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RE: Fire Sprinkler Thrust Loads

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For a fire sprinkler pipe with grooved joints (e.g., Victaulic), there is 
some longitudinal growth of the pipe due to cumulative movement at each of 
the joints.  If more than one brace per run is used to resist seismic loads 
in the longitudinal direction (along the pipe), some thrust will be induced 
on these supports.

Similarly, if the lateral braces (normal to the pipe) are close to a change 
in direction loads may also be imposed on the braces due to the same growth 
mechanism.  It would be a function of the stiffness of the pipe vs. the 
stiffness of the support.

A lesser amount of growth due to elastic action of the pipe under pressure 
loading can occur (because the pipe is placed in longitudinal tension to 
resist the pressure loading), but is usually much less significant.

Bill Cain, S.E.
Oakland, CA


-----Original Message-----
From:	Horning, Dick/CVO [SMTP:dhorning(--nospam--at)CH2M.com]
Sent:	Monday, October 19, 1998 12:34 PM
To:	'seaint(--nospam--at)seaint.org'
Subject:	RE: Fire Sprinkler Thrust Loads

As a free-body diagram will show, the thrust would be taken through the 
pipe
wall in longitudinal tension, as long as there are no unrestrained joints 
in
the pipe.

	-----Original Message-----
	From:	Joshua Matthews [SMTP:base.engr(--nospam--at)internetMCI.com]
	Sent:	Saturday, October 17, 1998 11:05 AM
	To:	seaint(--nospam--at)seaint.org
	Subject:	Re: Fire Sprinkler Thrust Loads

	I recently spoke with a friend who is a contractor who was being
requested to
	verify that a new metal building that they had constructed be
checked for
	"thrust" loads in the plumbing of the fire sprinkler system.  The
plumbing is
	braced back (and checked) to the structure for seismic loads but
Factory
	Mutual has requested that it be checked for "thrust" of the water
moving
	through the system (particularly at bends in the plumbing). It would
seem that
	most of the forces in the plumbing would be resolved within the
plumbing
	itself and not be exerted on the structure (two opposing bends might
create
	tension in the pipe)

	I have not heard of this before, has anyone else had this question
come up or
	have any experience with this situation?

	Any comments would be appreciated.

	Joshua Matthews