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RE: Connection of Pipe Pile to Concrete Cap Beam

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It sounds like this is a pier cap beam to foundation connection in a
bridge type application.  Are you counting on using the pipe steel
itself to develop the moment capacity you are looking for? If so, two
things to remember 1) You can only count this steel if there is
assurance that corrosion resistence is provided or you typically
discount the outside 1/4" to 1/2" (See the AASHTO code) assuming that it
will corrode.  2) you need to develop this pipe pile steel shell up into
the cap by either welding tabs or threading rebar through the can pile
or even welding A706 hooked Bars to the pipe itself to adequately
develop the steel shell. 
If you are discounting the "can" pile itself in determining moment
capacity then you can use the concrete core w/ reinforcing as you
mentioned.  Typically this detail would include approximately 40 feet of
concrete and the top twenty with reinforcing, BUT, this can caus
construction difficulties during concrete placement if the rebar cage is
hanging, ie sometimes it is much easier to set the cage to the bottom if
the piles are not significantly long.  The confinement steel in this
lower portion does not need to be greater than code minimum.  As far as
developing moment resistance assume that the concrete within in the pile
is a well confined column and design the required capacity accordingly
assuring that you develop the longitudinal steel up into the cap as well
as down into the pile.  You indicated the there was no net tension on
the pile, if you had then it would be a good idea to adequately develop
the pipe pile up into the cap as I mentioned above.

Brian Bellfi, PE
CH2M Hill-Bridge

>From: 	poly(--nospam--at)[SMTP:poly(--nospam--at)]
>Sent: 	Sunday, February 02, 1997 7:54 PM
>To: 	seaoc(--nospam--at)
>Subject: 	Connection of Pipe Pile to Concrete Cap Beam
>I have a 36" Diameter pipe pile that I'm attaching to a large reinforced 
>concrete cap beam, by embedding rebars into a concrete plug in the pipe pile,
>and hooking them into the cap beam.
>Does anyone have any criteria for how long a concrete plug I'll need?  It 
>would seem to me to be a function of the bonding force of the concrete to the
>pipe wall, but I have no available criteria for this.
>In my case, there is no net tension across the beam-pile interface, but there
>IS considerable moment that I'd like transferred, so as to make this a moment
>Any guidance would be welcome.