**PSDCOM****PSDCOM**, `SIGNIF`

, `COMODE`

, , `ForceType`

**Specifies the power spectral density mode combination
method.**

`SIGNIF`

Combine only those modes whose significance level
exceeds the`SIGNIF`

threshold. For PSD response
(**SPOPT**,PSD), the significance level is defined
as the modal covariance matrix term, divided by the maximum modal
covariance matrix term. Any term whose significance level is less
than `SIGNIF`

is considered insignificant
and is not contributed to the mode combinations. The higher the `SIGNIF`

threshold, the fewer the number of terms used. `SIGNIF`

defaults to 0.0001. If `SIGNIF`

is specified as 0.0, it is taken as 0.0.

`COMODE`

First `COMODE`

number of
modes to be actually combined. `COMODE`

must
always be less than or equal to `NMODE`

(input
quantity `NMODE`

on the **SPOPT** command). `COMODE`

defaults to `NMODE`

. `COMODE`

performs
a second level of control for the first sequential `COMODE`

number of modes to be combined. It uses the significance level
threshold indicated by `SIGNIF`

and operates
only on the significant modes.

**ForceType**Label identifying the forces to be combined:

**STATIC**
| — | Combine the modal static forces
(default). |

**TOTAL**
| — | Combine the modal static plus inertial
forces. |

## Notes

This command is also valid for PREP7. This command is valid
only for **SPOPT**,PSD.