Investigation on the variable damping mechanism and hysteretic behavior of novel STF-FS isolator

Abstract During strong earthquakes, insufficient stiffness of isolation layer may lead to isolator damages, while increasing stiffness is at the cost of isolation performance. Therefore, a novel STF-FS isolator, which integrated shear thickening fluid (STF) and friction sliding (FS) mechanisms, is developed and investigated in this paper. This novel isolator leverages the shear thickening behavior of STF to satisfy the seismic isolation requirements of structures under different intensities of excitations. In this paper, the theoretical model of the novel isolator was derived by Poiseuille’s law, and its working mechanism under different seismic effects was analyzed. The theoretical model of the isolator was verified through hysteresis performance testing. In addition, the impact of frequency variations and geometric parameters on the horizontal hysteresis behavior and damping coefficient were studied. The results show that the STF-FS isolator exhibits significant nonlinear damping characteristics at different loading frequencies. However, the damping coefficient tends to stabilize after the frequency increases to a certain critical range. By modifying the geometric parameters of the isolator, the damping coefficient can be continuously increased, thereby overcoming the limitations of STF rheological properties. This adjustment improves the hysteretic performance, enabling the isolator to achieve variable damping characteristics and energy dissipation in a wider range.