There are two solution methods for the linear time history analysis in the RF-/DYNAM Pro add-on module. What is the difference between both of them?

Answer

The two solution methods 'Linear Modal Analysis' and 'Linear Implicit Newmark Analysis' are available.

Linear Modal Analysis

This solution method uses a decoupled structure that is based on the eigenvalues and mode shapes of the structure. It is essential to assign a defined natural vibration case.

This method should only be used if a sufficient number of eigenvalues of the structure have been calculated in the natural vibration case. This means that care should be taken to achieve an effective modal mass factor of the total structure of approximately 1 in all governing directions. If this is not possible, this method will lead to inaccurate results.

Linear Implicit Newmark Analysis

This is a direct time stepping method that does not require a natural vibration case and requires enough small time steps to achieve exact results.

This method is recommended for complex structures, which would require a very large number of mode shapes in order to achieve an effective modal mass factor of around 1.

If a sufficient number of eigenvalues can be guaranteed by means of the linear modal analysis, both solution methods lead to approximately the same results. For more information about both methods see the RF-DYNAM Pro manual.

Keywords

Solution method Solver Time history Newmark Modal analysis

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