sign post ftg above frost line

huangyhg

sign post ftg above frost line
i have designed a sign post footing 12inch dia concrete and 3 feet deep. frost line is 6.5 feet deep. can i ignore it here?
does the owner care if it moves around? could it tip?
we tend to design sign footings down to frost line, but it is only 4 feet around here.
have you thought about a 6.5' deep caisson instead? this tends to be cheaper.
csd
can the sign structure stand the distortion and different loadings due to differential heaving? - can't be much of a sign if 3' is good enough on paper.
are you counting on the passive resistance of the soil against the pier to 'fix' the footing so the sign can canilever off the footing?
if so, i would be a bit careful. it is often recommended not to count on passive resistance of soil in the frost zone as the freeze/thaw action tends to break the soil up, particulalrly when subjected to cyclic loads.
jmho.
it is very standard stop sign just like you see on road side everyday. octogonal 2 feet x 2 feet. post height is 10 feet. assuming 20 psf wind load in trubutary area od 4 sf,= 80 lbs load at 9 feet high.
look up the aashto sign spec for that, i am sure that they have standard footings in there for small signs.
the maintanance workers of your local jurisdiction need the work.  don't cause unemployment.  stop the sign at 3 feet.
mike mccann
mccann engineering
if the ground is going to move (heave) much, you'd probably create more problems trying to anchor it below the frost line.  here in anchorage, alaska (design frost depth of 10 feet), 3 feet is the standard foundation depth for small signs.  rarely does that cause a problem, they may move a little with the surrounding ground.