Slab and Strip forces in Safe Program
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Author: salahcivil
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Slab and Strip forces in Safe Program
09-21-2010, 01:21 PM
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Slab and Strip forces in Safe Program
Dear Friends,
please advise me regarding the following
1-is the steel reinforcement that are calculated based on M11 or M22 result from analysis of slab by Safe program(any version) is sufficient or not.
2-is the strip moment or reinforcement calculated for the strip width for example i have a strip of 4m width and the program shows a moment of 100 t.m is this mean that the steel area is to be distributed across the 4m...
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09-21-2010, 02:07 PM
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RE: Slab and Strip forces in Safe Program
Dear Salahcivil,

Regarding your first question, if you think your input data is completely right, then the program's calculations are right too. Sometimes we enter some wrong data into the software and are not aware of that and when we get some unsatisfactory results, we think the software is doing wrong. "Garbage in, Garbage out!"
For the second question, the moments and reinforcement shown for a strip in safe program are for that strip only. It means the reinforcement shall be distributed along the width of that strip and for the next strip it might differ. It is for this reason that we have to define strips for the program and the program determines the moments and relative reinforcement of that strip based on what has been defined.

If this information does not satisfy or help you, please have a look at the manuals of the program where how the program calculates is explained.
I think a better choice might be to find some tutorials for the program and see how the modeling and design is done.

Regards,
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09-21-2010, 03:31 PM
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RE: Slab and Strip forces in Safe Program
Quote:... calculated based on M11 or M22 result ...

only appropriate for regular symmetric boundary condition (support&loading), take attention if twisting moment M12 is ten percent greater than orthogonal moment (M11&M22) it should be added. these method also known Wood&Armer/moment resultant.

take attention too with meshing since each method have different characteristics, W&A is more sensitive.
misspell, i mean ten percent of orthogonal moment. greater or less differences.thx
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09-21-2010, 04:32 PM
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RE: Slab and Strip forces in Safe Program
1. If you calculate based on the M11 or M22, you may not get stress averaging. Or in otherwords you have to average the stress according to the width considered. If the stress is not averaged, in some cases you may end up with stress singularity. Finite element based reinforcement may be very high at this location. Moreover its all depends on how good is your meshing. As 'parhyang' highlighted you have to use wood and armer rule.

2. As for as the strip, new version of SAFE allows you to define inclined as well. You can draw the strip line as per your column arrrangment. it is sipmple to define column strip and middle strip. The strip method consider all the efects and gives you the average reinforcement either for full width or per m run.

I suggest to design based on the strip method. You can model a simple slab and try your own to feel the difference.
regards,
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