Assessing Plug Welds with Blodgett Line Method 2

[jball1]

I am evaluating a plug weld joint using loads from FEA.

I would like to apply the Blodgett line method, if possible. Tables 6 and 7 in Blodgett (pg 7.4-8) seem to indicate that this is permissible?



I am struggling with calculating the section properties though, since the welds are discontinuous and are circular… can’t just reduce down to a line. However, Blodgett seems to indicate that reducing to a line is acceptable?

Would it be feasible to do something like this:




Basically what I did is treat the weld as a continuous line, and then calculate an effective throat size based upon the plug weld area.

I also did a calculation of the actual moment of inertia of the plug welds about the centroid of the weld, and then a calculation of the moment of inertia of a rectangle of area t_eff * L. The actual moment of inertia of the plug welds is significantly greater than the moment of inertia of my fictitious continuous weld, so that indicates that this method is perhaps conservative?

Or does it just not make sense to treat the plug welds like a line?

 

[Smoulder]

Treat each pkug as one item. Dimension is one unit with no length or area. Second moment of inertia I_weld = sum of y^2. Weld 'stress' = M*y/I = force per plug. Make sure member is stiff enough to distribute. Check on code limits for connection length.

 

[jball1]

Thank you. This is helpful!

 

[TRAK.Structural]

What is the "L" distance?

As Smoulder mentioned, in order for this approach to be realistic the member must be stiff enough to justify the stress distribution. For large values of L this method may be inaccurate.

 

[Enable]

If the orientation / magnitudes of your loads are such that the resultant places some of the plugs in tension, then I would say that this is all for not since you're generally not allowed to utilize plug welds for such applications (link).


However, if your plugs are large enough you can treat the welds as a circular fillet around the hole. That is a-okay as far as combined shear / tension (link).