The aim of Modal Analysis is to study the dynamic behavior of a model. It determines natural frequencies and calculates modal masses and participation factors. This task is described in detail in Natke [1], Tedesco [2], and Stelzmann [3].
The Modal Analysis add-on determines the lowest eigenvalues of a structure. You can specify how many eigenvalues are to be determined. You can import the relevant masses from load cases or load combinations (with the option of considering the total load or the Z component only), or you can define them manually as additional masses at nodes, lines, members, or surfaces. Furthermore, you can influence the stiffness matrix by considering axial forces or stiffness changes of a load case or a load combination.
The currently available design standards and a summary of the functional scope can be found in the respective product description of the Modal Analysis add-on for RFEM 6 / RSTAB 9.
