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"Standard" HSS beam to W Column connection 1

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LeonhardEuler

LeonhardEuler

Structural
Jun 19, 2017
200
For this project a cantilevered structure is being put in to an existing building. New beams are being placed inside of existing columns. The beams will see some torsion and thus I would like to make them closed HSS, or a W-shape with plates welded to either side to close them up, which is much more fabrication.

My first attempt is to go with the HSS so I am trying to find the best way to connect the HSS to a W-shape column. The best case scenario is that I find a connection that has been used before and has some design guidance/design examples. My proposed connection is as follows. Does anybody have any better ideas in this situation?

HSS_connection_m0pqfj.png
 
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I don’t know what kind of torques we are talking about here, but for minimal torques, I typically have beams framing into the girder (where the torque is applied). The clip angle connections (for simple shear) are typically enough to handle it. It goes into the beams as a flexural force. For modeling purposes, I assume about 10% of fixity for theses connections.
 
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This is for a cantilevered structure that has a 40' cantilever. There is a knee brace that provides a means of a force couple, but I don't feel comfortable using simple shear clips.
 
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I would think you'd want to get the load from the beam applied as close to the centerline of the column as possible to minimize torsion in the columns.

Perhaps the HSS just runs all the way to the column webs, provided you have clearance to get the HSS in and welded, and the web is thick enough.
 
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Or I could just put the plate closer to the web and provide fillet welds on the legs of the plate. Same connection just pushing the plate closer the centroid. I'm not sure I want to weld directly to the web, because this connection will be on each side of some columns.
 
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How about beams that match the depth of the columns and full-pen welds flange to flange?
 
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I still don't feel comfortable using a W-shape for a beam experiencing considerable torsion.
 
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What cantilevers 40'? Maybe you should give a more complete picture if you want better answers.
 
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Fitting a beam up to 2 existing columns with the tight tolerances required for welds seems like it would be a constructability challenge. Maybe shop weld a clip angle beam seat to your plate and leave 1/2" clearance on each end of the beam. Add a vertical clip angle if you need help with torsion at the connection. I think that would be much easier to erect.
 
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I still don't feel comfortable using a W-shape for a beam experiencing considerable torsion.
Click to expand...

The connecting beams shouldn't see any torsion if they are connecting along the same axis as your HSS members (as shown in your OP).....that is assuming I'm understanding the info correctly.

What kind of torques are we talking anyway?
 
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be sure to check your columns for the 2 added moments. i think the critical moment of the columns will also decrease which will further decrease capacities
 
 
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I agree that weld clearances would be a problem for direct connection between the HSS and the column web. Wouldn't you rather increase the thickness of the weld plate and then add flange stiffeners to get the same effect? In that case you might also need stiffeners at each end of the HSS much like the base of a sign pole.
 
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I will post a better drawing of the system tomorrow. Thank you all for the comments so far
 
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