Moment Connections to HSS Column

[mjs611]

I need to design a moment connections between wide flange beams to HSS tube columns. I know chapter K of the steel manual has moment connections of HSS to HSS but I can't seem to find any good examples or equations for my situation. I am debating on whether it is feasible to just take the limit states for wide flange and design for that connection then take the HSS concentrated force limit states to design for the column. If anyone could let me know if I should be looking in another direction or if these assumptions would work I would appreciate it. Thanks for your help.

 

[csd72]

AISC Hollow structural sections connections manual has this exact situation.

 

[youngstructural]

I don't know the american code, but I know how I have handled this situation in the past... Think about your load paths. Your shear is travelling in through the web of your beam member (I'm assuming you're dealing with a US W-section framing into a Hollow Structural Section), and your moment is travelling in through a tension (or compression) in your top flange and a corresponding compression (or tension) in your bottom flange. The HSS is going to carry the shear (at point of loading) in the wall facing your framing member, and the moment in the side walls. So you need to get the tension force from the flanges into the HSS side walls.

In cases where you have a low moment I've used the facing wall of the HSS as a small beam (considering a beam width of equal to the flange thickness plus the two weld thicknesses) and allowed that to transmit the load. Then I checked the section could take the moment input by looking at the tension and compression input as a crushing strength directly opposing each other on the HSS.

IF you have a larger (or substatial) moment coming in, then I would advocate splicing your HSS and inserting plates into the length of the column to act similarly to web stiffeners in a W column. These plates should be inserted at the same level as the flanges being connected, and I would also check to see if you need to weld in a diagonal stiffener.

Hope that helps,
With any luck someone knows the answer regarding your code (I'm assuming you're AISC LRFD - Should really post that),
Regards,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

 

[bjb]

In Chapter 12 of the 13th ed Steel Manual, there are details for moment connecting a WF to an HSS column. I've used welded Tee stubs and diaphragm plates, but I prefer the Tee stub. The reference csd72 mentions is also good. The main thing is to make sure that the tube walls don't get overstressed from the concentrated forces delivered by the WF flanges. You can download the 2005 spec from AISC for free, and you can get the equations that check the tube wall from Chapter K. With either approach I mention the stem of the Tee or the diapragm plate gets bolted to the top and bottom flange of the WF.

 

[csd72]

Just be careful how you design your welds. The faces of the tube are relatively flexible so any welds to the face wont take as much stress as those in line with the side walls of the tube.

 

[bjb]

Good point csd72. With the Tee stub, you have flare-bevel groove welds taking the flange force into the side walls.