Sign criteria in panels

[StructuralSilver55]

Hi! Im trying to undertstand how Robots gives moment maps.

I've done the next experiment:

In the beam, sign criteria is logical and correct (positive moments in central part)

In the panel, as yo can see, i can't draw the logical bending moments law in the shorter part, and its not logical, because it would be similar to the beam diagram. (its not logical to have negative moments in the center of the spam).

I've read about sign interpretacion in owner's manual, but it's not very useful..

File attached.

[Artur.Kosakowski · Accepted solution]

Please check  

http://docs.autodesk.com/RSAPRO/2014/ENU/filesROBOT/GUID-E73EA3A2-AEC8-40EA-8AC3-E7EDCA7644C2.htm

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[StructuralSilver55]

Hi !

I've thinking about the sign criteria applied in robot, and i think the drawing you shown me was nos very clear, (its not easy to understand directions fo the arrows). To verify, i have a question:

- In RSA (slabs), when it shows for example , positive Mxx , the meaning is that there is traction in the upper part of the section. In most schools and books they explain it like in beams, (possitive moment is when you have traction in the lower part of the secition) Why RSA does the opposite thing? There is anyway to change the sign of moments, or to show as positive moment when you have tractions in the lower part?.

Thank you very much for your help!

[Artur.Kosakowski]

There is no universal agreement on sign convention and e.g. in my country the understanding of the positive and the negative sign of a force may differ between a mechanical and a structural engineer. Just that was the decision made almost 20 years ago.

[kamel.guetat]

Could you please explain for me further the meaning of the sign criteria in panels.. I could not understand when the moment is positive and when it is negative.

[kamel.guetat]

Could you please explain for me the sign of moments in panels ...I have this convention from RSA but it is unclear for me.

when the bending moment is positive according to RSA?

[Rafacascudo]

It is related to the direction of the panel local Z axis . If value is positive ,it means tension on the panel face that is on the local Z positive side(upper layer) . If it is negative ,it means this same face is in compression.

[kamel.guetat]

Many thanks for your reply which is clear...nevertheless I could not understand the relation with the convention of signs showing clockwise/anticlockwise for Mxx and Myy. Could please clarify further..Thanks

[Rafacascudo]

Local Z is on that picture.It is clear to me that if local z is upwards  ,the moment curved arrow is showing tension on upper face of the panel.

What is needed is ,to understand where tension and compression are acting , and with this you can check if your model is being coherent or not, and if so you can design it correctly

[kamel.guetat]

Thanks for the reply, however why this principle is not applicable for the beam in the RSA?

it seems to be the opposite.

 

[Rafacascudo]

Check message above  ,@Artur.Kosakowski  has already answered this question 7 years ago.