Uncoupled spectral analysis with non-proportional damping

The use of normal modes of vibration in the analysis of structures with non-proportional damping reduces the number of governing equations, but does not decouple them. A common practice consists in decoupling the equations by disregarding the off-diagonal elements of the modal damping matrix. This paper proposes a method based on the asymptotic expansion of the modal transfer matrix to take into account the modal coupling in Gaussian spectral analysis. First, the mathematical background is introduced, then the relevance of the method is illustrated within the context of the analysis of a large and real structure submitted to wind loadings.