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Modeling of Seismic Motion Time Histories with Time-Variable Predominant Frequencies

Seismic motions occurring at sites with soft soils and located hundreds of kilometers away from the earthquake focus can be long-lasting and show changes in the frequency spectrum. Although these motions are characterized by low values of peak ground accelerations, they can lead to resonance vibration of buildings and structures. An especially dangerous situation occurs when the seismic load frequencies decrease simultaneously with the natural frequencies of the structure that is damaged during the earthquake. For designing buildings and structures, and for carrying out probabilistic assessment of seismic risk taking into account the changes in time of the seismic load spectrum, an ensemble of seismic motion time histories is required. The article presents a method for modeling unsteady random processes with a variable predominant frequency in the Simulink software system environment.