Slab on Grade - Wall Loading
Slab on Grade - Wall Loading
(OP)
See attached from the Army Manual. I am not sure of the origins of this formulation. Is it empirical? It does not make sense to me dimensionally.
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Slab on Grade - Wall Loading
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RE: Slab on Grade - Wall Loading
RE: Slab on Grade - Wall Loading
DaveAtkins
RE: Slab on Grade - Wall Loading
RE: Slab on Grade - Wall Loading
I agree that they do not work out dimensionally. Also, they don't seem to agree with values published in Table 3-2 of the same document.
BA
RE: Slab on Grade - Wall Loading
RE: Slab on Grade - Wall Loading
Maybe I was too hasty. The units of I are in^4/ft. The expression for λ is (12k/4EI)1/4. I think the factor 12 is converting feet to inches, so the units work out okay.
Using the final expression for P, with f'c = 4000 psi, te = 10 in. and k = 100 #/in^3, I find P = 1375 lb/lin ft.
This compares to Table 3-2 values of 1340 to 1605 for flexural strengths of 550 to 700 psi which seems reasonable, but I am not sure how flexural strength relates to f'c.
BA
RE: Slab on Grade - Wall Loading
http://www.cement.org/tech/faq_flexural.asp
Table 3-2 on page 3-5 gives a value of 1340#/ft when k = 100, t = 10 and flexural strength = 550.
The value of f'c corresponding to the above expression is:
f'c = (550/9)2 = 3734 psi which, when used in the final expression on page B-1, attached gives a value of 1340.
BA
RE: Slab on Grade - Wall Loading
BA
RE: Slab on Grade - Wall Loading
RE: Slab on Grade - Wall Loading
RE: Slab on Grade - Wall Loading
I did something similar the first time, too. It seemed right to consider I in units of in^4 whereas it should be in^4 per foot. I also was not sure of the relationship between flexural strength and f'c, but it seems that 9√f'c is what is normally used.
I still feel more comfortable reinforcing the slab to spread the wall load over a width determined on the basis of allowable soil bearing than to rely on unreinforced concrete to do the job.
Perhaps this would be a useful technique to use when adding a heavy wall load to an existing slab of known thickness and very little reinforcement. Is that your situation?
BA
RE: Slab on Grade - Wall Loading
The drawings indicated a 5" slab with 6x6 WWR, but the cores came out to anywhere between 6.5" to 7".
I had realized the 12 came from converting in^4/ft to in^4/in, but I made a math error in the denominator and did not get it work dimensionally.