The conditional mean spectra by disaggregating the eta spectral shape indicator

Mohammad Ali Mohandesi, Alireza Azarbakht, Mohsen Ghafory-Ashtiany

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Conditional spectra are a recent development in this field, which utilizes the advantages of spectral shape indicators, for example, epsilon and eta. The application of an eta indicator in conditional spectra calculations depends mainly on calculating the peak ground velocity epsilon, data about which are not readily available in the current literature. This issue has been solved by linear regression between the conventional epsilon and the peak ground velocity epsilon. However, not enough attention has been paid in the literature to the disaggregation of the eta indicator. For this reason, the disaggregation of seismic hazard based on the use of an eta indicator has been investigated in this paper, based on a simplified linear seismic source. The obtained results were compared with the available approach in the literature, which shows that this refinement has a meaningful effect on the conditional spectra specifically in the short period range. Furthermore, eta-based conditional spectra are used at different hazard levels to select ground-motion records. A three-storeyed building is then analysed, and the corresponding annual probability of failure is calculated based on the full dataset as well as on the records, which were selected based on conditional spectra.

Original languageEnglish
Article numbere1586
JournalStructural Design of Tall and Special Buildings
Issue number5
Early online date6 Jan 2019
Publication statusPublished - 10 Apr 2019


  • epsilon
  • eta
  • genetic algorithm
  • ground-motion prediction equation (GMPE)
  • seismic hazard analysis


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