Generalized Complex Damping and Spectral Integration

Abstract

The spectral analysis and the corresponding integrations of the seismic‐response spectra of an offshore platform are presented. Any shape of the input power spectrum of the ground motion is described by piecewise straight lines for approximation. Both the effects of nonlinear drag force and modal‐damping coupling are taken into account in the analysis. The nonlinear drag force is linearized by the method of the least squares in the statistical sense, and the modal‐damping coupling is uncoupled by the use of the concept of generalized complex damping. As a consequence, the integration formulas of the response spectra for all vibrational modes have been derived, which may prove useful and efficient for computation.