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Providing Smooth Design Spectra for Iran by Modifying the Newmark Method

Sanagar Darbani, Mohammad Ali | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54538 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Alijani Moghaddam, Hassan
  7. Abstract:
  8. Many regulations around the world use the Newmark method, directly or indirectly, in the design spectrum. Research on the Newmark design spectrum shows that this spectrum sometimes significantly differs from the earthquakes response spectra that have occurred; therefore, it is necessary to develop and introduce new design spectra by modifying the Newmark method to be more compatible with reality. The developed design spectra in seismic regulations around the world are directly affected by the records involved in their development. Thus, the appropriate design spectrum should be prepared based on the seismic characteristics of the faults of each country. Evaluation of the Iranian Seismic Code, Fourth Edition of Standard 2800, shows that this standard has some weaknesses. For example, firstly, it is only for the horizontal component. Secondly, spectral values are being calculated by multiplying the Normalized Pseudo-Acceleration to the peak ground motion. To be more accurate, for calculating Pseudo-Acceleration design spectrum, it needs to multiply peak ground acceleration, peak ground velocity and peak ground displacement respectively to the spectral values of the triple sensitive regions namely, acceleration sensitive region, velocity sensitive region and displacement sensitive region which is respectively normalized to peak ground acceleration, peak ground velocity and peak ground displacement. Third, there is no sensitive displacement region compared to the design spectrum of other countries, which leads to irrational spectral values for structures with very long periods.The main purpose of this study is to modify the Newmark method, developing new inelastic displacement spectra and smooth elastic design spectra for earthquakes that are recorded inside and outside Iran. Afterward, the spectra of earthquakes in Iran and abroad has been compared. It should be noted that the basis for modifying the Newmark method is based on the proper division of records by the magnitude of the earthquake, the distance from the site to the source of the earthquake and the type of soil. In this study, in addition to developing elastic and inelastic design spectra statistical studies have been done on a number of important seismic parameters. Finally, the validation of the proposed design spectra in this study, standard 2800 and ASCE7-16 regulations with a number of occurred earthquakes has been taken
  9. Keywords:
  10. Design Spectrum ; Iran ; Inelastic Displacement Factor ; Modifying Newmark Method ; Elastic Displacement Spectrum ; Inelastic Displacement Spectrum ; Statistical Analysis

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