Input windows require all data necessary for determination of natural frequencies, such as mass shapes and eigenvalue solvers.
The RF-/DYNAM Pro - Natural Vibrations add-on module determines the lowest eigenvalues of the structure. The number of eigenvalues can be adjusted. Masses are directly imported from load cases or load combinations (with optional consideration of total masses or a load component in the direction of gravity).
Additional masses can be defined manually at nodes, lines, members, or surfaces. Furthermore, it is possible to control the stiffness matrix by importing normal forces or stiffness modifications of a load case or combination.
![Reduction of Building to Cantilever Structure: The individual mass points represent the floors. The deflection due to the normal compression forces shown in (a) is (b) converted into equivalent moments of displacement or shear forces [2].](/en/webimage/009762/2420261/01-en-png-12-png.png?mw=512&hash=8189361dbff525c2ff39c36a72a1ca91810208f6)
![Reduction of Building to Cantilever Structure: The individual mass points represent the floors. The deflection due to the normal compression forces shown in (a) is (b) converted into equivalent moments of displacement or shear forces [2].](/en/webimage/009762/2420261/01-en-png-12-png.png?mw=350&hash=dd36dc43123116724231958668ad6cdcb13a0169)
