A gap condition, defined by the GP command, is the only nonlinearity allowed in a mode-superposition transient analysis (ANTYPE,TRANS with TRNOPT,MSUP). A gap condition is defined between two master degree of freedom (DOF) nodes or between master DOF nodes and ground. See the GP command for a detailed description of how to define a gap condition.
The following table lists all commands available for defining and managing gap conditions.
| GAP | Specifies "mode-superposition transient gap conditions" as the subsequent status topic. |
| GAPF | Defines the gap force data to be stored in a variable for use in time-history postprocessing. |
| GP | Defines a gap condition for transient analyses. |
| GPDELE | Deletes gap conditions. |
| GPLIST | Lists the gap conditions. |
Gap conditions are not supported when the QR damped mode-extraction method (MODOPT,QRDAMP) is used.
When gap conditions are defined, the default output frequency (OUTRES) is every substep.
Theoretical background for the gap condition is found in Gap Condition in Mode Superposition Transient.