Feasibility of welding

[lamar89]

I'm not too much experienced in welding but I have the following issue. There are two parts of steel flanges to be connected together with vertical web. But the access is only from outside.

It is a part of this section.

My question is if this is possible to weld this in this way?

 

[MintJulep]

No.

 

[lamar89]

Then what about two 1/2 V joints like below?

Or is it absolutely unfeasible?

 

[MintJulep]

Maybe.

You might want backing.

 

[kingnero]

What are the thicknesses?
I wouldn't be so fast to exclude the first drawing.

 

[lamar89]

There are two combinations of thickness: tf=30 mm + tw=20mm and tf=16mm + tw=15mm,
where
tf - thickness of flange
tw - thickness of web

 

[kingnero]

For both, put the flange on top of the web (like the top drawing, but 2-3 mm on the web).

 

[lamar89]

So you mean that it is possible even with thickness 30 mm. And with this 2-3 mm left for support I will have full depth of penetration of web?

 

[kingnero]

If you need the full width of the web welded, you'll need fine tolerances. Depending on length, probably finer than realistically achievable. In that case, you'll need backing strips as MintJulep suggested, and less support on the web (0-1 mm). Do you need full pen on the web?

 

[lamar89]

Indeed, I need full penetration of the web to maintain full capacity of this section. But as you said, backing plates should solve it.

 

[Tmoose]

"I need full penetration of the web to maintain full capacity of this section. "

Are the flanges part of an I-beam or channel?

 

[lamar89]

Yes, it is a part of steel box section (see the 1st post). Why you asked?

 

[kingnero]

Probably because generally the (shear) stresses on that location are relatively low, so only fatigue requirements would (again, generally) require full pen welding there.

 

[lamar89]

Sorry, just now I got what you mean. I realized that the weld is within the range of flange, so indeed shear stresses are low there. But in my opinion, welding with not full pen, for example 2-3 mm left for support, gives a local peak of shear stresses (blue in the figure below). However it is a footbridge, so fatigue is not an issue.

Generally I asked my question, because I was afraid about technological aspects of this kind of welding - thickness 30 mm with a gap.