PROTECTING PRECISION MACHINERY USING GUIDEWAY SLIDING ISOLATOR WITH GAP SPRING AND DAMPERS

Guideway sliding isolator can be one of the most efficient ways to protect precision machinery from damage in an earthquake. However, it brings large displacement between the machine and the floor. In order to improve the performance, viscous dampers, as the energy absorber to reduce the displacements, and gap springs, providing the resilient force to eliminate the relative and residual displacements, are both added to the sliding system. The special feature of a gap spring is that a spring is initially kept away from the machinery with a gap so that the isolation system does not have a constant nature frequency therefore reducing the resonant vibration. In this paper, a numerical model to simulate the machinery and a full scale shaking table test of a 22-tons-weight specimen were both performed to study the behavior of guideway sliding isolator with gap spring. Testing results showed that absolute acceleration transmitted to the specimen can be very low if the frictional coefficient of the guideway isolator is under 0.05, and the gap springs are effective to control the relative displacements of the system. Numerical model is shown to be satisfying since the test results are well correlated to the analyzed one.