Feasiblity of Viscous Mass Damper With Bingham Fluid Origined Force Restriction Mechanism for Base-Isolated Structure

Abstract eng:
Viscous mass dampers with friction origin force restriction mechanism (force restricted viscous mass damper, hereinafter called FRVMD) are considered for base isolated structures. From a series of analytical studies, FRVMD can reduce the displacement of the base isolation layer, but they cannot reduce the floor response acceleration of the superstructure depending on the input ground motions. To improve the damper, viscous mass dampers with Bingham fluid origin force restriction (Bingham fluid – viscous mass damper, hereinafter called BF-VMD) is suggested. The BF-VMD has four design variables to be determined, the amount of the apparent mass, the viscous damping coefficient, the stiffness of buffer spring, and the damping coefficient of the Bingham fluid. In this paper, base isolated fivestory reinforced concrete structure incorporated with BF-VMD, FRVMD, or ordinary oil dampers with relief mechanism (hereinafter called OD) at the base isolation layer are considered as a common isolated structure. Three kinds of design criteria that are the displacement of the base isolation layer, the floor response acceleration, and the coefficient of the shear force, are defined for three levels of input ground motions, and the design variables that can fulfill all the design criteria are chosen by the optimum design method. The maximum responses given by the optimization results show that the structure with optimized BF-VMD can satisfy all the design criteria, whereas the structure with FRVMD or OD cannot satisfy the design criteria of the floor response acceleration. The response magnification of the floor response acceleration shows that the high frequency component of the floor response acceleration in case of BF-VMD becomes smaller than that in case of FRVMD. We infer that this is because of the difference of the mechanism on the force restriction.

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