Geometric Nonlinearity Parameters

The Geometric Nonlinearity Parameter options appear on the Load Case Data form when the analysis type is nonlinear static or nonlinear direct-integration time-history.

The geometric nonlinearity options available for nonlinear static and nonlinear direct-integration time-history analysis consist of the following:

Tips:  The large displacement option should be used for cable structures undergoing significant deformation, and for buckling analysis, particularly for snap-through buckling and post-buckling behavior. Cables (modeled using frame objects) and other elements that undergo significant relative rotations within the element should be divided into smaller elements to satisfy the requirement that the strains and rotations within an element are small.

For most other structures, the P-delta option is adequate, particularly when material nonlinearity dominates.

If reasonable, it is recommended that the analysis be performed first without geometric nonlinearity, adding P-delta, and possibly large-displacement effects later.

When continuing one analysis case from another, it is recommended that they both have the same geometric-nonlinearity settings.

Note: Geometric nonlinearity is not available for the FNA method.