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# RE: Tension only thrust restraint

• To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
• Subject: RE: Tension only thrust restraint
• From: Dave Handy <dhandy(--nospam--at)trg.ca>
• Date: Fri, 9 Oct 1998 12:25:52 -0400

```Depends on the diameter of the rod. The rod has to become quite large in order to minimize the horizontal load effects. The rods can be treated as beams or cables. A small diameter rod will deflect so much under self wieght that it will act like a cable and those equations can be used (structural eng handbook Gaylord, et al 1997  p.27-4).

Tension =(QL^2)   (1+16(F/L)^2)^0.5   /   (8F)
Q IS UDL
L IS HORIZONTAL LENGTH
F IS VERTICAL SAG

As deflection approaches that of a beam then the tension effects will be reduced greatly.
Hope that helps!

David Handy, P.Eng
The Thompson Rosemount Group
dhandy(--nospam--at)trg.ca
The preceding was an off the record personal opinion only! (cya)

-----Original Message-----
From:	Bill Sherman [SMTP:SHERMANWC(--nospam--at)cdm.com]
Sent:	October 09, 1998 11:57 AM
To:	seaint(--nospam--at)seaint.org
Subject:	Tension only thrust restraint

I have a pipe thrust restraint problem which I could use some advice on.  I
have 21 kips of pipe thrust 20 feet above grade, which I would like to
resist
by use of a 30-ft long horizontal cable or rod from a vertical pipe support
back to a building structure.  I am trying to avoid thrust at the vertical
pipe support since its support structure below is not adequate to carry the
base reactions if the thrust is included.

I was thinking of using a cable - but in order to minimize cable sag as well
as minimize pipe movement under load, I would need to pretension the cable.
But this in turn puts a horizontal load on my vertical pipe support when
there
is no pipe thrust, which is the same as what I was trying to avoid in the
first place.  So does anyone know of a way to resist such tension due to
thrust without inducing tension due to the catenary effect?  Would a steel
rod
act much different from a steel cable?

```

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