W10 x77 Col to HSS 10 Col Splice

[marinaman]

I've been thinking about a column splice that I need to design. I have a W10x77 column running from the foundation, thru the second floor, to the roof of my building. At the roof elevation, due to geometry of the structure above, I'm going to need to transition my column from a W10x77 to an HSS 10 pipe column.

I've looked hard at the AISC steel manual and have not found a column splice that accomodates what I'm describing.

The loads are small, compared to the size of the columns. I've got around 80 kips thru the 10" pipe being sent thru to the W10x77.

My question is about the splice.

AISC recommends 1 1/2" thick butt plates for a W8 to W10 splice....and a 2" butt plate on W10 to W12's.

What I was thinking of doing is placing a 1 1/2" cap plate on my W10x77, then, a 1 1/2" baseplate on my HSS 10 columns, and then, setting the HSS 10 on top of my W10 and simply bolting the HSS 10 baseplate to the W10 cap plate via (4) 1" diameter A325 bolts. This splice would occurr at the roof framing diaphragm elevation and would therefor be laterally stable. I do not need moment capacity thru the splice.

Seems pretty simple, but wanted to be sure I'm not missing something here.

Any opinions on this splice? See a better way to do it?

 

[dhengr]

Marinaman:
You want to transfer the 80k from the pipe to the WF, mostly through bearing, since you don’t have much of a moment issue. Here’s what I’d do.... My base plates are maybe 1" x 12" wide (same axis as depth of WF) x 1'-5" long (same direction as flg. width). I would add stiff. pls. btwn. the flg. tips, and to the underside of the WF cap pl., thus; .5-.625" thick by [10.6 - 2(.87)] = 8.86" wide by about 12" in height, and set in .5" from the inside tip of the flgs. These stiff. pls. would be fillet welded (maybe some groove weld, if needed) to the cap pl. and the two flg. tips, from the outside. These stiffeners might be WT’s so you could weld the stems to the web of the WF col., since you want to get some of the pipe load into the WT col. web. The load from the pipe spreads out (corbels out?) through the base and cap pl. into the WF col., mostly in bearing, not in pl. bending. Look at AISC’s treatment of concentrated loads on beams and beam webs, bearing pls. and the like, and the “k” distance.

 

[JLNJ]

It sounds like all your load could be transferred from tube wall opposite the WF flanges to the WF flanges directly. Base plate to cap plate might work without stiffeners for your small load (ignoring the web). Since the WF is deeper than the tube you could even weld some doublers on the tube faces opposite the WF flange to "spread" the load out across the WF flange.

The splice then becomes more a matter of geometry and the space available for bolts. You might even get some blind bolts inside the limits of the WF web to work if you are limited on space outside the 10x10 of the column profile.