STUDY ON RESPONSE SPECTRA AND ITS RATIOS FOR NEAR-FAULT VERTICAL EARTHQUAKE GROUND MOTIONS

摘要

In order to make up for the deficiency of the current seismic design code and the near-fault vertical spectrum, based on selected near-fault earthquake records within 15 km of fault projective distance, the near-fault vertical earthquake ground motions database classified by earthquake magnitude and site condition is firstly constructed.The vertical response spectra ratio of near-fault ground motions was analyzed by using statistical method.The variation of ratio of vertical response spectra to horizontal response spectra was given.The reasonable values of the response spectra ratio were suggested with the change of earthquake magnitude and structural natural vibration period.Then, the proposed attenuation analytical model was established on the base of typical model of common engineering.The vertical response spectra curves and estimated expressions of its parameters had been derived by using the least square method.The difference between vertical and horizontal regression spectra curve was described to show the importance for near-fault vertical seismic design spectra.Finally, comparing with the existing results, the proposed attenuation expressions are reasonable to study the near-fault seismic response of large-span structure.