Stresses in members

[EngDM]

Hey all,

Do any of you have a resource or chart that has the stress equation for different shapes? I've used one before where I believe it was for weld design, but it was equations to find the stress for torsion, bending etc. I know the equation is something like sigma = Tc/J, but I'm looking for something that has it for multiple shapes. Idk maybe I sound like a lunatic but I cannot find it, and the CISC Steel book has next to nothing for torsion, and the AISC book is like $400.

 

[dik]

see CanWest's link...

thread507-496778

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[WinelandV]

Are you looking for welds treated as a line?

Please note that is a "v" (as in Violin) not a "y".

 

[EngDM]

The table looked similar to that, but had equations for stress (sigma).

 

[EngDM]

dik, canwest's link gives the torsional properties, not the equation for stress in the member itself.

 

[human909]

Are you talking about the BENDING of shapes? Isn't that you just referring to the moment over the section modulus?

σ = [Bending moment] / [section modulus]

σ = M/{S or Z) (depending on your relevant localities use of S / Z.)

 

[EngDM]

I'm referring to the stress induced by twisting.

 

[centondollar]

Stresses from twisting are not simple to calculate for general shapes. Pure torsion involves shear stresses, while warping torsion (present in most non-closed sections without symmetry) involves both axial normal stress and warping shear stresses. To evaluate these stresses, you'll need to calculate e.g., bimoments, torsional constants and warping constants. The easiest way to avoid this problem is to avoid torsion or, if torsion cannot be avoided, to use circular or square shapes - or any other shape that is not sensitive to warping. For such shapes, tables are often available for evaluating shear stresses in the walls of the cross-section.

 

[WinelandV]

EngDM,

That table is from one of Blodgett's books. I have personally never seen that table solving for stresses, because when doing weld design, the big question is usually "what size fillet (or effective throat) do I need?" By treating the weld as a line, the units that result from Tc/J come out as force/length - which lets you size your fillet weld (or required effective throat for a PJP weld) quickly.

Please note that is a "v" (as in Violin) not a "y".

 

[rb1957]

comments on welding are a red herring ? you want the torsion in a thin wall section ?

many texts cover this.

J = 1/3*b*t^3

but I suspect this is covered by the first reply ...

another day in paradise, or is paradise one day closer ?

 

[EngDM]

That is the torsional constant.

 

[human909]

That is the torsional constant.

Exactly. And to calculate stresses you just use your first equation that you yourself wrote in the first post.

That is why everybody here is running in circles trying to give you helpful answers but not the answer you seem to want because the answer you seem to want now is the one you yourself gave in your first post.

𝜏 = Tr/J

https://en.wikipedia.org/wiki/Torsion_(mechanics)

To find it for different shapes just substitute J for the desired shape. There are numerous ways previously cover in obtaining J.

 

[EngDM]

No my original post was referring to a table that is provided in a design textbook or something of the sort with visual aids. I was just inquiring if anyone had something like I was describing. I've looked for it and cannot find a reference. It is okay.

 

[rb1957]

@EngDM ...
"Do any of you have a resource or chart that has the stress equation for different shapes?" this is what you posted. How have we not answered this ??

"Idk maybe I sound like a lunatic" ... sorry, but it is starting to look that way.

What is it exactly you are looking for ? No, not a table of different shapes, what is the shape you have.

another day in paradise, or is paradise one day closer ?

 

[le99]

Here are several torsional stress equations for non-circular shapes, for which "r" is not defined, and "J" is difficult to get. Link

For open shapes (W, I, T..) you need to evaluate both torsional stress and warping stress. Here is a quick reading to get some ideas. Link

For the rest structural shapes, you shall resort to your textbook for the equation of each case.

Also, I think AISC has publication on torsional analysis of steel shapes. It may contain valuable information.

 

[robyengIT]

this is what I have