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