Abstract
In recent years, earthquakes have frequently occurred in Japan, and the occurrence of events such as the Nankai Trough earthquake and near-field earthquakes is predicted. Traditional seismic isolation systems are effective in reducing damage to buildings, but they are insufficient to prevent infrastructure shutdowns, such as urban gas and elevators, which typically occur at seismic intensities of 4 or lower. To reduce the impact of strong earthquakes to a seismic intensity of 4 or less on a seismic isolation device, we are currently considering a passive 3D seismic isolation system. This system uses fluid levitation for horizontal isolation and a parallel link mechanism with hydraulic cylinders for vertical isolation. In this report, based on prior knowledge of horizontal isolation, we developed a mock-up to determine the required performance of vertical isolation, aiming to reduce vertical acceleration by one-third. Excitations were conducted using random waves and observed seismic waves. The results showed that the vertical isolation behaved as a friction-type mechanism, without resonance, and successfully reduced acceleration by one-fourth. It was confirmed that by combining this with the fluid levitation-type horizontal isolation system, it is possible to reduce the impact of strong earthquakes to a seismic intensity of 4 or less.
