Method and apparatus for absorbing dynamic forces on structures
AssigneeMassachusetts Institute of Technology
InventorsJohn K. Vandiver, Shuhei Mitome
Life of this patent
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Abstract
An apparatus and method is provided for suppressing the dynamic response of structures such as offshore structures to forces, such as that of wind, wave or seismic excitation. A storage tank for liquid with a free surface is positioned on the structure and is designed to have a natural frequency equal to or nearly equal to the natural frequency of the structure. The storage tank containing the liquid reduces the dynamic response of the structure thereby reducing structural degradation such as metal fatique in the structure and increasing the useful life of the structure. The effect of the tank on the motion of the structure is that of a common dynamic absorber.
Claims8
In a fixed structure that exhibits a dynamic response to wind, water and/or seismic excitation, the improvement which comprises:
- means for damping said dynamic response comprising a storage tank containing a liquid with a free surface, said storage tank being positioned on and supported by said structure, the shape of said tank and the nature of the liquid being such as to effect a ratio of the uncoupled fundamental mode of the natural frequency of the tank containing liquid to the uncoupled fundamental mode of the natural frequency of the structure and the empty tank of between about 0.8 and 1.1.
The method for damping the dynamic response of a fixed structure to wind, water and/or seismic excitation which comprises:
- determining the fundamental mode of the natural frequency of the structure having an empty storage tank for a liquid positioned thereon and regulating the geometry of said tank and the extent to which said tank is filled with a liquid so as to effect a ratio of the uncoupled fundamental mode of the natural frequency of the tank containing liquid to the uncoupled fundamental mode of the natural frequency of the structure and the empty tank of between about 0.8 and 1.1.
Dependencies are inferred from the claim text.