weld size calculation for lift lug on a wide flange

[Samseleven]

A lift lug is attached to a wide flange (perpendicular to the web) inside on a structural skid, so it can be fillet welded to either sides of the web and inside top and bottom flange - either sides.
Is there a way to calculate the required weld size. If we consider the welds on the web only for the bending load, we can use d-squared/3 for the section modulus considering the weld as a line per Blodgett's book - design of welded structures. But I would like to get credits from the flange welds as well.

 

[msquared48]

I assume the welds look like a pair of C's back to back from what you describe.

If that is the case, the web welds will take the vertical load, and the flange welds the moment on the connection due to the eccentricity of the load on the weld.

Conservatively, not knowing the specifics of what you are welding to or with, I would figure the amount of weld needed at 600# per 1/16" of weld per inch of weld, but also considering the minimum thickness of weld needed based on the thickness of materials you are welding together.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[desertfox]

Hi rsampath

You can indeed calculate the weld size based on the stresses from your loading, have a look at this site it treats the welds as lines:-

http://www.roymech.co.uk/Useful_Tables/Form/Weld_strength.html

desertfox

 

[dhengr]

Rsampath:
I suspect there is a way to design the welds for a lifting lug, it has been done before. And, it is serious business so as not to drop the skid on someone, when using the lifting lugs. But, without a sketch with some dimensions, member sizes, loads, etc. imagine how many different lifting lug configurations could possibly be drawn, all meeting your verbal description; and all requiring slightly different design considerations, free body diagrams, weld sizes at different locations, etc.

 

[fancypants]

Yes, just use the S method like you are suggesting. However, this can be lifted overhead. Get a copy of BTH-1 (Below the Hook Lifting Devices) and use it. Dont skimp on the weld and be sure and check any block shearing etc.. that may come up.