Vertical and Three-Dimensional Seismic Isolation Tables with Bilinear Spring Force Characteristics (For Which a .LAMBDA.-Shaped Link Mechanism Is Used)

In this paper, the authors propose a nonlinear spring mechanism for a vertical seismic isolation table. The nonlinear spring mechanism consists of a A-shaped link, horizontal coil springs, vertical coil springs and a linear guide, and has an approximate bilinear-type spring force characteristic. A vertical seismic isolation table using the nonlinear spring mechanism and magnetic damping was made, and the seismic responses of a mass installed on the table board were measured using a permanent magnet type vibration machine. Next, the vertical isolation table was attached to a horizontal seismic isolation table which was developed in our previous study, and the three-dimensional seismic responses of a mass installed on the table board were measured using the vibration machine. These experimental results were compared with the calculated results, and the effects of vibration isolation in three-dimensional directions and the validity of the calculations were substantiated.