Resonant behaviour of base-isolated high-rise buildings under long-period ground motions

The resonant behaviour of base‐isolated high‐rise buildings under long‐period ground motions is investigated. The long‐period ground motions are known to be induced by surface waves. While the acceleration amplitude of such long‐period ground motion is small, the velocity amplitude is fairly large. It is expected that high‐rise buildings and base‐isolated buildings with long fundamental natural periods are greatly influenced by these long‐period ground motions. Especially base‐isolated high‐rise buildings with friction‐type bearings may have remarkable mechanical characteristics unfavourable for these long‐period ground motions. The purpose of this paper is to reveal that the long‐period ground motions recorded in Japan have the intensity to make base‐isolated high‐rise buildings in resonance with long‐period components and that careful treatment is inevitable in the structural design of these base‐isolated high‐rise buildings. It is pointed out that the friction‐type bearings are effective in general in avoiding the resonance with ground motions with a narrow‐range frequency characteristic, but are dangerous for ground motions with a wide‐range frequency characteristic in the long period range. Copyright © 2006 John Wiley & Sons, Ltd.