Weld Strength 5

[MJamesUW]

Hi,

I have a question regarding how to calculate the load bearing capacity of welded joints. I am somewhat practiced in Statics / Mechanics of Materials type calculations on a theoretical level, but I have never learned how to determine when a weld might break. I think I would be fine in calculating how, for example, square HSS tube might perform as far as the tube itself is concerned. However, my knowledge of the strength of the welded joint is lacking. In the past I have seen people over engineer racks/stands/etc.to save calculation time, but I’d like to understand the calculations. Could someone explain how to calculate weld strength / when a weld might break with an example?

Ex. Say I decided to make a stand.

- Rectangular top (4 pieces of ASTM A500 1.5” x 1.5” HSS welded together)
- 4 legs ( Same material and size – welded to the rectangular top)
- Some angle tabs welded to the bottom of the legs to lag the stand down
- Say, make the legs 3’ long

How can I determine the max mass this stand could support? I’ve been meaning to understand this for some time.

Thanks very much,

MJ

 

[PatBethea]

Blodgett's Design of Welded Structures is a great primer. And its very reasonably priced,

https://ssl.lincolnelectric.com/lincoln/apdirect/item.asp?prodnum=DWS.

 

[desertfox]

Hi MJamesUW

Try this site:-

http://www.gowelding.com/calcs/calc.htm

regards

desertfox

 

[zcp]

You could hire a consulting engineer experienced with this type of structure to evaluate your stand and provide their calculations. Be upfront and let them know that you want the calcs thoroughly explained for your own personal knowledge.

ZCP

http://www.phoenix-engineer.com

 

[MJamesUW]

Thanks for the direction guys. At this point I am just looking to understand the material and the stand was just an example I thought would help clairify what I was after learning.

 

[desertfox]

Your Welcome MJames

regards

desertfox

 

[dik]

Foxy... great link...

Dik

 

[arto]

Don't forget to check for buckling on you stand legs

 

[Tmoose]

Yeah, the weld strength might not be important if the pieces rest on top of each other, as in wood frame construction. First limits might be Leg buckling, and bending of the 1.5" top beams if a load is applied mid span. Weld strength would come into play for racking strength if there are no diagonal braces.