Design and Evaluation of an Innovative SMA-Based Three-Dimensional Isolation Bearing to Metro- and Earthquake-induced Vibrations

The increasing density of urban rail networks has resulted in substantial growth in metro-superstructure building development. These structures face dual engineering demands in high-seismic regions: ensuring occupant comfort by mitigating metro-induced vibrations while maintaining structural safety during seismic events. Traditional isolation bearing systems frequently fail to address both vertical and horizontal excitations simultaneously. To address this limitation, a novel three-dimensional seismic and vibration isolation bearing (3D-SVIB) is developed, exploiting the superelastic properties of shape memory alloy (SMA) materials. The 3D-SVIB incorporates thick laminated natural rubber (LNR) components and SMA wires arranged in a parallel configuration. The LNR module primarily accommodates vertical compression loads, while both components collectively resist horizontal shear forces, thereby achieving decoupled directional responses. Mechanical constitutive models were developed based on comprehensive experimental data, with testing demonstrating that the bearing’s vertical stiffness increases from 1,559 to 2,107 kN/mm under progressive compression loading. Furthermore, the horizontal equivalent stiffness increases from 2.95 to 4.76 kN/mm with increasing shear strain amplitude. The bearing system maintains structural stability under deformation levels reaching 150% and demonstrates superior energy dissipation capabilities. Coupling analysis reveals minimal interaction effects, with stiffness variations maintained below 10.05%, thereby validating the decoupled design philosophy. Additionally, frequency response analysis indicates significant resonance control improvements, with structural period elongation achieving 1.93 times (horizontal) and 5.33 times (vertical) compared to the original fixed-base structure. The -12 dB isolation thresholds are reduced to 1.04 Hz and 2.12 Hz for horizontal and vertical directions, respectively, representing 85% and 82% improvements over baseline structural configurations. Dynamic analyses demonstrate substantial vibration reductions under both excitation types. Metro-induced vertical accelerations decrease by 31.65–34.95% across building floor levels, with insertion loss reaching 10.1 dB. Under seismic loading conditions, the 3D-SVIB system limits top-floor displacement to 20.3% of fixed-base response levels, compared to 76.7% achieved by conventional isolation systems. Moreover, maximum interstory displacement ratios are reduced to 61.1% of non-isolated values. Engineering validation through a comprehensive Chongqing transit-oriented development (TOD) project confirms the system’s practical effectiveness for metro-superstructure applications in seismically active regions.