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Metal-based anti-quake device developed

The New Industry Research Organization (NIRO), Kawasaki Heavy Industries Ltd. and others have developed a seismic isolation system with friction bearings for use with bridge structures.
The device comprises two metal-based sliding bearings sandwiching a rubber-based horizontal spring. The entire assembly is placed between a bridge girder and a bridge pier, where it acts to support the weight of the bridge.
During an earthquake, the bridge girders slide above the metal sliding bearings to parry the force of the quake. At the same time, slide friction from these same bearings helps prevent excessive horizontal movement by the girders.
The result is that slippage between bridge girders and bridge piers is reduced by around half compared to conventional rubber-based attenuation devices.
Moreover, because the attenuation device is made from metal, the bridge girders will not sink perpendicularly over time, as would be the case with rubber-based attenuators.
If, after an earthquake, a girder stops in place rather than returning to its original position, that can be easily fixed by using the hydraulic jack mechanism built into to the attenuator: when the girder is lifted, the force from the rubber-based horizontal spring is enough to move it back into position.
Because of its simple structure, the new device costs around the same as conventional equipment.