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RE: LPILE or Other (Laterally Loaded Pile Analysis)

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I won't necessarily disagree with wanting to do the analysis yourself,
but...the lateral analysis of the pile (or drilled pier) is really more of
a geotech issue (OK, it is a little of both).  The moments, shears, and
deflection of the pile/drilled pier are more of a function of the soil
properties than the pile/drilled pier properties, so a geotech should be
more experienced/knowledgable in dealing with that analysis.  After all,
as a structural engineer, I don't typically determine/estimate how much a
footing may settle...I usually get that information from the geotech...but
I know enough about the issue to know if something "weird" is being given.
Would you want the geotech to design the reinforcing in the spread footing
for a building (not that he/she could not do it) or would you rather the
structural engineer be doing that?

On at least on occassion I have had the geotech run the lateral analysis
of a drilled pier through LPILE.  I then use the results of that analysis
(after assuring myself that it makes sense) to design the reinforcing (if
necessary since I am a low seismic zone) for the pier.

Basically, I look at it as the "expert" (the geotech) in soil response is
running the analysis on how the soil will effect the pile/pier and then
the "expert" (the structural engineer) will design the pile/pier.  This
method obviously may require a couple of iterations...i.e. a trial run to
get a preliminary pile/pier size then interate...

Ultimately, it comes down to each their own...if you want to do the
analysis yourself, then by all means do so.  :-)

HTH,

Scott
Ypsilanti, MI


On Tue, 12 Mar 2002, Bill Polhemus wrote:

> That's an idea, but to tell you the truth I'd rather do this analysis
> myself. I don't mind having the geotech giving me the data needed in the
> report but I like doing the foundation design myself not having it done for
> me.
>
> To tell the truth I have a nice "closed form solution" for doing a pretty
> close estimate of the pile head movement and (especially) the maximum moment
> in the pile. It is based upon a paper that was presented a few years ago at
> the Texas Section ASCE meeting, and I've received a copy of it from the guys
> who put it together.
>
> Essentially, they took several hundred LPILE runs, and collated the data
> then did a very fancy curve fit. The result is a ponderous-looking equation
> which nevertheless is easy to solve using e.g. Mathcad's ROOT function.
>
> But there are a few limitations on their method and the authors state that
> it is for "preliminary design" and should be followed-up with a more
> extensive analysis using LPILE or similar.
>
> One of the limitations is that it assumes a value for (50  (that's
> Epsilon-sub-50) of 0.01. The soil report I'm using recommends a value of
> 0.005. I'm not all that conversant as to how sensitive the analysis is to a
> change in the value of (50  (Epsilon-sub-50), but I wanted to explore that
> for myself.
>
> It seems to me, btw, that since (50  (Epsilon-sub-50) is defined as "the
> strain at one-half the ultimate shear stress of the soil" that a value of
> 0.005 would indicate a STIFFER soil than that of 0.01 and thus any analysis
> would be more conservative at the higher value, but I don't know the
> details.
>
>
>
> William L. Polhemus, Jr. P.E.
> Polhemus Engineering Company
> Katy, TX, USA
> Phone (281) 492-2251
> FAX (281) 492-8203
> email bill(--nospam--at)polhemus.cc
>
>  -----Original Message-----
> From: 	Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu]
> Sent:	Tuesday, March 12, 2002 10:35 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	Re: LPILE or Other (Laterally Loaded Pile Analysis)
>
> Bill,
>
> Your other option is to hire a geotech company that has LPILE to run the
> analysis for you.  This can be an especially good option if you have
> already sub'd out for a geotech report (which you would need to do anyway
> to get the necessary soil information for input into LPILE).  Just have
> the geotech company provide the lateral analysis as part of their geotech
> services.
>
> HTH,
>
> Scott
> Ypsilanti, MI
>
>
> On Sun, 10 Mar 2002, Bill Polhemus wrote:
>
> > Does anyone know if the latest version of the LPILE (PLUS?) software is
> > available anywhere for rent? Once every blue moon I have a laterally
> loaded
> > pile problem to solve, but it isn't worth paying the $900 or so for this
> > software. Seems like LPILE would be a perfect candidate for rental.
> >
> > Otherwise, does anyone know of a similar program for prediction of
> response
> > of piles under lateral loading, available at low or no cost?
> >
> > Thanks.
> >
> >
> >
> > William L. Polhemus, Jr. P.E.
> > Polhemus Engineering Company
> > Katy, TX, USA
> > Phone (281) 492-2251
> > FAX (281) 492-8203
> > email bill(--nospam--at)polhemus.cc
> >
> >
> >
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