Vibration Tests on Nuclear Power Station Stacks Equipped with Structural Control Oil Dampers

Abstract eng:
This paper presents forced vibration tests conducted on a 100m-high steel stacks at Hamaoka Nuclear Power Station, whose seismic margin has been widely enhanced through an upgrading project using structural control techniques. For this project, a new target earthquake load that is much stronger than the original design loads was set up. The original stack was designed as free-standing without any supporting frames, and we planned to link the with a supporting tower via oil dampers to improve structural damping as well as strength. In order to examine the dynamic characteristics of the stacks with the oil dampers, forced vibration tests were carried out before project completion by introducing three slide-mass-type exciters on the top level of the supporting tower. Although the observed displacement at the top of the stack was less than 10mm, which is much smaller than the response to the target design earthquake, the test results showed damping ratios of about 9% In addition, it was confirmed that the test results were well simulated by the numerical model used for seismic design by simply introducing a small friction element to the damper portion. This paper first describes the specification of the stack with oil dampers, and presents the results of vibration tests. Next, it presents simulation results and discusses the control effect of the oil dampers.

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