A novel disc-spring-based 3D isolator: Development, experiment, and nonlinear stick-slip modeling

Conventional seismic isolation systems exhibit high horizontal flexibility with substantial vertical stiffness to mitigate horizontal ground motions, while in lack of vertical vibration control capabilities. Recent investigations have extended isolation technologies into three-dimensional (3D) applications, though existing solutions face a critical trade-off between vertical isolation efficiency and gravity load-bearing capacity. This study presents an innovative 3D isolation system integrating conventional elastomeric bearings with a novel disc-spring-based vertical isolation subsystem through an optimized deformation-decoupling mechanism. The vertical isolation assembly incorporates loading rings and Polytetrafluoroethylene (PTFE) interface membrane to enhance deformation capacity while reducing vertical equivalent stiffness. Significantly, the reduced vertical stiffness yields a lower isolation frequency, thereby enhancing the vertical performance of the 3D-isolator. A nonlinear analytical model is developed, accounting for disc spring force-displacement relation and the interfacial stick-slip frictional behavior. Comprehensive experimental validation was performed through vertical cyclic loading and compression-shear test, revealing that: (1) The integrated 3D-isolator achieves more than 75% vertical stiffness reduction relative to standalone elastomeric bearings without compromising gravity loading capability; (2) Horizontal mechanical properties show only a slight influence by the integration of vertical isolation system; (3) Theoretical prediction shows a satisfying modelling of hysteretic loops, and less than 12% deviation in equivalent vertical stiffness. These findings validate the efficacy of the 3D isolation configuration, demonstrating its potential to deliver satisfactory vibration mitigation performance under both seismic events and transit-induced excitations. Future research should prioritize system-level dynamic performance validation under multi-directional excitation scenarios.