A Novel Passive Pseudo-Negative Stiffness Damper for Seismic Response Reduction

Abstract The concept of a pseudo-negative stiffness (PNS) damper using a fluid viscous variable damper has been introduced since early 2000s, which employed a semi-active control to produce PNS hysteretic loops by using a variable damper. The hysteretic loops were proven to be effective in reducing the seismic response of a structure. In this research, the development of a passive damper system capable of producing a PNS hysteretic loop is reported. The damper is based on fluid viscous damping. 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 grooves to larger grooves, the fluid flows from smaller grooves 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 at the piston. This will make the damping force small. Combination with another damper that has opposite characteristics produces complete PNS hysteretic loops. Based on the designed passive damper, the theoretical model of the hysteretic loops was numerically simulated under seismic loading for a base-isolated structure employing the damper. The hysteretic loop was proven effective in reducing the seismic response of the structure.