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*BOUNDARY

Keyword type: step or model definition

This option is used to prescribe geometrical boundary conditions applied to the structure. Optional parameters are OP and AMPLITUDE. OP can take the value NEW or MOD. OP=MOD is default and implies that previously prescribed displacements remain active in subsequent steps. Specifying a displacement in the same node and direction for which a displacement was defined in a previous step replaces this value. OP=NEW implies that previously prescribed displacements are removed. If multiple *BOUNDARY cards are present in a step this parameter takes effect for the first *BOUNDARY card only.

The AMPLITUDE parameter allows for the specification of an amplitude by which the boundary values are scaled (mainly used for nonlinear static and dynamic calculations). This only makes sense for nonzero boundary values. Thus, in that case the values entered on the *BOUNDARY card are interpreted as reference values to be multiplied with the (time dependent) amplitude value to obtain the actual value. At the end of the step the reference value is replaced by the actual value at that time, for use in subsequent steps.

A distinction is made whether the conditions are homogeneous (fixed conditions) or inhomogeneous (prescribed displacements).

Subsections

- Homogeneous Conditions
- Inhomogeneous Conditions

Next: Homogeneous Conditions Up: Input deck format Previous: *BEAM SECTION Contents