SEISMIC VIBRATION ATTENUATION IN SHEAR BUILDINGS USING NONLINEAR ENERGY SINK WITH ASYMMETRIC BI-LINEAR ELEMENT

Nonlinear Energy Sinks (NES) have gained popularity as passive vibration palliatives because have no preferred natural frequency and can resonate with any mode of the primary structure to which they are attached. Unfortunately, NESs are energy-dependent devices, characterized by energy thresholds where optimal NES design regions can be very close to low effective ones. It is then frequent that even negligible changes in the level of the exciting energy can significantly reduce the performance of previously tuned NES designs. Preliminary studies have shown that NES sensitivity to energy variations can be reduced by adding negative linear stiffness or bistable characteristics. In this work, the robustness of a tuned cubic NES is improved by adding an asymmetric bilinear element. This proposed modified NES is composed by a common cubic NES and a non-constant bilinear stiffness which includes a rope and two linear springs. In this numerical study, the vibration reduction performance of a cubic NESs and a Bilinear NES (BNES) is compared when the absorbers are attached to a three-story shear building structure. The building structure is excited using numerically generated seismic excitations characterized by different energy intensities while the vibration reduction performance of both absorbers are quantified using a specific index.