Seismic performance improvement of a three-dimensional isolated spherical reticulated shell structure using pseudo-negative-stiffness magnetorheological dampers

Three-dimensional (3D) isolation is a promising solution for providing comprehensive seismic protection to large-span spatial structures against both horizontal and vertical ground motions. This study introduces an innovative 3D isolation system for spatial reticulated shell structures using pseudo-negative-stiffness magnetorheological dampers (PNSMRDs). In the vertical direction, the PNSMRDs are connected in parallel with a prepressed spring device (PSD)-based bearing (PSDB) to form a PSDB-PNSMRD isolator that supports the reticulated shell roof. A set of semi-active control methods was established for the real-time current input to the PNSMRDs, simulating the related pseudo-negative-stiffness and energy dissipation behaviors of the damping device. A single-layer spherical reticulated shell with surrounding columns was taken as a prototype structure. The PSDB-PNSMRD isolators and concave sliding bearings were designed as a decoupled 3D isolation system for this prototype structure. For comparison, a counterpart 3D isolation system featuring passive viscous dampers was also evaluated. Seismic responses of the isolated and non-isolated structures under triaxial seismic excitations were modeled using an integrated OpenSees‒MATLAB platform. The numerical results reveal that both isolation systems are effective in mitigating structural responses, with the PSDB-PNSMRD bearings providing superior vertical isolation effects compared to passive vertical isolation bearings.