Parameter

Values

Description

GBUCK

YES, NO, 1 or 0 Default = 0

Controls global buckling constraint.

Use 0, NO, or omit this parameter for no global buckling constraint.

Use 1 or YES to activate global buckling constraint.

When activated, the global buckling constraint affects those subcases in which buckling eigenvalues (LAMA) are constrained. For these subcases, when this parameter is activated, only a single buckling mode needs to be constrained with a lower bound. The GBUCK parameter will then ensure that all buckling eigenvalues that are less than or equal to the lower bound defined in this constraint will be considered within the optimization problem.

If there is more than one buckling eigenvalue constraint (or if the single constraint is not a lower bound) in any buckling subcase, OptiStruct will terminate with an error.

In addition, when this parameter is activated, the EIGRL card referenced within the buckling subcase must define a range of eigenvalues between 0.0 and some value larger than the lower bound defined on the buckling eigenvalue constraint definition. If a range is not defined, OptiStruct will terminate with an error.

The MAX_BUCK parameter on the DOPTPRM card controls the maximum number of buckling modes for each subcase that are considered in the optimization. This has a default value of 10. If more critical modes are involved, this parameter may need to be increased.

Although the MAX_BUCK parameter controls the number of modes considered in the optimization, the EIGRL card referenced in the subcase controls the number of modes calculated at each iteration.