Weld requirement for plated girder 1

[sybie99]

Good Day Folks

I am designing a plate girder. I also need to specify weld sizes for web to flange welds.

My question is, how do I calculate the weld requirement, I need to first know the shear stress flowing between flange and web, correct? Can I assume this to be the same as maximum stress in member, ie at top or bottom edge of the section? Then calculate a weld size with the equivalent longitudinal capacity?

What is the simplest way to do this?

Thanks

Seb

 

[asixth]

The shear stress in the weld between the flange and web plates can be calculated by V*Q/(I*t). The Blodgett textbook Design of Welded Structures has an excellent example of plate girder design.

I started writing this spreadsheet last year when I was designing a prefabricated plate girder. From memory, the weld between the web plate and the flange plate was an 8mm continuous fillet weld structural purpose. If you are using english units, this would be equivalent to a weld 1/3" throat thickness.

The second tab of the spreadsheet has an excerpt from the blodgett text. The stress in the weld isn't directly proportional to the 'stress in the flange' but the 'change in stress in the flange' which is a result of shear in the web.

 

[ToadJones]

There was an EXTENSIVE posting on here about shear flow a few months back that you could search....I think it was like 200 entries long.

 

[sybie99]

Thanks guys, I have subsequently found about 3 threads on this topic explaining it clearly.

 

[vandede427]

with rolled shapes it's almost never an issue, but DO NOT forget to do shear design on your girder's web.