A Novel Passive Pseudo-Negative Stiffness Viscous Damper: Prototype Design and Effectiveness in Seismic Response Control

The concept of a pseudo-negative stiffness (PNS) damper using a fluid viscous variable damper with semi-active control has been introduced since the early 2000s and has been proven effective in reducing the seismic response of a structure. In this research, the development of a prototype fluid viscous passive damper system capable of producing a PNS hysteretic loop is reported. The prototype damper can be an alternative to the PNS damper that does not need any external control or utilization of advanced elements and materials. To produce the hysteretic loops passively, the tube of the damper is modified so that the damping force is controlled by the flow of viscous fluid between the piston and the tube by providing grooves at the tube's inner wall. The groove's dimensions are smaller at one end and larger at the other end. When the piston moves from the position of smaller to larger grooves, the fluid flows from smaller to larger grooves. This will make the damping force shift from large to small. When the piston moves back from large to small grooves, a valve will make the fluid flow freely through the orifice and produce a small damping force. Combination with another damper with opposite characteristics produces a complete PNS hysteretic loop. Based on the designed passive damper, the theoretical model of the hysteretic loops was numerically simulated under seismic loading for a base-isolated system employing the damper. The hysteretic loop was proven effective in reducing the seismic response of the system.