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ALTER TO PERFORM MODAL TRANSIENT ANALYSIS ON A 
STRUCTURE WITH NON-ZERO INITIAL ACCELERATION

Alter Name    mtacca.v2001


Purpose

To allow use of modal transient analysis to solve for a structure 
which has non-zero 
initial accelerations.  This DMAP Alter assumes that the initial condition 
is a 
steady-state acceleration based on the initial loading. The alter 
performs a static 
solution (in modal coordinates) to the initial loading, subtracts 
the initial loading from all 
applied loadings, solves the transient analysis, then adds the initial 
static solution to the 
results.

Solution Sequence

SOL 112.

Input

  Executive Control

    Include 'mtacca.v2001'.  

  Case Control

    Standard Case Control for modal transient analysis

  Bulk Data

    PARAM,RBMODES,ii      - default = 6

    RBMODES is the number of rigid-body modes in the solution.

    If RBMODES is positive, then the rigid-body displacements will be 
    removed from the solution    

    IF RBMODES is negative, the rigid-body displacements are not removed 
    from the solution.      

Output

Standard output from a modal transient solution.

Limitations

  The structure is assumed to be in a steady-state acceleration at time 
  0.0.

Sample Files


Two files are included to demonstrate the use of this DMAP Alter.


  mtacc1.dat - free-free model with 6 rigid-body modes and an initial 
  acceleration. Rigid-body displacement included.       

  mtacc2.dat - free-free model with 6 rigid-body modes and an initial 
  acceleration. Rigid-body displacement not included.      


Additional Documentation

None.