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Development of an Improved Semi-active Damper Based on the Reduction of the Effects of Brace Flexibility

Rasoulnia, Akbar | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43820 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ahmadizadeh, Mehdi
  7. Abstract:
  8. Considerable research work has been dedicated to the development of structural control systems to improve the performance of structures and reduce the casualties resulting from earthquakes. It is generally accepted that semi-active control systems result in better structural performance compared to what can be achieved using passive systems. However, it has been observed that the majority of the performance improvement obtained from semi-active control systems stems from the reduction of brace flexibility effects, rather than the control algorithm used. In this study, it is attempted to utilize this fact to improve the performance of passive control systems, or develop simple semi-active control systems.
    In this study, it is first attempted to obtain an improved relationship between the velocity and force of passive viscous dampers, in order to reduce the effects of brace flexibility. The LQR control algorithm and another control logic based on the reduction of brace flexibility effects are considered herein. However, it was observed that the required relationships are too complicated to generate the desired control forces in passive mode. On the other hand, these observations supported the major role of brace flexibility on the performance, rather than the control algorithm in use.
    Based on the findings of the first part of this study, the rest of this work was concerned with the development of a simple semi-active damper that automatically reduces the effects of brace flexibility without the use of active control algorithms. While this damper results in structural performances that are comparable with those of customary semi-active control devices, its design is less dependent on the dynamic properties of the structure, and has less delay. Furthermore, simplicity, reduced instrumentation requirements, non-centralized performance, and fewer design parameters can be counted as other characteristics of the proposed semi-active damper. Several structural models have been analyzed to demonstrate the effectiveness of proposed semi-active damper. Furthermore, the arrangement and performance of the single-degree-of-freedom model is shown schematically using SIMULINK software
  9. Keywords:
  10. Brace Flexibility ; Semiactive Damper ; Hydraulic Damper ; Damper Force Velocity Relation

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