Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: (no subject)

[Subject Prev][Subject Next][Thread Prev][Thread Next]

	You appear to be on track with your design except that I might try to
have the 210' section braced about 130' to 140' from the turn.  Your
idea of providing sliding expansion in the longitudinal direction and
constraining the other direction seems reasonable.  If you can eliminate
some longitudinal members and make the rack into two (or more) separate
structures that would be even better than using expansion joints.

	If the pipe is not anchored to the rack there are no anchor forces. 
Sliding friction would appear to be the largest horizontal force on the
rack; but you will have to check this out.  Mind you, if wind or seismic
does actually exceed sliding friction you will need to provide some
guides to prevent the pipe falling off the rack.

	Regarding the piping: I would suggest that you do not simply ignore it
because the client doesn't have anyone to check it out and they have
"done it this way for years".  A very old version of ANSI B31.1 Code had
an equation that I once worked with.  The code stated that if this
equation was not satisfied a more detailed review of piping stress was
required.  That equation is

	D*Y/(L-U)^2 =< 0.03

D = pipe nominal diameter in inches (all pipe must be the same size)

Y = resultant movement to be accommodated in inches

Y = A*U*T (times 12. of coarse)

A = thermal expansion coefficient, 6.5E-6 in./in./degree F.

T = temperature change (from ambient, normally assumed to be 70 degrees
F) in degrees F.

U = straight line distance between anchors (or ends) in feet.

L = length along the centerline of the pipe in feet.

I would personally feel a lot better in your position if this equation
were satisfied than if it were not.

	Good luck.


				H. Daryl Richardson

Jnapd(--nospam--at) wrote:
> Thanks for the input the can of worms is now opening.
> 1.    The client has nobody to give me the forces from any of these
> pipes.  There idea is just lay them on the supports as tthey have for
> years.  About 10 - 4" cold, hot water or steam.  Dead weight full is
> approx. 150 #/ft.  Also at the ends of the 210' run the racks turn
> 90degrees and extend another 50-100ft.  I was bracing both directions
> at the turns and maybe one in the middle of the 210'.  Another
> question is the expansion joint can be a slip joint in the long
> direction with uplift and short direction restraint ?
> thanks for your input.
> Joe Venuti
> Johnson & Nielsen Associates
> Palm Springs,  CA

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*   Questions to seaint-ad(--nospam--at) Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: 
******* ****** ****** ****** ******* ****** ****** ********