Coljumn base plates - shear keys

[bkal]

Hi,

I have recently come across designs of column base plates with shear keys into the concrete foundation made of structural sections (H section or similar) welded to the underside of the base plate. Generally, the checks have involved bending of the section loaded with an assumed contact pressure distribution between the section and concrete. If the main pressure components is applied to the flange of the shear key section, I have a feeling that a local bending of the flange needs to be checked (and usually, that would be a limiting criterion).

I am correct in assuming that this check needs to be done?

Thanks.

 

[a2mfk]

Also called "shear lugs". I don't think I had thought about checking local flange bending before with an embedded connection like that. Usually the weld or some other mechanism controls (concrete shear), but I suppose it should be checked. But I also think you would split the flange loading in bending between both the top and bottom flanges, as both flanges would compress against the confining concrete. And then, what effect does the confining concrete have? Quite a lot I would imagine? Sounds like something that would need testing to know for sure, but a conservative approach may be to check the top flange for 60-80% of the load, and the rest is picked up by the bottom flange?

 

[SAIL3]

yes I would check the FWD fla for bending...the AFT fla will only see what the block of conc between the flanges can deliver in conc shear ....in this case it would be grout and I would not depend on it to be sound so I would take the full shear out in the FWD flanges....this is one reason I use flat pl as shear lugs...less welding