Friday, November 30, 2007

Re: HSS welds & HSS in general

Just a quick question (or point of discussion).....On the side of the flair groove weld, check with the corner radius of the tube that is being welded to.  In larger sections the corner radius might be quite large.  If the wall thickness of the  perpendicular tube is small there may not even be contact.  Not sure, but I seem to remember a situation I had  like this several years ago.  had nothing to do with welds, but actual dimensions of the tube and corners may be a consideration.  Might need backing bars at the groove weld sides.  check into it though, Saturday night after cocktails and dinner my memory is a bit fuzzy.
Joe Grill
----- Original Message -----
Sent: Friday, November 30, 2007 1:36 PM
Subject: re: HSS welds & HSS in general

Jerry,
I agree with our colleague Conrad from Down Under on all accounts. Technically that is a flare groove weld where you are welding to the radii of the HSS. But many times we don't technically call out the welds exact where it is more of a flare than a standard groove, or a groove and not a fillet, etc etc, but steel fabricators to me are generally top notch compared to other trades and they know we mean or call us or clarify in shop dwgs. They "getter done". Of course if this is a critical connection, we should all pay close attention and make sure we are specifying exactly what we need. And we should all remember that welding, especially in the field, is very expensive and just throwing unnecessary welds on there can be costly.
 
I know you said "nevermind" why you would want to do this, but if this is a theoretical question you have your answers, so allow me to pontificate on a Friday. If you have low weld stress, you probably don't need the side welds (the flare grooves), you can get enough out of the fillets on the flat faces of the HSS. Also, beware I think there are some reductions or warnings per AISC when welding to the corner of the HSS because of fatigue stresses at the corners where they bent the plate to form the tube, but that is off the top of my head and forgive me if my steel mechanics-speak is off.
 
I did a moveable rack for an industrial client all out of HSS members, and we needed full welds all around. I simply downsized the members framing into the faces of the other HSS so I could get a nice and easy fillet weld all around (easy for me to say).
 
Other options are side plates that sandwich the two members and then you get fillet welds all over the place, or a knife plate in the center if you have just shear and need to conceal the connection. I find these two options work great for diagonal braces or odd angles. If your tubes are perpendicular a shelf angle bottom and/or top works well and allows to shop weld in the angles on the vertical member so they have something to set the horiz member on in the field before welding...  At the risk of sounding like a complete structural geek, HSS members are my favorite structural section since they make great columns, beams, braces, misc members, exposed architectural members, etc. and are great unbraced in bending and in axial compression. And you cannot forget about them in torsion! I should get a kickback for this stuff :)
 
Have a good weekend all.
 
Andrew Kester, PE
Principal/Project Manager
ADK Structural Engineering, PLLC
1510 E. Colonial Drive, Suite 301
Orlando, FL 32803
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