Seismic response of the double variable frequency pendulum isolator

The double variable frequency pendulum isolator (DVFPI) is an adaptation of single variable frequency pendulum isolator (VFPI). The principle benefit of the DVFPI is its capacity to accommodate larger displacements compared to the VFPI of identical plan dimensions. Moreover, there is the capability to use sliding surfaces with varying isolator geometry and coefficients of friction of top and bottom sliding surfaces, giving the designer greater flexibility to optimize performance. This paper describes the mathematical modeling and force–displacement relationships of the DVFPI. Behavior of the DVFPI is studied by varying isolator geometry and coefficient of friction of the two sliding surfaces and criteria to optimize the performance of the DVFPI are proposed. Further, influences of the initial time period, the coefficient of friction and the frequency variation factors at the two sliding surfaces are investigated. The combined effect of change in the initial time period and the coefficient of friction on the seismic response of the DVFPI is also studied. It is observed that the best performance of the DVFPI can be achieved by designing it with different friction coefficient and different initial time period of the two sliding surfaces. Copyright © 2010 John Wiley & Sons, Ltd.