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Re: Pile force check for orthogonal load combinations

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Title: Pile force check for orthogonal load combinations
        For structural components we do consider orthogonal loads (bi-axial bending + axial load + shear) because it is the same material resisting all of these loads at the same time.  For pile foundations this is not necessarily so.
        Consider end bearing piles subjected to lateral load.  The soil resisting vertical load is located below the pine at the bottom; the soil resisting the lateral load for the most part is located beside the pile at the top end.  Neither parcel of soil can "know" whether or not the other is subjected to significant forces let alone be significantly affected by the load case.
        Friction piles are another matter.  Friction forces are a function of the compressive force perpendicular to the direction of action of the friction force.  For a laterally loaded pile this compressive force will increase on one side of the pile while decreasing on the other, hence the frictional forces around the pile will not be uniform.  I think you are right to assume that the net change may not be zero.  That said, again, most of the vertical load will be resisted by soil deeper in the ground, while most of the lateral load will be resisted by soil nearer the top of the pile.
        This sounds like a geotechnical problem requiring advanced geotechnical expertise and maybe a significant amount of site work to get the answer you are looking for.
H. Daryl Richardson
----- Original Message -----
From: Vasu, Ravi
Sent: Wednesday, July 27, 2011 1:38 PM
Subject: Pile force check for orthogonal load combinations


In the design of non building structures like pipe rack in SDC D, we design the steel pipe rack
for orthogonal load comb. also.  When we design the foundation, is there any exception that the fdn & piles
need not be checked for orthogonal load combinations?  The ASCE 7-05, section 12.5.4 is
not clear about foundation check.  It says about column or wall design in any direction.
(I am not sure about orthogonal condition check for column/wall)

Can anyone point to ASCE/IBC 2009 section about taking or not considering ortho load
Comb for fdn and Pile design?


Ravi Vasu