Investigations on the Seismic Responses of Structures with a Suspended Mass

This paper presents the shaking table tests and an analytical study of structures with a suspended mass under coupled horizontal and tilting ground motions (CHT) caused by an earthquake. Shaking table tests of a 1:10 scaled model for a converter valve hall with a suspended mass in a high-voltage direct current electric power transmission station are carried out. The equations of motion for the structure, including the influence of the rotary inertia of the suspended mass, are derived. The responses of the model to different ground motions during an earthquake are investigated. It is found that the tilting ground motion plays a significant role in predicting the seismic response of the structure, and it needs to be considered in association with the horizontal ground motion. The response of the structure with a suspended mass to CHT ground motion is much larger than that to horizontal ground motion. The possibility of replacing the steel cables with springs as the suspending components is also investigated, and the spring is shown not to influence the acceleration and displacement responses greatly, but it significantly reduces the tension in the suspending components. Therefore, when a suspended mass is used as a mass-pendulum mitigation system, it is more advantageous to use springs or members having a low axial rigidity as the suspending components. In addition, the effects of the length of the cables and springs on the seismic response of the model with a suspended mass are also explored. It is found that the shorter the cables (or springs), the better the mitigation effects of the suspended mass on the main structure.