Characteristics of floors and their installation. Construction of interfloor ceilings in a private house How to make a ceiling from channels

One of the main structural elements used for the construction of floors of attics or rooms on the second floor, mainly in low-rise individual construction, is a wooden or metal beam, which simultaneously performs the functions of a floor log and a basis for fixing ceiling coverings. The wide distribution of beam ceilings was facilitated by the low cost of the original building materials and the possibility of laying floors without the use of lifting mechanisms.

Deflection lag

When entering some, especially old, houses, even with the naked eye, one can notice the deflection of the ceilings of the second, or, less often, the floor of the first floor, which is the result of an incorrect calculation bearing capacity lags or excesses permissible load on the floors. As the practice of operating multi-storey buildings built in the first half of the 1950s, where wooden interfloor floors were used, calls for, by 2000, the ceiling deflection ranged from 70 to 100 mm, which led to the need for overhauls buildings with reinforcement of load-bearing elements of floors. And this is provided that an accurate engineering calculation of loads and lag sections is carried out at the design stage. And what can we say about individual buildings, when the calculation of the bearing capacity of the lag was carried out "by eye" on the advice of "competent" specialists.

Very often, the quality of the material used, the excessive moisture content of the wood, the insufficient thickness of the rolled metal from which the beam is made, and many more various reasons, leading to sagging, for example, overlapping the second floor under load. Incorrect calculation of the bearing capacity can lead not only to the deflection of the log, but also total destruction structures and the collapse of the floor down, and when no one expects it.

When is it necessary to strengthen the lags?

If the owner of the house noticed the sagging of the upper floor, then the first thing to do is to take simple measurements and assess the condition of the structures, the magnitude of the static load in order to determine the amount of sagging of the ceiling or changes in the curvature of the floor in order to decide on the need to strengthen the log.

Any floors under the influence of their own weight, static load of the structures and objects installed on them sag over time. The allowable sagging value is assumed to be 1:300, that is, if a three-meter beam is bent by 10 mm, there is no reason for concern, but if this value is greater, then measures must be taken to eliminate deformation and strengthen the structure.

Strengthening of metal structures

Metal structures used as beams interfloor overlap, can be enhanced with additional products from rolled metal by welding or bolted connection. To do this, the surface of the floor or ceiling is disassembled, if necessary, adjustable supports are placed under the floor beams to eliminate deformation, and the structure is reinforced with standard rolled metal products of the required section, the calculation of which is performed using special tables and methods.

Reinforcement of wooden elements

Existing structural elements hardwood floor Depending on their condition, they can be strengthened in several ways:

With the help of overlays from a beam, by performing a simple mathematical calculation, when the width of the existing beam is subtracted from the tabular value of the section of the required floor beam. The beam and beam are fastened with bolts with metal plates that prevent the destruction of wood at the point of attachment and the weakening of the structure. The existing beam is lifted by jacks until flat surface floor, after which the lining and the beam are fastened together;
Using metal strips 10 mm thick and 10-20% less than the height of the beam as overlays. To prevent deformation of the strip and reduce the strength, the number of fixing bolts should be increased by 25% compared to wooden elements. Linings are installed on one or both sides of the beam, depending on the load on load-bearing elements floor of the upper floor;
Wooden floor beams damaged by insects or putrefactive bacteria can be reinforced with prostheses welded from a bar in the form of a spatial truss, or with the help of a channel required size. The channel, installed as a prosthesis, is selected from a standard range of rolled metal, and for the manufacture of a spatial bar truss, it is required to perform a rather complex strength calculation, which only a qualified specialist can do.
Strengthening the bearing capacity interfloor structures can be done by installing an additional number of beams, but these works require making holes in load-bearing walls, which is difficult to achieve in some cases.

When using metal elements to reinforce the load-bearing interfloor structures, especially for the destroyed parts to be removed, it is necessary to provide for the installation of elements on which the floorboards of the upper floor will be fixed. The fastening must be reliable and durable, excluding the possibility of loosening and the appearance of squeaks.

Reinforced different ways logs allow you to increase the load capacity of load-bearing interfloor structures and general security operation of existing buildings without significant capital investments and a large amount of construction work.

For interfloor or attic floors not economical to use. For example, when the span is too large and therefore it requires wooden beams large section. Or when you have a good friend who sells not lumber, but rolled metal.

In any case, it will not be superfluous to know how much the ceiling can cost if you use metal beams rather than wooden ones. And this calculator will help you with this. With it, you can calculate the required moment of resistance and moment of inertia, which for selection of metal beams for ceilings according to assortments from the condition of strength and deflection.

The floor beam is calculated for bending as a single-span hinged-supported beam.

Calculator

Related Calculators:

Instructions for the calculator

Initial data

Operating conditions:

Span length (L)- the distance between the two inner faces of the walls. In other words, the span spanned by the calculated beams.

Beam pitch (P)- a step in the center of the beams through which they are laid.

Type of overlap- in case the last floor You will not live, and he will not be heavily littered with things dear to your heart, then he gets out "Attic", in other cases - "Interfloor".

Wall length (X)- the length of the wall on which the beams rest.

Beam characteristics:

Beam length (A)- most big size beams.

Weight 1 p.m. - this parameter is used, as it were, in the second stage (after you have already selected the desired beam).

Design resistance R y - this parameter depends on the steel grade. For example, if the steel grade is:

C235 - Ry = 230 MPa;
C255 - Ry = 250 MPa;
C345 - Ry = 335 MPa;

But usually Ry = 210 MPa is used in the calculation in order to protect oneself from different kind"force majeure" situations. Still, we live in Russia - they will bring rolled metal from steel of the wrong grade and that's it ...

Elastic modulus E- This parameter depends on the type of metal. For the most common, its value is:

steel - E = 200,000 MPa;
aluminum - E = 70,000 MPa.

Values normative and design loads are indicated after their collection for overlapping.

Price for 1 ton- the cost of 1 ton of rolled metal.

Result

Strength calculation:

W required - required section modulus. It is located according to the assortment (there are GOSTs for profiles). The direction (x-x, y-y) is chosen depending on how the beam will lie. For example, for a channel and an I-beam, if you want to install them (i.e. larger size directed up - [ and Ι ), you need to select "x-x".

Deflection calculation:

J required - the minimum allowable moment of inertia. It is selected according to the same assortments and according to the same principles as W req.

Other options:

Number of beams- the total number of beams, which is obtained when laying them on the wall X step by step P.

total weight- weight of all beams length BUT.

Price- the cost of buying metal floor beams.

How to choose the right channel for floors, knowing its calculations for bending

During the construction of a residential building, garage, summer houses on the suburban area, other buildings and structures, everyone is faced with the need for proper calculation and installation of the ceiling. The ceiling is a horizontal structure located inside the building, which divides it into adjoining premises vertically (floors, attic, etc.). In addition, this structure is load-bearing, because it takes all the loads coming from furniture, people, equipment and the floor itself and transfers them either to the walls or to the columns (depending on the type of structure).

Types of ceilings and channel for ceiling from APEX metal

By purpose, the floors can be divided into: basement, interfloor and attic. The first separate the first floor of the building from ground floor or basement. From the name of the second type it follows that they are aimed at dividing the floors of the building among themselves. The latter separate attic space from a residential building.

Depending on the design features their overlaps can be divided into slab and beam. Tiled floors are most often mounted in large-sized stone houses using reinforced concrete slabs. Beam ceilings most often used in the construction of low-rise residential buildings. For their installation, metal or wooden beams, and filler material can be used.

Let us consider in more detail the structures of the channel for overlapping as a supporting base. It is they who perceive the entire load falling on the floors of the second floor. If U-shaped rental is used for the installation of the ceiling, then the following points must be taken into account:

firstly, it must be laid vertically, since the section modulus in this direction is several times greater than the value of the moment in the opposite direction;
secondly, the scheme of their laying is as follows - from the middle of the overlap, the profile must be turned in the opposite direction, since the center of gravity of the channel does not belong to its wall.

Therefore, such a laying scheme is necessary to compensate for tangential stresses. It should be remembered that the channels for overlapping are subject to bending stresses.

Calculation of the bending of the channel from APEX metal used for floors

We will calculate the channel for overlapping based on following conditions. There is a room with a size of 6x8 m. The step of the whips of the floor channel is p = 2 m. It is logical to assume that the channel should be laid along a short wall, which will reduce the maximum bending moment acting on it. Regulatory load per square meter will be 540 kg/m2, and the calculated one is 624 kg/m2 (according to SNiP, taking into account the reliability factors for each component of the load). Let the floor channel on each side rest on a wall 150 mm long. Then the working length of the channel will be:

load on one running meter channel will be (normative and calculated, respectively):

qн=540∙р=540∙2=1080 kg/m=10.8 kN
qр=540∙р=624∙2=1248 kg/m=12.48 kN

The maximum moment in the section of the channel will be equal (for the standard and design load):

Мн= qн∙L2/8=10.8∙6.22/8=51.9 kN∙m
Мр= qр∙L2/8=12.48∙6.22/8=60 kN∙m

Let us determine the required section modulus by the expression:

Ry \u003d 240 MPa - resistance of steel C245, calculated
γ=1 – coefficient of working conditions

Channel bending calculation - section selection and stiffness test

According to the reference book (GOST), we select the channel profile, which has a moment of resistance greater than the calculated one. In this case, a 27P channel is suitable, Wx=310 cm3, Ix=4180 cm4. Next, it is necessary to check the strength and bending stiffness of the channel (lash deflection).

Test of strength:

σ=Mr/(γ∙Wx)∙1000=60∙1000/(1∙310)=193 MPa

Stiffness test, channel bending where the relative deflection f/L must be less than 1/150 and is determined by the expression:

The rigidity condition is provided. Therefore, this channel can be used for overlapping according to the described scheme. You can reduce the channel number if the whips are laid with a smaller step.

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1. Collection of loads

Before starting the calculation of a steel beam, it is necessary to collect the load acting on the metal beam. Depending on the duration of the action, the load is divided into permanent and temporary.

own weight metal beam;
own weight of the floor, etc.;

long-term load (payload, taken depending on the purpose of the building);
short term load ( snow load, is taken depending on geographical location building);
special load (seismic, explosive, etc. This calculator does not take into account);

The loads on the beam are divided into two types: design and standard. Design loads are used to calculate the beam for strength and stability (1 limit state). The normative loads are established by the norms and are used to calculate the beam for deflection (limit state 2). Design loads are determined by multiplying the standard load by the reliability load factor. Within the framework of this calculator, the design load is applied when determining the deflection of the beam to the margin.

After collecting the surface load on the floor, measured in kg / m2, it is necessary to calculate how much of this surface load the beam takes on. To do this, you need to multiply the surface load by the step of the beams (the so-called cargo lane).

For example: We calculated that the total load turned out to be Qsurface = 500kg / m2, and the step of the beams was 2.5m. Then distributed load on a metal beam will be: Qdistribution \u003d 500kg / m2 * 2.5m \u003d 1250kg / m. This load is entered into the calculator

2. Plotting

Next, the diagram of the moments, the transverse force is plotted. The diagram depends on the beam loading scheme, the type of beam support. The plot is built according to the rules of structural mechanics. For the most commonly used loading and support schemes, there are ready-made tables with derived formulas for diagrams and deflections.

3. Calculation of strength and deflection

After plotting the diagrams, the strength (1st limit state) and deflection (2nd limit state) are calculated. In order to select a beam for strength, it is necessary to find the required moment of inertia Wtr and select a suitable metal profile from the assortment table. The vertical limit deflection fult is taken according to Table 19 of SNiP 2.01.07-85* (Loads and impacts). Paragraph 2.a depending on the span. For example, the maximum deflection is fult=L/200 with a span of L=6m. means that the calculator will select the section of the rolled profile (an I-beam, a channel or two channels in a box), the maximum deflection of which will not exceed fult=6m/200=0.03m=30mm. To select a metal profile according to the deflection, the required moment of inertia Itr is found, which is obtained from the formula for finding the ultimate deflection. And also from the assortment table, a suitable metal profile is selected.

4. Selection of a metal beam from the assortment table

From the two selection results (limit state 1 and 2), a metal profile with a large section number is selected.

In the construction of residential buildings and other structures, everyone is faced with the need for proper calculation and installation of the ceiling. The ceiling is a horizontal structure located inside the building, which divides it into adjacent rooms vertically (floors, attic, etc.). In addition, this structure is load-bearing, since it takes all the loads coming from furniture, people, equipment and the ceiling itself and transfers them either to the walls or to the columns (depending on the type of structure).

Types of floors

According to the purpose of the overlap can be divided into:

basement - separate the first floor of the building from the basement or basement
interfloor - aimed at dividing the floors of the building among themselves
attic. First. From the name of the second species it follows that they. The latter separate the attic space from the residential building.

Depending on the design features of the floor, they can be divided into tiled and beamed:

Tiled floors are most often mounted in large stone houses using reinforced concrete slabs.
Beam ceilings are used in the construction of low-rise residential buildings. For their installation, metal or wooden beams can be used.

Floor channel

the channel must be laid vertically, since the section modulus in this direction is several times greater than the value of the moment in the opposite direction
the laying scheme is as follows - from the middle of the overlap, the profile must be turned in the opposite direction, since the center of gravity of the channel does not belong to its wall

Such a laying scheme is necessary to compensate for tangential stresses. It should be remembered that the channels for overlapping are subject to bending stresses.

Calculation of the bending of the channel for floors

We will calculate the channel for overlapping based on the following conditions. There is a room with a size of 6x8 m. The step of the whips of the floor channel is p \u003d 2 m. It is logical to assume that the channel should be laid along a short wall, which will reduce the maximum bending moment acting on it. The normative load per square meter will be 540 kg/m2, and the calculated load is 624 kg/m2 (according to SNiP, taking into account the reliability factors for each component of the load). Let the floor channel on each side rest on a wall 150 mm long. Then the working length of the channel will be:

L = l+2/3∙lop∙2 = 6+2/3∙0.15∙2 = 6.2 m

The load per linear meter of the channel will be (normative and calculated, respectively):

qн = 540∙р = 540∙2 = 1080 kg/m = 10.8 kN
qр = 540∙р = 624∙2 = 1248 kg/m = 12.48 kN

The maximum moment in the section of the channel will be equal (for the standard and design load):

Мн = qн∙L2/8 = 10.8∙6.22/8 = 51.9 kN∙m
Мр = qр∙L2/8 = 12.48∙6.22/8 = 60 kN∙m

Let us determine the required section modulus by the expression:

Wtr = Мр/(γ∙Ry)∙1000, where

Ry = 240 MPa - resistance of steel C245, calculated
γ = 1 – coefficient of working conditions

Then Wtr = 60/(1∙240)∙1000 = 250 cm3

Section selection and channel stiffness test

According to the reference book (see GOST 8240-97 or GOST 8278-83), we select the channel profile, which has a moment of resistance greater than the calculated one. In this case, a 27P channel is suitable, Wx = 310 cm3, Ix = 4180 cm4. Next, it is necessary to check the strength and bending stiffness of the channel (lash deflection).

Test of strength:

σ = Мр/(γ∙Wx)∙1000 = 60∙1000/(1∙310) = 193 MPa< Ry = 240 МПа, что подтверждает условие прочности

Stiffness test, channel bending where the relative deflection f/L must be less than 1/150 and is determined by the expression:

f/L = Мн∙L/(10∙Е∙Ix) = 60∙103∙620/(10∙2.1∙105∙4180) = 1/236<1/150

The rigidity condition is provided. Therefore, this channel can be used for overlapping according to the described scheme. You can reduce the channel number if the whips are laid with a smaller step.