Minimum bar size in footing

[bashabo]

Can anyone tell me what is the minimum bar size per ACI code in Footing as well as in Column for residential (6 storied) construction. My engineer mentions 12 mm (#4) is the minimum for flexure members and 16mm (#5) for compression members. Another structural engineer said #5 (16 mm) is the minimum size for both flexure and compression members. Appreciate your feedback. Thanks..

 

[dik]

#4 is OK for flexure... just a caution with slabs that #4 can be readily bent by walking on... #5 OK for compression members... Dik

 

[JAE]

There isn't such a thing as a minimum bar size in concrete design.

Its the number of bars and the total area that matter. Usually you want to provide more smaller bars than fewer larger bars. Design the bars either for strength (against applied loads) or for minimum required area of steel.

 

[archeng59]

it is my experience that some local building codes (supplements to the IBC, BOCA, UBC, SBC) require a minimum bar size, #5 typically, for footings. this is likely based on prescriptive residential code requirements where the foundation was not designed by an engineer. I have experienced difficulties with city inspectors on foundations I designed and #4 bars were ok, but since the city code required minimum #5, the inspector would not approve the footing reinforcing.

JAE is correct, the area of steel is what matters.

 

[UcfSE]

dik has a good point. While there may not be a minimum bar size required by engineering or by code, you may help with constructibility by holding to a given size. If the bars are for a structural slab for instance, you may want a minimum of #4 or #5 just so workers walking on the bars won't bend them all out of shape and mess up the design strength or cover, and so on.