Weak axis moment on column base plate

[braves25]

Good morning, I am designing a "gateway" structure. Columns are loaded in the weak axis and are to be fixed at the base. I am having a hard time finding any guidelines to design the base plate that supports a column having moment only in its weak axis. Everything I see deals with moment in the strong axis of a column. Thanks for your help.

 

[WARose]

Assuming the bolts are on the outside of the column (i.e. the distance between the bolts is > bf; which is as it should be if you are modeling the base as fixed in that direction), there isn't a whole lot of mystery to it: you just cantilever the uplift (from the moment) to the face of the flange and design the plate for that moment. (While also checking bearing stresses on the other side as well as flange & weld stresses.)

 

[KootK]

Yeah, there isn't much available in the literature. My recommendation:

1) On the compression side, designate yourself a couple of fictional beam strips at the flange tips running perpendicular to the flanges. Make these work in flexure and bearing.

2) Obtain your bolt force using the moment arm extending from the bolts to the center of the the beam strips mentioned above.

3) Design the base plate between the bolt and the nearest point of stiffness (flange/web) using either WARose's method or the yield line procedure.

4) Design your column to base plate welds in a manner consistent with what you've done above. It won't make sense to us M/Sx here as you will not have created a rigid base plate, only an economical one.

The other way to go is to assume a rigid base plate. I've heard recommendations that a rigid base plate should not cantilever more than 5 x t from the column face. I'm not a big fan of this method.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[neznajko]

Try AISC Design Guide 1.

AISC gives difference coefficients relative to the orientation/shape of the column.