Component Mode Synthesis of Structures with Geometric Stiffening in Msc/nastran

Implementation of modal synthesis in MSC/NASTRAN is usually done using structural solution sequence based Direct Matrix Abstraction Programs, DMAPs. However, modal synthesis in MSC/NASTRAN without using structural solution based DMAPs is possible. But either method is tailored towards supporting components that have no non-linearity. Certain components, such as the solar arrays of the space station, exhibit non-linear behavior in the form of geometric stiffening. For structures with such components, the standard method of modal synthesis does not work. Special DMAPs need to be developed for these components. Realizing that the only difference between components with no geometric stiffening and those with geometric stiffening is in the method of obtaining the stiffness matrix, a simple solution is provided in this paper. The solution is to use the procedure for modal synthesis for components with no geometric stiffening by replacing the stiffness matrix with the one obtained from geometric stiffening. This approach, along with the recommended check runs, has been shown to work successfully in this paper. The method is also shown to be extremely efficient.