Optimization of a self-centering frictional damper (SCFD) and its application to non-linear structures
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Date
2019
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Abstract
Self-centering dissipating devices have been developed in the last decades to both mitigate seismic response and reduce residual drifts of structures. Recent large magnitude earthquakes have shown that most of the repair cost of structures with seismic damage is related to residual drifts, so the study of new devices able to efficiently reduce residual drifts is necessary to develop earthquake-resilient structures. This study describes a new self-centering frictional damper and analyze the seismic behavior of structures that includes this device. The first part of this study describes the behavior and optimizes the design of a new energy dissipating device, the Self-Centering Frictional Damper (SCFD). This device is based on conic friction surfaces that lead to a flag-shaped hysteretic behavior. Different possible configurations and geometry together with its self-centering behavior makes it a very versatile device to be used in seismic applications of high-rise buildings subjected to earthquakes. A simple mathematical model is presented first to describe the cyclic behavior of the device. Then, important variables related to the geometry and materials used in the device are analyzed to better understand their influence on the hysteretic behavior and to optimize the damper’s design. Different friction materials, rubber samples and coil springs are tested in the laboratory for the design of a preliminary prototype. To test the
theoretical model, a 12 tonf large-scale damper was manufactured and dynamically tested in the laboratory obtaining excellent agreement between the theoretical and experimental results. Finally, a detailed finite element model was generated to study the local stress concentrations in the different components of the device as well as to compare the hysteretic behavior for different possible configurations using springs and rubber. The second part of this research studies the seismic performance of a structure with SCFD dampers considering non-linear behavior not only of the dampers but also of the primary structure. To achieve this, a five story building was modeled using sophisticated fiber elements, and dampers were modeled using a non-linear stage routine. A non-linear capacity spectrum method was proposed to design the optimum dampers to be used in the structure generating a more accurate design than the traditional linear capacity spectrum method. After selecting the optimum dampers, several time-history analyses were computed using Chilean records to study the behavior of the structure with and without dampers. Performance was assessed by maximum story drift, ductility of the structure, energy dissipated and maximum story residual drift, obtaining significant reductions in all variables when the dampers are included. Finally, fragility curves of the structure with and without dampers were developed concluding that these dampers guarantee life safe performance level and prepare the structure to avoid collapse.
Description
Tesis (Master of Science in Engineering)--Pontificia Universidad Católica de Chile, 2019
Keywords
Seismic protection, Frictional damper, Self-centering behavior, Experimental validation, Design using FEM, Non-linear structure, Fiber elements, Non-linear design, Performance assessment, Fragility