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Welded Connection
5

Welded Connection

Welded Connection

(OP)
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

RE: Welded Connection

(OP)
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

RE: Welded Connection

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?

RE: Welded Connection

Quote (dik)

... 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.

RE: Welded Connection


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

Quote (Welds in connections at the ends of tubular members should be in accordance with 11.1.3 or should not be less than required to develop a capacity equal to the lesser of: 1. Strength of the branch member based on yield, or 2. Strength of the chord based on punching shear (where applicable).)


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




RE: Welded Connection

(OP)
MegaStructures:

Quote (Blodgett's method of welds treated as a line? Is your difficulty in determining the weld throat)

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

RE: Welded Connection

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

RE: Welded Connection

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.

RE: Welded Connection

(OP)
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

RE: Welded Connection

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

RE: Welded Connection

(OP)
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

RE: Welded Connection

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

RE: Welded Connection

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.”

RE: Welded Connection



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


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.

RE: Welded Connection

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.

RE: Welded Connection

(OP)

Quote (for that reason i proposed you to look API RECOMMENDED PRACTICE 2A-WSD Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms.)


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

Dik

RE: Welded Connection

(OP)

Quote (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.)


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

RE: Welded Connection

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?

RE: Welded Connection

(OP)
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

RE: Welded Connection

Dik,
Can you spec 1-1/4" diam x-strong pipe instead of round HSS? Same O.D. but .191" wall.

Or weld a plate on to the back of the pipe like a gusset and weld the bar to the plate with flare bevel?

RE: Welded Connection

(OP)
Thanks dold... with pipe, I still have difficulty in determining the strength of the fillet weld between the BAR and the pipe... my original problem. Pipe has the advantage of a thicker wall, but a lower strength. The question is moot because I've resolved the problem by adding a compression strut to take the vertical load and this was acceptable. I'd still like to have an answer and will put this in my 'todo' file. My use of drawing tools is very limited as you can see.


Dik

RE: Welded Connection

Does this thing have to be galvanized so you have to consider vent holes?

RE: Welded Connection

(OP)
Buggar... yup and already accounted for. Thanks

Dik

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