$-----------------------------------------------------------------------
$ 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 a Modal TAM reduction
$
$ Kammer, D.C., "Test-Analysis Model Development Using an Exact
$ Modal Reduction," The International Journal of Analytical and
$ Experimental Modal Analysis, October 1987, pp. 174-179
$
$ A Modal TAM reduction is an alternative to the static reduction
$ implemented using ASET cards in Nastran. It uses the FEM mode shapes
$ to construct reduced mass and stiffness matrices that will predict
$ the FEM shapes as long as the shapes are linearly independent at the
$ measured (ASET) DOF.
$
$ The equations for the Modal TAM shapes are as follows:
$
$ T -1 T
$ GOAT = [PHIO]*([PHIA] *[PHIA}) *[PHIA]
$
$ where:
$
$ PHIA - A-set partition of FEM mode shapes
$ PHIO - O-set partition of FEM mode shapes
$
$ 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)
$
$ The FEM mode shapes must be made available. If these are stored in
$ OUTPUT2 or OUTPUT4 forma using the write_modes alter they must be
$ assigned using INPUTT2 or INPUTT4 cards as follows:
$
$ ASSIGN INPUTT4=fem_modes.op4 UNIT=11
$
$ or
$
$ ASSIGN INPUTT2=fem_modes.op2 UNIT=11
$
$ Note that a formatted OUTPUT4 file can be used as follows
$
$ ASSIGN INPUTT4=fem_modes.op4 UNIT=11 FORMATTED
$
$-----------------------------------------------------------------------
$ 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:
$
$ PARAM,OMODES,I <0 : Read FEM modes from OUTPUT2 file UNIT = |OMODES|
$ 0 : Read FEM modes from DMIG cards in bulk data
$ >0 : Read FEM modes from OUTPUT4 file UNIT = OMODES
$
$ PARAM,N1,I : 1st FEM mode to use for hybrid TAM (default = 1)
$
$ PARAM,N2,I : Last FEM mode to use for hybrid TAM (default = all)
$
$ If the FEM modes are defined on DMIG cards, these must be included
$ in the bulk data
$
$-----------------------------------------------------------------------
$ EXAMPLE NASTRAN DECK
$
$
$ ASSIGN INPUTT4='gpsc_modes.op4', UNIT=13
$ ASSIGN MASTER='gpsc_aset.MASTER'
$ ASSIGN DBALL ='gpsc_aset.DBALL'
$ $
$ SOL 103
$ INCLUDE modal_tam.v2001
$ CEND
$ $
$ TITLE = GENERAL PURPOSE SPACECRAFT
$ SUBTITLE = MODAL TAM 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
$ $
$ PARAM,OMODES,13
$ $
$ ... Standard Bulk data including ASET cards ...
$ $
$ ENDDATA
$
$-----------------------------------------------------------------------