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Multi-Variable Optimization of Off-Center Bracing System

Shamshiri Guilvaee, Missagh | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45083 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Esmaeil Pourestekanchi, Homayun
  7. Abstract:
  8. Since the advent of earthquake engineering, several methods have been created to repel earthquake forces. One of these methods is to decrease lateral stiffness of structure at its base level. Some systems, such as base isolations which are installed at the base level of structures can provide this softness. In recent years a new kind of bracing system named geometrical (off-center) bracing system has been presented with three convergent members that can increase the main period of structure by applying high displacement at first floor in order to prevent high frequencies from entering structures. Despite of previous researches, in this study the mentioned bracing system has been assessed and non-linear behaviour of materials has been considered.In this research, changes of spring stiffness and eccentricity of off-center brace in the first floor has been evaluated and interaction effect of these two parameters in amount of base shear has been shown in results. The structures with 3, 7 and 12 floors were modeled in OpenSees software and the base shear optimization has been achieved with consideration to the results of time history non-linear dynamic analysis and endurance time (ET) methods. According to the results, this bracing system can only satisfy performance limitations for structures with 3 and 7 floors. In general, by decreasing the number of floors, effectiveness of this system increased. For example, the system can keep three floor buildings in linear zone for earthquake with more than 2% occurrence possibility in 50 years. On the other hand, for buildings with higher number of (or more) floors, this system did not have economic justification. For example, by using this system in twelve floor buildings the final amount of used steel increased in comparison to the building with diagonal braces
  9. Keywords:
  10. Nonlinear Dynamic Analysis ; Endurance Time Method ; Optimization ; Off-Center Brace ; Base Isolation ; Vibration Isolators

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