Ecc. Footing Deisgn Resultant Load outside The Kern

[struc100]

For Ecc. Footing design with resultant load outside the kern

Is ther any design guide or code ref. about the min. ratio requirements between bearing lengthh vs actual footing length (L2/L1)?

see attach sketch.

 

[msquared48]

I believe there have been other threads on this subject. I know I have posted the equations for this too in the past here.

Mike McCann
MMC Engineering

 

[InDepth]

Sounds like if you have this situation you may not be making effective use of your footing. Mya want to look into pile foundation or micro-pile foundation.

 

[hokie66]

I don't know of a rule or guideline as to limiting the eccentricity, but the more eccentric it is, the less efficient and logical your footing design. If you can't move the footing, can you make it rectangular so the eccentricity is less? Or tie it to another footing to rectify the overturning?

 

[DRC1]

Typically L2 should not be less than L1. If it is there are equations to predict the actual bearing stress. When e is inside the middle third of the footing (e=1/6L),an increase in e leads to a coresponding increase in q. Once e is outside the middle third, an increase in e results in a reduction of bearing area that results in a significantly larger increase in q. If q causes settlement, e could increase farther, causing higher q and mor settlemnt. Therfore it is generally desirable to keep L2= L1