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Proper Shape, Size, Type of Alloy and Orientation of Shape Memory Alloy Wires in High Damping Rubber Bearing based on Performance Assessment

Mataranlouei, Saeed | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 48752 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Khaloo, Alireza; Kazemi, Mohammad Taghi
  7. Abstract:
  8. In an effort to reduce the building and structural damages due to earthquakes, the researchers have created a new alternative to isolate structures from the ground movement. Base isolation (BI) as one of innovative means can provide a very effective solution to protect constructions from the hazard of earthquakes. The proposed smart isolation system combines a laminated rubber bearing with a device made of shape memory alloy (SMA). In Japan and United States, many bridges have been designed or retrofitted with seismic isolation devices in the last 20 years. In the other words, isolation bearings can substantially improve the seismic performance and consequently reduce the post-disaster cost for repair and rehabilitation. Innovative techniques for controlling structural response are looking for smart materials which can introduce new possibilities in earthquake protection methods. One class of such materials are metallic alloys known as shape memory alloys (SMAs). The smart base isolation utilizes the different responses of the SMA at different levels of strain to control the displacements of the rubber bearing at various excitation levels. Systems providing re-centering force (BI-SMA) sacrifice damping for the ability to reduce residual deformation after a seismic event. In this research, some different configurations of SMA wires are considered for HDRB. The effect of using SMA bars, changing the angle of SMAs and diameter size of SMA wires are investigated on the performance of the five story structure. This study shows that, isolator units reduced the base shear force from 20% up to 60% depending on frequency content of used excitation and also, reduction for drift ratio between the stories could be up to 80%. However, this technique used as an alternative, drift ratios between isolator’s elements is increased up to 1400% during the event or at the end of event. Also, using the SMA wires is considered as an alternative to remove the residual displacement and control the displacement in isolator’s elements. In this case the equipped isolators lead to reducing the residual displacement up to 99%, and using the SMA wires also leads to reducing the drift ratio between the stories up to 45%. Equipped isolators make more stiff systems and provide less reducing the base shear force in comparison non equipped isolators, subsequently. Using the SMA wires with small angle leads to more good results but more cost. Also area section changing of the SMA wires provides different initial stiffness but it has no significant effect on the residual drift’s results. So using the possible lowest radius for the wires is more convenient than focusing on maximum drift ratio because of economical reason. Bigger radius leads to reducing the maximum drift ratios but there is not an economic justification
  9. Keywords:
  10. Shape Memory Alloy ; Base Isolation ; Nonlinear Dynamic Analysis ; High Damping Rubber Bearings (HDRB)

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