When a structure includes non-linear elements (such as cables, unilateral supports, and material plasticity), calculations are performed incrementally.

Non-linear analysis consists of incremental application of a load. Calculations and loads are not considered as a whole, but are gradually increased until successive states of equilibrium are solved.

Non-linear structure behavior may be associated with a single structure element (structural or material non-linearity), or it may result from a non-linear relation between forces and deformation in a whole structure (geometric non-linearity).

The dialog presents the following values (defined in the Non-linear analysis algorithm options dialog):

- Number of load increments (used in division of loads into smaller intervals) effects the number of calculation runs. The greater number of increments, the higher probability of calculation convergence.
- Maximum number of iterations at each load increment. This is used to control the calculation process during one load increment.
- Allowable number of reductions (modifications) of the step length defines the maximum number of times that the load increments change if the calculations are not convergent.

Convergence checks are made and iterations are stopped as soon as the state of equilibrium is reached. Displacement increments dUn and the unbalanced forces dFn are then equal to zero, less than the defined accuracy values for both quantities.