HSS Knife Plate Shear Tab Lateral Stability

[jdgengineer]

When you have an HSS column with a knife plate acting as a shear tab with beams framing into two parallel sides, has anyone tried to justify this connection providing lateral stability to the column in the out-of-plane direction of the knife plate? I'm assuming it wouldn't meet the AISC Appendix 6 provisions for stiffness and would require to have a beam or kicker framing into the other direction, but just curious what other peoples thoughts are.

 

[malikasal]

it will not provide enough restraint for the out of plane direction, i only consider it to restrain the in plane direction.






ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[jayrod12]

Well wait, First thought is no. But to me that would really depend on a few other things. Can you post a sketch of the framing plan? Where would be the first instance of restraint on each side of the column? If there were intermediate beams framing into the primary beams fairly close to the column location I could probably be persuaded. We also need to have an idea of how much load in the column we're talking about so we know that that out of plane bracing force would be.

 

[KootK]

I've done this on occasion to avoid unsightly top of column kickers in applications where that mattered and there wasn't framing naturally tying into the column. With steel joists, I've considered the top flange of the beam as a stand alone element spanning from the column, past the nearest brace, to the next brace point beyond. A lateral propped cantilever essentially. With infill beams instead of joists, I'd be willing to draw upon the strength and stiffness of both beam flanges. It's worked fine by the numbers and in real life to date. Obviously, if it's a wind column etc, then there's a bit more to think about.

 

[lexeng18]

Why not just model the column as fixed base and see if your baseplate can transfer enough moment to provide the necessary stability?

You could analyze this as a fixed base cantilever column with a lateral load at the beam elevation equal to 2% of the total axial load. This method, column buckling would have to check for K=2.1.

Alternatively you could go with the direct analysis method and use notional loads and reduced material properties ect to determine if the column/baseplate checks.