huangyhg

hss column splices
i'm designing a column to be fitted for a four-storey building. the ground & 2nd floor will be hss 6x6, while the last two floors will be hss 4x4.
are there visual examples that can be used as detailing for the splicing connection of these two different size columns?
what beam types are framing into the hss columns?
mike mccann
mccann engineering
these are columns to be spaced at 10 ft o/c - with w10x15 framing to each side. i'm planning to splice the hss6x6 ±18" above the floor. (it's all within the wall composition.)
i have used telescoping hss splices for this type of situation almost exactly, except the size difference of the column below to the one above was a lot smaller. like 1/2 size difference i believe it was with shear tabs welded on the sides of the upper column. i just posted something about that on here not too long ago. you may need to use bolted plates at the splices due to the size difference.
instead of baloon framing this, to simplify the connections, why don't you have the w6 beams rest on top of the hss sections with steel bearing plates, and the hss columns rest on top of the beams on steel plates? typical steel detail construction. kiss! then there is no problem with the hss 6 to hss 4 connection.
mike mccann
mccann engineering
i have used steel beams continuous over columns before, and i have seen it done a million times, but i never really liked this detail that much just because any moment being transferred from the beam into the lower column is ignored. at floor cantilevers i put it in of course, but for a standard interior column i don't normally use it. i worked with another engineer before that also avoided this connection for the same reason. it is likely fine but i don't normally use it.
i normally would prefer mike mccann's solution, but with such small beams, you need to make sure that the column load can get through the beam via stiffeners. if the beam cantilevers, the stiffeners also will need to brace the bottom flange.
i'm not sure about your rational for decreasing the column sizes, but have you considered that the extra labor to fab and install your splices (or stiffen beams) may well offset any savings from just keeping hss6 x 6 continuous.
thanks for all the responses so far. grizzman, i might just increase the thickness of the lower columns so that the splice detail is simpler; or, go for hss5x5 throughout.
it's just that there are close to 170 columns to deal with.
i'm not a big advocate of "stiffening" the beam over the column.
i agree with keeping the same size column thruout and then using welded tabs bolted together on the sides to erect the column. connection can be field welded and tabs removed.
for different size columns, use a cap plate on the lower column and field weld the upper column to it.

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