Need a book? Engineering books recommendations...
Return to index: [Subject] [Thread] [Date] [Author]
Re: Pole Embedment Formula
[Subject Prev][Subject Next][Thread Prev][Thread Next]- To: seaint(--nospam--at)seaint.org
- Subject: Re: Pole Embedment Formula
- From: "Joseph R. Grill" <jbotch(--nospam--at)blissnet.com>
- Date: Fri, 24 Sep 1999 18:20:48 -0600
You might also AASHTO specifications. The have formulas which are written for discrete vertical elements in bedrock in their retaining wall section. I haven't used the bedrock formulas but have used the other formulas for embedded H piles with treated timber framing horizontally between. Joseph R. Grill, PE "Swingle, Mark" wrote: > On 9/16/99 EDT, you wrote: > > Both of the pole embedment formulas indeed contemplate ordinary soils that > are not very rigid compared to the pole, over the pole's depth of embedment. > Embedment into bedrock is quite a change from that. > > The formulas came from work done in the 1940's at Notre Dame and one other > university for the Outdoor Advertising (billboard) Assn, and involved hole > diameters of a foot or two, and depths of ten feet or so. The formulas got > into UBC a long time ago. Several editions later the allowable lateral soil > loads in the UBC table were considerably reduced, making the result more > conservative than originally. > > The "Constrained" condition is for when there is a hard resistance to > lateral movement at grade (hard compared to the soil below) and that acts as > a pivot point or fulcrum to the horizontal forces acting on the pole, the > pole being modeled as a rigid free-body. Max pole moment is at this > constraint. > > For "unconstrained" conditions (all-dirt embedment) the max pole moment is > at the point of zero pole shear, a depth that varies according to how low or > high above grade the lateral force is, compared to the embedment depth. I > worked up a table of values; > M = P (h + .17d) is about as bad as they got for small h compared to d. > > If you are developing all your resistance in bedrock, I submit that neither > of the UBC formulas applies. > > Why not go back to the soil engineer for an interpretation of what he/she > had in mind? Keep principles of mechanics in mind at all times; it ain't > voodoo. > > Charles O. Greenlaw SE Sacramento CA > > ------------------------------- > > Charles, can you elaborate on your reply? > > 1. If the pole formlae don't apply in rock, then how would one > determine the depth of embedment required to resist the > lateral force P? > > 2. Then, how would one determine the point of fixity in rock? > How did you come up with fixity at d/6 below the surface? > I was "taught" by several engineers that fixity is at d/3, > although no justification was given. Sometimes soils > engineers would allow fixity at 2' below the top of rock, > but not all are willing to give an answer. > > Thanks > > Mark Swingle, SE > Oakland, CA >
- References:
- RE: Pole Embedment Formula
- From: Swingle, Mark
- RE: Pole Embedment Formula
- Prev by Subject: RE: Pole Embedment Formula
- Next by Subject: RE: Pole Embedment Formula
- Previous by thread: RE: Pole Embedment Formula
- Next by thread: RE: Pole Embedment Formula
- About this archive
- Messages sorted by: [Subject][Thread][Author][Date]