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. 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 fill in non-flammable insulation ala expanded clay, then there will be nothing to burn there at all (the house is made of foam blocks).
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
[
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 floor will bend in 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?
appointed after fulfilling a number of requirements. So, removing the side elements of the formwork does not load bearing from the weight of the structures, 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 negative temperatures Concrete without special additives does not gain strength at all. Therefore, the decision to strip the formwork and load 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 using non-destructive testing methods. At sites with a total volume of work of less than 50 m3, receiving ready-mixed concrete mix 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 concrete mix manufacturer without making control 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 Concrete strength measurements are usually not taken, since most construction companies There are simply no construction laboratories working in the private housing construction sector. Therefore in 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.
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. Moreover, it is metal steel beam 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 steps and the length of the runs.
|
Span3 m |
Span4 m |
Span6 m |
|||||||
|
I-beam number at step |
I-beam number at step |
I-beam number at step |
|||||||
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:
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Installation of wooden beams in the floors of houses is not uncommon. Their main purpose is to evenly distribute the load on the walls and foundation of the building. To beam structure performed its functions, it is necessary to select the right material for it, calculate the length and cross-section.
All wooden beams are divided among themselves according to their purpose and the type of material from which they are made. According to their purpose, they can be: interfloor, attic, basement and basement. Depending on the type of material, beams can be made of solid wood or laminated wood.
wooden floors in aerated concrete house
The interfloor span must be strong and reliable. Sound and vapor barrier fillers are placed in the internal volume between the ceiling and floor. The ceiling part is sewn up necessary material, the floor is laid on top.
The attic floor can be installed as an element of the roof, being part of it truss structure. Can be installed as a separate independent element. In order to preserve heat, it must be equipped with steam and thermal insulation.
Basement ceiling and ground floor must be of great strength and withstand high loads. These spans are equipped with heat and vapor barriers to prevent the penetration of cold from the basement.
Beams differ in types, which have their own advantages and disadvantages.Hardwood is used to make solid beams. A significant disadvantage of solid wooden beams is the length limitation, which cannot exceed 5 meters.
Beams made of laminated wood combine high strength and aesthetics. Their use significantly increases the maximum length, which can be up to 20 meters. Considering that glued floors look beautiful, they are often not covered with a ceiling and serve as a design element.
They have several more significant advantages, which include:
- ability to cover large spans;
- ease of installation;
- small weight;
- long period of operation;
- high level of fire safety;
- cannot be deformed.
The wooden parts of the floor beams may have rectangular section, which is typical for timber or boards, or round, made from logs.
Requirements for wooden floor beams
Installation of wooden beam floors entails a number of requirements that must be taken into account. They are as follows:
- Beam products must be made coniferous species wood, which have a high margin of safety. At the same time, the moisture content of the wood should be no more than 14 percent, otherwise the joists will have a large deflection under load.
- It is prohibited to use wood that is susceptible to fungal diseases or damaged by insects to make beams.
- Before installation, beam elements must be treated with an antiseptic.
- To ensure that the ceiling or floor does not sag even under load, it is necessary to perform a construction lift. The ceiling of the lower floor will receive a slight rise in the center, which will become even under load.
- If the beams are planned to be laid with great frequency, then instead of them you can use boards that need to be installed on the ribs.
The procedure for calculating wooden beams
Before installation wooden floor, it is necessary to carry out calculations in which to determine the number and dimensions of beams. To do this you need:
- determine the length of the span on which they will be installed;
- calculate the possible load they will bear after installation;
- Having the specified data, calculate the cross-section of the beams and the step with which they will be installed. For this, special tables and programs are used.
Beam length consists of the length of the span that needs to be covered and the stock of the beam that will be mounted into the wall. The span can be determined using any measuring device. The supply of beams that will be mounted in the wall depends on the material from which the wall is made.
Important!
If the building is built of brick, then the margin for beams made from boards should be at least 10 cm and at least 15 cm for beams made from timber. IN wooden buildings special grooves are made, with a depth of 7 cm or more, for laying beams. If the beams serve as the basis for the roof rafters, then they are made 4-6 cm longer than the span.
The most used span, which is covered with beams, ranges from 2.5 to 4 meters. The maximum length of beams made of timber or boards cannot exceed 6 meters. If the span length exceeds this size, then it is recommended to install beams made of laminated veneer lumber. In addition, to cover spans longer than 6 meters, you can install a wooden truss.
Load carried by a wooden beam consists of a mass of span parts (beams, internal filling, ceiling and floor coverings) and a mass of temporary elements (furniture, Appliances, people present in the room).
Accurate calculations bearing capacity beams are usually carried out by specialized organizations. At independent execution The following system is used for calculation:
- attic floor with lining, in which the insulation is mineral wool, carries a constant dead load of 50 kg per square meter. With such a load, according to SNiP standards, the standard load will be 70 kg per square meter with a safety factor of 1.3. Finding out the total load is not difficult: 1.3x70+50=130 kilograms per square meter;
- if a heavier material than cotton wool is used as insulation, or thick boards were used as lining, then the standard load will be 150 kg per square meter. AND total load will have a different value: 150x1.3+50=245 kg per square meter;
- if the calculation is carried out for attic room, then the weight of the material from which the floor is laid and the objects located in the attic is taken into account. The load in this case will be 350 kg per square meter;
- in the case where the beams serve as interfloor spans, the calculated load is 400 kg per square meter.
Calculation of wooden floor beams
Determination of the section and pitch of wooden beams
By calculating the load and length of the beams, you can determine their pitch and cross-sectional dimensions or diameter.
These indicators are interrelated and are calculated according to established rules:
- The width and height of the beams should be in proportion 1:1.,4. In this case, the width of the beams should be in the range from 4 to 20 cm, and the height from 10 to 30 cm, taking into account the thickness insulation material. Logs for floors should have a diameter in the range from 11 to 30 cm.
- The installation step should be in the range from 30 to 120 cm, taking into account the insulation and lining materials that will be in the space between the beams. If the structure is frame, then the step should correspond to the distance between the frames.
- The cross-section of wooden beams is determined using developed tables or using certain programs. When calculating sections, it is necessary to take into account that the maximum bending attic beams should not exceed 1/200, and between floors 1/350.
Application of wooden trusses, advantages and disadvantages
Floor trusses made of wood look like two parallel logs or bars located above each other, which are connected to each other by supports located at an angle or vertically in relation to these logs or bars. The main task that trusses solve is covering long spans if the installation of additional support posts is impossible.
For the manufacture of trusses, developed tables and programs are used, which take into account the type of connections, installation pitch, cross-section of structural parts and its overall dimensions. Often, trusses are made industrially using high-precision equipment. Along with this, you can make a farm with your own hands.
By comparing wooden beams and floor trusses, you can determine the advantages and disadvantages that the trusses have. The advantages include:
- the ability to cover a span of significant size without additional support posts;
- insignificant mass, which entails a small load on the load-bearing elements of the building;
- high strength and resistance to deflection, which entails long-term operation of lining and flooring materials;
- ease of installation on any load-bearing elements of the building, regardless of the material from which they are made;
- the ability to change the width of the truss laying step;
- possibility of installing internal communication lines;
- excellent sound insulation;
- beautifully made trusses can be left unsewn and used as a decorative element.
In addition to advantages, farms have some disadvantages, which include the following:
- due to design features, the thickness of interfloor ceilings increases significantly;
- significant labor costs when making a farm with your own hands, the need for special equipment;
- high price for a finished structure.
Design wooden trusses