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# RE: stresses in pipes

• To: "'seaoc(--nospam--at)seaoc.org'" <seaoc(--nospam--at)seaoc.org>
• Subject: RE: stresses in pipes
• From: James Hagensen <JHAGENSEN(--nospam--at)HNTB.com>
• Date: Wed, 5 Nov 1997 14:32:54 -0600

```If I correctly understand the problem, the stress on the edge of the
pipe is created by the bearing force against the edge of the socket.
This would be somewhat similar to a "saddle" support for a pipe since I
would assume that the inside socket diamater would be very close to the
outside pipe diameter.  I have a reference which I have used for pipe
which is quite good that you could look at.  It is "Tubular Steel
Structures, Theory and Design", by the James F. Lincoln Arc Welding
Foundation.  My copy is Second Edition, 1990 and the information related
to pipe saddles is located in section 9.14.  I think using the saddle
equations would be a reasonable approximation.   The reference states,
"Saddle Supports cause high local stresses both longitudinally and
circumferentially in unstiffened, comparatively thin wall pipe at the
tips and edges of the supports. Their intensity is practically
independent of the width of the saddle."  In your case you would
essentially have a "line support" (much like a very thin saddle) which
would occur over a portion of the pipe circumference at the edge of the
socket.  I would assume that other piping related books would also
address the issue of saddle supports and would have the equations in
them as well.  Just an idea anyway.  Good Luck.

Jim Hagensen S.E.

> -----Original Message-----
> From:	Brandon Erickson [SMTP:erickson(--nospam--at)smtp.degenkolbsf.com]
> Sent:	Tuesday, November 04, 1997 3:17 PM
> To:	seaoc(--nospam--at)seaoc.org
> Subject:	stresses in pipes
>
> Does anyone have a suggestion for finding the stresses induced in a
> pipe by a
> point load?  We are looking at the design of a davit for an exterior
> window
> washing scaffolding system.  The moment created by the weight of the
> workers'
> platform is resisted by the davit bearing on the sides of the socket
> it is
> placed in.  The industry standard for the davit design is a 5"
> schedule 80
> aluminum pipe, but we are having a hard time to make it "work" (i.e.
> the local
> effects of the bearing appear to overstress the pipe section) with
> simple hand
> calculations.   The required FS is 4 against yielding per CAL-OSHA.
> Perhaps
> only a computer model will give accurate results, but we would like to
> explore
> other options first.
>
> B. Erickson
>
>
>

```