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RE: Sewer Aerial Crossing

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I can't vouch for its applicability to your conditions, but Type 304 stainless
is the most readily available.  I recommend you use that if it suits your

-Keith Fix, PE
-Little Rock, Arkansas

--- "Speck, Todd M" <tmspeck(--nospam--at)> wrote:
> Thanks for the responses; feel free to add should one wish.
> A few other items to clarify.
> It is a stream crossing.
> The total length is 60' +/-.  Each individual span length will be 20', equal
> to the lay length of the pipe.
> The pipe is continuously supported by a concrete "beam" or cradle or
> straddle.  The cradle spans between abutments and bents.  The cradle is a
> flat rectangle with a semicircle cut from the top to hold the pipe.  The
> pipe will be strapped to the cradle using stainless steel brackets at each
> pipe segment end.  
> I'd still like to hear what type of stainless steel one would recommend.
> Straight pipe with a slight vertical grade.
> Any thoughts on the differential vertical movement due to soil heave?
> Thanks, again.
> Todd
> -----Original Message-----
> From: Speck, Todd M [mailto:tmspeck(--nospam--at)]
> Sent: Wednesday, August 28, 2002 8:16 AM
> To: SEAInt (E-mail)
> Subject: Sewer Aerial Crossing
> Importance: High
> I'm designing a sewer aerial crossing bridge.  The bridge will only support
> the sewer itself, no vehicular traffic.  It's a 16" ductile iron pipe
> continuously supported by a cast in place cradle/saddle spanning between
> single column bents/abutments.  The pipe/bridge at 100 yr occurrence will be
> completely submerged.  The overall span length is only 60'.  I don't believe
> expansion/contraction will be an issue.
> 1.  I'd appreciate any words of wisdom with respect to general design
> issues.  I also have a few specific questions.
> 2.  I'll be specifying stainless steel brackets and bolts to connect pipe to
> the cradle.  What type of stainless steel should I specify?
> 3.  The soil has a potential vertical rise of 2.5".  The abutment foundation
> will be drilled shafts socketed into hard limestone and will not move.  What
> is done to assure the pipe can handle the differential movement at the
> abutment?
> 4.  Sitting in a cradle with a semi-circle cut out to hold the pipe I can
> envision water being held in contact with the pipe indefinitely.  Is
> corrosion of the pipe a concern.
> Thank you in advance for your comments.
> Todd M. Speck, P.E.

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