Risa Foundation Pedestals vs. Risa3d Concrete Column

[bootlegend]

Is there a suggested maximum height limit for using pedestals in RISA Foundation? For example, I have a steel structure supported on 8 feet tall, 3 feet square pedestals/columns that are supported on a mat foundation. I like the punching shear checks that Foundation does, but I'm skeptical of modeling these as pedestals in the program. I don't think there is any P-delta design in the Foundation program, and I don't see any options for changing the Icracked factor in Foundation either. My approach has been to model the upper portion of the concrete columns in RISA 3D and then attach to a shorter pier (say 12 inches tall)in Foundation so that I can get the punching shear checks.

Does my approach sound reasonable?

 

[JAE]

Yes - you might even use 1" tall pedestals. I don't think there is anything in the punching shear checks that depends on pedestal height.

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[bootlegend]

Thanks JAE. I was sticking with 12" for the height of the pedestal because RISA3D doesn't show design results for concrete members under that length. However, that isn't an issue in RISA Foundation so 1" tall pedestals is more convenient.

 

[JoshPlumSE]

Bootlegend -

That's a good point. Pedestals will be designed as columns when their aspect ratio exceeds 3. But, that only means the column provisions for minimum steel (1% vs 0.5%) will be enforced and possibly different requirements for shear ties. It does NOT cover P-Delta effects for the column / pedestal. That would have to be accounted for by hand... i.e. by adding in some manually magnified moment or such.

 

[bootlegend]

Thanks Josh!