What is the sign convention for slab or strip moments in S-Foundation?
What is the sign convention for slab or strip moments in S-Foundation?
Correct me if I'm wrong, it appears that positive moments require top reinforcing, and negative moments require bottom reinforcing?
Is there a way to reverse this sign convention in S-Foundation settings, so that a "positive moment results in a smile"?
Answers
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Hello Todd, I think I might be able to help you.
The sign convention for S-FOUNDATION is the same as S-FRAME's, as seen below:
Fx acts on the ‘X-Face’ in a direction parallel to the X-axis. Mx is the moment that
works on this same face and thus is the moment resulting from spanning parallel to the X-axis.Another way to think of this in the context of modeling slabs is that rebar parallel to the X-axis resists Mx. Fxz is
the out-of-plane shear force acting on the X-face. All these forces have their Y-axis equivalents.With that said, regarding your second question, you are correct, positive bending moments Mx and My will cause tension on the positive z-surface of the element.
In S-FOUNDATION these results can be with respect to different coordinate systems at the user's choosing (Global or Panel) so you can invert the positive direction of the Z-axis so the positive moments act "downward", thus, requiring reinforcement on the bottom.
I hope that you find this information useful, please let me know if you have any additional questions.
Best regards,
Tayen Aguilar
Altair Support
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