Experimental testing of a re-centring viscous damper with non-Newtonian damping fluid
Hybrid damping devices combining different energy dissipation mechanisms can provide an overall response which can perform across a large range of near-fault and far-fault earthquakes with different frequency and velocity characteristics. Prior research has investigated the combination of ring-springs and viscous fluid dampers to create an overall re-centring viscous fluid damper, but only with linear force-velocity response in the viscous damper component. Non-linear force-velocity behaviour from the use of Non-Newtonian damping fluid has several advantages over linear viscous dampers that use a standard Newtonian fluid. In most structural applications, the likely damper input velocity is relatively unknown due to uncertainty in the input ground acceleration that may be experienced at a given site. This research experimentally investigates a hybrid damper that uses re-centring ring springs with a viscous fluid damper with high viscosity silicone fluid to provide a non-linear force-velocity response. Proof-of-concept experimental testing with sinusoidal displacement inputs are undertaken on the hybrid device as well as its individual components. Input amplitudes of [20-30] mm over a range of frequencies [0.1-4] Hz are used to create input velocities [10-300] mm/s. At peak speed, maximum resistive device force is ~50kN where ~25kN comes from the ring spring and ~25kN from the viscous damper. A non-linear force-velocity characteristic is seen in the viscous damping component of the hybrid device, as a result of the Non-Newtonian characteristics of the silicone damping fluid. The individual components of the device are tested in addition to the hybrid device to delineate the contributions to response.