| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程系 === 93 === It is the common practice that the viscous dampers are connected in series with braces while installed to a building structure. This sub-system composed of the viscous damper and connecting brace may reveal a visco-elastic behavior rather than a viscous behavior if the stiffness of the brace is insufficient. However, the design formulas provided by current design codes and provisions have implied a sufficiently stiff behavior for the connecting braces such that the sub-system is purely viscous and reveals no storage stiffness. Therefore, it is the aim of this study (1) to ascertain the effect of the stiffness (or more exactly the flexibility) of the connecting braces in affecting the control effectiveness of the viscous dampers; and (2) to derive the design formulas of viscous dampers considering the effect of the stiffness of the connecting braces. Four often used installation schemes of viscous dampers including the diagonal-brace-damper system, K-brace-damper system, Upper toggle-brace-damper system and lower toggle-brace-damper system are included in this study. The amplification factors corresponding to these four installation schemes are included in the formulations, in addition to the effective stiffness of the braces in the axial direction of the dampers.
Numerically examples are used to illustrate the loss of effectiveness of the viscous dampers in controlling the seismic responses of building structures when the stiffness of the connecting braces to the dampers is insufficient. It is also demonstrated that design formulas proposed in the study considering the effect of the bracing stiffness can be used to design the viscous dampers to achieve the target damping ratio contributed by the viscous dampers. The proposed formulas are numerically validated and should be used for the design for viscous dampers to be installed to building structures.
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