Welded Connection 5

[dik]

Does anyone have a handy formula to calculate the weld strength for the following? If not a formula, then a paper that I can use. The HSS tube is 1.66x0.140 and the BAR stock is 1/2"x3" and the live load moment is Mf = 1.5 K-ft.

Dik

 

[desertfox]

Hi dik

This link might help

https://roymech.org/Useful_Tables/Form/Weld_strength.html

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[dik]

Thanks... already checked there... the issue is the connection to the relatively thin tube. I'm almost at the point of suggesting the vertical rails be changed from HSS to BAR stock. I can easlily calculate the forces in the flare bevel welds... just don't know how that plays out with the tubing again. Cannot find anything on the AISC, CIDECT, or Jeff Packer's book... The alternative is to cantilever the rail from the wall, not knowing what the backing is, yet.

Dik

 

[MegaStructures]

I'm just curious.. what is stopping you from using the generally recommended Blodgett's method of welds treated as a line? Is your difficulty in determining the weld throat / base material contribution due to the curved surface that is part of the weld?

 

[r13]

... the issue is the connection to the relatively thin tube.

I think you need a good welding procedure though. Why not to check on Welding Forum.

 

[HTURKAK]

I will suggest you to look API RECOMMENDED PRACTICE 2A-WSD ..The same reference states ;


and 11.1.3 , pls find below picture copied and pasted from API RECOMMENDED PRACTICE 2A-WSD ..

 

[dik]

MegaStructures:

Problem is the thin tube strength... with a rectangular tube, I can use a small yield line solution. May be necessary to find a simpler connection.

HTURKAK: The issue isn't the weld itself, but the strength of the tube.

retired13: I'll try the welding forum later... most of the welders hang on structural... almost at the point of welding bar stock to bar stock... a lot simpler... not the way I like to do things.

If the client wants the condition... may do a small load test.

Dik

 

[desertfox]

Hi dik

If you use the tube wall thickness and set it to be the maximum leg of the fillet weld, then I am struggling to understand your dilemma because fillet welds fail in shear across the throat of the weld, so that in my opinion would be the weakest point given that the weld electrode has similar strength properties to the steel tube.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[r13]

I prefer the left hand side option with all around fillet/bevel weld. All add a square plate on the anchor bar, then weld the tube on this/near side and other/far side.

 

[dik]

desertfox... I'm welding BAR 1/2 to 0.14 thick tube and cannot get HSS 1.66 in thick enough wall section. I'm not concerned about the weld failing; I suspect the tube wall will fail before the weld.

Dik

 

[desertfox]

Hi dik

What is it you are making? Handrail? and how is the joint loaded? I have read the posts but I don’t really know what you are making. I agree that welding thick and thin section materials isn’t ideal because you can get lots of distortion due to the heat input required.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[dik]

df: it's a exterior ladder that is over 2' from the wall to clear a projecting 'string course', and I cannot develop the moment at the wall so the tube has to take it... I think I will do it in BAR material... the HSS is a little more 'attractive'. I have a personal issue in that I like solving interesting problems, if I can, more than I like simple staightforward ones. I get bored and sometimes add complexity simply to make it interesting.

Dik

 

[r13]

We are standing in the opposite ends. Simple is the beauty, how to make things simple is the art. Never bored either.

 

[MegaStructures]

I still don’t see why the base metal can’t be checked just like normal. Weld treated as a line and area is total line length*material thickness.

“Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands.”

 

[HTURKAK]

Dear Mr DIK, for that reason i proposed you to look API RECOMMENDED PRACTICE 2A-WSD Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms. IMO, a very good reference for tubular structures and joints.

 

[phamENG]

dik - at 0.14", doesn't the tube fall under AISI's light gauge specs? You might want to take a look at AWS D1.3 and the AISI S100.

 

[dik]

Thanks... in the process of picking up a copy... will take a look at it.

Dik

 

[dik]

I'll check... don't know if that has any impact on CSA S16, our steel code... but, it would be nice to know.

Dik

 

[phamENG]

Right...sorry, dik. Forgot that you're in the great white north.

Does Canada have an specific light gauge spec, or is it all wrapped into CSA S16?

 

[dik]

I sent a query on to the CISC about a month or so back to know if there were any limitations to wall thickness and have not had a response. Our HSS typically goes down to 1/8" wall thickness (0.125).

we have a CFS standard.
Dik