Skewed Beam to Column Moment Connection

[Accumulated]

Hi everyone,

It is my first post here. I've been lurking around and reading answers to questions I've for a while now. I've just graduated last year and I'm in my training period. I still have a lot to learn and a lot of questions I need answers to. And for a fact I know there are lots of experienced and knowledgable people to answer my questions. Pardon me for my english as well, as it is not my first language.
So back to the question, I've a connection design to verify against Eurocode(or British Standards) as shown in the attached picture. The end force I've gathered from STAAD is 106kN in Compression, 13.4 +Vshear and 11.3kN +Mz. For verification of axial force, is it just a matter of resolving the force and use same method as you would for a moment connection? If so, What about moment verification?
Are there any good books or tutorial for verification of connections using Eurocode?

 

[JAE]

BUMP

Anyone have any ideas from the land of the Eurocode?

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[WARose]

For verification of axial force, is it just a matter of resolving the force and use same method as you would for a moment connection? If so, What about moment verification?

It's hard to say without seeing more of the model (especially how the forces are applied at nodes 66 & 67, and how those diagonal braces are supported at those nodes).

By the way, do you have an offset where those diagonals frame into the columns? Just eyeballing your pic from STAAD.....I don't see it.

[red]EDIT[/red]: By the way, looking at your pic....if you are intending the diagonal connection to be fixed (in either the strong axis or the weak axis), you are missing 2 bolts below the lower flange.

 

[KootK]

The end force I've gathered from STAAD is 106kN in Compression, 13.4 +Vshear and 11.3kN +Mz.

I'd expect something closer to 70 kN for the shear in the joint.

or verification of axial force, is it just a matter of resolving the force and use same method as you would for a moment connection?

I would say no, it's not the same. Similar principles but substantially different procedure.

Are there any good books or tutorial for verification of connections using Eurocode?

Not Eurocode but good places to start are:

- Design of Welded Structures by Blodgett
- Handbook of Structural Steel Connection Design by Tamboli

Principles are the main thing that you need. The code clause checks should come easy after that if you have the code at your disposal. I'm pretty sure that some of the steel industry organizations have excellent, free eurocode info that you can use. I've downloaded it myself, I think, but never got around to filing it usefully.



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.

 

[amec2004]

When do the moment connection, the axial compression force of beam can be ignored.

For your case, decompose your inclined beam axial compression to a normal compression to column and shear force component,
ignore the normal compression component, add the shear component to the existing shear for MC design.

AISC Steel Connection Design Software

http://asp.civilbay.com/connect

 

[KootK]

When do the moment connection, the axial compression force of beam can be ignored.

Axial, especially when it dominates, will affect the need for stiffeners etc in the column. I guess it depends on what you're calling "the connection"

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.

 

[Accumulated]

Thanks everyone.

By the way, do you have an offset where those diagonals frame into the columns?

Not in STAAD analysis I've modeled. Inventor model wasn't done by me and I need to check back if their centreline meet each other. But by looking at it, it seems so? These connections were done by draftsmen and I am here to check and change to whatever it is necessary.

Main load on the structure would be Belt Stall Tension load from the driving drum and the weight of the housing being supported.

Thanks @KootK. I will look into the books. It is hard to learn when nobody in the company is really teaching me and I'm just self learning myself.

@amec2004 I will look into the way you have suggested today.

Thanks everyone!

 

[CANPRO]

When do the moment connection, the axial compression force of beam can be ignored

Are you suggesting to completely ignore the axial and just design for the moment? If so, I have to strongly disagree with that suggestion. A critical part of a moment connection is carrying the flange forces of the beam into the supporting member, and the axial forces in the beam have a direct effect on the flanges forces.

Accumulated, I think you should get some clarification from amec2004 before proceeding with his suggestion. Considering the loads at your connection, you absolutely have to consider bending + axial.

 

[12345abc6ttyui67]

I believe there are "Design Guides to Eurocode XYZ" available. I don't use Eurocodes, and I've not checked out the design guides, but maybe they will be useful.

There are also the "Joints in Simple Construction" and "Moment Connections" manuals by the BCSA / Steel Construction Institute. They might not be to Eurocode (can't remember and don't have to hand) but they will certainly have examples of this type of connection and how you resolve the forces and what aspects of the connection you should check.

I also second the comment above and would not discount any applied force without proper care and consideration of the impacts of doing so.

If the moment is reversible (can also create tension in the lower flange of the diagonal at the connection) you should have two bolts outside the connection (below the lower flange) too, otherwise you can't consider it fixed.

 

[Accumulated]

Are you suggesting to completely ignore the axial and just design for the moment?

I think what he means was to resolve the axial load into compression and shear going to the column using triangle of force? That's what I have done for now. Got around 70kN of shear like @KookK suggested. And I need to check my column web for buckling from compression after that I assume. What I am unsure right now is to whether I could just use M/depth to get tension and compression in upper and lower flange? Because that's what I usually do but this time around the beam is at an angle. Not really sure if I would be able to use the same method.

@RandomTaskkk Thank you. I've got those book with me. But they don't describe what to do on this sort of situation unless I missed it. I will have a look into it again.

There are also the "Joints in Simple Construction" and "Moment Connections" manuals by the BCSA / Steel Construction Institute.

They have published for both the old BS5950 and Eurocode.
And I have told the draftsmen to put 2 bolts below the lower flange as well before it gets release for manufacturing.

 

[WARose]

[blue](Accumulated)[/blue]

Not in STAAD analysis I've modeled. Inventor model wasn't done by me and I need to check back if their centreline meet each other. But by looking at it, it seems so?

I'm not sure what you mean, but that diagonal brace needs an offset going into that column.

[blue](Accumulated)[/blue]
It is hard to learn when nobody in the company is really teaching me and I'm just self learning myself.

...

And I have told the draftsmen to put 2 bolts below the lower flange as well before it gets release for manufacturing.

No offense, but hopefully someone is checking your work (as well) before this goes out.

 

[Accumulated]

No offense, but hopefully someone is checking your work (as well) before this goes out.

None taken! There is one chartered engineer who will be checking it after I've done everything.

I'm not sure what you mean, but that diagonal brace needs an offset going into that column.

Sorry, but Could you care explaining why I need an offset on the diagonal beam?

 

[WARose]

[blue](Accumulated)[/blue]

Sorry, but Could you care explaining why I need an offset on the diagonal beam?

It adds moment that the column will see. The offset I refer to is where it frames into the column.

 

[dik]

Can we adopt a convention in these forums to simply place edits in italic font? It's a lot easier. Edited post...

Dik

 

[canwesteng]

Whether or not you need an offset depends on how you detail the connection and where your workpoint is. Conventionally you don't add offsets to braces and resolve the moment into the gusset, or in this case it is capture by additional moment in the brace. You just need to detail the connection so that this behavior is possible. Looking at the structure I don't understand why you need a moment connection for the diagonal - if you want the simplest possible solution, model the diagonal as a truss and offset it from the column (and beam above) per WARose's suggestion, and design the connection for shear and axial.

 

[Accumulated]

if you want the simplest possible solution, model the diagonal as a truss and offset it from the column (and beam above) per WARose's suggestion, and design the connection for shear and axial.

I might just do that. Give it a full depth end plate connection and design only for axial and shear.

 

[KootK]

I second canwesteng's suggestion. That's exactly what I would do unless there was a compelling reason to do otherwise.

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.

 

[JLNJ]

Are all your connections moment connections? The model looks like it might be that way.

Keep moment connections to an absolute minimum. Start with pinned connections and proceed from there.