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The Effect of Earthquake Repeated Cycles in Performance Based Design Methodology Utilizing Energy Concept

Keshavarzi, Behrooz | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43115 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Bakhshi, Ali
  7. Abstract:
  8. Due to structural and nonstructural damage after the occurrence of Northridge 1994 and Kobe 1995 earthquakes, Seismic design basics was modified and philosophy of performance based design was suggested. In this novel solution, Predefined limitations are considered. Performance criteria were usually related to displacement or other correlated factors such as hinge plastic rotation. All the mentioned limitations are related to different damage states.Most of the codes and articles use following assumptions for assessing structural performance: 1) considering first vibrational mode for structural response to any seismic excitation regardless of seismic input acceleration records or structural properties. 2) Approximating structural nonlinear behavior by computing equivalent damping energy benefiting from maximum displacement. 3) Equating MDOF structure with some SDOF structures in desired modes and using linear or nonlinear spectra for design and control of main structure.
    Some researchers benefit from energy concept for expanding theoretical equations for avoiding the complex behavior of nonlinear structures.
    The effect of cumulative damage has come under scrutiny recently. In this research one of the articles that suggest a method for considering this phenomenon is investigated. The main advantages of this article are consideration of different modes contribution in structural response and taking into account stories weakness by using AE factor. Disadvantages of this article are as follows: 1) Not offering a rational way for selecting the governing modes with consideration of structural properties and record’s dominant Periods. 2) The main deficiency of this article is an assumption about the constant rate of absorbed hysteretic energy related to a desired damage index to pushover analysis (a factor) In this project 5 frames from 4 stories to 8 stories initially designed according to Iran’s national building code section 9. After doing this the suggested method is investigated. For selecting effective modes, modified CSM method that is suggested by Chopra is used. According to results, it is shown that the assumption about a factor isn’t generally true. Matching all the input records spectra with one defined spectra leads to accuracy of main assumption about a factor. Benefiting from hysteretic input energy spectra that are developed from elastic-perfectly plastic models enforce us to reject the suggested procedure from a known step
  9. Keywords:
  10. Performance Based Design ; Earthquake Hystersis Energy ; Cumulative Damage ; Structural Assesment by Energy Method ; Seismic Hazard Analysis

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