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Optimization of Performance of the RBS Semi-Active Brace in Steel Frame with Case Study on the Soft Story

Haeri, Amir Hossein | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42393 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Golafshani, Ali Akbar
  7. Abstract:
  8. One of the most common failure modes of structures in earthquakes is soft story failure which causes by discontinuity of lateral force resisting elements like braces. so the ground floor acts as a soft floor. In this case columns are imposed to large deformation and plastic hinges are formed at top and bottom of the columns. This case is named as story mechanism (severe drift of the story). In most of this case building collapsed or going to collapse. To resolve this problem, different solutions are presented. One of the strategies under section (2-10) 2800 code is increase of designed load in columns of the soft floor. This measure cause to Significant increases in the sections of the ground floor columns that in most cases there is no economic and executive justification. The use of Concentrically Brace by attention to buckling effect and a significant reduction in the bearing load during an earthquake is not logical. New high-performance semi-active bracing system that has been provided by Dr.Golafshani and colleagues is capable to remove the permanent drift of stories at the end of excitation and concentrated structural damage in braces.In the conventional bracing systems it is assumed that the braces buckle under little compressive forces; but in this new presented completely tensile ribbed bracing system (RBS) buckling of compressive member is prevented by using of a ribbed shape cylinder. This study reviews the behavior of semi-active bracing system in two case of completely closed RBS and semi active RBS 0.5% on soft-story structures and be done a comparison between the behavior of this system and methods mentioned above to remove the soft floor. For this purpose, the frame 3, 6 and 9 floors with a soft ground floor is used. Modeling is done in OpenSEES and semi-active bracing system RBS results showed better behavior in soft floor especially in high acceleration of the earthquake
  9. Keywords:
  10. Structural Control ; Ribbed Bracing System (RBS) ; Buckling Restrained Braces Frame (BRBF)System ; Soft Story Failure

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