Influence of Equipment–Structure Interaction on Seismic Response of Seismically Isolated Substation Building

All-indoor substations, where all the electric equipment is set in one building, have been progressively promoted and utilized. Under seismic excitation, both the equipment and the building structures experience dynamic responses, which influence each other. In design practice, floor-mounted electrical equipment is often treated as nonstructural elements and modeled as vertical loads. However, per ASCE 7-23, if such equipment significantly affects the building’s lateral stiffness, it should be modeled with its stiffness and mass considered together as a nonbuilding structure. To investigate the impact of equipment–structure interaction on the dynamic response of the system, a 220[Formula: see text]kV indoor substation was taken as the research subject. A frame-element model of the equipment building and a solid finite element model of the floor-mounted Gas-Insulated Switchgear (GIS) were established. Modal analysis and seismic time-history response analysis were conducted. Three seismic ground motion records (El Centro, Tangshan-NS, and an artificial Lianzhou-1 wave) are used in the time-history analysis, scaled to peak ground accelerations (PGAs) of 0.2g and 0.3g to represent frequent and rare earthquake scenarios, respectively. The results indicate that the interaction between the structure and equipment significantly affects the seismic response of both the structure and the equipment. Under rare earthquake conditions, equipment–structure interaction increases the floor acceleration response of the building, with a maximum increase of 33%. The higher the floor where the equipment is located, the greater the impact of interaction on the structural dynamic response. After seismic isolation for the building, the structural acceleration response and base shear are significantly reduced. However, the equipment–structure interaction still has a notable effect on the seismic response of the structure, resulting in a maximum increase of 12.5% in the story shear.