The beams in the house are usually slinge system or overlapping, and to get a reliable design, the operation of which can be carried out without any fears, must be used calculator beam.

What is the calculator beams

When the walls are already connected under the second floor or under the roof, it is necessary to do, in the second case, smoothly turning into the rafting legs. At the same time, the materials should be chosen so that the load on the brick or log walls did not exceed the permissible, and the strength of the structure was at the proper level. Consequently, if you are going to use wood, you need to choose the right beams from it, make calculations to determine the desired thickness and sufficient length.

Sailing or partial destruction of the overlap can serve different reasons, for example, too much a step between lags, a deflection of the crossbar, too small area of \u200b\u200btheir cross section or defects in the structure. To exclude possible excesses, it is necessary to find out the estimated load on the overlap, whether it is a base or inter-storey, after which we use the beam calculator, given their own mass. The latter may vary in concrete jumpers, the weight of which depends on the density of reinforcement, for wood and metal with a certain geometry, the mass is constant. The exception is the removal wood that is not used in construction work without pre-drying.

On the beam systems in overlaps and stropil structures Age of the force acting on the cross section bending, torsion, for deflection in length. For rafters, it is also necessary to provide snow and wind load, which also create certain efforts attached to the beams. You also need to accurately determine the necessary step between jumpers, since too a large number of The crossbar will lead to an extra mass of overlap (or roof), and too small, as mentioned above, weakens the design.

You may also be interested in an article about the calculation of the amount of unedged and edged board cubed:

How to calculate the load on the ceiling beam

The distance between the walls is called the span, and there are two of them in the room, and one span will necessarily be less than the other if the shape of the room is not square. Inter-fitting jumpers or attic overlap It should be placed on a shorter span, the optimal length of which is from 3 to 4 meters. With a larger distance, beams may be required. non-standard sizesthat will lead to some ziyobility of the floor. The optimal output in this case will be the use of metal crossing.

As for the cross section wooden bar, There is a specific standard that requires that the side beams relate to as 7: 5, that is, the height is divided into 7 parts, and 5 of them must draw up the profile width. In this case, the deformation of the section is excluded, but to deviate from the above indicators, then the width exceeding the height is a deflection, or, with the opposite inconsistency - bend to the side. So that this does not work out due to the excessive length of the bar, you need to know how to calculate the load on the beam. In particular, the allowable deflection is calculated from the ratio to the jumper length, as 1: 200, that is, there must be 2 centimeters of 4 meters.

In order for the timber to be lagged under the severity of lags and flooring, as well as interior items, it is possible to pull it out of several centimeters, giving the form of the arch, in this case its height should have the appropriate reserve.

Now let's turn to the formulas. The same deflection referred to as previously calculated: F norm \u003d L / 200, where L. - The length of the span, and the 200 is a permissible distance in centimeters for each unit of seeding of the bar. For reinforced concrete beam, Distributed load q. On which 400 kg / m 2 is usually equal, the calculation of the limiting bending moment is performed according to the Max \u003d (Q · L 2) / 8 formula. In this case, the number of reinforcement and its weight is determined by the following table:

Cross sections and a mass of reinforcement rods

Diameter, mm.	Cross-sectional area, cm 2, with the number of rods									Weight 1 pm, kg	Diameter, mm.
Wire and rod fittings
Class K-7 seven-level ropes

The load on any beam from a fairly homogeneous material is calculated for a number of formulas. To begin with, the moment of resistance w ≥ m / r is calculated. Here M. - this is the maximum bending moment of the accompanying load, and R. – estimated resistancewhich is taken from directories depending on the material used. Since most often the beams have a rectangular shape, the moment of resistance can be calculated otherwise: W z \u003d b · H 2/6, where b. is a width of beams, and h. - Height.

What else should be known about the load on the beam

The overlap is, as a rule, is at the same time and the floor of the next floor and the ceiling of the previous one. So, you need to make it such that there is no risk to combine the upper and lower rooms by banal overlap with furniture. Especially such probability occurs at a very big step between the beams and the failure of lags (the militant floors are laid directly on the bar laid in the spans). In this case, the distance between the crossies directly depends on the thickness of the boards, for example, if it is 28 millimeters, then the board length should not be more than 50 centimeters. If you have lags, the minimum gap between the beams can reach 1 meter.

Also be sure to take into account the mass used for the floor. For example, if mats are stacked from mineral wool, then square meter The base overlap will weigh from 90 to 120 kilograms, depending on the thickness of thermal insulation. The opilk concrete will increase the mass of the same area twice. The use of the same clay will make the overlap even harder because the load is 3 times more on the square meter than when laying mineral wool. Next, we should not forget about the useful load, which for inter-storey floors is 150 kilograms per square meter at least. In the attic enough to take permissible load 75 kilograms per square.

The possibility of insane overlap of large areas significantly expands architectural possibilities when designing a house. The positive solution of the Ballery Question allows you to "play" with the volume of rooms, install panoramic windows, build big rooms. But if it is not difficult to cover the "tree" a distance of 3-4 meters, then what beams to use 5 m on the span and more is a difficult question.

Wooden beams overlap - dimensions and loads

Made wooden overlap in brusade house, and the floor is shaking, begins, the effect of "trampoline" appeared; We want to make wooden beams overlap 7 meters; It is necessary to overlap the room with a length of 6, 8 meters so as not to be laid down the intermediate supports; What should be the beam of overlapping for a span of 6 meters, a house from a bar; If you want to make a free layout - such questions are often asked forum users.

Maxinova. User forumhouse.

I have a house of about 10x10 meters. I "threw" wooden lags to the overlap, their length is 5 meters, the cross section is 200x50. The distance between the lags is 60 cm. In the process of operating the overlap, it turned out that when the children run in the same room, and you stand in another, then a fairly strong vibration goes on the floor.

And this case is far from the only one.

elena555 User forumhouse.

I can not understand which beams for inter-storey floors are needed. I have a house of 12x12 meters, 2-storey. The first floor is composed of aerated concrete, the second floor is attic, wooden, blocked with a 6000x150x200mm bar, laid every 80 cm. Lugges are laid on a boutique, which relies on a pole installed in the middle of the first floor. When I go on the second floor, I feel shaking.

Beams on long spans Must withstand heavy loads, so to build a durable and reliable wooden overlap with a large span, they need to be carefully calculated. First of all, it is necessary to understand what load will be able to withstand wooden lag. of one or another cross section. And then think over, having determined the load for the beam overlap, which it will be necessary to make a draft and finishing floor covering; What will the ceiling will be felt; Will the floor there is a full-fledged residential room or a non-residential attic above the garage.

Leo060147. User forumhouse.

1. Load from our own weight of all structural elements Overlapping. This includes the weight of beams, insulation, fasteners, floor coverings, ceiling, etc.
2. Operating load. The operational load may be constant and temporary.

When calculating the operational load, the mass of people, furniture, household appliances is taken into account, etc. The load temporarily increases with the arrival of guests, noisy celebrations, rearrangement of furniture, if you push it away from the walls to the center of the room.

Therefore, when calculating the operational load, it is necessary to think about everything - up to which furniture is planned to be installed, and is there a chance in the future of the installation of a sports simulator, which also weighs far from one kilogram.

For the load acting on the wooden beams overlapping a large length, the following values \u200b\u200bare taken (for attic and inter-storey floors):

• The attic overlap is 150 kg / sq.m. Where (on SNiP 2.01.07-85), taking into account the reserve coefficient - 50 kg / sq. M. This is a load from its own overlap weight, and 100 kg / sq. M - regulatory load.

If in the attic it is planned to store things, materials and other items necessary in everyday life, the load is taken equal to 250 kg / sq. M.

• For inter overlap and overlaps mansard floor The total load is taken from the calculation of 350-400 kg / sq. M.

Overlapping boards 200 to 50 and other running sizes

These are the beams on the span 4 meters are allowed by standards.

Most often, the construction of wooden floors uses boards and a timber of so-called running sizes: 50x150, 50x200, 100x150, etc. Such beams satisfy the standards ( after calculation) If it is planned to overlap with no more than four meters.

For overlapping a length of 6 or more meters, dimensions 50x150, 50x200, 100x150 are no longer suitable.

Wooden beam more than 6 meters: Subtleties

The beam for flight is 6 meters and no longer should be made from a bar and boards of running size.

It should remember the rule: the strength and stiffness of the overlap in more than Depend on the height of the beam and to a lesser extent - from its width.

A distributed and concentrated load is valid for the ceiling beam. Therefore, wooden beams for large spans are designed not "in principle", but with a margin by strength and permissible deflection. It provides normal and safe operation Overlapping.

50x200 - overlap for opening 4 and 5 meters.

To calculate the load that the overlap will endure, you must have the appropriate knowledge. In order not to delve into the formula of the conversion (and during the construction of the garage it is precisely excessively), it is enough to use online calculators on the calculatory on the calculatory of wooden single-puck beams.

Leo060147. User forumhouse.

Samostroik Most often is not a professional designer. All he wants to know is what beams need to be mounted in overlapping so that it meets the basic requirements of the strength and reliability. This is allowed to calculate online calculators.

Use such calculators simply. To make the calculations of the necessary values, it is enough to enter the size of the lag and the length of the span, which they have to be blocked.

Also to simplify the task you can apply ready-made tables represented by the guru of our forum with nickname Roracotta..

Roracotta. User forumhouse.

I spent a few evenings to make tables that would be understood even a novice builder:

Table 1. It presents data that meets the minimum load requirements for the second floor seats - 147kg / sq. M.

Note: Since the tables are based on American standards, and the size of sawn timber over the ocean is somewhat different from the sections adopted in our country, then it is necessary to apply in the calculations in the calculation, highlighted in yellow.

Table 2. Here are the data on the averaged load for the first and second floors - 293 kg / sq. M.

Table 3. Here are the data under the calculated enlarged load of 365 kg / sq. M.

How to calculate the distance between ducts

If it becomes closely familiar with the tables presented above, it becomes clear that with an increase in the length of the span, first of all, it is necessary to make an increase in the height of lags, and not its width.

Leo060147. User forumhouse.

You can change the rigidity and strength of the lag in the direction of the increase by increasing its height and making the "shelves". That is - a wooden 2-way beam is made.

Independent manufacture of wooden glued beam

One of the solutions for overlapping a large length of a large length is to use in the floors of a wooden beam. Consider the span of 6 meters - which beams will be able to withstand a greater load.

By type of cross section, a long beam can be:

• rectangular;
• bivalve;
• boxed.

Among the self-building there is no consensus, what section is better. If you do not take into account purchased products (foreign manufacturers), then simplicity of manufacturing in " field conditions", Without the use of expensive equipment and snap.

Just grandfather User forumhouse.

If you look at the transverse cut of any metal heap, it can be seen that from 85% to 90% of the metal mass concentrated in the shelves. There is no more than 10-15% metal on the binding wall. This is done on the basis of calculation.

What board to use for beams

On the rustling: the greater the "shelves" cross section and the farther they are separated from each other in height, the larger loads will withstand a foreign one. For self-building optimal technology The manufacture of a heap - this is a simple box design, where the upper and lower "shelves" are made of the board, plaff. (50x150mm, and the side walls are made of plywood with a thickness of 8-12 mm and a height of 350 to 400 mm (determined by the calculation), etc.).

Plywood to the regiments is nailed with nails or fastened with self-tales (not black, they do not work on a slice) and necessarily sits on glue.

If you install such a dual-meast to a six-meter span with a step of 60 cm, then it will endure a larger load. Additionally, a 2-meter consuming ceiling beam can be laid by insulation.

Also, using a similar principle, you can connect two long boards, collecting them into the "package", and then put them on each other on the edge (take the boards in 150x50 or 200x50), as a result, the segment of the beam will be 300x100 or 400x100 mm. The boards are placed on glue and tighten with studs or squeeze on the muffuhari / waders. You can also fasten the side surfaces of such beams to the side of such a beam, having pre-lubricate it with glue.

Also interesting is the experience of memberschanin under the nickname Taras174, Which decided to independently make a glued height beam to overlap the span of 8 meters.

For this, the forumchanin acquired sheets of osp with a thickness of 12 mm, cut them along a length of five equal parts. Then I bought a board of 150x50 mm, 8 meters long. Cutter " dovetail"Chose in the middle of the boards of the groove 12 mm depth and 14 mm width - so that the trapezium with the expansion of the book. OSP in groove Taras174.intended by means polyester resin (Epoxy), pre-"shooting" by the stapler to the plate of the slab striped fiberglass width of 5 mm. This, according to the forum, would strengthen the design. To accelerate drying, the glued portion warmed the heater.

Taras174. User forumhouse.

On the first beam, I trained "stuck hand." Secondly made for 1 working day. In price, taking into account all materials, turn on one piece 8 meters, the cost of the beam is 2000 rubles. For 1 pc.

Despite the positive experience, such a "samostroy" did not escape several critical comments made by our experts. Namely.

Overlapping beams from wood provide not only the strength of the horizontal design. The overlap is intended to give stiffness to the entire building. It is for this reason that the choice carrier elements And their installation is worth paying special attention.

Pros and disadvantage of wood overlap

To mount the overlap with their own hands it is necessary to prepare. The floor in the house should rely on a solid and rigid design. Before starting work, you will have to explore the requirements for elements, the features of their calculation and types of sections.

The following advantages of Wooden Overlap are available:

• attractive appearance, the ability to make a wooden floor without additional events;
• low weight, reduced load on walls and foundations, economy in construction;
• the ability to carry out repairs during operation;
• installation speed, performance without additional machines and mechanisms.

Wooden beams do not lose design and quickly mounted

But it is also worth allocating disadvantages:

• flammable wood, the need for special impregnation antipirens;
• less compared to reinforced concrete or metal elements;
• shrinkage and deformation with temperature and humidity drops;
• exposure to rotting, fungus and mold with high humidityIt is necessary to carry out the processing of antiseptics at the construction stage and periodically during the service life.

Woodble Requirements

Wooden beams overlap must comply with the following requirements:

• matching the size of the section of the load, span and the step, for this you need the calculation of the beams;
• good strength and rigidity;
• fire safety;
• the absence of serious wood defects and damage.

For work it is necessary to prepare qualitative material

There are also certain requirements for the material from which the beams are made. It is recommended to choose wood coniferous rocks. It contains a lot of resin, so it is better resisting various microorganisms. Best Material Those trees that have grown in harsh conditions are considered. The density of the barrel is higher. For this reason, it is worth buying a pine tree or spruce, which rose in the northern regions of the country.

You also need to pay attention to the time of the workpiece. The best is considered the period at the end of winter. At this time, the tree is in sleeping condition, it is less than juice, therefore the moisture of material will be less.

What are wooden floors

Wooden overlap beams are used for almost all levels at home. The beam frame must be provided for the following types of design:

• basement or ground overlap (floor of the first floor);
• intergenerational overlap;
• clear overlap.

The thickness of the bearing timber for the attic range is from 10 to 20 cm

From the type the normalized payload, which takes into account the wooden beams of overlapping. Also, the difference will be in the thickness of the insulation and its necessity.

Between the beams above the basement are usually placed from 5 to 15 cm mineral wool, foam or extruded polystyrene foam. In intermediate structures, it will be enough to provide a couple of centimeters for sound insulation. The cold attic requires the most material. Here, the thickness can be from 10 to 20 cm. The exact values \u200b\u200bdepend on the climatic area of \u200b\u200bconstruction.

Between the beams of the basement laid mineral Wat

Sometimes the basement is preferred to do from wood, but from metal and reinforced concrete. In this case, the beams are used as beams or a channel or a channel, and the concrete is poured into the formwork from the proflist. This option will be more reliable in the probability of flooding. It will also better resist dampness from the basement.

What are the beams

There are several signs for which the classification of wooden beams of overlaps is carried out: in size, material, type of section. The length of the ceiling beams depends on the distance between the walls. This magnitude needs to be added to the reservoir on both sides. Optimally, it is necessary to provide 200-250 mm.

By material, elements are divided into the following types:

• from a whole timber or board;
• from glued timber.

Both beams made from glued bars

The latter are significantly more expensive. But this is the material will suit For overlapping large spans. The usual beam can work for 4-6 m, while glueding well copes with distances 6-9 m. The glued bar practically does not give a shrinkage, fireproof and resistant to moisture action. You can make not only linear elements, but also bent. The essential disadvantage of such material will be the presence of unfulfilled components (glue).

The beam section may be the following types:

• square;
• rectangular;
• loop.

The latter has exhausted elements in the upper and lower part. In the middle of the section it is reduced to the maximum possible sizes. This option allows rational to use wood and reduce its consumption. But it is not easy to make such an element. For this reason, the boutique is not so often used in construction.

Most often a timber rectangular shape

Optimal option will be a rectangle. In this case, the long side is located vertically, and short - horizontally. This is due to the fact that an increase in height better affects the strength than widths. Install the beam from the board the plaffus is almost useless.

The most unfavorable from the submitted can be considered a square cross section. It is less than all adjacent to the effort of the effort in the element.

Also for overlapping you can use logs. But this option was not popular. The cross section from the board is much more profitable and more convenient in the installation, so it is used much more often.

Calculations

The calculation of the section will allow not to doubt the strength and stiffness of the structure. At the same time, the maximum length is determined, which is allowed with any section. To calculate the calculation, you need the following data:

• the length of the wooden beam overlap (more precisely, the distance between the carrier walls);
• distance between beams (their step);

To calculate you need to know the distance between the beams, the width of the span and the load on the design

The load consists of two values: constant and temporary. Permanent involves the mass of the beams themselves (as long as the preliminary), insulation, ceiling liner, rough and clean floor. Temporary load is a lot of people and furniture. By regulatory documents For residential premises, it is taken equal to 150 kg / m2. For the attic you can take less, but it is recommended - the same. This will not only provide a certain margin of safety, but also will provide an opportunity in the future to re-equip your attic into the attic without reconstructing the carrier elements.

Blook frame should count on such formulas:

• Mmax \u003d (Q * L2) / 8;
• Wetreb \u003d MMAX / 130.

In these formulas Q is a load on a sq. m overlap, which includes a lot of structures and 150 kg useful value. At the same time, the specified values \u200b\u200bneed to be multiplied by the distance between the beams. This is caused by the fact that for calculations you need loading on raman meterAnd initially the value is designed for square. L2 - the distance between carrier walls, which relies runs, taken in the square.

Knowing the wtreb, you can choose the cross section overlap. W \u003d b * h2 / 6. Knowing W, you can easily make an equation with one unknown. It is enough only to set one geometric characteristic B (the width of the section) or H (its height).

Most often, the wooden beam already has a well-known width. It is more convenient to produce it from a 50 or 100 mm width board. You can also consider the option with a composite section. It is made of several boards with a thickness of 50 mm.

The calculation in the specified case find the necessary height of the element. But there are such cases that you need to fit into a certain overlap pie, so as not to reduce the height of the premises. In this case, a cross section is added as a known value to the equation, and they are width. But the smaller the height, the more uneconomical there will be a frame of overlapping.

For tightening two or three boards, it is convenient to use metal studs with each other. At the same time, when twisting the nuts, wider washers must be used. They prevent metal indulgence in more soft tree. Between the tree and steel fasteners, it is necessary to provide insulation. To do this, you can use such material as the technoelast of the EPP brand.

Wooden bars Before installation, it is necessary to hydroize

Before use wooden elements They are treated with antiseptic composition. It is necessary to prevent molding and posting. It is also recommended to perform processing with antipirens that will increase fire safety. When describing the walls on the wall of the brick or concrete, their ends are wrapped with technoelast, linocur, waterproof or rubberoid.

01.10.2010, 11:47

payment:
1) Bar 200 * 200 * 6000 in 0.5 m \u003d 22 tr (deflection 20 mm)
2) 2B 20B C / s 1.2m \u003d 27 tr. (deflection 20 mm)

By weight 1) -90 kg Bar, 2) - 120 kg beam

In the theory of solutions are very similar. Interested in practice that all the same is better?

Green Cot

01.10.2010, 11:55

Bar.
Iron should not do any bearing structures For in a fire, the tree holds to the last, and iron - violating and ready.

01.10.2010, 15:55

The temperature in which the deformation of the dual-letter is incompatible with life. Especially if it all will be covered with drywall.

If you still decide to do with a tree, I advise 200x60x6000 with a pitch of 600 mm.

01.10.2010, 16:55

"varn and ready" - and not all will be equal)))

It can be deformed in one place, and fly to another, where there are still conditions for life ... :) But in general, you are right.
+ The tree in itself will support the burning, but there is no iron ...

Green Cot

01.10.2010, 17:41

The temperature in which the deformation of the dual-letter is incompatible with life.
Wrong.
It's one thing when he is by itself, but the other when it is under load.

Until recently, it was generally banned to use as a rafter met. Profile, now I look Magnifying.

I advise 200x60x6000 with a pitch of 600 mm
Malawato will be, Malawato - watch the cake.

01.10.2010, 20:32

In one room, I turned 5.7 meters, overlapping between 1 and 2 floors. I chose a 2bl 20b after 1.3 meters, it seems to calculate the boutique, it was stronger than a tree. It is worth considering that the tree can be found 6.5 meters, and the length of the alter 11.7 meters or 12 meters (for overlapping the span of 6 meters, you must at least 15 cm per side). It would be more correct to lay the plates, but I did not work. The difference between the tree and the boutique was somewhere 10-12%. When laying the walls, it was installed between the neckline in the gas-block and the foam of the foam 3 cm.
At the expense of a fire-need to be proteated.

02.10.2010, 00:47

And I put a 5.8 meter zhb plate on 6 m, and I don't think about anything else. It does not burn, it does not melt, not bend ...

02.10.2010, 09:00

Thanks to everyone, I still bow to the boutique, because it's stronger, I want to put the wall internal foam block 100 cm. (although probably it was possible to put 2 bars under the wall)
That Wawan001 span 6m is on the axes of the walls, that is, 15 cm on each side of the support will be.
then the cat, I guess if you fall asleep the non-flammable insulation, Ala Ceramzite, then there will be nothing to burn there (a house of foam block).

And another question, if you block the boutique, it is possible to use a wooden one instead of extreme beams, say 50-ku fixed to the side walls ??

02.10.2010, 18:30

There is another option.

02.10.2010, 19:12

There is another option.
Doing carrying beam (Let it from the heated), which is placed by simple wooden beams overlap. It will be much cheaper.
There are one or two, but powerful. For the price anyway will be cheaper.

I did so myself

02.10.2010, 20:01

dENGT, I have this idea from the point of view of the technological device in the future floors, if the wooden floors are installed inside the heap, and on top of making a counterclaim (calculating beams). The distance from the edge of the beam to the heaters 40 is secure. After all, according to the calculations on the extreme beam, the load is less than in 2 times than in the neighboring, you can put the beam 150x200 or take 2 pieces of the boards 50x200 and between them set the cuts of the board of the same size of 1.5 meters long, and 50-ka think chlipcat, although if The wall can be attracted and will be fine. If confident in the fastener, then probably yes.

04.10.2010, 05:57

I overlap the span of a 5m rear of 150 * 150 folded twice and pulled stiletto, i.e. It turned out the beam 150 * 300. It turned out pretty hard, but I would still make a concrete if it were possible :(

05.10.2010, 09:32

[
I did so myself
Span 11 on 6, divided into three parts by two heates and laid wooden beams, and so that it would not increase the thickness of the overlap put them inside the brand. Previously welded the corner to the brand and secured the beams on the bolts.

I so understand the 6 meter bows?
Here 25b2 is needed at least, it is 5 cm thicker crossings, it seems not deadly.

Regarding the fastening of the side beams to the walls, I worries me that all other beams will be fed and the extreme is not, then the crossing will drive "bubble"? What will it come to?

05.10.2010, 10:11

food 6-dimensional 20b1 - two pieces across length, it turned out 3 zones, two with the support of the beams of one side on the wall, and the second on the 2-way, and one zone with beams clamped between the heaters. Bending did not notice, the dual-letter does not go to such a length.

06.10.2010, 13:06

06.10.2010, 13:47

it depends on how to ship, if the theory of 400 kg / m then in your case 20b1 will drive 77 mm

I wonder how you counted it?

assigned after the fulfillment of a number of requirements. So the removal of the side elements of the formwork, not carrying the load on the weight of the structures, is allowed only after reaching the concrete strength that ensures the safety of the surface and the edges of the angles.
More stringent requirements are presented to removal of the carrier formwork reinforced concrete structureswhich is allowed to shoot only after reaching the concrete the values \u200b\u200bof the strength of the project:

• carrier structural elements by flying up to 2 m- 50%;


• carrier structures of beams, riglels, runs, plates and sections with a span 2-6 m- not less than 70%;


• carrier structures by flying more than 6 m- not less than 80%;


• carrier structures reinforced by carrier welded frames are at least 25%.

It can be estimated that after 3 days, the concrete on Portland cement will type strength about 30%, after 7 days - about 60% and after 14 days - about 80% in relation to 28-daily strength. However, the hardening of concrete continues and after the occurrence of 28 daily age. So by the 90th day of hardening concrete can be recruited with an additional 30-35% strength.
The standard solutions of concrete conditions are considered: temperature 20 ± 5ºC and air humidity above
90%. It should be borne in mind that in practice, as a rule, real conditions do not meet standard standards, and the process of hardening the concrete is either slowed down or accelerated. For example, at a temperature of 10ºC after 7 days, the concrete pulls the strength of 40-50%, and at 5ºC - only 30-35%. In the case of hardening at a temperature of 30-35ºC, concrete after 3 days will drop 45% strength. For negative temperatures Concretes without special additives do not gain strength at all. Therefore, the decision to relaspison and load the design should be applied after testing concrete for strength.
The timing of the achievement of concrete of a given strength establishes a construction laboratory on the results of tests of control samples or methods non-destructive testing. At facilities with a total work of less than 50 m 3, receiving a commodity concrete mixture from plants or installations located at a distance of no more than 20 km, the strength of concrete is allowed according to the manufacturer's laboratory concrete mix Without the manufacture of control samples at the place of laying. However, this indication does not apply to responsible paired and thin-walled structures: beams, columns, slabs of floors, as well as monolithic joints of prefabricated structures.
Of course, when the suburban residential buildings are erected, it is usually not measured by concrete for strength, since most construction firms There are simply no construction laboratories working in the private house-building sector. Therefore, in this case, you will have to focus on the data of the laboratory of the manufacturer of the concrete mix. Additionally, you can conduct your own tested concrete for strength. To do this, you need to take a metal ball with a diameter of at least 20 mmi to throw from the same height on concrete surface: Control and test. In the height of the rebound ball, it will be possible to make a reservation immediately - with a large stretch, determine whether the strength of concrete has reached to the desired value.
The total estimated load in the raft reinforced concrete structure can only be allowed after the acquisition of design strength concrete.
The metal beam of overlappings in the form of a foreign profile - has near indisputable advantages. So a metal donkey beam can be blocked big spans With a significant load. Besides metallic steel beam Absolutely non-combustible and resistant to biological influences. However, the metal beam when exposed to aggressive ambient It can corrosive, so it needs to apply a protective coating.
In most cases, in private house-building, the metal beam has hinge supports - its ends are hard not fixed, for example, as in a frame steel construction. The load on the overlapping with steel 2-level metal beams, taking into account its own weight, should be calculated without a screed of 350 kg / m 2 and 500 kg / m 2 with a screed.
The step between foreign metal beams is recommended to do equal to 1000 mm, however, in order to save items, it is possible to increase the step between metal beams up to1200 mm.
The following table shows the choice of the number of the 2-way metal beam at different steps and the length of the runs.

Poly3 M.			Poly7 M.			Poly6 M.
№ отегуев at step			№ отегуев at step			№ отегуев at step

As can be seen from the table when total load 500 kg / m 2 and the length of the span6 m, you should choose a higher number of a two-way, and select the beam installation step less.

Added: 05.26.2012 08:21

Discussion of the issue on the forum:

We poured the overlap between the first and second floor of I-caulial No. 12 span 6 meters with a 1-meter release from carrier wall first floor. The distance between the 2 meters of 2 meters, from the bottom between them from the reinforcement number 12, the cellular grid is connected on top of the mesh No. 5 of the cell 10 cm. Question: After how many days you can remove the formwork and after how many days you can make the masonry of the walls, including on the release?