Analysis of the application of the near-fault ground motion functions

Abstract eng:
Near-fault ground motions are characterised, in case of inter-plate earthquakes, by pulse actions with large periods and velocities, and moderate ones in case of intra-plate earthquakes. The pulse period depends on the earthquake magnitude. The same relationships exist between ground motion velocities and pulse periods. Using the main characteristics of near-fault ground motions, some research works have proposed simple models of pulse shapes that describe these ground motions. We suggested the new possibility to modelling the velocity pulses to use algebraically functions and calculated the acceleration response spectra from our artificial excitation functions in case of different magnitude. The magnitudes were changing between 5.5 and 8.0 M. The large differences were in the values in the time of the motion (5.25 and 0.88 s) and maximum of the velocities (605 and 14.1 cm/s). The maximum of the ground accelerations were 1.0 g and 0.15 g. We found that the period when is the maximum of the spectrum is larger than in the Eurocode and depends from the magnitude. The ratio of the maximum acceleration and the zero period acceleration is larger than in Eurocode (3.46 > 2.5) too. It is very interesting that there are periods, where the values of the spectra at less magnitude are larger than in case of the larger magnitude. The obtained results for structure response, when this is subjected by the near-fault ground motions, show important differences in comparison with the code provisions, especially in case of inter-plate earthquakes, characterized by large velocities and long pulse periods. Calculating the acceleration spectra we have seen that between 0,45 and 1,5 s time period the values of the calculated spectra are larger than in Eurocode 8. The maximum of the calculated spectra was larger than in the standard by 50%.

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