Converting Stress to Moment in a Foundation Slab Model: Best Practices?

[mohamed hassan 2014]

Hello,

I have modeled a foundation slab using solid elements and applied four vertical concentrated loads on top of it. As a result, I observe tensile stresses at the bottom of the slab and compressive stresses at the top.

Could someone advise me on how to convert these stresses into moments and if there is a normal force or not as they are vertical loads only? Should I consider each stress as a force and multiply it by the corresponding moment arm?

The photo below shows the stress at every node at mesh intersections.

Thank you for your assistance!

 

[CJLCivilStruct]

Probably the easiest solution is to remodel it with 2D plate elements - sometimes simple is best?

 

[mohamed hassan 2014]

Probably the easiest solution is to remodel it with 2D plate elements - sometimes simple is best?

Unfortunately I need to do it solid element as I have several components with contact elements I have to model them

 

[JoshPlumSE]

Do your solid elements provide Nodal forces? If so, that's the only way I can see to do it. Ideally, the software would have a way to get moments at specific cut lines through the solids.

Depending on what software you are using, of course. Maybe start with a forum that's specific to that software (if one exists). If not, tech support from the software.

 

[STrctPono]

Agree with JoshPlumSE. Most modern FEA softwares will have integrated tools that allow you to cut a plane through a group of nodes where it will integrate your stresses for you to produce a force.

 

[ANE91]

Most modern FEA softwares will have integrated tools that allow you to cut a plane through a group of nodes where it will integrate your stresses for you to produce a force.

I had a hell of a time figuring this out in VisualAnalysis. Might not be super obvious to the OP.

 

[SWComposites]

how to convert these stresses into moments

if the material is homogenous and linear, stress at surface = N/t + Mc/I where c = t/2 and I = (t^3)/12 (N is lb/in, M is in-lb/in)
you have the stress on two surfaces, so solve for N and M