Effects of spatial variation of ground motions on large multiple supported structures

The spatial variability of ground motions recorded during 17 earthquakes by a strong motion accelerograph array in Taiwan (SMART-1) is used. The power spectral density functions and envelope functions of the ground motion are presented and compared to previous results. A coherency function is suggested for pairs of stations as a function of both frequency and also the projected separation distance between the stations in the wave propagation and transverse directions, respectively. The apparent velocities of the seismic waves are studied in different time windows as a function of frequency. A method is developed to simulate and interpolate multiple ground motions that are spatially correlated, quasi-stationary, and response spectrum compatible. Also, the equations that describe structural response under multiple ground motion excitations are formulated in the cases both with and without soil-structure interaction effects. Numerical methods for solving these equations in the frequency domain are presented.; A computer program SSIAM is developed. It can simulate and interpolate spatially correlated, stationary or quasi-stationary multiple ground motions compatible with the prescribed ground motion properties and the given response spectrum. It then uses these simulated ground motions as the multiple inputs to solve the structural responses. By using program SSIAM, some examples of ground motion simulation and interpolation are calculated. The results are presented and compared to the prescribed ground motion properties; also, some examples of structural responses under the simulated multiple ground motion excitations are calculated with soil-structure interaction effects. The results are presented and discussed. The results show that it is important to consider the ground motion wave propagation effects in the large dimensional structure seismic response analysis.