| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程系 === 96 === In the current design practice, the design of viscous dampers to be added to building structures has been following the design formulas provided by FEMA specifications and MCEER reports based on a target damping ratio to be added to the structures. However, in construction, the viscous dampers are often connected with braces which may possess some flexibility such that the subsystem composed of a viscous damper and a connecting brace reveals a visco-elastic rather than viscous behavior. As a consequence, the desired target damping ratio may not be achieved. In the analytical work of design process, if the connecting brace is assumed to be rigid, the added damping ratio will certainly be smaller that what is expected in the design. According to a previous study, it was then proposed by Kasai et al. to require the stiffness of the connecting braces has to be at least 5 times the lateral stiffness of the story where the dampers are to be installed. However, this requirement may result into unreasonably large braces that are not acceptable in practical construction. Therefore, it is one of the purposes of the study to derive a design formula that takes the flexibility of the connecting brace into account when deriving the equivalent damping ratio of the structure with added viscous dampers so that the appropriate damping coefficients of viscous dampers can be determined based on the desired target damping ratio. In addition, numerical study has concluded that if the stiffness of the connecting braces is too small the desired design damping ratio cannot be achieved no matter how much damping coefficient of the viscous dampers has be added to the structure. This is particularly true while the desired added damping ratio is larger, e.g. larger than 15%.
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