Model testing of a nonlinear base isolation concept

Abstract

This chapter proposes a unique response reduction strategy for complex structures subjected to base or ground shock-induced vibrations. The proposed design is based on the concept of nonlinear localization, where the induced vibrational energy is passively confined to a preassigned secondary system and away from the primary structure to be isolated. The structure to be isolated is a two-degree-of-freedom system, which is weakly and linearly coupled to a single-degree-of-freedom intermediate or secondary system. This, in turn, is connected to ground through a hardening spring, which is produced by the parallel combination of two linear springs, one having clearance nonlinearity. The structural system to be protected is weakly coupled to an intermediate system consisting of a subfoundation and linear spring, which is tuned to a mode of the structural system. A clearance spring acts to excite the appropriate nonlinear normal mode, the clearance being a design parameter, which determines the onset of nonlinear behavior as a function of the input to the system. The performance of the system is examined for pulse-type inputs using simulation.