Numerical and experimental study on the damping performance of the fluid viscous damper considering the gap effect

As a typical passive energy dissipation device, the fluid viscous damper (FVD) is widely utilized for structural vibration control. However, performance degradation in FVDs has been highlighted, particularly concerning the gap effect resulting from the imperfect installation and insufficient fluid. This study proposes three analytical models to characterize the gap property in the hysteresis behavior of FVDs, including the Gap model (G. model), the Equivalence model (E. model), and the Stiffness Degradation model (S. model). The purpose of the G. model is to reproduce the zero-force platform in the hysteresis curve. The E. model and S. model are both simplified models, aiming to consider the gap effect by altering the damping coefficient, velocity exponent, and stiffness based on the energy and maximum force equivalence principles. Shake table tests of a single-degree-of-freedom system are carried out to validate and assess the effectiveness and accuracy of these three methods. The results indicate that the gap effect will significantly degrade the vibration mitigation performance of FVDs, and hence it needs to be considered in simulations. The displacement and force obtained using the G. model under distinct loads highly correspond to the experimental results. By adopting the simplified models, satisfactory results can be derived with a lower implementation cost. Among them, the E. model is more appropriate when subjected to harmonic loads, while the S. model is suggested for cases under seismic excitations.