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Treatment of R/C slabs

Treatment of R/C slabs

Treatment of R/C slabs

(OP)
I have a [existing] reinforced concrete slab on some caissons that I have analyzed. It is so complicated that rather than look at it from the standpoint of combining the orthogonal moments with the twisting moments (i.e. the Wood-Armer method). I thought maybe I could just look at it from the standpoint of stress. The only problem is: I know how to interpret the shear stresses; but not the bending stresses. Do I just make sure my compressive and tensile stresses don’t exceed certain allowables? Do the principal stresses given take into account the twisting aspect of it?

RE: Treatment of R/C slabs

3doors:

A couple of points:
1. It really depends on the code you are using and what the particular element includes.
2. By definition principal stresses are the max's of all stress components that were used to compute he prin values.

Best guesses on what you said.....

Since you are talking about orthogonal and twisting moments I assume you are using shell or plate elements....Usually neither formulation includes twisting...i.e a moment vector normal to the element surface (even if the nodes have 6 dof each)...so your "twisting moments" may not be what you think it is...

Typically "bending stress" correlates directly to the m y/I beam bending stress (and may or may not include any p/a direct components...again check the code and element)..

The max "bending" and "shear" stresses do not ocur at the same points on the cross section (bending at outer surface & shear at neutral axis) so be careful in combining the components.....in general the principal values should be much closer to the actual max's but if checking against some code values that are "bending" and "shear" related you may not want the principal values...

Ed.R.

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