Weld under eccentric out of plane loading

[kaffy]

Good Morning fellow engineers,

I am working on a project where I have a fillet weld under eccentric loading as shown in attached file. Initially I was following

https://www.roymech.co.uk/Useful_Tables/Form/Weld_...

and doing my calculations based on that (calculate direct and secondary shear stress and then resultant) but then I came across certain similar example where the maximum generated shear stress(direct and secondary shear stress calculations are same, only the resultant is different) is different than one shown in roymech (book example also shown in attachment). I could probably do both and choose the worst case scenario but I would like to know how do you guys calculate the resultant shear stress.

(Ignoring LRFD or ASD at this point) I am supposed to compare the resultant shear stress with allowable shear stress as all the fillet weld fail in shear. Is that right?
Also I am confused between allowable shear stress of welds.
Is it 0.3*minimum tensile strength or is it 0.3*minimum yield strength?

Thank you
Kaffy

 

[dik]

Welding strengths are generally based on the the UTS. I'd just determine the shear stress from flexure and combine it with the shear stress from P and use the sqrt(SUM OF SQUARES) to determine the max stress...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[kaffy]

@Dik Thank you

 

[desertfox]

Hi kaffy

The formula to me both look the same so I don’t see why there would be a difference in the resultant figures, sorry if I have missed something.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[kaffy]

@Desertfox, Please see the comparison in attachment

 

[desertfox]

Hi kaffy

It appears that in the latter example the formula is using the tensile bending stress in the fillet weld, as opposed to the Roy Mech calculation which appears to be using the shear stress due to bending and the direct shear in the fillet weld.
see below from the Roymech site:-

For butt welded joints subject to bending the butt weld stresses result from a tensile/compressive stress σ b and a direct shear stress τ s .
In these cases the design basis stress should be σ r = Sqrt (σ b2 + 4τ s2)

For Fillet welded joints subject to bending the stresses in the fillet welds are all shear stresses. From bending τ b and from shear τ s
In these cases the design basis stress is generally τ r =Sqrt (τ b2 + τ s2)

note also the former statement from this link that the formula is for butt welds σ r = Sqrt (σ b2 + 4τ s2

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein