Design example or textbook - Reinforced Concrete Column design for axial, shear and torsion loads

[StructuralJoe]

Does anyone know of any ACI design examples for a reinforced concrete column with axial, shear and torsion load applied (torsion and shear are from PT barrier cables and are much higher than the initial design intent).

I would prefer it be to ACI 318-11 but I will consider newer ACI codes.

Thanks in advance!

 

[WARose]

I can't think of any.....but in general the results are additive (for a lack of a better way to put it). What I have always typically done is do the axial-moment design......and then consider the additional steel from shear-torsion. The longitudinal steel required for torsion (if any) is additive to the steel from other forces. However the code makes clear that placement for longitudinal torsional steel must meet certain spacing and placement requirements.

You can typically do these designs fast with Alex's spreadsheets.

 

[StructuralJoe]

WARose,

I agree, but since the shear is inducing the torsion do I need to add the shear twice? In other words it isn't an independent shear and torsion load, the torsion is caused by the eccentricity of the shear. So do I engineer of shear then basically double the load for torsion? It doesn't make complete sense, that's why I would prefer to see an example. I have seen plenty of examples for beams but they address this better than they do for columns...

Thanks,

 

[EDub24]

It should still be additive as WARose says. When you create the free-body diagram you 'move' the shear to the COG of the column and then add the torsion based off the eccentricity of the shear load. You design the column for the shear and axial load. Then design for the torsional load. Add the required reinforcement together to determine the minimum amount of reinforcement you need. The concepts between a beam and a column aren't different. Besides code requirements for rebar, spacing etc the only difference between a beam and a column for design purposes is one has a relatively high axial load.