Reinforcing Connection Angles Subject To Prying Action

[Norby_acn]

Thanks in advance for any and all help.

I have an odd situation. I am doing some subcontracted connection design and have had an issue come up on a braced frame connection.

I have a W14x61 column, a W24x55 beam, and an HSS10x10x3/8 brace coming down to the joint from above. The beam's connection is to be designed for 320 kips (LRFD) tension force. I am trying to use a double angle connection and even with 5/8" thick angles, I am 67% over capacity. Is there a good reference for how to reinforce connection angles to resist prying action? My first thought is to put little stiffener plates in between bolts but I'm not sure how to design such a thing and I can't find any good AISC references that would really apply to this situation.

Are there any suggestions as to how to deal with this prying action or design for it?

Thank you,

 

[skeletron]

Definitely a sketch would help. My understanding is you are connecting the beam with angles B/S web.

Some questions:
1. Is the beam framing into the column flange?
2. How is the HSS framed into the beam/column?
3. Are you married to this connection style?


Seems like a good situation for an extended endplate. Weld on a gusset for the brace connection. You can squeeze more axial and shear capacity than the angle connection. If you are framing into the column web, you could use an extended shear tab with some fancy fabrication and stiffeners.

If my understanding is correct (angles connecting the beam web) and my assumption is in the right ballpark (there is some axial load in the connection) a connected web is inefficient for the forces.

EDIT: I just noticed the 320 kips tension force. Connect the flanges. Use an extended endplate.

-----------



...but I can't recall if I have ever solved that problem yet.

 

[Earth314159]

I would think about changing the connection concept. Connect a knife plate to the W24 and the HSS brace. Connect the same plate to the W14 column. The connection force looks too big to be using angles. Even if you can make the angles work for strength, the connection will be soft.

If you use angles with prying, one option would be to assume full prying. The bolt is the fulcrum and just use statics (assume a statically determine condition with no moment transfer between the angles and the beam web). This is the safe way to go. The other option is to use plastic design. Assume a plastic hinge in the angle closets to the web and design the connection between the angle and web to develop the plastic hinge. The problem with this, is that you may end up getting more tension in the bolt than the plastic design would assume so this is not as safe. The reality is somewhere between the two cases.

 

[CANPRO]

Agree with skeletron, you need an extended end plate. You're using most of the webs capacity in tension in your scenario, and I'm assuming the web is also transferring significant shear. Even with the flanges connected, you'll have a significant tension + shear interaction in the beam web that should be checked.

 

[hokie66]

skeletron and CANPRO are on the right track. Change the connection concept to an extended end plate.

And when you connect that big HSS brace, assuming it is in compression, take heed of the information in this recent thread.

thread507-457982

 

[KootK]

There aren't many ways to pass that kind of an axial force without making yourself a beam / column moment connection inadvertently. So I say own that and do the thing right. No doubt you're stuck adhering to the capricious whims of an EOR however.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[KootK]

Another thing to consider is that much of the 320kip might be getting transfered into the brace before it even gets to the beam/column connection. So demand there might only be a fraction of that 320kip you've been considering.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[Norby_acn]

Thank's everyone for your help. It is kind of what I was afraid of, that this is a square peg-round hole situation. I think I just need to step back and look at a different style of connection.

 

[sbisteel]

I'm late to the thread, but the "Handbook of Structural Steel Connection Design & Details" by Akbar Tamboli has a section on reinforcing double angle connections to mitigate prying forces in the bolts. The reinforcement is just a simple bar washer on the OSL of the angles, which I've found useful in several circumstances.

I would also question if the 320k is in fact an axial transfer force that has to go through the column, and not just the axial load inside the W24 as part of the braced frame.