Has anyone any idea what an acceptable maximum floor loading might be for a typical concrete floor in an integral garage? It would be good to know max load over an area of about 12 square inches and max total load over entire gge (although I can't believe this would be a problem). I've no idea how thick the floor is, the house was built about 20 years ago (on chalk if it makes any difference).
Dave S
The OP said 12 square inches. One inch = 25.4 mm. So your calculation should be 25.4*25.4*12 newtons.
Mark
Lets guess its a concrete floor, laid directly onto the ground. The concrete will be say C20 or better, so thats 20 Newtons per mm squared if my understanding is right.
12 inches is about 300mm so its 300*300*12 netwons, and at 1 standard gravity a Newton is 1 KGAs thermalite block is 3.5N per mm square which is still by my maths
90 metric tonnes per square foot, for something you can cut with a bread knife.To me this sounds like a huge ammount, so my feeling is I must be wrong .........
Rick
You corrected my approximation of 12 square inches with a formula for one square inch. I have no issues with being corrected, but please get the correction right
9.8(6?)N/Kg.
3.5N/mm^2 = 3.5MN/m^2 = 325100N/ft^2 = 33200Kg/ft^2. However... This is the point loading figure. You can only put (say) 33 tons/m^2 on 3.5N/mm^2 materials if it's supported underneath by a firm surface, or very thick (several meters).
Is it 'eck! Doesn't anybody do physics at school any more?
A newton is the force required to accelerate a mass of 1 kg by 1 metre per second per second (m/s^2).
The acceleration due to gravity is 9.8 m/s^2, hence the weight of a 1kg mass is 9.8 newtons, which is near enough to 10 N for most practical purposes.
Hence one newton is approximately the weight of a 100 g mass - it's roughly the weight of an average apple, as any fule kno.
If you think of weights in kg (which is wrong from a purist physics POV, but we all know what we mean) then there are 10 newtons to the kilo, or 100 kg to the kilonewton (kN).
Familiarity with the kN is useful since structural engineers do most of their calculations this unit. A kN is about the weight of a fairly heavy bloke (~16 stone).
Assuming by "tonne' you mean a metric ton, you win this weeks award for mixing as many different unit systems in one sentence as possible :-)
So I was a decimal point out, a 3.5N thermalite block can take a load of 9 tonnes per square foot, assuming its well supported. This sounds much more reasonable. So back to the OP question
Assuming your floor is made out of thermalite blocks, and they are supported by the ground then its 9 tonne a square foot. In relaity a concrete floor is much stronge (the RC35 mix I have just used for my foundations is 10 times stonger). Its also fully and evenly supported by the ground as it molded to the ground when laid. If your ground has sunk, washed away or was soft then this maths is useless, but the BCO should have looked for that before he approved the excvations ....
I would guess that that tank you found on eBay won't crush the garrage floor, but what about surface damage from the steel tracks ?
Rick
That's simply flexible thinking. Those of us brought up to think in base 12 / base 14 / base 16 / base 20 etc. can do it much better than the youngsters who only know base 10 units.
Colin Bignell
"nightjar .uk.com>" > >> So I was a decimal point out, a 3.5N thermalite block can take a load
I work only in metric - using multiples of 2.54 mm :-)
(I question your figures, I can't see how you get 9 tons/square foot).
However, this is for point loading only.
This is not a load you can apply all over the structure, as it will fail. As an example, take a cream cracker, and support it on some paper towels
Now, balance a 1m 2mm diameter wire on it. The cracker can support this with no problem. Replace with a 50mm diameter 1m bar, and though the point loading is exactly the same, the cracker will snap into many bits.
Well if it's a tank he's found, then the load is spread over such a large area by the tracks, that the loading is going to be lower than for a normal car, so no problem ;)
Steve W
300mm * 300mm is approx 12 inches * 12 inches = 144 square inches, no? So 300mm*300mm*12 is 1080000 mm^2 A square inch is 25.4*25.4=645.16 mm^2 so 12 square inches=7741.92mm^2 so you're off by a factor of over 100.
...snipped
Thanks to all. A tank - now there's an idea! I'm actually considering replacing my Chipmaster lathe for a Holbrook C10 that reportedly weighs getting on for 1500kg (trying to get into the habit of newfangled units but I got lost when all the sensible unit names that meant something got changed for Scientists names). The total garage slab load must be getting on for about 1500kg now (without the car) but it looks like I don't need to worry too much.
Dave S
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