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Subject: Re: STRUC - Modal Analysis Following Nonlinear Analysis.
Author: Keith DiRienz
Date: 2003-02-13 20:27:00

Kasidit,
The correct procedure is discussed in detail in Section 3.13 of the
Structural Analysis Guide - "Prestressed Modal Analysis of a Large
Deflection Solution" in the online documentation.
Keith

Keith DiRienz, P.E.

FEA Technologies
33822 Bridgehampton Drive
Dana Point, CA 92629
Ph. 949.481.4946
Fax: 949.481.4947
Email: fea-technologies@c...
Web site: www.members.cox.net/fea-technologies

At 2/13/2003 05:17 PM, you wrote:
>Dear ANSYS Users:

>I'm trying to perform a modal analysis after a nonlinear analysis. Some
>elements of my structure yield after being subjected to a load in a
>nonlinear analysis. If the modal analysis following the nonlinear
>analysis is correctly done, natural frequencies of this structure are
>supposed to be lower, as the yielding elements result in a lower
>structural stiffness matrix.

>However, after I performed a modal analysis after the nonlinear analysis,
>natural frequencies of the structure were still the same as the "virgin"
>structure. Could you please tell me what is the right way to do a modal
>analysis after a nonlinear analysis? A part of my input file is shown
>below:

>! Last Load Step in Nonlinear Analysis

>solve
>finish

>! Modal Analysis

>resume,file,db
>/solu
>antype,2
>modopt,lanb,40
>m,all,all
>outpr,basic,1
>outres,all,1
>save
>solve
>finish

>I think I must have missed some points between the nonlinear analysis and
>modal analysis. Thank you for your helps.

>Best Regards,

>Kasidit Chansawat

>Graduate Student
>202 Apperson Hall,
>Oregon State University,
>Corvallis, OR 97331
>Phone: 541.737.2728
Posts possibly associated with message #46756AuthorDateScore
46755STRUC - Modal Analysis Following Nonlinear Analysis.Kasidit Chansawat2003/02/13 
46756Re: STRUC - Modal Analysis Following Nonlinear Analysis.Keith DiRienz2003/02/13 
46772Re: STRUC - Modal Analysis Following Nonlinear Analysis.William VanFossen2003/02/14