Experimental study on the coupled structure-isolated equipment system under near-fault pulse-like ground motions

In recent years, seismic isolation systems have gained popularity for protecting equipment. However, designing isolation for floor-mounted equipment presents greater challenges than for ground-mounted equipment due to the interaction between structure and equipment. This study investigates the seismic performance of equipment isolation under conditions of strong interactions and near-fault earthquakes. A series of shaking table tests were conducted to compare the seismic behavior of coupled structure-equipment systems with and without isolators, considering the stiffness characteristics of the equipment and the tuning effects within the systems. Additionally, numerical analyses were performed to elucidate the mechanisms of equipment isolation and assess the influence of pulse properties on the isolated equipment. The results indicate that the effectiveness of equipment isolation correlates with the frequency ratio of the coupled systems. Isolation can reduce the interaction forces, thereby impacting both the equipment and the structure. Notably, significant responses were observed when the equivalent period of the isolated equipment was relatively shorter than the pulse period. However, tuning effects on floor-mounted isolated equipment require further consideration compared to ground-mounted systems.