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Evaluation and Comparison of Seismic Fragility Curves of Self-Centering Braced Frames with Butterfly Dampers and Buckling-Restrained Bracing Systems using Incremental Dynamic Analysis Related to Structural and Non-Structural Component Damage

Yaghoobi Yeganeh, Hediyeh | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57615 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khaloo, Alireza; Yekrangnia, Mohammad
  7. Abstract:
  8. Buckling-Restrained Braces (BRBs) have favorable ductility and energy dissipation capacity; however, since they do not buckle under compression, they exhibit residual deformations. The high level of structural damage and the resulting economic consequences from past earthquakes have highlighted the need to develop limited-damage systems capable of redistributing seismic energy to replaceable members. This study aims to provide a practical comparison of the seismic performance between two structural systems: one with Buckling-Restrained Braced Frames (BRBF) and the other with Self-Centering Braced Frames (SCBF) equipped with butterfly-shaped fuses. For this purpose, first, a 3-story SCBF model with dampers was validated using experimental results, ensuring the accuracy of the modeling. Finally, to meet the research objectives, three 2D frames with 3, 5, and 9 stories were modeled and designed using both structural systems in ETABS software. The design of the BRBFs was based on the American steel structure code [1], and seismic checks were conducted using the American seismic regulations for steel structures [2]. The SCBFs were designed according to the method described later in this study. The designed structures were then modeled nonlinearly using the open-source OpenSees software and Python language. They were subjected to incremental dynamic analyses under 44 far-field ground motion records taken from FEMA-P695 [3]. The Probabilistic Seismic Demand Models (PSDMs) were calculated based on Peak Ground Acceleration (PGA) at four damage levels: slight, moderate, extensive, and complete, considering maximum inter-story drift, floor accelerations, and residual inter-story drifts. Fragility curves were derived from these results. The findings indicate that SCBFs, at 50% probability of exceeding the complete damage level in the maximum inter-story drift criterion, can withstand, on average, 58% larger PGA for 3-story frames, 30% for 5-story frames, and 36% for 9-story frames compared to BRBFs. Additionally, SCBFs, at a 50% probability of exceeding the complete damage level in the residual inter-story drift criterion, can tolerate 63% larger PGA for 3-story frames, 45% for 5-story frames, and 63% for 9-story frames compared to BRBFs. Furthermore, it was found that BRBFs, at a 50% probability of exceeding the complete damage level in the maximum floor acceleration criterion, can tolerate, on average, 4% larger PGA for 3-story frames, 42% for 5-story frames, and 55% for 9-story frames compared to SCBFs
  9. Keywords:
  10. Buckling Restrained Braces Frame (BRBF)System ; Incremental Dynamic Analysis ; Fragility Curve ; Peak Floor Acceleration ; Self-Centering Braced Frame (SCBF)with Butterfly-Shaped Fuse ; Maximum Inter-Story Drift ; Residual Inter-Story Drift

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