams

Wooden floor beams are classified according to the type of section, material and size.

The length of the floor beams depends on the distance between the walls. To this value, you need to add a margin for resting on the wall - usually add 200-250 mm on each side ..

According to the cross section, wooden beams are divided into the following types:

square;

rectangular;

I-beam;

round or oval.

The square section of the beam is considered the most unfavorable, since it is the least fitted to the force diagram in the element.

For reference! Plots of forces - graphical display of the change in internal forces along the entire length of the bar. They are used in the calculation of permissible loads.

The best option when choosing wooden floors are beams with a rectangular section, while their short side is placed horizontally, and the long side is vertical, since the increase in height affects the strength better than the width.

The I-section of the floor beam is a broadened element at the bottom and upper parts, and in the middle reduced to the maximum possible size. This section option significantly reduces the consumption of wood and allows its rational use.

Buying I-beams will not be so easy, as they are distinguished by complex manufacturing technology. For the same reason, they are rarely found in construction.

Wooden beams of round or oval section are used, as a rule, for the installation of attic floors. Depending on the diameter, round beams have a high bending resistance. In addition, it must be borne in mind that the floor beams are wooden, the dimensions are quite limited. Their maximum length is 7.5 p.m.

According to the material, wooden floor beams are classified into the following types:

from a solid bar or board;

from glued timber.

On our site you can find contacts of construction companies that offer house design services. You can directly communicate with representatives by visiting the exhibition of houses "Low-Rise Country".

The use of boards and solid timber in a beam structure

An ordinary board or solid timber can be no more than 4–6 m long, which is almost half the distance that glued laminated timber can handle.

Builders often make beams from boards fastened together on site. In terms of quality and strength, they can far exceed the solid beam structure. In addition, it is possible to vary the thickness of the beams by the number of boards pulled together.

Connections are made using bolts with nuts and rubber or plastic washers. They will prevent moisture from entering the metal fasteners and subsequent corrosion and will not allow the nut to cut into the wood when tightening.

If you need to increase the length or strength of solid beams, then they are fastened together and this is usually done manually when installing floors. Glued laminated timber initially consists of several bars glued together at the enterprise. The thickness of the glued beam is set by the number of layers of material glued under the press. In this way, wood is given additional strength qualities, a beam made of glued laminated timber can be up to 12 meters long.

After gluing, the beam retains all the qualities of wood, that is, it is perfectly nailed, sawn, cut. But glued wooden floor beams are much more expensive, so before you opt for them, you need to think about whether the end justifies the means. Often this kind of beams is used to create an arched ceiling.

Wood for the manufacture of floor beams

For floor beams small houses and buildings, wood is used in the vast majority of cases coniferous trees.

But it is not worth categorically rejecting the use of local wood species. Since ancient times, in the steppe regions, where there are no coniferous trees, oak, acacia, and maple have been used. The main requirement for them is humidity with optimal indicators of 12-14%.

IN attic floors Where, by definition, it must always be dry and air circulates, local wood beams only become stronger over the years, with performance characteristics that are not inferior to metal beams.

On the quality and strength of wooden floor beams

Designers in the calculations of floor beams lay building materials with specified characteristics and operating standards, based on the laws of applied mechanics and strength of materials. Knowing this, the question arises: how did the builders of individual houses a hundred years ago do without this knowledge? At the same time, the houses they built are still alive today.

The explanation is simple: they left a much greater margin of safety for the materials used. A little later, Soviet GOSTs were deliberately calculated and approved with large, sometimes up to 100% safety margins. It is uneconomical, sometimes cumbersome and pretentious, but reliability was a priority, and will always remain the most important indicator in construction. Today, this practice is being replaced exact calculation wooden beam- this allows you not to overpay for excessive, unclaimed strength.

Comparison with the old methods would look out of place in the description of floor beams, if not for one circumstance.

Buying a bar or beam of a certain size on the market, with pre-calculated characteristics, a private developer without much experience often acquires the wrong material that guarantees reliability.

Many seemingly insignificant nuances can nullify all calculations:

high humidity;

irresponsible storage;

hidden defects;

sorting;

poor linear geometric parameters;

predetermined wood diseases.

There is only one conclusion and way out: the market will always try to deceive a novice builder, therefore The best way to save money is to entrust the work to a professional.

Basic starting points for calculating dimensions

Before starting the installation of wooden beams, they should be cut to required dimensions or splicing.

The ends of the beams are deepened into the walls by at least 15 cm, with or without embedding.

The thickness of the bearing walls of the building is usually at least one brick, or 25 cm, when using wall blocks - 20 cm. This means that the ends of the beams resting on the walls will be protected from external atmospheric influences.

For a glued beam, the launch into the walls can be reduced to 10 cm. In extreme cases, the beams can go to a depth of 7 cm, but the material of the timber used must be of the highest quality.

Video description

For more information on how to calculate wooden floor beams, see the video:

Runs, spans, step, anchoring: 10 basic concepts and installation conditions

Floor beams are a load-bearing element, this is the basis of the strength of the entire structure.

The scheme of beams with a span (beam length) of 6 m or less assumes a load from the weight of the filling between the beams and the floor.

Beams are laid in a direction parallel to the smaller side of the span. The distance between the beams, called the pitch, depends on the material and section.

The step of the beams, depending on their type: plank - from 60 to 80 cm; from a bar - from 60 to 100 cm; from logs and glued beams - from 60 to 120 cm.

Spans of more than 6 m are covered with beams (girders) with a large cross section.

The cross section of wooden beams is determined by calculation; in practice, its height is in the range of 4–5% of the span length.

To fasten walls and floors, the ends of the beams are either anchored into the walls, or steel ties are used.

It is possible to step anchors through one beam, but not less often.

In rooms with high humidity, ceiling beams should be left open.

For the installation of floors along the beams, logs or logs from a bar are laid, floor boards are nailed to them.

To calculate, you need to know the distance between the beams, the span width and the load on the structure. Source piorit.ru

How to calculate

To calculate wooden floor beams, an online calculator is not always required. It is enough to know a few formulas and the following data:

length of the wooden floor beam (distance between bearing walls);

the distance between the beams (their step);

load on the structure.

The calculation of floor beams will allow you to have no doubt about the rigidity and strength of the structure, determine the maximum length allowed for a particular section.

Video description

Why the floor beam burst, look at the video:

In order to find out the load on the structure, it is necessary to add the variable value and the constant. The latter includes the preliminary mass of the beams themselves, insulation, ceiling filing, rough and finishing floors. Temporary refers to the mass of furniture and people - approximately 150 kg / m2 - according to regulatory documents residential premises.

For the attic, the value of the live load may be less, but it is better not to risk it, and use the same one in the calculations. So you will provide a certain margin of safety and in the future, if you wish, you will be able to equip the attic in the attic without reconstructing the load-bearing elements.

The calculation of a wooden beam is carried out according to the following formulas:

Mmax = (q*l2)/8;

Wreq = Мmax/130.

q is the load per sq. m of overlap, including a mass of structures and 150 kg of useful value. The indicated values ​​\u200b\u200bmust be multiplied by the distance between the beams, since the calculations require loading per linear meter, and initially the value is calculated per square meter.

l2 - the distance between the bearing walls on which the run rests, taken in a square.

Knowing Wreq, you can choose the cross section of the floor. W = b*h2/6. Knowing W, an equation is drawn up with one unknown. Here it is enough to specify one geometric characteristic b (width of the section) or h (its height).

It is important! Despite the apparent simplicity of the calculations, it is better not to trust them to people without specialized education, since the cost of an error can be very high.

Metal beams: traditional reliability

When the developer has the opportunity and request for a more ambitious and large-scale construction, he uses metal floor beams of various sections: a corner with different sizes shelves, channel, taurus, I-beam. If we exclude the possibility of metal corrosion, then there is no replacement for such beams in terms of strength. But the use of metal in individual housing construction is also limited by a number of indicators:

it is difficult to work with metal at height;

special mechanisms for installation are required;

welding, cutting metal and protecting it from corrosion are additional costs;

high cost of the material;

metal beams are subject to insulation from the attic.

Metal beams also have positive points:

they do not burn;

more durable;

metal spans can be made longer and the distance between the floor beams can be made larger;

types of metal beams are very diverse and allow you to create almost any design complexity.

Conclusion

The choice of the type of floor, the material for the beams, the careful preparation of the project, the calculation of loads, including the use online calculator- these are all pleasant worries that can be safely shifted onto the shoulders of professionals. And then it will be pleasant to remember these worries in a year, enjoying the coziness and comfort in a good, solid house.

Beams TYPES OF BEAMS AND THEIR STATIC SCHEMES Metal beams are bending elements and are mainly used for covering spans of multi-storey industrial and civil buildings 6-18 m, as well as one-story industrial buildings in the form of crane beams for overhead transport tracks and less often load-bearing roof beams with spans of 18-24 m The most rational in use are rolling beams of I-beam and channel section due to the simplicity of their manufacture. With insufficient power of rolling beams, welded composite beams are widely used ...

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METAL CONSTRUCTIONS

Lecture 9m. beams

TYPES OF BEAMS AND THEIR STATIC SCHEMES

Metal beams are bendable elements and are mainly used for covering spans of multi-storey industrial and civil buildings 618 m, as well as single-storey industrial buildings in the form of crane beams, overhead transport paths and, less often, load-bearing roof beams with spans of 1824 m.

The most rational in use are rolling beams of I-beam and channel section due to the simplicity of their manufacture. With insufficient power of rolling beams, welded composite beams of an I-section are widely used, and for structures subjected to dynamic and vibration loads, composite beams on high-strength bolts and riveted beams (Fig. 1 9 d, e ). For spans up to 6 m, instead of rolled steel and extruded aluminum beams, it is advisable to use steel beams made of bent sections of channel or box type. Welded composite beams can be solid-walled or with a wall with round, oval or polygonal holes, which are used for laying utilities and other purposes (Fig. 2 9a, b). In the intervals between the holes, transverse stiffeners are arranged to ensure the stability of the wall.

Recently, beams with a perforated wall have been used in construction (Fig. 2 9, c, d). Perforated beams are obtained by cutting a hot-rolled I-section with a broken line in the longitudinal direction. Then both parts are shifted until the ridges are joined end-to-end, after which they are welded. Depending on the length and height of the profile, as well as the shape of the broken line, it is possible to obtain different openings and different heights of the perforated beam. The most optimal profile can be with an increase in height up to 1.5 N.

Perforated beams have the same mass as rolled profiles. At the same time, their bearing capacity and rigidity are much higher than that of the original profile, and therefore, it can be used with a larger span and greater load. It is best to use such beams for large spans and low loads. In this case, the influence of transverse forces on the stresses in the vertical wall is insignificant. The design of perforated beams allows you to save steel up to 2030%. However, given the higher manufacturing cost, their use should be economically justified.

With an increase in the span or an increase in the design load on the beam, it is rational to use prestressed steel beams (Fig. 2 9, e) in which the prestressed cable is located in the zones of maximum tension.

In static terms, beams can be single-span split, double-span and multi-span continuous. They can be console and non-console (Fig. 3 - 9). Single-span split beams are most widely used in construction as they are the easiest to install and operate. In terms of labor intensity of manufacturing, continuous beams are inferior to the first, however, in terms of material consumption and rigidity, they are more efficient, which determines them. wide application in multi-storey frames, while Special attention is given to the consideration of temperature effects and settlement of supports, since continuous beams are very sensitive to such effects.

The general dimensions of the beam are its design span. l e f and section height h (Fig. 4 - 9). Actual or constructive beam size l are assigned taking into account the dimensions of the support areas, the size of which depends on the bearing capacity of their material. clear distance l 0 between support nodes depends on the operating conditions of the structure and is assigned in the design process.

The optimal value of the beam height depends on the design span, load, steel class, purpose of the beam, etc. and lies within h / l e f = (1/101/16). The minimum values ​​​​of the height of the beam section in the preliminary design can be taken from Table. 1-9 at q p / q d = ​​1.2 (where q p and q d per linear normative and design load) depending on the tensile strength of the steel and the relative deflections of the beams to the span.

In buildings and structures, metal beams are used in the form beam cells , i.e. floors, consisting of a system of beams. The beam cage includes the main beams spanning the main span with a step L=6 9 m, and auxiliary beams based on the main beams with a step of B = 1.5 3 m (Fig. 5-9).

Depending on the relative position of the main and auxiliary beams, four types of beam cells are distinguished: with an upper arrangement of auxiliary beams (Fig. 5-9, a); with the location of auxiliary beams with the main ones at the same level (Fig. 5-9, b); with a lowered arrangement of auxiliary beams (Fig. 5-9, V) ; a complicated system that has two types of auxiliary beams, transverse and longitudinal (flooring beams) in relation to the main beams (Fig. 5-9, d). Floor beams are designed in increments of 0.51.2 m.

The choice of a beam cage depends on the floor structure (metal flooring, reinforced concrete slabs, etc.), on the presence of technological equipment, false ceiling and other factors, so the type of beam cage is determined for each specific case by variant design.

The simplest in construction and economical in terms of material consumption are beam cages with an upper location of auxiliary beams, but they have the disadvantage of a large construction height of the ceiling. When limiting the construction height of the floor, the most appropriate solution is a beam cage with the location of auxiliary beams with the main ones on the same level. Beam cages with a low location of auxiliary beams and with a complicated system are used in most cases when supporting technological equipment or small-sized floor slabs.

CALCULATION OF THE SECTION OF ROLLED AND COMPOSITE WELDED BEAMS

In most cases, a uniformly distributed load acts on the beam cage, which, when calculated, leads to a linear load on the floor beam, auxiliary and main beams from their loading areas (Fig. 6-9). The calculation of beams is carried out in the same sequence in which the load is transferred: to the flooring element, auxiliary and main beam. The selection of sections is preceded by a static calculation of the beams, as a result of which the design bending moments are determined M and design shear forces Q in characteristic sections.

The calculation of beams is carried out according to two limit states: bearing capacity and deflections. The calculation of rolled beams made of rolled or bent I-beams, channels and other profiles comes down to determining the required profile number according to the assortment and checking it for strength in terms of normal and shear stresses, stiffness and stability according to the formulas that we wrote out for bending elements in the last lecture . These formulas in the simplest cases can be reformatted in such a way that the desired geometric characteristic is on the left side of the inequality. However, in most cases it is necessary to carry out multivariate analysis. And it, most often, is performed by the selection method, using various auxiliary tables. For example, a table of approximate beam heights (Tables 1 - 9). And in the future, when you gain experience, you will simply ask based on own experience values ​​of geometric characteristics and with them to check the bearing capacity and ability to operate and in the explanatory note to give the results of these checks. By the way, this is exactly what the State requires of us. expertise.

JOINTS OF ROLLING AND COMPOSITE BEAMS. BEAMS FASTENING ASSEMBLY

Joints are factory, performed at the factory in order to increase the length of the elements included in a separate shipping element, and assembly, manufactured at the construction site; they are designed to interface individual sending elements into a working structure (Fig. 7-9).

The number of mounting joints and their placement are designed according to the condition of transportation. Mounting joints are much more expensive than factory ones, since they require additional material for butt plates and mounting bolts, so their number should be minimal.

The simplest is the joint, the belts and the wall of which are joined in one section. However, such a joint in the zone of action of the maximum bending moment does not provide equal strength of the joint and the base material. As a result, in the most stressed zones, a seam is arranged in a staggered manner, performing an oblique butt seam in the shelves, which ensures high reliability of the connection (Fig. 7-9, a, b). To reduce the effect of shrinkage deformations arisingwhen welding, the butt weld is performed in the sequence shown by the numbers in fig. 7-9, c. After welding butt weld at a distance of 500 mm on both sides of it, the shelves are welded to the wall.

An increase in the reliability of the joint in rolled and composite beams under the action of significant moments and transverse forces can be achieved using horizontal plates installed along the upper and lower flanges and vertical double-sided plates along the beam wall (Fig. 7-9, d). In this case, the section of the trim and the flank welds that attach the trim to the flange are calculated from the force S , determined by the formula

S \u003d (Mb M w) / z, (1-9 m)

where M total design bending moment at the beam joint; M w \u003d M . (/ J w / J b ) bending moment perceived by the beam web; J w and J b moments of inertia of the web and full section of the beam; z the distance between the centers of the top and bottom shelves.

The seams attaching the lining to the beam web are checked for the weld metal and for the metal of the fusion boundary, respectively.

Beams rest on columns from above or adjoin from the side. In one-story industrial and civil buildings the first case is predominantly used, the variants of which, depending on the design solution of the column, are shown in Fig. 8-9.

Jb

In the first variant (Fig. 8-9, a), the beam rests on the column with a hinged-vertical support stiffener, which extends beyond the bottom flange by 10 15 mm. The ends of the supporting stiffeners are attached to the centering plate, which is welded to the base plate of the column head, to provide the required crushing area. When the beams are supported on a two-branch column (Fig. 8-9, b), the supporting stiffeners are removed from the end of the beam and coincide with the plane of the walls of the column branches. In this case, it is necessary to fit and weld the supporting stiffeners not only to the beam wall, but also to its flanges.

In the case of beams adjoining columns on the side, a hinged and rigid solution of the interface node is distinguished. With hinged support, the fastening does not prevent the free rotation of the beam in the support node, which determines the operation of the beam as a single-span split system (Fig. 9-9).

Depending on the purpose, the beam can adjoin either the column flange (Fig. 9-9, a, d, e) or the column wall (Fig. 9-9, b, c). The transfer of the support reaction of the beam to the column is carried out through a bolted flange connection (Fig. 9-9, a, b) or using support tables in the form of a flat plate or an unequal angle (Fig. 9-9.0, d, e) welded to shelves or column wall. From the point of view of the convenience of work, the transfer of the support reaction through the support table is preferable.

Rigid fastening of beams to columns is provided in the case of designing a frame frame or when the floor beam simultaneously performs the function of a spacer beam in the vertical bracing of the frame (Fig. 10-9).

With rigid fastening, the upper and lower flanges of the beam are rigidly attached to the columns with the help of horizontal strips (Fig. 10-9, a) or kerchiefs of vertical ties (Fig. 10-9, b), which prevents the beam from turning in the support node.

Butt strips and scarves perceive the horizontal components of the force S \u003d M / H, arising from the action of a bending moment in the support node. The support reaction in the case of a rigid fastening of the beam is transferred to the column in a manner similar to the transfer of the support reaction in the case of a hinged fastening of the beam to the column. The use of a rigid joint is more laborious than a hinged joint, but it reduces the consumption of metal for beams by 30%.

The attachment points of beams to beams can also be articulated and rigid (Fig. 11-9).

Preference should be given to articulated assemblies as the easiest to work with. With a one-sided junction of auxiliary beams to the main ones (Fig. 11-9, a c) from the bending of the auxiliary beams, torsion of the main beam occurs, which is highly undesirable. To prevent this phenomenon, a stiffener is arranged at the junction with the opposite auxiliary beam, and a scarf is inserted under the auxiliary beam, welded to the wall and shelves of the main and auxiliary beams (Fig. 11-9, d, e).

Rigid fastening of beams to beams is done, as a rule, in the case of bilateral junction of auxiliary beams to the main ones (Fig. 11-9, e) . Structurally, such a pairing is performed like a rigid joint of a beam with a column.

The connection of the chords with the wall in welded beams is carried out by continuous fillet welds. The seams prevent the mutual shift of the belt and the wall, as a result of which shear stresses arise in them, which are a function of the action of the transverse force (Fig. 12-9).

Consequently, the highest values ​​of shear stresses will occur near the support. The thickness of the weld that attaches the shelf to the wall is determined from the conditions of its work on the weld metal and on the metal of the fusion boundary.

The calculation and design of pressed and welded beams made of aluminum alloys is carried out similarly to steel beams. However, given the large deformability of aluminum alloy beams, their minimum height should be greater than that of steel beams, so the values N t gp and N 0 p1 for beams made of aluminum alloys are determined, respectively, by the formulas:

(2-9 m )

(3-9 m )

When designing beams from aluminum alloys, one should take h  5 b .

Coefficient b when checking the overall stability of an aluminum beam, it should be taken taking into account the requirements of Ch. SNiP 2.03.06-85 "Aluminum structures".

Lecture 10m. columns