AASHTO LRFD Long or Short Footing Heel 1

[cap4000]

Does any one have the AASHTO figure C3.11.5.3.1a which explains the difference between long and short footing heels. Rankine and Coulomb outer failure surfaces is whats at issue and when each occurs. Any information will be appreciated.

 

[crossframe]

Figure C3.11.5.3-1a is the top figure shown on page 3-65 (LRFD 2nd Ed.).

Hope this helps.

 

[cap4000]

crossframe

I don't have that manual. Only looking for a basic explanation between the failure surface criteria and when each occurs.

 

[miecz]

There doesn't seem to be a written definition, at least I can't find one. Looking at the figures, it appears that a long heel is such that the failure shear zone is not interupted by the stem. That is, if you begin at the end of the heel and draw a line at an angle to the vertical equal to 0.5*(90+beta-phi-epsilon), that line doesn't touch the stem. beta is the angle of the backfill to the horizontal; phi is the angle of internal friction of the backfill; epsilon is the angle whose sin is sin(beta)/sin(phi).