PERFORMANCE CURVES FOR BASE-ISOLATED BUILDINGS REFLECTING EFFECT OF SUPERSTRUCTURE VIBRATION PERIOD

Base isolation has become increasingly used not only for short buildings but also tall buildings, especially in Japan. It is recognized as an effective strategy for reducing displacement and acceleration in the superstructure. In design, rigid superstructure is generally assumed. However, for tall buildings, flexibility of the superstructure also plays an important role in the response of the structure. As a result, expensive rigorous dynamic analysis is required. This study, therefore, aims to propose a simplified approach which takes into account flexural superstructure to approximate the maximum response of base isolated structure using response spectra. Verification of the proposed theory indicates good accuracy. Hence, the theory can be used to design the isolation system to achieve a desired performance level.