Statistical modeling of evolutionary power spectral density parameters of ground motions
In engineering practices,the deterministic values of the response spectrum in accord-ance with seismic design codes are generally applied as evolutionary power spectral density(EPSD)parameters of ground motions.Although this treatment is convenient for engineering ap-plications,it comes with two evident disadvantages.On the one hand,parameters are not ob-tained from measured strong motion records,which makes them highly empirical.On the other hand,the ground motion samples generated by deterministic parameters are extremely regular and exhibit unitary engineering characteristics,which cannot fully reflect the randomness of ground motions.To overcome the abovementioned challenges,we selected 1 766 strong motion records in the main axis direction from PEER and divided them into 15 groups based on the site categories suggested by the Seismic Ground Motion Parameters Zonation Map of China.Subse-quently,the EPSD parameters of strong motion records were identified.Combined with the K-S test and BIC information criterion,the optimal probability models for each parameter were determined.Finally,based on statistical modeling results of EPSD parameters,representative time histories of site categories Ⅱ and Ⅲ were generated through the dimension reduction meth-od.In contrast to the recommended values from the Code for Seismic Design of Buildings,the parameters suggested in this study were derived from measured records and possessed significant randomness,thus avoiding the simplification and regularization of engineering characteristics of ground motion samples.