how can we analize the ducting.

Is it possible in CAESAR-II?

what are the methods to do it?

can any one help me.

CAESAR II can only analyze circular cross sections, so if your ducting is rectangular CAESAR II is the wrong application. Even if you have a circular cross section, CAESAR II uses a linear elastic 3D Beam Element. Second order effects (such as buckling) are beyond the abilities of this element - so again CAESAR II is the wrong application.

Can you be more specific with what you're trying to do?

Even if the ducting is circular, the name suggests very thin wall and high D/t ratio ... quite probably outside any Code limits to start with ?

As Rich points out you are not going to find much in the way of valid duct analysis software that employs beam theory for structural analysis, and as MoverZ points out there are several good reasons for that. The ASME B31 Codes for Pressure Piping do not apply to what we generally consider ducting (non-circular cross sections and/or very large D/t ratios).

Perhaps you should look to the SMACNA Standards and the ASHRAE Standards for design/analysis help. Also there is a ASCE book that is sometimes helpful:

"The Structural Design of Air and Gas Ducts for Power Stations and Industrial Boiler Application" ISBN-0-7844-0112-8.

This ASCE book is quite comprehensive and it is even more useful than its name implies.

Duct systems OFTEN employ expansion joints to accommodate expansion / contraction and support design methods are very important. Also duct systems often require "stiffening rings" as both positive and negative pressures are common. There are some free guides that address seismic design of ductwork. Look to the "American Lifelines" series of publications for seismic design help.

Also look here:

www.fema.gov/library/file?type=originalAccessibleFormatFil...55-11dc-8099-000bdba87d5b

Good luck, John.