Shear stresses in FEA 2

[oneintheeye]

hi, can anyone help me in determining shear stresses at any location on a mesh using FEA? this is a reinforced concrete slab.

Thanks

 

[johnhors]

Attend a course on the basics of stress analysis using FEA. Nafems run a suitable course.

 

[oneintheeye]

yeah that would be great. Unfortunatly I haven't got one running today! No seriously I am looking out for one (I am UK based). Just to 'stress' I am using FEA software for cetain functions. I then check everything by hand. I would like a 'general' approach for assessing shear stresses. Not 'attend a course, do some training'. I could reply that to every post on this site.
I will not be relying on this output to design on its own merits. I am just after some broad advice before going to formal training.

 

[cbrn]

Hi,
well, so, supposedly the FEM you are using can express stress results at nodes in terms of:
- max, mid and min principal stresses
- stress intensity
- equivalent VonMises stress
- stress components in a chosen reference system

Among the 6 stress components of the last expression of stress, as you know, the first three are normal stresses and the last 3... the shear stresses !!!
Problem is to have a reference system oriented as you need, but that's a thing that depends on the FE program you're using, not on this forum ! ;-)

Regards

 

[johnhors]

http://www.damt.co.uk/damttraining.html

 

[ThomasH]

Hi

What exactly are you trying to do?

If you are designing a concrete slab, why not use shear forces instead of stresses. Or are you working with solids? In that case, another why ?

Regards

Thomas

 

[oneintheeye]

ok, shear forces, stresses. I am checking my slab against shear failure. I said shear stresses to compare against shear stress capacity of my section. I do sometimes use solids if modelling a piled foundation to help load spread to the piles. Either way I still need to find my shear stresses at various points in the slab to check zones where I may need shear reinforcement of thicker slab etc. This is primarily for punching shear checks.

 

[OzEng80]

If you are just concerned about punching shear, why don't you use the column reaction as your shear force? This should be easily obtainable.

Cheers

 

[oneintheeye]

due to overlapping zones, irregular edge distances, non uniform arrangement of piles.