| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 105 === Taiwan, located on Pacific Rim seismic belt, frequently experience earthquakes; hence structures need to be not only designed with the consideration of earthquake hazard, but also need to remain functional after earthquakes. Further developments of technology have shown that ductility design is no longer the only way to resist earthquakes. Passive or semi-active control systems have been developed and are being widely used. Viscous dampers are widely utilized in buildings, bridges and structures as a passive damping energy dissipating elements. However, the dampers on the market adjust their mechanical behaviors through altering physical geometry, which have high-cost production and modification in both the developmental and manufacturing phases. Furthermore, dampers cannot be customized, thus engineers will be limited by the fixed damper size during structural design.
This study is dedicated to the development of a passive-type nano-fluid viscous damper, which is a simple physical mechanism and only requires suitable compound ratio of the nano-fluids to achieve the purposes of controlling the damping coefficient C and non-linear coefficient α of the damper’s mechanical formula: F = CVα. Nano-fluid viscous dampers have three main advantages: First, due to uncomplicated physical geometry, the production cost is relatively low. It is also needless to produce new dampers for calibration after testing, just to replace the internal filling of the nano-fluid, which may save on considerable R & D funding. Second, according to the characteristics of variability viscosity of the nano-fluid, nano-fluid viscous dampers are dual-α value damper, matching α>1 and α<1 performance under small and large velocity respectively. If designed properly, the damper may ameliorate the existing bridge damper oil seal wear caused by daily temperature difference and vehicle vibration. Furthermore, the damper enhances isolation system performance during small earthquakes. Last, through the establishment of a full range nano-fluid database, the manufacturer can produce customized dampers in the future, and consequently meet the engineers’ design, which can improve the accuracy and security of the structure.
In this research, the fluid solvent and solute filling in nano-fluid viscous dampers are poly propylene glycol (PPG) and silica nanoparticles. The independent variables of the nano-fluid are PPG molecular weight, different types of silica particles, and fluid concentration due to rheology testing. The numerical model was established to fit the test results, and further analysis of the parameters were gathered from nonlinear regression. We deduced the mechanical behavior of the nano-fluid viscous damper based on the material properties of nano-fluid and fluid dynamics theories. Finally, a damper with a double rod and annular gap were designed and manufactured. Afterwards, we verified the correctness of the theoretical and numerical models through a series of damper performance test with different nano-fluids.
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