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).
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.
Calculations
The calculations dialog for the Incremental method shows the values defined in the Non-linear analysis algorithm options dialog.
- The number of load increments (used in division of loads into smaller intervals) affects the number of calculation runs. The greater the number of increments, the higher the probability of calculation convergence.
- Maximum number of iterations at each load increment. This number is used to control the calculation process during one load increment.
- The 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.
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