Performance and design method of a novel three-directional hybrid seismic-shock isolation system

Explosions and other impulsive sources can induce multidirectional ground shocks (GSs) that severely damage structures, even those equipped with seismic isolation systems. Existing isolation systems primarily address either seismic or unidirectional shock loading, limiting their effectiveness for three-directional seismic-shock isolation scenarios. To address this gap, this paper proposes a three-directional hybrid seismic–shock isolation system (HSSIS) capable of simultaneously mitigating earthquake and GS excitations. The HSSIS comprises four integrated components: springs for vertical support, friction pendulum bearings (FPBs) for seismic isolation, wire rope loops (WRLs) to constrain relative displacement, and eddy current dampers (ECDs) to deliver concurrent horizontal and vertical damping. Cyclic loading tests of WRLs were performed to obtain their hysteretic behavior. A detailed finite element (FE) model of the HSSIS is developed, including FPB nonlinearity, WRL hysteretic behavior via an equivalent plasticity approach, and ECD response through nonlinear damping elements. Performance evaluation demonstrates that the HSSIS achieves acceleration reductions of 89.25% (horizontal) and 78.02% (vertical) under GSs, and 40.56% (horizontal) and 20.51% (vertical) under seismic excitation. Also, a simplified FE model is developed, which retains high accuracy while achieving an 18-fold improvement in computational efficiency. Parametric studies identify ECD inclination, maximum damping force, FPB radius, and friction coefficient as critical design parameters. Finally, a design method is presented to facilitate rapid HSSIS configuration for practical applications. Through comparison with HSSIS without CP, HSSIS without WRLs, and the spring-ECD system, the proposed HSSIS demonstrates superior structural stability and design flexibility.