Reinforced Concrete Design - Structural holes 2

[architrave]

Hello,
I am just wondering if one can plan for shaft/chase holes near columns. Is there a rule of thumb in placing holes?

Your response would be appreciated. Thank you very much.

 

[jayrod12]

Obviously it isn't ideal, but I don't see the issue with it provided you do the appropriate punching shear checks taking into account the affect of the hole. The effect on punching shear isn't just the reduction of the hole width on the failure surface, but the projected width of the hole at the punching shear perimeter. The further you can keep any holes away from the column, the less of an impact they have on the total failure surface.

 

[KootK]

I design pretty much every interior column punching zone assuming that there will be one 6" penetration right beside the column. Coordinating the placement of integrity top bars around the penetration often warrants some careful attention.

 

[architrave]

Thank you very much guys!

 

[WARose]

Is there a rule of thumb in placing holes?

You generally try to have openings in the "middle" strips (where possible). See Sect. 13.4 of ACI 318-11 for some guidelines.

What you are talking about can be done (with the checks performed).

 

[Lomarandil]

WARose is correct for the most common case of flat plate/flat slab floors.

Note that in the less common case of two-way beam-supported slabs, the ideal location is in the intersection of column strips (but not in the beam). Depending on your floor, some shear and deflection checks may still be required, but these are generally easy to solve.

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just call me Lo.