Bi-normalized Response Spectra for Various Frequency Content Ground Motions

Abstract

This article focuses on bi-normalized response spectra for recorded strong ground motions with various frequency contents. The bi-normalized response spectrum introduced in Xu and Xie [2004] is obtained by dividing the spectral response by the corresponding peak parameter and by dividing the vibration period of the SDOF by a frequency content-related parameter. More than 100 seismic motions recorded in 17 countries in the past 70 years are analyzed. The ground motions are classified into several categories according to: (a) the peak ground acceleration PGA and (b) the control period TC of the response spectra or the mean period, TM. The analyses performed on bi-normalized response spectra aim at highlighting the differences between the various categories of strong ground motions. The influence of the peak ground acceleration and of the frequency content on the bi-normalized response spectra is emphasized. This article also compares the computed spectra with the elastic response spectra given in EN 1998-1. It can be concluded that the bi-normalized response spectra could be used in seismic design codes and that the design spectra from EN 1998-1 should be re-shaped for the near-field region (due to the limited database).