| Summary: | 碩士 === 國立成功大學 === 建築學系碩博士班 === 93 === A base isolation design for precision machinery in a high-tech factory building is required for low acceleration transfer and a small amount of sliding displacement because of the limited permissive space between equipment. Therefore, this thesis studies a scheme, rolling frictional guideway isolators added vicious dampers, for the base isolation design. This mechanism reduces acceleration transferred from floor to machinery with guideway isolators, minimizes displacement with gapped springs, and dissolves energy with added dampers.
According to the result of computer simulation and full-scale shaking table test, this thesis has obtained following conclusions:
1. While the friction coefficient of sliding surface reduces, this isolation system will be obviously effective if the System Frequency lower than the excitation frequency.
2. The System Frequency with small gap opening is composed of the mass of machinery and total stiffness of springs on one side. The isolation system will reduce acceleration peak values if System Frequency is lower than the excitation frequency. Larger stiffness of spring accomplishes limited spacing purpose, but makes machinery to behave in higher acceleration.
3. System Frequency may be reduced because of the enlarged gap opening. Large gap opening can reduce the intensity of System Frequency component when excitation frequency is higher than the System Frequency. Excessively large gap opening not only causes the Low-frequency System a severe low-frequency shaking, but also may raise the intensity of high-frequency acceleration and displacement peak values of the High-frequency System. Excessively large gap opening may also lead to harmonic response if certain high-frequency waves were in the input motion.
4. Increasing the damping coefficient of the Low-frequency System can reduce effectively low-frequency shaking and displacement peak values, but causes higher acceleration peak values.
5. The Base isolation designs against floor response waves caused by near field earthquakes have to dissolve energy with added viscous dampers. Low-frequency System reduces effectively the acceleration peak values. The damping coefficient and the damping exponent should be appropriately improved to reduce relative displacement peak values at the same time.
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