## Simulation Mechanical and Multiphysics

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# Von Mises BEAM STRESS

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Hello Everyone,

What is the reason why Simulation does not calculate the Von Mises stress of beams?

Is it wrong from the physical point of view to make analysis of beams using such stress?

Because Simulation does have a result that is the "Worst" stress.

Basically what I want to to do is to compare the stress (either the Von Mises of the "Worst") on the beam and compare with the allowable value given by the material definiton. Is this correct to do?

Thanks a lot!

# Re: Von Mises BEAM STRESS

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if you want von mises stress, you need to use 3d elements.so make a 3d model and mesh it with solid elements.

if you use beam elements (2d or 3d),you get stresses(no von mises),strains,displacements only at nodes.

if you need more sophisticated answer, you can wait for more replies.

ASIMM 2012

# Re: Von Mises BEAM STRESS

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Hello madg1,

I appreciate the answer, but that does not answer so much my question.

I wanted the know simply what is the reason for not having Von Mises stress.

Basically, why are they not shown in the vertices of the beams? Specially if you have one beam whose lines are split into several (so you can see the progression of stress on the beam.

Thanks!

# Re: Von Mises BEAM STRESS

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Hi,

My thought is that Simulation Mechanical does not calculate any shear stress in the beams (nor torsion). So without those results, the von Mises stress would be inaccurate.

Mechanical Engineer

Pittsburgh, PA

16 years experience with Simulation Mechanical

# Re: Von Mises BEAM STRESS

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Hi AstroJohn,

Indeed it does not. But it does also calculate the following properties:

With the Section Modulus, it should be possible to calculate the Shear Stresses on the beams, right?

It should be ShearStress = ShearForce / Moment of Inertia

Why doesn't simulation calculate this?

I am asking because,l well, if it does not calculate if could be wrong to assume the abovementioned equation....

Thansk for the intel!

# Re: Von Mises BEAM STRESS

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Shear stress is NOT shear force/ moment of inertia. It is VQ/Ib. I'll leave it to you to look up what that means. Some references may use t instead of b.

In addition, even though Simulate does indeed have beam elements. Designing beams usually in done in programs such as STAAD.Pro, RISA 3D, or SAP 2000. In other words, something specifically meant to find the forces and moments in beams then apply the AISC code to determine if theyare OK. Not to be unkind, but it sounds like you're out of your depth on this.

# Re: Von Mises BEAM STRESS

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we can use asim for aisc code check.

ASIMM 2012

# Re: Von Mises BEAM STRESS

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**True. My mistake.** Your answer was quite arrogant as well and I did not appreciate the unpoliteness.

It is not because you say "not to be unkind" that you cease to be unkind. I am not a master of this - WHICH GIVES MORE REASON TO ASK THE QUESTION.

Regardless of that, the shear formula has everything constant for the beam except the first moment Q; The highest value - worst case - of Q is on the neutral axis; therefore the "worst shear stress" could be calculated.

By the way, saying that:

In addition, even though Simulate does indeed have beam elements. Designing beams usually in done in programs such as STAAD.Pro, RISA 3D, or SAP 2000.

Is entirely useless to the discussion, which was - may I recall - what is the reason why Simulation does not calculate the Von Mises stress of beams?

Sincerely,

# Re: Von Mises BEAM STRESS

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Vonmisses Index is used when a region is subjected to various stresses. It could be combination of a shear and normal stresses or only normal stress.

Coming to the point, in a beam shear stress distribution starts from zero on top fibre and reaches maximum at the centre of the cross section. But Bending stress is maximum in the top fibre or bottom fibre (could be compression or tension) and zero in the centre of the cross section. While considering a maximum we have case of Max normal stress on the top without shear and other case of shear stress at the centre without tension.

So there is no necessity of calculating vonmisses in beams.

Hope this helps, although late reply.