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February 22, 2001
The dampers are being installed in the Hotel Kintetsu Universal City under construction adjacent to Universal Studios Japan in Osaka. The vibration dampers consist of zinc-aluminum alloy plates, 300 mm by 300 mm and 10 mm thick, which are inserted between steel plates and covered by a steel frame. The dampers are being placed in eight locations, four on the top floor of the 25-story building and four on the rooftop structure. The vibration dampers developed by Kobe Steel and Takenaka clear many of the technical problems faced by conventional dampers. The new dampers do not suffer from lower performance that can occur with conventional steel dampers or a sudden loss of function when subject to temperature changes as in the case of viscous dampers. Oil dampers require period inspection to prevent leakage, whereas the new zinc-aluminum alloy dampers are virtually maintenance-free. Kobe Steel succeeded in reducing the grain size of the new alloy to the nanometer level (1 nanometer is one-billionth of a meter) by using thermo-mechanical controlled processing (also known as TMCP), which has been used to produce high strength, high performance steels. The zinc-aluminum alloy, having ultrafine grain, is noted for its high strain rate superplasticity. This enables the material to undergo tremendous deformation or elongation, much like candy. As a result, vibration dampers made using the new zinc-aluminum alloy are able to return to their original form, and there is no need to replace them after earthquakes. Nor is there a need for periodic inspections. Owing to the superplasticity of the alloy, which has an elongation of over 100%, the dampers can withstand large earthquake amplitudes. As the dampers are maintenance-free, they will last as long as the building. The material in the dampers can also be melted down and reused to make more dampers.
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