Subfunction > Rayleigh coefficients
Calculation of the equivalent Rayleigh coefficients ALPHA and BETA by specifying damping ratios valid for 2 different frequencies. RmBridge does not offer an inverse function for calculating the effective damping ratio for a certain frequency from predefined Rayleigh coefficients.
Note: Design codes and guidelines commonly define a relevant damping ratio not dependent on frequency. In order to approximate this presumption with Rayleigh damping as accurate as possible, the relevant natural frequencies should be determined, and the given damping ratio assigned to the 2 most important ones (w1, w2). The effective calculatoric damping of vibrations with frequencies between w1 and w2 is less, and that of frequencies outside this range is higher.
| Setting | Description |
|---|---|
| w1 | First frequency value (defined as angular velocity rad/sec) with predefined damping ratio (ksi1). Usually the first relevant natural frequency (mind the excitation direction for relevance). |
| ksi1 | Damping ratio (ratio of actual damping to critical damping) of vibrations with frequency w1. |
| w2 | 2nd frequency value (defined as angular velocity rad/sec) with predefined damping ratio (ksi2). Usually the first relevant natural frequency (mind the excitation direction for relevance). |
| ksi2 | Damping ratio (ratio of actual damping to critical damping) of vibrations with frequency w2. |