Currently, it has mandatory for seismically isolated buildings to apply earthquake motions in notification since the Building Standards Act was revised in 2000. There is a possibility the notification level exceeds an earthquake motions level had been applied before 2000. Moreover, it is concerned a long-period ground motion is occur. Therefore, it is necessary to assess difference of the response performance due to these ground motions. This paper shows one example of assessing each response performance for seismically isolated buildings designed before 2000. Furthermore, it confirms if improvements by using energy balance method can enhance performance.
