Seismic response of selective pallet racks isolated with friction pendulum bearing system

The concept of base isolation for storage racks is still a developing subject and has not been addressed in the recently updated seismic codes for storage racks. The friction pendulum bearing system (FPS) generates a natural period independent of the structure’s seismic mass. This property makes FPS an ideal choice for isolating rack structures since merchandise may be placed on the racks in several possible arrangements. The results of a comprehensive parametric study aimed at evaluating the seismic performance of a four-shelf, two-bay selective pallet rack isolated with FPS is presented in this paper. The influence of radius of curvature of the FPS, seismic mass, and mass irregularity on the rack’s seismic response is examined. The effect of variation of the coefficient of friction due to axial loading is studied by choosing friction values from two distinct friction characterization studies. The coefficient of friction calculated from these studies shows mild and significant variations, respectively, for the whole range of static axial loads expected on the isolator, and from different pallet mass arrangements considered. The optimum radius of curvature and the appropriate range of friction coefficient, for the defined range of static axial loads, to attain a desirable seismic performance are determined.