An overview of Ritz and Eigen vectors, taken from the CSI Analysis Reference Manual (Modal Analysis > Overview, page 323), is given as follows:
- Eigenvector analysis determines the undamped free-vibration mode shapes and frequencies of the system. These natural modes provide an excellent insight into the behavior of the structure.
- Ritz-vector analysis seeks to find modes that are excited by a particular loading. Ritz vectors can provide a better basis than do Eigenvectors when used for response-spectrum or time-history analyses that are based on modal superposition.
You, the engineer, may
The user should determine the type of modes which you feel are the most appropriate.
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- Sources of flexibility available during calculation of Eigen and Ritz modes include:
- Consideration of P-Delta and other nonlinear effects
- Modes at different stages of construction
- Frequency shifts for specialized loading