Built up beam+channel & brace connection

[IC3D]

Hi All,
Detailing a job right now with W18x35 and W16x36 with cap channel C8x11.5. Some bays have vertical bracing ranging from 45 to 20 kips and I was wondering if the C8x11.5 cap channels should be notch to allow the brace gusset plate to be welded directly to beam top flange ends or weld the gusset plate to C8 and weld continuous the channel ends for the length of the gusset plates.
Thanks in advance.

 

[a2mfk]

A sketch would help out.

 

[IC3D]

Thanks for responding, I've uploaded the snapshot file, hope it works.
It's basically a channel welded to beam similar to crane beam with a typical brace gusset plate on the beam ends. Just wondering if it's typical to notch the channel around the gusset plate or weld the gusset plate directly on top of the channel.
Thanks.

 

[civeng]

Personally, I would notch the channel, since I would want the load to be transferred directly to the beam and its connection.
I'm guessing that the channel is there to help the beams' deflection (moment) more than the shear capacity of the beam. So connecting the brace to the channel is more a headache than anything else, since then, you'd have to ensure that the load from the brace goes into the channel, and then goes completely into the beam and its connection.

 

[IC3D]

Exactly my thinking but wanted a second opinion.
Thanks.

 

[a2mfk]

Do you want the reaction force from your diagonal brace going into your beam and the beam shear connection? You could move the diagonal brace gusset plate up on the column so the force goes directly brace>gusset>column, and you don't have to notch the channel. You are also creating a restraint at the top flange and making it a moment connection, not sure if that also is your intent. I don't know anything about your design, just my two cents from what I see there.

 

[IC3D]

I have both cases where I am connecting to column and where the gusset is strictly on the beam due to the acute angle of the bracing. HSS columns so making it one big knife connection.

 

[SAIL3]

if you could ensure that their was only horiz shear transfer between gusset & beam then you probably could get by w/o notching the channel, otherwise, it would be prudent to notch it....the detail does not show the centerlines of brace, beam & col ligning up and as a result their will be an additional moment introduced , at least, in the beam ...hard to tell from these "picture" cad programs, though...

 

[civeng]

Don't forget, if you move the working point of your bracing, you will be creating moments in the gusset to column connections, which is not always the best thing.

 

[IC3D]

Not moving working points.

 

[hokie66]

Agree that your snapshot is a good detail.

 

[humanengr]

What purpose does the channel serve? Does the channel transfer horizontal forces to the column? If so, be careful
to ensure the load path is not compromised? Can you terminate the channel at the gusset? This would save some detail / fabrication work if it can be done and the load path or integrety of the beam are not compromised.

 

[CELinOttawa]

humanengr beat me to my question: Do you really need the cap channel for the full length of the beam? I would find it hard to believe that it is contributing significantly to the shear capabilities of this layout!

Cut the channel back as far as possible along the beam, and get it the heck out of this connection design. If for whatever reason it was "needed" up at the column face, swap it for a flat cap plate or diamond back that you can actually include in the detail without having to be crazy with the coping, cutting and welding. Your owner will thank you whan he/she/it/(trying not to judge and be inclusive here) gets the bill.

 

[paddingtongreen]

There is only one person who can answer this, the Professional Engineer who sealed the drawing. The channel may be there to add lateral stability to the top flange of the beam, or the sections might form a compound section, we don't know how it is welded to the beam. Basically, we don't know the function of the channel, we should not assume we can safely guess.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin