Drilled Pier Foundations EQN 18-1
Drilled Pier Foundations EQN 18-1
(OP)
Hello all,
I'm a structural engineer in North Dakota and I'm designing drilled piers that will support softball scoreboards. I'm running into an issue when I'm trying to call out the depth of my drilled piers using EQN 18-1 from section 1807.3.2.1 in the 2012 IBC. The geotechnical engineer has dictated that the first 5 feet from grade be ignored for passive resistance. Equation 18-1 does not seem like it allows you to specify an "ignored" depth.
My first thought was to increase my "height" of my scoreboard so that I effectively treat the -5ft elevation as grade level and whatever result I get from EQN 18-1, I just add 5 ft. However this seems really conservative to me. I get ignoring the first 5 feet for passive bearing, but this approach negates any vertical effective stress above -5 feet, effectively shifting my bearing stress triangle down 5 feet.
I feel I should be able to use the original allowable passive pressure stress triangle, but I would just truncate the part of the triangle above -5ft. Does anyone know of a method to account for this ignored depth using EQN 18-1 or any other approach?
Thanks,
I'm a structural engineer in North Dakota and I'm designing drilled piers that will support softball scoreboards. I'm running into an issue when I'm trying to call out the depth of my drilled piers using EQN 18-1 from section 1807.3.2.1 in the 2012 IBC. The geotechnical engineer has dictated that the first 5 feet from grade be ignored for passive resistance. Equation 18-1 does not seem like it allows you to specify an "ignored" depth.
My first thought was to increase my "height" of my scoreboard so that I effectively treat the -5ft elevation as grade level and whatever result I get from EQN 18-1, I just add 5 ft. However this seems really conservative to me. I get ignoring the first 5 feet for passive bearing, but this approach negates any vertical effective stress above -5 feet, effectively shifting my bearing stress triangle down 5 feet.
I feel I should be able to use the original allowable passive pressure stress triangle, but I would just truncate the part of the triangle above -5ft. Does anyone know of a method to account for this ignored depth using EQN 18-1 or any other approach?
Thanks,






RE: Drilled Pier Foundations EQN 18-1
RE: Drilled Pier Foundations EQN 18-1
RE: Drilled Pier Foundations EQN 18-1
But first, do as Jed says.
Mike McCann, PE, SE (WA)
RE: Drilled Pier Foundations EQN 18-1
Mike McCann, PE, SE (WA)
RE: Drilled Pier Foundations EQN 18-1
DaveAtkins
RE: Drilled Pier Foundations EQN 18-1
RE: Drilled Pier Foundations EQN 18-1
I'd contacted this geotech specifically about the allowable passive pressure for designing these piers, so yes that recommendation was for this specific application
msquared48- I'd previous designed my piers using the method you suggest which makes me feel better about my logic, so thanks.
Our frost depth here in ND is 5 ft, so I kind of understand where the geotech is coming from with a slightly larger ignored depth, but I agree that 5 ft. seems extremely conservative. Anyway, I'm going to get another opinion about the depth I need to ignore from another geotech and see if I can't reduce my required depth a little.
Thanks all,
RE: Drilled Pier Foundations EQN 18-1
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Drilled Pier Foundations EQN 18-1