7.7.           IRS_TAM Alter

 

$-----------------------------------------------------------------------

$  Rigid Format 103 - Normal modes analysis

$  MSC/NASTRAN Version 2001 or NX Nastran Version 1.0

$

$

$     ******************************************************

$     *****            COPYRIGHT  (C)  2003            *****

$     *****          BY ATA ENGINEERING INC.           *****

$     *****             ALL RIGHTS RESERVED            *****

$     ******************************************************

$

$     09-03- ATA/Paul Blelloch

$

$  Description:

$

$  This alter performs an Improved Reduced System (IRS) reduction

$

$  O'Callahan, J, "A Procedure for an Improved Reduced System (IRS) Model,"

$  7th International Modal Analysis Conference, Las Vegas, NV 1989

$

$  The IRS reduction is a modification of the standard Guyan reduction

$  implemented using ASET cards in Nastran.  It adds a dynamic correction

$  term that can result in more accurate modes using the reduced mass and

$  stiffness matrices.

$

$  The equations for the IRS shapes are as follows:

$

$                    -1                     -1

$  GOAT = GOATS - KOO  (MOA + MOO*GOATS)*MAA  *KAA

$

$  where:

$                                                     -1                                            

$  GOATS - Standard Guyan reduction shape matrix (-KOO  *KOA)

$  MAA   - Standard Guyan reduced mass matrix

$  KAA   - Standard Guyan reduced stiffness matrix

$

$  No special processing is required to use this alter.  Simply include the

$  alter with standard ASET cards defining the reduced DOF.  If the reduced

$  mass matrix is desired it can be requested with a PARAM,EXTOUT,DMIGPCH.

$

$

$  Special instructions to use this alter:

$-----------------------------------------------------------------------

$  FILE MANAGEMENT SECTION (FMS)

$

$   No special input is required.

$

$-----------------------------------------------------------------------

$  EXECUTIVE CONTROL DECK

$

$    SOL 103

$    Include this alter immediately before the CEND statement.

$

$-----------------------------------------------------------------------

$  CASE CONTROL DECK

$

$    No special input is required.

$

$-----------------------------------------------------------------------

$  BULK DATA DECK

$

$    Optional parameters:

$

$

$-----------------------------------------------------------------------

$  EXAMPLE NASTRAN DECK

$

$

$    ASSIGN  MASTER='gpsc_aset.MASTER'

$    ASSIGN  DBALL ='gpsc_aset.DBALL'

$    $

$    SOL     103

$    INCLUDE irs.v2001

$    CEND

$    $

$    TITLE    = GENERAL PURPOSE SPACECRAFT

$    SUBTITLE = IRS REDUCED MODES

$    LABEL    = MY ASET DOF

$    $

$    SPC = 1

$    METHOD = 50                 $ Modes to 50 Hz

$    $

$    DISP(PLOT) = ALL            $ Recover but don't print displacements

$    $

$    BEGIN BULK

$    $

$    ... Standard Bulk data including ASET cards ...

$    $

$    ENDDATA

$

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