Bladed modal analysis cannot cope with a support structure which contains too large a variation in element stiffness or mass. There is a limit on the stiffness values that can be used as explained in this article
Users may want to insert an offset node and therefore define a massless and rigid element. However this cannot be done by editing mass and stiffness of the element as it causes numerical problems like ill-conditioned matrices which cannot be used in the calculation. The solution is to use project info to define rigid elements.
Versions of Bladed affected: 4.0 onwards.
Last updated: 25.04.2023
1. Define low density dummy members in the "Tower" screen, for example like the member 153 in the following figure.
2. Go to "File" -> "Project Info" -> tick the option "Turbine calculations(dtbladed.exe)"-> click "Define"
3. In the "Special Data" screen, list all the dummy members using the following code. Then, the dummy members will be rigid. The stiffness property defined in the "Tower" screen will be replaced.
