Experimental and Theoretical Investigations on an Asynchronized Parallel Double-Stage Viscous Fluid Damper

The parameters of most conventional passive dampers are constant, which may not sufficiently satisfy the different energy dissipation capacity demands of the structure under different load conditions. The development of passive dampers with variable performances has become an emerging and vital trend in energy dissipation technologies and smart structures. This study proposes a novel passive viscous fluid damper with variable performance under different deformation levels called an asynchronized parallel double-stage viscous fluid damper (APDVFD). It is expected to exhibit an asynchronized double-stage working mechanism based on a variable annular gap. In the first stage, only the primary piston provides the damping force. When the deformation reaches a preset value, the primary and second pistons work in parallel, providing a damping force concurrently. Circular orifices are adopted for the piston head to provide a sufficient damping force. The double-stage operating mechanism and fatigue performance of the APDVFD were validated and investigated through a full-scale experiment with 46 load cases. Based on these, a theoretical model capable of predicting the hysteretic behavior of the APDVFD was developed and validated against test data.