Bulk Data Entry Controls the calculation of inertia relief.

Parameter Values Description
VALUE <-2, -1, or 0>

Default = 0, for static subcases

Default = -2, for modal frequency response subcases

INREL controls the calculation of inertia relief. The VALUE parameter can be set equal to -2, -1, or 0.
Requests inertia relief analysis without the need for a SUPORT/SUPORT1 entry.
Requests that inertia relief be performed. SUPORT or SUPORT1 cards are required in the Bulk Data section to restrain rigid body motion. The total number of degrees-of-freedom specified on SUPORT and SUPORT1 cards must be less than or equal to six.
Requests that constrained analysis be performed. SUPORT and SUPORT1 cards are treated like SPC in this case.
METHOD Default = Blank

(Integer > 0)

The METHOD parameter is only applicable if the VALUE parameter is set to -2.

The METHOD parameter references an EIGRL or EIGRA Bulk Data Entry to support inertia relief analysis for models with more than six rigid body modes. Eigenvalue subcases are automatically generated internally to calculate the rigid body modes. Based on these rigid body modes, inertial loads and support points are determined. Refer to Comments 1 through 7.


  1. Eigenvalue subcases are automatically created and do not have to be specified in the model.
  2. The lower bound (V1) of the EIGRL/EIGRA entries should be less than or equal to zero.
  3. If specified, the upper bound (V2) of the EIGRL/EIGRA entries should be greater than or equal to the value set by PARAM,FZERO.
  4. If V2 is not defined, ND field on EIGRL/EIGRA should be input.
  5. ND is recommended to be set greater than the actual number of rigid body modes in the model.
  6. Support degrees of freedom will be generated internally, so SUPORT entry is not required.
  7. It is recommended to use PARAM, FZERO to make sure that the intended rigid body modes are being used to perform inertia relief analysis when using the METHOD parameter.
  8. Inertia relief is supported for nonlinear static analysis. Any nonlinearity (contact, geometry and material) can be included in nonlinear static analysis with inertia relief.