Torsion on HSS with slotted shear tabs on both ends

[STpipe]

Hey all,

I'm currently performing a review on design calculations submitted to us and one of the HSS beams in the structure has two point loads with an eccentricity to the beam's centroid. The connection of the beams to the columns is achieved using a plate slotted through the HSS and bolted to shear tabs that are welded on the column. This seems like a bad design and I'm not even sure how to even begin quantifying the torsional resistance of the connection. Is this simply a case where the connection detail needs to be changed?

 

[dhengr]

Stpipe:
Well then, give us a damn hint, instead of some b.s. about the scale of your sketch. Is the col. 72” in dia., and only .125” thk. and the beam a 6”x6” x .5”thk., or what? A sketch to reasonable proportions does not have to be exactly to scale, but the proportions help reveal a lot about the overall problem. And, they reveal a lot to an experienced engineer in the way of possible directions to solutions. If you can’t draw a sketch which is even slightly to reasonable proportions, never mind exact scale at the moment, how do you expect another engineer to understand what you are talking about? KootK’s sketches are almost always excellent, they reveal general (maybe not final thk., size, etc.) sizes and you can generally read his intent from them.

I can’t force you to reread my orig. post, assuming you may have scanned it once already. Read it for meaning and think and sketch a little while doing the reading. Take two shear pls. about 12-16” long and the height and same thk. as the RHS beam. Drill and bolt them to the outsides (one on each side) of the RHS beam. Now, put this to the CHS col. and weld the ends of the two shear pls. to the col. The two shear pls. will apply their loads in a much more tangential orientation w.r.t. the col. wall thk., not as one line load (your orig. sketch) in the weakest (through thickness) orientation on the round col. The two shear pls. can take the shear loading, and they are spread out by the RHS width so they can take some torsional loading about their strongest orientation. Now, you can unbolt the beam and it will “slip down btwn. the two shear tabs” for erection.