steel canopy - beam column connection 3

[mats12]

Im designing a steel canopy. All steel elements are hollow profiles (box profiles). All connetions are asummed as pinned. Because of that I braced a construction in roof plane

I have some thoughts about top of column - beam connection. I dont have much experiences with hollow/box profiles but in this case I have to use them.

Im wondering if connection shown in picture is alright in your opinion? Is there a better way?


Bolts are inside of a box profile so the beam would need to rotate quite a bit in order for considerable tension in bolts to develop. Is that right?

Bolts are definitely in tension when winds in blowing upward (resisting uplift) but forces are small.

Shear demands on bolts will be small too.

Is there anything Im missing? im not so confortable with shown connection (but it is aesthetically pleasing) so I want to make it sure before proceeding.

 

[mats12]

tnx for suggestions, however:

- cut ends of column and beam at 45º and butt weld; - beam and column are not the same dimensions so 45 degree is not an option. Column is 100 x 100 mm and beam in 100 x 150 mm

- keep your bracing at roof level - horizontal forces are very small and whole construction is 2,5 x 3,2 m, i think there is no need for that if beam is welded to a column

- design connection as pinned - i would agree with that if I had larger construction and horizontal forces. If connections are pinned then I really DO need to make horizontal bracing in roof plane, otherwise the construction is labile.

i have seen many canopies similar to this one in my country. They are mostly welded together. Almost none of them has an additional bracing in roof plane.

 

[kingnero]

if you use cold bend tubes you are not allowed to weld at the corners

Do you mean EN 1993-1-8 § 4.14 ? If not, could you please elaborate?

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[klaus.]

Well...doing cold bending the corners of the tubes get some material damages ( or whatever) and in this area the ding cannot be used as load carrying connection ...
You can weld ...but this weld cannot be used for structural design


best regards
Klaus

 

[Ron]

mats12....I have designed many, many canopies with concealed fasteners similar to what you proposed. I would suggest a 4-bolt pattern rather than 2 bolts. Most of mine had embedded columns at the base, so moment carried to foundation to eliminate knee braces or gussets. Have done many different configurations....99% in aluminum....some welding, some bolting. Have ranged in size from simple "lean to" like yours to 100' clear span trusses.

Keep the lateral bracing since you are pinned everywhere.

Most of mine were in high wind areas but some in high snow load areas as well.

 

[SAIL3]

Klaus...what is your reasoning for not counting welds @ corners of cold-bent tubular members....any references that one can refer to?....thanks

 

[kingnero]

Also interested in any source or reference...
This is a topic in european construction code, which allows for interpretation and widely different views.

Always happy to see another point of view, as I think I got the answer (see the ref. I mentioned above) but there's always more than one side to every story.

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[klaus.]

Well the reason is easy.... because of cold bending the materiel internal structure is somehow changes because of the plastic deformation of the steel ... therefor the steel might not be weldable anymore and thus you cannot use the weld in that zone for design
This is written in Eurocode ...but is also common practice (in Germany)


best regards
Klaus

 

[MacGruber22]

This is written in Eurocode ...but is also common practice (in Germany)

Can you site the section number? I am not aware AISC has this provision, for statically loaded members, at least.

One in the hand is worth two in the bush.

 

[SAIL3]

Klaus...one of the reasons I am interested in the suspect condition of the corners of tubular members is I had a case awhile back where a 316SS member developed a crack in the corner as per attached...this occurred during lifting a module multiple times....it left a question in my mind as to the state of the material in these corners as far as any buildup of residual stresses..........

 

[kingnero]

This is written in Eurocode

Can you site the section number?

Any chance for the standard and paragraph?

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[klaus.]

EN 1993-1-8
Section 4.14 Welding in cold-formed zones



best regards
Klaus

 

[MacGruber22]

Klaus - Link

there have been misunderstandings in the interpretation
of Clause 4.14 of EN 1993-1-8 [4] for welding in cold-formed
zones. CIDECT (International Committee for the Development
and Study of Tubular Construction) has therefore
prepared a proposal for corrections to ECCS TC10, for submission
to CEN (European Committee for Standardization).
The text and note in EN 1993-1-8, Clause 4.14 should
be corrected to make clear that, for the conditions specified,
welding in the cold-formed corners and the adjacent
zones is permitted.

Flare bevel groove welds are used all the time between standard structural tubing in the US. Its approval is specifically documented in US design codes. I imagine it is not hard to meet the material and dimensional requirements of EN 1993-1-8 to allow the same.

One in the hand is worth two in the bush.

 

[kingnero]

Attached is Table 3 from EN10219, (Cold formed welded structural hollow sections of non-alloy and fine grain steels - Part 2: Tolerances, dimensions and sectional properties)
where you will find that, if you apply Table 4.2 from EC3-1-8 on cold-formes hollow profiles, you might (depening on the actually used radius) encounter problems starting from a wall thickness of 12mm, which is thicker than the most common used hollow profiles for carports and similar structures.


Edit: Thx MacGruber22 for the article, I have added the file to my library dedicated to this problem. I've had this discussion several times before, but I hadn't seen this document yet. (I hope you get some sleep nowadays!)

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[KootK]

Yes, thanks for your effort in sorting that out MacGrubber. I was starting to get a little concerned about some of my existing work. I've experienced issues with weld quality on these kinds of welds but that's a separate issue.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[MacGruber22]

I appreciate it, but I don't deserve much credit. It was a 20 second Google search from someone who hasn't used Eurocode for much of anything. All I knew is that it sounded very suspicious to be categorically wrong.

One in the hand is worth two in the bush.

 

[KootK]

Hey, I didn't find it. And I consider myself to pretty much be the Optimus Prime of structural Googling. Ergo you can count on this surely being the most phallic related image available on all the interwebs.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[MacGruber22]

There's a thine line between being a hero and being a memory.

One in the hand is worth two in the bush.