# Sequential

Sequential analysis is any type of structural analysis performed on a structure under prior loading (also termed preloading or prestressing).

The response of a structure is affected by its initial state, which is affected by the preloading/prestressing applied prior to the analysis of interest. Examples of sequential analysis include analysis of rotorcraft blades under centrifugal preloading, pillar-like structures under compressive preloading, preload arising from the pretensioning of bolts on a structure, and so on. Use SimSolid to account for such preloading or prestressing effects.

You can add or remove loads from sequential analyses to simulate additional loading or unloading, respectively.

## Example

- Structural 1 – Preload
- Immovable 1
- Structural 2, Linked to Structural 1 – Loading
- Immovable 1
- Structural 3, Linked to Structural 2 – Unloading
- Immovable

When the prestressing subcase is linear static, the prestressed stiffness matrix is given by:

- $\overline{\text{K}}$
- Prestressed stiffness matrix
- $\text{K}$
- Original stiffness matrix
- ${\text{K}}_{\text{\sigma}}$
- Geometric stiffness matrix that defines the prestressing. This is based on the stresses of the preloading static subcase.

- If the preloading is compressive, it typically has a weakening effect on the structure (for example, column or pillar under compressive preloading).
- If the preloading is tensile, it typically has a stiffening effect (for example, rotorcraft blade under centrifugal preloading).

When the prestressing loadcase is a non-linear static subcase, the prestressed stiffness matrix $\overline{\text{K}}$ includes the geometric stiffness matrix ${\text{K}}_{\text{\sigma}}$ , and also accounts for the changes of $\text{K}$ due to the converged contact status carried over from the prestressing loadcase to the prestressed loadcase.