Rayleigh damping
Posted: Sat Jul 25, 2026 5:38 am
Dear STKO,
I have a question regarding the implementation of Rayleigh damping in OpenSees/STKO for seismic analysis of semi-infinite soil domains.
In conventional Rayleigh damping, the mass- and stiffness-proportional coefficients are usually determined from the first and second natural frequencies of the system. However, in the case of a semi-infinite soil domain modeled with absorbing boundaries (e.g., ASDAbsorbingBoundary or Lysmer boundaries), the soil does not possess discrete natural modes in the classical sense, since it represents a continuous medium with a continuous spectrum rather than a finite system.
In such a case, how should the two reference frequencies required for computing the Rayleigh damping coefficients be selected?
Thank you very much for your time and valuable guidance.
I have a question regarding the implementation of Rayleigh damping in OpenSees/STKO for seismic analysis of semi-infinite soil domains.
In conventional Rayleigh damping, the mass- and stiffness-proportional coefficients are usually determined from the first and second natural frequencies of the system. However, in the case of a semi-infinite soil domain modeled with absorbing boundaries (e.g., ASDAbsorbingBoundary or Lysmer boundaries), the soil does not possess discrete natural modes in the classical sense, since it represents a continuous medium with a continuous spectrum rather than a finite system.
In such a case, how should the two reference frequencies required for computing the Rayleigh damping coefficients be selected?
Thank you very much for your time and valuable guidance.