Abstract
The 2003 Tokachi-oki Earthquake (M8. 0) caused severe damage to oil storage tanks at Tomakomai, igniting fires and sinking floating roofs. The cause of this damage was the liquid sloshing of oil storage tanks excited by long-period strong ground motion. After the earthquake, the technical standard of the Fire Service Act regarding the sloshing of floating roof tanks was revised in 2005 and a certain number of floating roofs are scheduled to be reinforced before 2017 if necessary in order to prevent similar damage to large oil storage tanks as a result of future earthquakes.
However, thorough verification of the dynamic behavior of a floating roof due to liquid sloshing is difficult using an actual oil storage tank, especially when the non-linear sloshing is remarkable. There have been few studies on the formulation of the non-linear sloshing of the actual floating roof. The non-linearity is a foundation of the technical standard for the strength evaluation in the Fire Service Act. Therefore, the adequacy of the formulations of the large-wave-height sloshing with a floating roof must be confirmed experimentally using an actual oil storage tank.
In the present study, we conduct sloshing experiments by directly vibrating the floating roof of an actual 38-m-diameter tank. The goal is to examine the formulations of the non-linear liquid sloshing behavior for a floating roof and the formulations of the strain produced at the pontoon of the floating roof.
Based on the experimental results, we concluded that the formulations of the non-linear liquid sloshing behavior and the strain at the pontoon are adequate. The viscous damping factor of the liquid sloshing with a single-deck type floating roof is less than 0. 5% when the sloshing height is considerable.
