Shock Mitigation by Means of Low to High Frequency Nonlinear Targeted Energy Transfers in a Large Scale Structure

Abstract

In this computational study, the implementation of passive nonlinear vibroimpact attachments (termed nonlinear energy sinks (NESs)) for shock mitigation of an otherwise linear multistory largescale structure is investigated. This is achieved by inducing passive targeted energy transfer (TET) from the fundamental (lowestfrequency and most energetic) structural mode to highfrequency modes, through a series of vibroimpacts induced by the attachments. The functionality of the passive attachments is based on singlesided vibroimpacts (SSVIs), enabling rapid and oneway scattering of shock energy from lowto highfrequency structural modes. Hence, redistribution of shock energy in the modal space of the structure occurs as energy gets nonlinearly scattered to high frequencies. In turn, this energy scattering rapidly reduces the overall amplitude of the transient structural response, and increases the effective dissipative capacity of the integrated NESstructure assembly. The effective modal dissipation rates of the integrated assembly can be controlled by the inherent damping of the NESs, and can be qualitatively studied in detail by defining appropriate dissipative measures which track the TETs from lowand highfrequency structural modes. Ideally, the optimized NESs can passively scatter up to 80% of the input shock energy from the fundamental structural mode to highfrequency modes in the limit when their inherent damping is zero and the coefficient of restitution during vibroimpacts is unity. When dissipative effects are introduced into the NESs, additional energy exchanges between the NESs and highfrequency modes occur. Our study facilitates the predictive design of vibroimpact NESs for optimal and rapid shock mitigation of largescale structures.