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Development of Fragility Curves for Middle-rise Steel Structures with Additional Viscous Dampers

Rahimiasl, Mehdi | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 51873 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Bakhshi, Ali
  7. Abstract:
  8. The objective of this research is to introduce a new comparative performance measure based on seismic fragility curve of structures. This measure is used here to investigate the efficiency of viscous dampers on the behavior of a weak mid-rise steel structure. Viscous dampers are commonly utilized to reach purposes such as decreasing the risk of the structure failure and restoration costs, weight reduction, and seismic rehabilitation of existing structures. These systems cannot be satisfactorily investigated using static loading concepts, and in order to achieve optimum design, conducting a nonlinear dynamic analysis is usually the most reliable procedure. Therefore, 5-span 12,15 and 18 story steel frames are equipped with three patterns of viscous dampers and their seismic performance is studied under ground motion records. The distribution of dampers along the height of the structure is optimized in 3 hazard levels using genetic algorithm (GA) subjected to 12 ground motion records scaled to levels of 50%, 10% and 2% probability of exceedance in 50 years. The objective function of the optimization process was defined to achieve IO, LS and CP performance levels at three considered hazard levels, respectively. Then, the performance of the base and rehabilitated structures were investigated using fragility curves and a suggested reliability factor. This factor named as Performance Improvement Factor (PIF) can be used to compare the seismic performance of two structures. A larger PIF indicates a more effective improvement on the reliability and safety of the structure. It is shown that the suggested method is an effective approach to study and compare the safety and reliability of steel structures
  9. Keywords:
  10. Fragility Curve ; Viscous Damper ; Genetic Algorithm ; Performance Improvement ; Incremental Dynamic Analysis ; Seismic Performance Factors

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