PARAM, TRAKMETH

Bulk Data Entry Used to select the criterion employed for mode tracking.

Parameter Values Description
TRAKMETH <0, 1, 2>
Defaults:
  • The value of this parameter is 0 if it is not included in input file.
  • If this parameter is included in the input file, but no value is provided, then running the program will result in an error.
 TRAKMETH is a parameter that can be used to select the criterion employed for mode tracking. This can also be controlled via the MODTRAK Bulk Data Entry.
There are three tracking criteria available for selection in the current implementation:
  • Mass cross-orthogonality check (CORC)
  • Modal assurance criterion (MAC)
  • Modal assurance criterion square root (MACSR)
0 (Default)
The Mass cross-orthogonality check (CORC) criterion is used for mode tracking. This performs a mass orthogonality check of the current and previous eigenvectors after reanalysis. CORC is implemented as:
CORC ( Φ ( k − 1 ) , Φ ( k ) ) = ( Φ ( k − 1 ) ) T M ( k ) Φ ( k )
1
The Modal assurance criterion square root (MACSR) criterion is used for mode tracking. This criterion essentially calculates the dot product of the two unit vectors associated with the current and previous eigenvectors. MACSR is implemented as:
MACSR ( Φ ( k − 1 ) , Φ ( k ) ) = ( Φ ( k − 1 ) ) T Φ ( k ) | Φ ( k − 1 ) | | Φ ( k ) |
2
The standard modal assurance criterion (MAC) is used for mode tracking. MAC is implemented as:
MAC ( Φ ( k − 1 ) , Φ ( k ) ) = [ ( Φ ( k − 1 ) ) T Φ ( k ) | Φ ( k − 1 ) | | Φ ( k ) | ] 2
Where,
Φ ( k )
Current eigenvector.
Φ ( k-1 )
Previous eigenvector.
M ( k )
Mass matrix.

Comments

  1. PARAM, MODETRAK, YES or the subcase selector MODTRAK = YES or SID should be added to the input file to activate mode tracking.