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Numerical Study of Two Novel Metallic Dampers with Torsional Mechanism

Khalooei, Shayan | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51777 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Mohtashm Dolatshahi, Kiarash
  7. Abstract:
  8. The aim of this study is introducing and assessing two torsion-based metallic dampers which are named Torsional Disc and Torsional Cylinder dampers based on their geometry and energy absorption mechanisms. As expected, a steel disc and a steel cylinder are exposed to torsion in the Torsional Disc and Torsional Cylinder dampers respectively, and energy absorption occurs through torsional yielding of those two elements. In the introduction section, a mechanism is introduced to put the dampers under pure torsion so as to yield a desirable performance. The dampers are designed to be placed between Chevron braces and the floor beam, and the pure torsion is exerted, through the mentioned mechanism, as a result of the relative drift between the upper part of the braces and the beam. In the Torsional Disc damper, the disc is welded to a torsional pipe through its outer edge to create rigid boundary condition. Besides, the torsion is applied to the disc by a steel shaft which is connected to the disc through its inner side. In the Torsional Cylinder damper, the cylinder has a rigid boundary condition in one end and is welded to a steel plate with a specific thickness through the other end; the mentioned plate is named torsion arm and exerts torsion on the cylinder through the previously mentioned mechanism.
    The introduced dampers were studied with the goal of analyzing their performance and force-displacement behavior under torsion through both analytical and numerical modeling methods, using finite element analysis software, ABAQUS. Since no experiment was conducted on these two dampers in this study, using damage models was not possible in the finite element analysis section. According to this lack of data, a damage index, independent of experimental results, was used in the modeling to study relative damage conditions. Results of the numerical modeling of the Torsional Cylinder damper were compared to a number of other yield-based steel dampers to analyze its performance using the results of one of the many different experiments conducted on cylinders under torsion; the comparison shows the desirable energy absorption of the Torsional Cylinder damper. In the end, both dampers were separately put in a simulated structure to evaluate their performance and were modeled with OpenSees software. Incremental Dynamic Analysis and Fragility Curves were used to assess and compare the performance of the controlled structure with the damper with the uncontrolled one. Results of the Incremental Dynamic Analysis show the desirable performance of dampers in enhancing the behavior of structures under earthquakes
  9. Keywords:
  10. Passive Control ; Metallic Damper ; Finite Element Modeling ; Incremental Dynamic Analysis ; Torsional Mechanism

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