PARAM, PBUSHTF

Bulk Data Entry Specifies the reference frequency value for scaling factor lookup to update the nominal PBUSH Stiffness (K) values.

Parameter Options Values Description
PBUSHTF FREQ <Real>

No default

 This parameter is used to specify the reference frequency value for scaling factor lookup to update the nominal PBUSH Stiffness (K) values. The scaling factor values are multiplied with the nominal PBUSH Stiffness (K) values to generate the scaled K values.
The scaling factor lookup utilizes the following two options:
  1. TIDi tables for corresponding dof on the KSCALE continuation line on PBUSHT and/or,
  2. TRA and/or ROT tables on this parameter (overridden by KSCALE TIDi).
See Comment 1
TRA <Integer>

Default = Blank

 Used in conjunction with FREQ, to lookup the scaling factor to update the nominal PBUSH Stiffness (K) values for Translational Degrees of Freedom (DOF 1 through 3). The specified integer value references a TABLED1 Bulk Data Entry consisting of Frequency (X) vs Stiffness Scaling Factors (Y).
ROT <Integer>

Default = Blank

 Used in conjunction with FREQ, to lookup the scaling factor to update the nominal PBUSH Stiffness (K) values for Translational Degrees of Freedom (DOF 1 through 3). The specified integer value references a TABLED1 Bulk Data Entry consisting of Frequency (X) vs Stiffness Scaling Factors (Y).

Comments

  1. In the presence of KSCALE scaling factor tables (on PBUSHT), the specified FREQ is used to lookup the corresponding scaling factors from the KSCALE tables for corresponding degrees of freedom. In such cases, the TRA/ROT values are ignored. However, if some degrees of freedom on KSCALE are blank, then, the TRA/ROT tables are used for scaling factor lookup for those degrees of freedom.
  2. This parameter only applies to the stiffness (K) values on the PBUSH entry.
  3. These updated nominal PBUSH Stiffness (K) values are used in Normal Modes calculations in Modal Frequency Response Analysis. This parameter does not affect the PBUSH stiffness values in the Modal FRF part of the solution. In the Modal Solution phase, the PBUSH properties used for the solution would be based on the original PBUSH values and the scaling on PBUSHT (not affected by PBUSHTF).
  4. If PBUSHT and PARAM,BUSHSTIF are not present, then PBUSHTF applies to all degrees of freedom on the PBUSH entry depending on the TRA and/or ROT tables. If only TRA is present, then only dof 1 through 3 are scaled, and if only ROT is present, then only dof 4 through 6 are scaled.
  5. If PARAM,BUSHSTIF is present and PBUSHT is not specified, then stiffness of all corresponding degrees of freedom that are below BUSHSTIF are scaled based on PBUSHTF. However, if the value of a dof's stiffness is greater than BUSHSTIF, the value is replaced by BUSHSTIF and scaling via PBUSHTF is not applied to this particular stiffness.
  6. Scaling for multiple PBUSH via PBUSHTF follows the same process as mentioned above.
    PBUSHTF KSCALE (dof 1-6) + TRA + ROT KSCALE (dof 2,5) + TRA + ROT Only TRA Only ROT Only TRA+ROT
    TRA Table Scaling (dof 1-3) No Yes (dof 1,3) Yes (dof 1-3) No Yes (dof 1-3)
    ROT Table Scaling (dof 4-6) No Yes (dof 4,6) No Yes (dof 4-6) Yes (dof 4-6)
    KSCALE Table Scaling (wherever TID is specified) Yes (dof 1-6) Yes (dof 2,5) No No No