Silo for pellets and resistance screed

[chatelot16]

don't break your head so much

if it were to install a heavy industrial machine which vibrates and whose different feet must remain perfectly aligned it would merit a serious study

but a silo on the ground what can happen? a crack under a foot which will sink a few more mm?

if the ground under the concrete is very compact the concrete is only a decoration, it will hold anyway

if the ground is a poorly packed embankment, the concrete must be more solid and reinforced to transmit the load where it holds

if you are sure to have a thin layer of concrete on poorly packed soil, you have to dig a hole under each post and plug it in with concrete: this work is only to be done if you are on problem ... otherwise it is better to do nothing, and hope that it holds, and only reinforce if there is a problem

[manet42]

According to my memories according to standards, unless I am mistaken, a standard slab on a reinforced concrete floor (detached house) is designed to resist 3,5 daN / mm2.
This means that if each foot of the silo ends with a 10cm by 10cm plate, it can support 35T per post.
In other words as Chatelot says, it is not worth asking the question if the ground is hard and to write it off (hedgehog) made in the rules of the art (as we say).

JC

[bnohit]

Super, thank you very much for all this rather reassuring information. Here I am less worried about the coup!

[Obamot]

In general I do not intervene, since the law obliges to follow the regulations, but there ... as an engineer, I am obliged to warn you and to correct certain points.

I could read everywhere, that a standard concrete garage slab was planned to support a load of 250kg / m2 (I find that really very little, even for a big car

The strength of concrete also depends on the strength of the soil on which it is poured.

According to my memories according to standards, unless I am mistaken, a standard slab on a reinforced concrete floor (detached house) is designed to resist 3,5 daN / mm2.

I'm scared to read a number of inaccurate things about concrete!

Some seem to confuse everything!
1) CP 250Kg /m3 (and not m2) is the dosage of cement in concrete (CP = Portland cement). From 250Kg / m3, we are dealing with a high dosage (resistance in tons / cm2)!

2) Reinforced concrete has no problem of resistance to compression (if poured in the rules of the art and garage slab / raft poured on gravel of ad hoc particle size, spreads on the ground).

3) It is the tensile strength that concrete resists (very) badly (shearing effect on support or tension in a critical area in the center of the slab.

4) In the case of a pour on a properly prepared floor, there is none (except bad soil, wet etc.) since the fulcrum is distributed over the entire surface of the slab !) So IF this is the case, I mean IF, a welded mesh reinforcement is a luxury, or in any case a good precaution, and there you have to see with what weight you are going to load (unless made with " all coming "and not pervibrated, in principle no problem)! So I suspect more in your case, a frame with a technical void underneath, so watch out for that! Because in this case, the raft or slab was not calculated to receive a significant load => attention: depending on the load, risk of cracks near the supports and in the center of the span.

5) The strength of concrete depends on:
- the composition of the reinforced concrete, which differs greatly if a) it is reinforced concrete poured according to the rules of the art b) it is reinforced concrete which has been poured without a pervibrator c) it is made concrete with "everything";
- dosage and quality / distribution of aggregates and cement.
- calculation of the reinforcement.

6) The only way to know the resistance of a concrete after the fact (without plan and without guarantee of what is underneath, nor of how the work was carried out) is a) the use of the dynamometer + b) loading the slab with sandbags until the expected load, and laser measurement to see if there is sagging (but it is risky).

So as Ahmed says, in this case => IF the slab does not rest on a technical void => THEN it will depend on the resistance of the ground on which it is poured AND on the quality of concrete used CF at the expected admissible load! In this case (without technical void underneath and a concrete poured in the rules of the art, as described above) it would eventually withstand compression very well, you could load without too much problem, the only concern, it is the ground, if there is subsidence, you risk cracks / micro-cracks which will not be visible (since located opposite to where load) with risk of rising humidity or even flooding in severe cases. But these are extreme cases. By cons you must be very sure of your diagnosis before, because as an improvised and unqualified project manager, you take sole responsibility (to see if above this garage there is a living space, etc. ... What would happen if the load in the garage leads to a break? What consequences / s on the load-bearing wall (s) and the rest of the construction (party wall, etc.).

In any case, it should not be taken lightly. So you do well to educate yourself. Call on a BE, their role is to remember nothing, and they take responsibility.

[manet42]

Good evening;
It seems to me to have made no confusion .....
The standard dosage for a concrete slab on ground hard in a single house is 250/300 kg / m3.
With base and trellis (bought all done by the mason) as indicated by bnohit, done in the rules of the art, I said several tonnes / cm2 (35T for 100cm2).
I therefore maintain that placing the 4 feet of a silo 5T on such a slab is not a problem.
I built my silo in the basement without BE in accordance with the usual rules of construction. No trouble.

JC

[Obamot]

... uh, no, read again ... you were talking about concentration per m2 (first line)

... while following my post, you corrected and now use my own words in "Kg / m3".

Now, not knowing exactly the local configuration, since I was not there. I will refrain from any validation whatsoever.

In addition, it is necessary to see the lorcal rules of request for authorization of building for the change of allocation of premises ...

Finally, although I think a silo is a good solution, in this case the load is redistributed on 4 poins, while without silo, all the load is distributed on the ground. And again, impossible to validate anything "to the good franquette" (since no knowledge of the local configuration ..) to everyone to take responsibility.

[aerialcastor]

Dtu 21 (nf P18-201) indicates a minimum cement dosage of 350kg / m3 for reinforced concrete. Only unreinforced concrete can have a lower dosage.

According to the same dtu the compressive strength of concrete dosed at 350kg / m3 is 16Mpa.


PS: I think there is confusion in the use of the term to write off. A raft is more or less a thicker concrete slab. I think MAnet means hedgehog which is a "bed" of machine-packed limestone rubble.

[manet42]

For Obamot,
Sorry to insist, you read wrong here is my message a few pages before:

For calculations, not simple, it's complicated you need to know the dosage of concrete, the diameter of the irons, their spacing ..).
In principle for a single house, 300kg / m3, the trellis, I don't know!

To Aerialcastor:
Absolutely I wanted to talk about the hedgehog.

[Obamot]

Yes I admit for the dosage (I was answering Bonohit) but you use the conditional, suggesting that "you don't know about the frame ..." It's confusing, it's not just the problem of the framework ... We need a comprehensive approach.

In addition on the Internet, you never know which guy is going to read you. So I prefer to display more caution, if you know what I mean ....

Now that the info has gone around, I stick with what I said.

[manet42]

Ah! "Mousiu" the engineer finds that I am confused ...
Well not me, I have just reread myself and I find on the contrary that despite my little IQ of "braquaillon" (a little contemptuous term ...), I expressed myself clearly.

JC