Development and experimental study of disc spring-based negative-positive-uncoupled stiffness devices for structural multi-level seismic fortification

Abstract

To achieve the structural multi-level seismic fortification objectives, this paper proposes a novel negative-positive-uncoupled stiffness device (NPUSD) based on combined disc springs with multi-linear elasticity characteristics. This device allows for independent variations in the negative stiffness range under small deformations and the positive stiffness range under large deformations. It primarily utilizes the negative stiffness mechanism for seismic mitigation during medium and small seismic events referring to existing research on traditional negative stiffness devices (NSDs) while providing positive stiffness to prevent collapse during major seismic events. The configuration and working principle of the NPUSD are discussed. By replacing the preloaded linear elastic spring of traditional NSDs with multi-linear elastic spring, the NPUSD can effectively and conveniently achieve stiffnesses decoupling. A design algorithm based on the successive area equivalence principle for the multi-linear elastic spring is proposed. Finally, based on a 56-story steel core-outrigger structure, a comparison between NSDs and NPUSDs is made under the four seismic intensity levels. Results show that the novel NPUSDs contribute to achieving structural multi-level seismic fortification objectives.