Dear Mr Joshi,
May I preface this by saying that I am not a structural engineer.
In vibrating applications such as in a coal prpeparation plant (sometimes referred to as a coal washery ) the vibrating screens cause vibrations for the structure. In my experienc ethe structural engineers were always concerned about the natural frequency of the building in respect of the exciting frqequency. they would go to great lengths to change beam sections in order to avoid this occurence.
There are of course other means of excitation such as earthquakes that require a pectrum analysis to determine if the excitation is in harmony with the dynamic response.
I use Algor's pipepak for modal analysis of piping systems to establish the response to excitation from positive displacement pumps. This package has a FEA component that allows the input of AISC sections as structures for pipe supports. I doubt if it is comprehensive enough to cover a whole structure as in a building but you should check with Algor. They are very helpful and may be able to provide you with more information.
Geoff Stone
--- Mandal Pankaj <Pankaj.Mandal@siemens.com> wrote:
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Dear Mr. Joshi,<BR>
<BR>
Normally piping systems are more flexible than supporting systems (of
course<BR>
with exceptions). The reason behind this is that as a piping engineer, a<BR>
flexible piping system is always preferred whereas a structural engineer is<BR>
interested in making the structure rigid by adding bracings etc.<BR>
<BR>
Eigen frequency of a piping systems is determined by the supporting of the<BR>
piping system which in many cases are governed by stress analysis and hence<BR>
controlling the stifness of the piping system by adding guides is not
always<BR>
possible. Of course, we can modify stifness of the piping system by adding<BR>
snubbers but again the cost and utility of the same should be investigated.<BR>
On similar lines, civil structures have also their own limitaions in the<BR>
range of eigen frequencies.<BR>
<BR>
In general, making one system more flexible than the other is often not<BR>
possible from engineering point of view. What you have to look for is the<BR>
comparative study of the eigen frequencies of the piping and the supporting<BR>
structure. You may refer to the FEMA302, 1997 code for a comparative study.<BR>
<BR>
However, I am still unable to understand your last question.<BR>
<BR>
Regards,<BR>
Pankaj Mandal.<BR>
<BR>
-----Original Message-----<BR>
From: KAUSTUBH JOSHI [mailto:kvj@epc.ltindia.com]<BR>
Sent: 28 May 2002 17:07<BR>
To: PipingDesign@yahoogroups.com<BR>
Subject: [PipingDesign] Query<BR>
<BR>
<BR>
Hi all,<BR>
<BR>
When designing the piping and support structure, what is better:<BR>
1) To have a rigid piping and flexible support structure?<BR> 2) To have a flexible piping and rigid support structure?<BR> 3) To have a rigid piping and rigid support structure?<BR> 4) To have flexible piping and flexible support structure?<BR>
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