Technology for Optimum Mitigation

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Professor: Kohju IKAGO
Assistant Professor:  Jia GUO

Research summary

We develop innovative and high-performance seismic response control devices for civil structures and high-density concrete containers to shield the radiation from cesium contaminated soil; the former is to ensure higher earthquake resistance of civil structures against future-expected extreme seismic events such as near field or long-period/long-duration ground motions, and the latter is to promote disposal of the soil polluted in the accident at the Fukushima Daiichi Nuclear Power Plant on March 12, 2011.

Development of an inerter-based tuned mass damper with an apparent mass amplifying mechanism

A device that controls vibrations in an oscillatory system by adding a weight is designated a dynamic vibration absorber (DVA), whose application is found in wide range of engineering fields. It is also well known through the ages that an amplified large apparent mass can be obtained from a small physical mass by using mechanisms such as leverage, rack and pinion, ball-screw, and so on. We developed an innovative and high-performance damper for civil structures by replacing the mass element in a DVA with an apparent mass yielded by ball-screw mechanism. The seismic control system we have developed has been put to practical use in a building recently completed in Sendai, Japan.

An application of the innovative damper


Research for validated and sophisticated real-time hybrid simulation technology

A large amount of time and money is required to test a newly developed device to be incorporated into a civil structure, since the experimental setup becomes very large. The real-time hybrid simulation (RTHS) is a technology that has been accepted and applied in wide range of engineering fields, which puts software and hardware simulations together to achieve substantial reduction in the experimental cost; a whole structure to be tested is divided into two substructures, physical and numerical ones and a test is conducted in real-time connecting the two substructures on-line. For example, a physical experiment is conducted on a newly developed device, and numerical simulation is conducted on a building structure whose behavior can be numerically well simulated.

Real-time Hybrid Simulation


Development of a high-density concrete shielding container useful in disposing radioactive cesium contaminated soil

After a disastrous accident at the Fukushima Daiichi Nuclear Power Plant on March 12, 2011, a large amount of radioactive material was dispersed into the air and polluted a large land area with radioactive Cesium (134Cs and 137Cs). To address this issue, we develop a high-density concrete shielding container that is useful in disposing radioactive cesium contaminated soil.