Abstract
The 2003 Tokachi-oki earthquake (M8. 0) caused the sinking of floating roofs of seven oil storage tanks in Tomakomai City. After the earthquake, the technical standard of the Fire Service Act regarding the sloshing of floating roof tanks was revised in 2005 and some floating roofs are to be reinforced until 2017 if necessary in order to prevent a similar damage on large oil storage tanks in future earthquakes.
However, it is difficult to say that the behavior of a floating roof due to the second order-sloshing mode was verified thoroughly in a real-scale storage tank. The behavior is described as “ovalization” and “deflection of a deck”, which are theoretical background for the strength evaluation of the technical standard in the Fire Service Act. Especially, there were very few researches about the formulations of the effect of the second order sloshing mode upon the behavior of floating roofs. Therefore, it is needed to confirm the adequacy of the formulations of the sloshing, experimentally.
In this study, we conducted shaking experiments by using a large shaking table and a model floating roof tank of 7. 6m-diameter, which is comparatively large tank.
Considering the results obtained from the experiments, ovalizations were observed on the second order sloshing mode and the relationship between the deflection of the deck and the radial displacement of the floating roof was clearly confirmed. Then, we concluded that the formulations and the assumptions of the deflection and the ovalization defined in the Fire Service Act are adequate in comparison with the results from the experiments.
