Numerical investigation of three-dimensional isolator and mitigation for single-layer lattice shell structure

Abstract

Three-dimensional (3D) isolators need to have capabilities to support the dead weight of superstructures and mitigate both horizontal and vertical seismic responses of structures. However, the lack of self-centering capability under horizontal loadings and large stiffness under vertical loadings of the 3D isolators might limit their isolation performance in practical engineering. This study presents a novel 3D isolator (hereinafter referred to as DS-SMA-FS) to achieve self-centering capability under horizontal loadings and quasi-zero stiffness under vertical loadings. The self-centering capability is provided by shape memory alloys U-shaped dampers (SMA-UDs), and the quasi-zero stiffness (QZS) property is realized by the negative stiffness of disc spring (DS) isolator and positive stiffness of SMA-UDs. The working mechanism and analytical model of the DS-SMA-FS isolator were developed first. The finite element model of the DS-SMA-FS isolator was furtherly established. Numerical results revealed that DS-SMA-FS can exhibit SC capability under horizontal loadings and QZS property under vertical loadings. Subsequently, single-layer lattice shells were established to explore the isolation performance of the DS-SMA-FS isolator. Structural analysis results indicated that the DS-SMA-FS isolator can prolong the natural vibration periods of the shell and effectively prevent the shells from tri-directional earthquakes.