Spectral representation-based efficient simulation method for fully non-stationary spatially varying ground motions

As one of the most commonly-used simulation methods, the spectral representation method (SRM) has been utilized to generate fully non-stationary spatially varying ground motions. However, this method usually fails to simulate these ground motions at a large number of interesting locations because of the heavy computational cost of the decomposition of spectral matrices and the superposition of harmonic functions, especially for simulations with time-frequency coupled modulation functions. To address this issue, this study develops an efficient SRM-based method based on a simple interpolation strategy and a quadratic regularization projected Barzilai–Borwein assisted non-negative matrix factorization (QRPBB-NMF). Concretely, the distribution of interpolation nodes is predetermined via spectral feature analysis and only the spectral matrix decomposition at these nodes is required. Then, QRPBB-NMF is introduced to decouple the decomposed spectra into the sum of the products of various time and frequency expressions. Finally, a simple spline interpolation is carried out for these expressions, thereby approximately achieving the SRM-required matrix decomposition in a decoupled manner. The developed method can decrease the operand of the matrix decomposition and invoke the Fast Fourier Transform to speed up the harmonic superposition. A case study in which the fully non-stationary spatially varying ground motions of a tunnel are simulated proves the effectiveness of the developed method in terms of accuracy and efficiency.