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steel sheet piles

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Gary,
As you've found, most hot-rolled steel sheet piling is now made
overseas; I think both Bethlehem and USS are out of the business
(Bethlehem, I believe, is completely dissolved).  However, there's a lot
of cold-formed piling produced domestically.  If you can get the section
properties you need, cold-formed is usually cheaper.  If you're doing
cells, where the only thing that matters is the interlock, cold-formed
usually is not suitable.

As others have said, check out Pilebuck's web site for a current listing
of available pile shapes and material strengths.  It's an impressive
list.  Because of this, we now specify a required yield strength and
section modulus per running foot rather than calling out a particular
section.

Bear in mind that sheet piling tends to get pulled and re-used a lot.
For shoring that's fine, but if you're using it for  something that's
going to be exposed, say a marina seawall, you may want to specify new
material.

The few times I've designed sheet pile walls, I've used the method
Bowles outlines (I have his 5th edition).  It's a little messy (it
involves solving a quartic equation, if I remember), doesn't give
deflections, and can't handle intermediate walers.  But, I can
understand his explanations; his equations aren't just empirical.  I
don't have much experience with commercial software.  A long time ago,
we used a Corps of Engineers program that allowed layered soils and
multiple lines of walers, and gave deflections.  But, the input involved
counting spaces in ASCII files; it was difficult to verify the input and
there was absolutely no way to check the results.

As far as allowable stresses, 0.66 Fy seems a little high to me
considering the gross uncertainty of the loading most walls experience,
especially for permanent work.  The Army Corps of Engineers allowable
stresses are lower for many good reasons:  They often use sheet piling
for permanent work; what they're protecting may be an entire town (with
a floodwall) so the cost of a little more steel is peanuts; deflection
may be a concern; and they are about as risk-averse a group as you will
find.  It you're concerned about, for instance, local buckling due to
bending, the AISC equations should predict that well enough.  Buckling
during driving is another matter, and pretty much out of your control.
You're designing the steel in place; the pile driver has to get it there
without damage.  I would carefully and explicitly state that in your
drawings.  The pile driver may wish to choose a heavier section just to
allow faster driving.

Speaking of risk-averse, shoring design always sets off little alarms in
my head.  There's a tremendous range of contractors who may need this
kind of design; some of them are excellent, and some of them are two
steps ahead of their creditors.  The work itself (installing shoring
systems) is risky by its nature, with a lot of things in the ground to
find by accident (like old tunnels, or the tiebacks for the basement
wall of the building next to you).  The few times I've done it, I've
tried hard to build enough fee into my estimate to allow time on site
during installation.  A guy I used to work with used to demand a check
before he'd hand over plans for this kind of work.  Good luck.

Mike Hemstad, P.E.
TKDA
St. Paul, Minnesota

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