Checking Flexure @ Edge of Base Plates

[kk88818]

Under what conditions do I need to manually check for flexure at the edge of base plate? When P is high? When -P is high? When anchor rods are located "outside" the col? All the time? Have the design examples provided in the SDG's (both 1st and 2nd ed) already considered this?

 

[Lion06]

The moment at the free edge of the baseplate is always 0, just like a cantilevered beam.
If you are talking about the "edge" of the plate where it meets the column, you always check the moment there - that is how you size the plate.

 

[271828]

Which edge? Gonna have to be clearer about what failure pattern you're typing about.

 

[kk88818]

Failure mode is flexure of the base plate and whether it is sufficiently stiff. Not actually the edge of the base plate, but the "edge" of the plate where it meets the column, per StructuralEIT. Do you have to check whether it will fail in bending due to the axial compressive load? Do you have to check whether it will fail in bending due to uplift? Does it matter whether the anchor rods are situated "inside" the column, or situated "outside" it? The formulas as presented in AISC Steel Design Guide Series, both the original 2003 version and the 2006 second edition, have they taken account of the failure by bending?

 

[Lion06]

The design of the baseplate for thickness is based on this failure that you are talking about - so yes, you have to check it. That is what drives the thickness of the baseplate. For gravity only the location of the anchor rods will not matter. For uplift the location of the anchor rods will make a difference. For Moment at the base of the column with or without gravity/uplift, the location of the rods will matter, not only for the base plate thickness but also for the actual anchor rod design.

 

[csd72]

kk88818,

You need to look at AISC design guide 1 - Design of Column Base plates.

csd

 

[msquared48]

If you have a moment on the column in addition to the P load, you will also have to consider prying action in the design of the plate.

Mike McCann
McCann Engineering

 

[faromic]

You can consider the base plate portion in flexure is from the the point where the plate meets the column to the anchor/expansion bolts. This is the length of your "cantilevered beam" with the base at the column and the load P equal to the sum of all the tension loads. If you size the plate stiff enough, you can "neglect" the prying action. I use neglect with caution, so use your judgement.