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RE: H-Piles Cap Plates

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This was researched and tested several years ago by Lehigh and GAI
Consultants.  Reference "The Steel Pile Pile Cap Connection", 1982,
published by AISI.  Basically, leave the cap plates off.  The only time a
connection plate may be required is for uplift.  I know the bearing stresses
get high, but the concrete is confined. The same holds true under the head
of anchor rods, tests by the Texas DOT and TVA (for ACI 349 appendix B) show
that the high local bearing stresses are not a problem. 

The confined bearing strength of concrete was quantified for the first time
in "Strength Design of Anchorage to Concrete", by Cook, 1999, PCA.  You will
see the strength can go to 8.0 * f'c.

Harold Sprague

> -----Original Message-----
> From:	Olive, Harry [SMTP:HOlive(--nospam--at)]
> Sent:	Monday, March 13, 2000 1:14 PM
> To:	'seaint(--nospam--at)'
> Subject:	H-Piles Cap Plates
> I was wondering what the concensus is on the use of pile cap plates (or
> cover plates) to the transfer of the load in the pile cap to the steel
> H-piles.  I always use pile cap plates to transfer the loads because the
> stress in the piles (9 ksi or higher) is usually much greater than the
> bearing strength of the concrete.  Lately, I have had several piling
> contractors ask why I specify the use of cap plates.  I am not adverse to
> changing my ways, but first I would like to find some "good" articles on
> the
> subject.  The CRSI manual touches lightly on the lack of cap plates
> ("increase pile embedment to 6 inches to avoid use of cover plates"), and
> I
> assume the "prevent vertical edge splitting" clause is a phenomena
> associated with lack of cover plates due to the high bearing stresse in
> the
> concrete over the exterior flange of the outer piles.  Does anyone know
> where I might find some "good" articles which will shed some light on this
> topic?
> Regards
> Harry Olive, P.Eng., P.E.
> Neill and Gunter