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Investigating the Performance of Friction Dampers with Variable Slip Loads Together with the SMA Materials to Control the Seismic Response of Steel Structures

Khaldar, Milad | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47981 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Rahimzadeh Rofouei, Fayyaz
  7. Abstract:
  8. The parallel combination of friction damper with shape memory alloys has been proposed as a self-centering friction damper (SFDB) in the past. The aim of this study is to improve the performance of the SFDB as M-SFDB and investigate its effect on seismic responses of steel moment resisting structures. The basic idea used in the proposed M-SFDB damper is to create sloped surfaces and using SMA bolts to change the slip load of friction during the loading and unloading cycles. In order to evaluate the effect of the proposed mechanism, four types of 4, 8 and 12-story structures located on site classes B and D are designed using ASCE_7-10 and AISC_360-10 codes. These structural models include (1) special moment resisting frame systems, (2) structural systems with friction dampers, (3) structural systems with SFDB and (4) structural systems with M-SFDB. For designing structures equipped to damper, the design forces were reduced by 25%. Designing the optimal damper properties with the aim of minimizing the maximum stories’ drift ratio was done through performing time history analyses for structural models using the earthquake records related to the considered soil types for both near and far field records (7 record for each case) that were scaled to 0.4g and 0.6g. After fixing the damper characteristics in an optimized manner, the seismic responses including mean maximum drift ratio, permanent drift ratio, maximum absolute acceleration and maximum story shear force are obtained. The results indicate that all three cases with dampers have performed almost similar in terms of reduction in shear force and drift ratio. But, the permanent drift ratio responses for all structural models with M-SFDB are less than other models. In some cases using M-SFDB causes increase in absolute acceleration, which is probably due to the frequency content of the earthquake records. In total, the least number of plastic hinges in columns of structures with SFDB and M-SFDB were observed. In this study OpenSees software were used for performing the dynamic analyses
  9. Keywords:
  10. Seismic Response ; Steel Structures ; Shape Memory Alloy ; Friction Damper ; Variable Slip Load

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