01.10.2010, 11:47
calculation:
1) beam 200*200*6000 through 0.5M = 22 t.r (deflection 20 mm)
2) I-beam 20B h/w 1.2 m = 27 tr. (deflection 20 mm)
By weight 1) -90 kg timber, 2) - 120 kg beam
In theory, the solutions are very similar. I'm interested in practice, which is better?
Green Cat
01.10.2010, 11:55
Beam.
You shouldn't do any work with iron at all. load-bearing structures for in a fire, wood holds out to the last, and iron is grunted and ready.
01.10.2010, 15:55
The temperature at which the I-beam will deform is incompatible with life. Especially if the bottom is covered with plasterboard.
If you still decide to make it with wood, then I recommend 200x60x6000 with a step of 600 mm.
01.10.2010, 16:55
“Crack and it’s done” - but won’t it matter anyway)))
It can be deformed in one place and fly to another, where there are still conditions for life... :) but in general you are right.
+Wood itself will support combustion, but iron will not...
Green Cat
01.10.2010, 17:41
The temperature at which the I-beam will deform is incompatible with life.
Wrong.
It’s one thing when he’s on his own, and another when he’s under load.
Until recently, it was generally prohibited to use meth as rafters. profile, now I see they are doing it with all their might.
I recommend 200x60x6000 with a pitch of 600 mm
It will be too small, too small - let's look at the cuckulator.
01.10.2010, 20:32
In one room I had a span of 5.7 meters, the overlap between the 1st and 2nd floors. I chose an I-beam 20B at 1.3 meters, it seems that according to calculations the I-beam was stronger than wood. It is worth considering that a tree can be found 6.5 meters long, and the length of an I-beam is 11.7 meters or 12 meters (to cover a span of 6 meters you need at least 15 cm on one side). It would have been better to lay the slabs, but I didn’t succeed. The difference between the tree and the I-beam was somewhere around 10-12%. When laying the walls, I installed 3 cm of foam between the cutout in the gas block and the I-beam.
Regarding the fire, you need to take precautions.
02.10.2010, 00:47
And I laid a 5.8 meter reinforced concrete slab on the 6 m span and don’t think about anything else. Doesn't burn, doesn't melt, doesn't bend...
02.10.2010, 09:00
Thanks to everyone, I’m still leaning towards an I-beam, since it’s stronger, I want to install internal walls made of 100 cm foam block for the ceiling. (although it was probably possible to put 2 beams under the wall)
then wawan001 the span is 6M along the axes of the walls, that is, there will be 15 cm of support on each side.
then Cat, I guess if you fall asleep non-flammable insulation ala expanded clay, then there will be nothing to burn there at all (the house is made of foam block).
And another question, if you cover it with an I-beam, is it possible to use, say, a 50 piece of wood attached to the side walls instead of the outer beams??
02.10.2010, 18:30
There is another option.
02.10.2010, 19:12
There is another option.
Do you do load-bearing beam(albeit from an I-beam), on which you lay simple wooden floor beams. It will be much cheaper.
You will need one or two I-beams, but powerful ones. The price will still be cheaper.
I did it to myself
02.10.2010, 20:01
dengt, this idea came to my mind from the point of view of the manufacturability of installing floors in the future, if wooden floors are installed inside the I-beam, and a counter-lattice is made on top (beams according to calculations). The distance from the edge of the beam to the I-beam is 40 cm - reliable. After all, according to calculations, the load on the outermost beams is 2 times less than on the adjacent one, you can put a 150x200 beam or take 2 pieces of 50x200 boards and between them install pieces of boards of the same size 1.5 meters long, and I think 50 is flimsy, although if to It can be attracted to the wall and it will be fine. If you are confident in the fasteners, then probably yes.
04.10.2010, 05:57
I covered the span with a 5m beam of 150*150, folded in half and tied with pins, i.e. The result is a beam 150*300. It turned out pretty tough, but I would still make it out of concrete if possible :(
05.10.2010, 09:32
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I did it to myself
the span is 11 by 6, divided into three parts by two I-beams and laid wooden beams, and in order not to increase the thickness of the ceiling, laid them inside the T-beam. I first welded the corners to the tee and secured the beams with bolts.
As I understand it, the I-beams were 6 meters high?
here you need at least 25B2, it’s a 5 cm thicker covering, it doesn’t seem to be fatal.
What worries me about attaching the side beams to the walls is that all the other beams will sag but the outer ones will not, then the flooring will bend like a bubble? What will this lead to?
05.10.2010, 10:11
6-measure I-beam 20B1 - two pieces across the length, it turned out 3 zones, two with beams resting on one side on the wall, and the other on the I-beam, and one zone with beams sandwiched between the I-beams. I didn’t notice any flexing; the I-beam doesn’t work at that length.
06.10.2010, 13:06
06.10.2010, 13:47
depending on how you load it, if according to theory it’s 400 kg/m then in your case the 20B1 will bend by 77 mm
I wonder how you calculated this?
In order to build a reliable wooden floor, it is necessary to select the correct dimensions of the beams, and for this it is necessary to calculate them. Wooden beams ceilings have the following main dimensions: length and cross-section. Their length is determined by the width of the span that needs to be covered, and the cross-section depends on the load that will act on them, on the length of the span and the installation pitch, that is, the distance between them. In this article we will look at how to independently make such a calculation and select the correct beam sizes.
Calculation of wooden floor beams
In order to determine how many wooden beams and what sizes will be required for the flooring, you must:
- measure the span that they will cover;
- decide on ways to secure them on the walls (to what depth they will go into the walls);
- make a calculation of the load that will act on them during operation;
- using tables or a calculator program, select the appropriate pitch and section.
Now let's look at how this can be done.
Length of wooden floor beams
The required length of floor beams is determined by the size of the span that they will cover and the margin required to embed them in the walls. The length of the span is easy to measure using a tape measure, and the depth of embedding in the walls largely depends on their material.
In houses with brick or block walls, beams are usually embedded in “sockets” to a depth of at least 100 mm (board) or 150 mm (timber). IN wooden houses They are usually placed in special notches to a depth of no less than 70 mm. When using a special metal fastening(clamps, angles, brackets) the length of the beams will be equal to the span - the distance between the opposite walls on which they are attached. Sometimes, when installing roof rafters directly on wooden beams, they are extended outward, beyond the walls by 30-50 cm, thus forming a roof overhang.
The optimal span, which can overlap wooden beams, is 2.5-4 m. Maximum length beams from edged boards or timber, that is, the span that it can cover is 6 m. For a longer span (6-12 m), it is necessary to use modern wooden beams made of laminated veneer lumber or I-beams, and you can also rest them on intermediate supports(walls, columns). In addition, to cover spans longer than 6 m, wooden trusses can be used instead of beams.
Determination of the load acting on the floor
The load acting on the floor along wooden beams consists of the load from the own weight of the floor elements (beams, inter-beam filling, lining) and permanent or temporary operational load (furniture, various household devices, materials, weight of people). It usually depends on the type of floor and its operating conditions. The exact calculation of such loads is quite cumbersome and is carried out by specialists when designing the floor, but if you want to do it yourself, you can use its simplified version given below.
For attic wooden floors, which are not used for storing things or materials, with light insulation (mineral wool or others) and lining constant load(from its own weight - Rown) is usually taken within 50 kg/m2.
The operational load (Rexpl.) for such an overlap (according to SNiP 2.01.07-85) will be:
70x1.3 = 90 kg/m2, where 70 – normative meaning load for this type of attic, kg/m2, 1.3 – safety factor.
The total design load that will act on this attic floor will be:
Rtot.=Rown.+Rexpl. = 50+90=130 kg\m2. Rounding up we take 150 kg/m2.
In case the design attic space heavier insulation, material for inter-beam filling or lining will be used, and if it is intended to be used for storing things or materials, that is, it will be used intensively, then the standard load value should be increased to 150 kg/m2. In this case, the total load on the floor will be:
50+150x1.3 = 245 kg/m2, round up to 250 kg/m2.
When using attic space to construct an attic, it is necessary to take into account the weight of floors, partitions, and furniture. In this case, the total design load must be increased to 300-350 kg/m2.
Due to the fact that an interfloor wooden floor, as a rule, includes floors in its design, and the temporary operational load includes the weight of a large number of household items and the maximum presence of people, it must be designed for a total load of 350 - 400 kg/m 2.
Section and pitch of wooden floor beams
Knowing the required beam length wooden floor(L) and having determined the total design load, you can determine their required cross-section (or diameter) and laying step, which are interconnected. It is considered that the best is rectangular section wooden floor beams, with a height (h) and width (s) ratio of 1.4:1. The width of the beams, in this case, can be in the range of 40-200 mm, and the height 100-300 mm. The height of the beams is often chosen so that it corresponds to the required thickness of the insulation. When using logs as beams, their diameter can be in the range of 11-30 cm.
Depending on the type and cross-section of the material used, the pitch of the wooden beams 
the ceiling can be from 30 cm to 1.2 m, but most often it is chosen within the range of 0.6-1.0 m. Sometimes it is chosen so that it matches the size of the insulation boards laid in the interbeam space, or ceiling sheets. In addition, in frame buildings, it is desirable that the pitch of the beams corresponds to the pitch of the frame posts - in this case, the greatest rigidity and reliability of the structure will be ensured.
You can calculate or check the already selected dimensions of wooden floor beams using reference tables (some are given below) or using online calculator"calculation of wooden floor beams", which is easy to find on the Internet by typing in the corresponding request in a search engine. It is necessary to take into account that their relative deflection for attic floors should not be more than 1/250, and for interfloor floors - 1/350.
Table 1
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Step,m\ span,m |
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Table 2
Table 3
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Step,m/ span,m |
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Table 4
appointed after fulfilling a number of requirements. Thus, removal of the side elements of the formwork, which do not bear the load from the weight of the structure, is allowed only after the concrete has achieved strength that ensures the safety of the surface and edges of the corners.
More stringent requirements are imposed on the removal of load-bearing formwork of reinforced concrete structures, which can be removed only after the concrete reaches the design strength value:
- load-bearing structural elements with a span of up to 2 m – 50%;
- load-bearing structures of beams, crossbars, purlins, slabs and vaults with a span of 2-6 m – at least 70%;
- load-bearing structures with a span of more than 6 m – at least 80%;
- load-bearing structures reinforced with load-bearing welded frames - at least 25%.
Standard conditions for concrete hardening are: temperature 20±5ºC and air humidity above
90%. It should be borne in mind that in practice, as a rule, real conditions do not correspond to standard standards, and the concrete hardening process either slows down or accelerates. For example, at a temperature of 10ºC, after 7 days concrete will gain 40-50% strength, and at 5ºC - only 30-35%. If hardened at a temperature of 30-35ºC, concrete will gain 45% strength within 3 days. At subzero temperatures, concrete without special additives does not gain strength at all. Therefore, the decision on stripping and loading the structure should be made after testing the concrete for strength.
The time frame for concrete to achieve a given strength is established by the construction laboratory based on the results of testing control samples or methods non-destructive testing. At sites with a total volume of work less than 50 m3, receiving ready-mix concrete from factories or installations located at a distance of no more than 20 km, it is allowed to assess the strength of concrete according to the laboratory of the manufacturer concrete mixture without making test samples at the installation site. However, this instruction does not apply to critical paired and thin-walled structures: beams, columns, floor slabs, as well as monolithic joints of prefabricated structures.
Of course, when constructing suburban residential buildings they usually do not measure concrete strength, since most construction companies There are simply no construction laboratories working in the private housing construction sector. Therefore, in this case, you will have to rely on the laboratory data of the concrete mix manufacturer. Additionally, you can conduct your own concrete strength testing. To do this, you need to take a metal ball with a diameter of at least 20 mm and throw it from the same height to concrete surface: control and subject. Based on the height of the ball’s rebound, it will be possible, I’ll make a reservation right away - with a big stretch, to determine whether the strength of the concrete has reached the required value.
Full design load in stripped form reinforced concrete structure can be allowed only after the concrete has acquired its design strength.
A metal floor beam in the form of an I-beam has a number of undeniable advantages. So a metal I-beam can cover large spans with a significant load. In addition, the metal steel beam is absolutely non-flammable and resistant to biological influences. However, a metal beam when exposed to aggressive environment may corrode, so a protective coating must be applied to it.
In most cases in private housing construction, a metal beam has hinged supports - its ends are not rigidly fixed, for example, since in a frame steel structure. The load on the floor with steel I-beams, taking into account its own weight, should be calculated without a screed of 350 kg/m2 and 500 kg/m2 with a screed.
It is recommended to make the step between I-beams equal to 1000 mm, however, in order to save money, you can increase the step between the metal beams to 1200 mm.
The table below shows the selection of I-beam number metal beam at different pitches and lengths of runs.
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Span3 m |
Span4 m |
Span6 m |
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I-beam number at step |
I-beam number at step |
I-beam number at step |
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As can be seen from the table, with a total load of 500 kg/m2 and a span length of 6 m, you should have chosen an I-beam of a higher number and chosen a smaller beam installation step.
Added: 05/26/2012 08:21
Discussion of the issue on the forum:
We poured the ceiling between the first and second floors along I-beam No. 12, span 6 meters with an outlet 1 meter from load-bearing wall first floor. The distance between the I-beams is 2 meters, from below between them a mesh of cell 20 is connected from reinforcement No. 12, on top of mesh No. 5, cell 10 cm. Question: after how many days can the formwork be removed and after how many days can the walls be laid, including at the outlet?
Beams in a house usually belong to rafter system or overlap, and to get reliable design, the operation of which can be carried out without any fear, must be used beam calculator.
What is the beam calculator based on?
When the walls have already been brought under the second floor or under the roof, it is necessary to make, in the second case smoothly turning into rafter legs. In this case, the materials must be selected so that the load on the brick or log walls did not exceed the permissible limit, and the strength of the structure was at the proper level. Therefore, if you are going to use wood, you need to choose the right beams from it, make calculations to find out required thickness and of sufficient length.
Subsidence or partial destruction of the ceiling may be caused by various reasons, for example, too large a pitch between the joists, deflection of the cross members, too small cross-sectional area or defects in the structure. To eliminate possible excesses, you should find out the expected load on the floor, be it basement or interfloor, and then use a beam calculator, taking into account their own weight. The latter may change according to concrete lintels, the weight of which depends on the density of the reinforcement; for wood and metal at a certain geometry the mass is constant. The exception is damp wood, which is not used in construction work without pre-drying.
On beam systems in floors and rafter structures load is exerted by forces acting on section bending, torsion, and deflection along the length. For rafters it is also necessary to provide snow and wind load, which also create certain forces applied to the beams. It is also necessary to accurately determine the required pitch between the jumpers, since it is too large number crossbars will lead to excess weight of the floor (or roof), and too little, as mentioned above, will weaken the structure.
You may also be interested in an article about calculating the amount of unedged and edged boards in a cube:
How to calculate the load on a floor beam
The distance between the walls is called a span, and there are two of them in the room, and one span will necessarily be smaller than the other if the shape of the room is not square. Interfloor lintels or attic floor should be laid along a shorter span, the optimal length of which is from 3 to 4 meters. Longer distances may require beams non-standard sizes, which will lead to some instability of the flooring. The best solution in this case would be to use metal crossbars.
Regarding the section wooden beam, there is a certain standard that requires the sides of the beam to be in a ratio of 7:5, that is, the height is divided into 7 parts, and 5 of them must make up the width of the profile. In this case, deformation of the section is excluded, but if you deviate from the above indicators, then if the width exceeds the height, you will get a deflection, or, if the opposite discrepancy occurs, a bend to the side. To prevent this from happening due to the excessive length of the beam, you need to know how to calculate the load on the beam. In particular, the permissible deflection is calculated from the ratio to the length of the lintel as 1:200, that is, it should be 2 centimeters per 4 meters.
To prevent the beam from sagging under the weight of logs and flooring, as well as interior items, you can grind it from below a few centimeters, giving it the shape of an arch; in this case, its height should have an appropriate margin.
Now let's turn to the formulas. The same deflection mentioned earlier is calculated as follows: f nor = L/200, where L is the span length, and 200 is the permissible distance in centimeters for each unit of beam subsidence. For reinforced concrete beam, distributed load q which is usually equated to 400 kg/m 2, the calculation of the limiting bending moment is performed using the formula M max = (q · L 2)/8. In this case, the quantity of reinforcement and its weight is determined according to the following table:
Cross-sectional areas and mass of reinforcing bars
Diameter, mm | Cross-sectional area, cm 2, with the number of rods | Weight 1 linear meter, kg | Diameter, mm |
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Wire and rod reinforcement |
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Seven-wire ropes class K-7 |
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The load on any beam made of a sufficiently homogeneous material is calculated using a number of formulas. To begin with, the moment of resistance W ≥ M/R is calculated. Here M is the maximum bending moment of the applied load, and R– calculated resistance, which is taken from reference books depending on the material used. Since most often beams have rectangular shape, the moment of resistance can be calculated differently: W z = b h 2 /6, where b is the width of the beam, and h– height.
What else should you know about beam loads?
The ceiling, as a rule, is at the same time the floor of the next floor and the ceiling of the previous one. This means that it needs to be made in such a way that there is no risk of combining the upper and lower rooms by simply overloading the furniture. This probability especially arises when the step between the beams is too large and logs are abandoned (plank floors are laid directly on the timber laid in the spans). In this case, the distance between the crossbars directly depends on the thickness of the boards, for example, if it is 28 millimeters, then the length of the board should not be more than 50 centimeters. If there are lags, the minimum gap between the beams can reach 1 meter.
It is also necessary to take into account the mass used for the floor. For example, if mats are laid from mineral wool, That square meter basement floor will weigh from 90 to 120 kilograms, depending on the thickness of the thermal insulation. Sawdust concrete will double the mass of the same area. The use of expanded clay will make the flooring even heavier, since the load per square meter will be 3 times greater than when laying mineral wool. Next, we should not forget about the payload, which for interfloor ceilings is 150 kilograms per square meter minimum. In the attic, it is enough to accept a permissible load of 75 kilograms per square.
Table of floor spansTable of floor spans frame house helps to choose the correct section of floor joists, which means avoiding problems with sagging floors, creaking and vibration when walking. Our homegrown approach - taking larger beams - is not economically justified. The board is cheaper than timber, especially large section. Most often, the length of floor spans is within 3.5-4.5 meters and, observing correct section and step, you can install a reliable overlap.
Let me remind you that floor joists are installed with a certain pitch, a multiple of the long side of the rough sheathing slab, namely 305 mm, 407 mm, 488 mm and 610 mm for osb boards/ plywood measuring 2240 x 1220 mm.
For pitch 305 mm (12" OC)
For pitch 407 mm (16" OC)
For pitch 488 mm (19.2" OC)
For pitch 610 mm (24" OC)
Where did the data in these tables come from?
How to work with tables correctly and what is residential and non-residential load?
Living space is everything that is located and moves around the floor space: people, objects. Non-residential load is the weight of building elements. For example, the weight of floor joists and subfloor slabs.
Depends on what will be located on top: a double bed or regular chair. Finish coating gender maybe lightweight laminate, or maybe a heated floor screed with tiles.
Typically for residential premises the total load is in the range of 200-250 kg per sq.m. If you plan to install cast iron bath, then look at its weight and add a lot of water and your loved one in it.
What type of wood are these values taken for?
Since our markets do not have a quality system and precise definition lumber grades, the tables indicate the values for ordinary spruce and grade II pine according to the North American classification.
The actual cross-sectional dimensions of the boards in American tables are smaller than European ones, what should I do?
This is true. If Americans say that the board is 2" x 6", then it is not 50.8 mm x 152.4 mm. In fact it is 38.1 mm x 139.7 mm. The cross-section of the board is reduced as a result of drying and planing. At our sawmills, lumberyards and markets, it’s also not furniture store. Sellers claim that the board has a cross-section of 50 mm x 150 mm, but in fact it can be 40-50 mm x 135-150 mm.
