Geometric Stiffness Models

Geometric stiffening models account for changes in structural response due to structural deflection from the reference (undeflected) state. Bladed provides models that include contributions from element axial and shear internal forces.

There are three geometric stiffness settings available for the blades:

• AxialLoadsOnly: The effect of internal forces along the element axis on dynamic response is included. This primarily accounts for “centrifugal stiffening” in the blade dynamic response. Geometric stiffness axial and shear forces are included when calculating the internal member loads. See Geometric stiffness due to element axial forces for more details.
• FullModelWithOrientationCorrection: The effect of internal axial and shear forces on dynamic response is included. This model can enhance the prediction of torsion deflection in the blade. This model should be used with caution as it is only accurate when deflections within each blade part remain small (less than ~5-7 degrees). If several blade parts are used then this model can be activated to improve the accuracy of the solution, and will allow use of fewer blade parts than when using the AxialLoadsOnly model. See Geometric stiffness due to element shear forces for more details.
• InternalLoadsOnly: Not a recommended option. Geometric stiffness forces are ignored for the purposes of evaluating the dynamic response, but are included when calculating the internal member loads.

When evaluating the geometric stiffness effect of shear forces, it is crucial to consider to account for the change in orientation of the torsion axis of the blade elements due to deflection. Whether this effect is included depends IgnoreAxesOrientationDifferencesForShear is set true or false. For more details see Geometric stiffness due to element shear forces or the theory section about Translation and orientation offset between neutral and shear axes.