Three-dimensional decoupling isolation bearing: Experimental validation, design methodology, and seismic response

Most existing seismic isolation systems primarily target horizontal excitations, offering limited protection against potentially damaging vertical seismic effects. Although various three-dimensional isolation bearings have been developed, they often suffer from undesirable coupling between horizontal and vertical responses and inadequate vertical load-bearing capacity. To address these challenges, this study proposes an innovative Three-Dimensional Decoupling Isolation Bearing (3D-DIB), composed of a Lead Rubber Bearing (LRB) for horizontal isolation and a Ring-Spring Vertical Isolation Bearing with a Central Ring (RSVIB-CR) for vertical isolation. These two elements are arranged in series to realize independent control and effective decoupling of multidirectional seismic responses. To validate the proposed system, cyclic shear-compression tests under varying axial loads were conducted, confirming the decoupling capability. Corresponding design methodologies were also established for the horizontal and vertical isolation subsystems based on their dynamic properties. Subsequently, the proposed isolation system was integrated into a multi-story reinforced concrete frame, and finite element analyses were conducted to investigate its seismic performance under 3D excitations. Experimental results confirmed effective directional decoupling, with the LRB showing stable hysteretic behavior and significant energy dissipation under horizontal loading, and the RSVIB-CR demonstrating excellent vertical load-bearing performance and energy dissipation capability. Numerical analyses further revealed that, compared with a non-isolated structure, the 3D-DIB significantly reduced peak horizontal accelerations by approximately 50 %–75 %, vertical accelerations by 30 %–55 %, and effectively controlled inter-story drifts and displacements. These findings confirm the 3D-DIB's capacity for robust multidirectional seismic protection. The system demonstrates strong potential for application in high-rise buildings in regions of high seismic intensity.