Need a book? Engineering books recommendations...

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

Re: Damping percentage

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

On Sep 30, 2008, at 5:40 PM, Daryl Richardson wrote:

The stacks that I have designed are smaller in diameter, and taller. For the most part they are designed to resist wind loading and are intended to remain in the elastic range. They also have less attachments. I usually use 0.5% to 1.0 % for welded steel stacks and up to 1.5% for reinforced concrete stacks.

The USNRC mandates the following unless other values can be justified.

		OBE	SSE
Piping
  >12" OD	2%	3%
  <12" OD	1%	2%
Steel
  Welded	2%	4%
  Bolted	4%	7%
Concrete
  Prestress	2%	5%
  Reinf	4%	7%

OBE means operating basis earthquake with stresses generally below yield. SSE means safe shutdown earthquake with stresses exceeding yield but not so the equipment is inoperable. I've done some measurements of small items in a sine sweep test and gotten numbers between 0.7% and 2%, but the items weren't highly stressed.

So yer pays yer money and yer takes yer choice.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/members/chrisw/



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
* Questions to seaint-ad(--nospam--at)seaint.org. 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: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********