Footing Minimum Contact Area

[EngrJS1]

Hi,

I am designing an isolated footing based on ACI 318-14.

1. Is there any provision/clauses in the said code which prescribes a minimum %footing area that should remain in contact with the soil?
2. Are we allowed to provide footing design that would experience loss of contact?
3. If yes, can you recommend any minimum %footing area? (If you have any recommendation, please also mentioned your reference)

 

[le99]

I don't recall there is such a provision in the ACI code, but there are many good-practice recommendations readily available all over the place. In general, for static load, the resultant force should fall within the middle-third of the base; for dynamic load, the resultant force should remain in the base. For all cases, the allowable bearing strength is not to be exceeded, and the footing must be capable of generating adequate shear friction force to resist its share of lateral load.