Re: Pipe supports

From: <Christopher>
Date: Tue Feb 15 2005 - 15:12:00 EST

On Feb 14, 2005, at 11:49 PM, Pankaj.Mandal@fluor.com wrote:

> It we really go into construction of these supports, in most cases, it
> locks one or more additional degree of freedom, not accounted for in
> our
> analysis.

You're right about high bending moments, but in practice, it's very difficult to restrain rotation fully without going to a great deal of trouble. Ordinary supports are usually flexible in rotation, either because of fabrication tolerances or the support construction or because of the pipe itself. Moreover, the actual displacements and loads aren't applied the way we model them. Our model assumes that the system is constructed perfectly before any load is applied. Then all loads are applied simultaneously. In the real world, the gravity load of the pipe itself is applied incrementally as the pipe is fabbed and placed. I can't speak to every piping system in the world, but to one degree or another the pipe simply rests on a support while the pipe run is completed and leveled; then the actual supporting connection is made up to hold the pipe secure, probably in a partially deformed state. I doubt that anyone takes account of the loading associated with forces and deformations required to jack a piece of pipe into place and account for manufacturing tolerances. The pipe wall, especially in large diameter low pressure systems. has some flexibility as well as the shoe or hanger, and because contact loading is non-linear it's very difficult to assess accurately.
Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=xPsNeUvTq0BMFk54cZlrZ8k3mUgRHkxj3Az8q6EUhHaIYbz77EnWxoScMrwfR0q29Si6ixoZJ3lR">chrisw@skypoint.com</a> | this distance" (last words of Gen.

.......................................| John Sedgwick, Spotsylvania

1864)
<a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a> Received on Tue Feb 15 15:12:00 2005