Isolation Story Structure of Umeda Tower, Osaka, Japan

The Hyogo-ken Nanbu Earthquake (Great Hanshin Earthquake) in 1995 resulted in devastating damage to the Kansai area of Japan. Many cases of collapse and of other major damage to structures were reported. The lesson learned is that building functions must be maintained as well as the building itself following an earthquake. Story isolation can reduce not only the force but also the acceleration when a building is subject to an earthquake. The Umeda Tower is a super high-rise office building extending 130 m above ground. The structural features of the building are the mega-frames on the first through to the third floors and the story isolation on the intermediate floor immediately beneath the third floor. These features enable the use of existing already-installed structures on site, to realize the building's safety requirements against earthquakes and to maintain the building functions following the earthquake. The details of the features are described in this paper.