Duct Analysis

Can any one help me in how do we perform duct analysis using Caesar II.
and which code shall be applied to evaluate the same. (ANSI B31.1 ??)

Maybe.

If your duct is circular, then yes you can analyze it with CAESAR II, being aware of the following limitations:

1) CAESAR II uses the "3D beam" element. This is essentially an infinitly thin stick element. Your analysis is subject to the limitations of this element.

2) Most piping codes develop SIFs assuming the D/t ratio of the pipe is less than 100. If you duct exceeds this, your SIFs are outside the scope of the codes.

3) Your results will be global, system results. Don't expect CAESAR II (or any other piping program) to tell you about local buckling, or any other 2nd order effects.

4) As to what code - where is the duct, what does it transport?

If you duct is not circular, you can't use CAESAR II.

I suggest some reading of Back Coade Newsletters found here.... http://www.coade.com/company_newsletter.asp

And a review of some of the follwing references found here.... http://www.coade.com/support_reference.asp?varflag=Reference

All of this along with a thorough read of one or more codes and a few years experience and Voila your done!

Hi
Please clarify any one of our discussion forum members is it nessasary considering settlement of duct supports in duct analysis.Because recently i have read one turbine exhaust duct analysis report in which, they have been prepared two types of report one is no considering settlement and second one is considering settlement in specific supports.

regarding

Read the code your working under... but in general if its a significant load that will occur it should be considered.

................also, most duct systems are "thin wall" construction (e.g., D/t greater than 100). One of the major considerations in round section industrial duct systems is keeping them "round" (they even want to "flatten" from their deadweight when they are being shipped). You should look for discussions (articles) regarding ring stiffeners and proper ways to reinforce branch connections. There are some pentstock design books that will give you an insight. Look for AISI publications on steel penstock design and look at AWWA manual A-11. Also look at the Lincoln Arcwelding Books for design of "saddle supports". Sometimes rolled angles are used (rolled into circles) as "flanged connections" and this is the ideal place to connect your hangers/supports.

Good luck, John.