Session: SE-02-02 Seismic Isolation and Structural Dynamics-2

Paper Number: 121826

121826 - Study on Vertical Sloshing Load Acting on Roof of Cylindrical Tanks Under Seismic Wave Excitation 

During an earthquake, sloshing occurs in a cylindrical tank when a frequency component close to the natural frequency of sloshing is included in the seismic wave. When high amplitude sloshing occurs, the free liquid surface level fluctuates greatly in the tank, and the liquid surface collides with the roof of the tank. In tank design, it is important to evaluate the sloshing load acting on the roof.
In a previous study, authors proposed a predictive evaluation method of the vertical load acting on the roof of cylindrical tanks. The method consists of a nonlinear sloshing model and an impact pressure model, assuming sinusoidal excitation by sloshing natural frequency. Except for some special cases, this method almost agreed with test results and CFD analysis, in sinusoidal excitation.
In this study, we extended this method to deal with seismic wave excitation. In seismic wave excitation, the tank is excited by irregular wave, and the phenomenon of sloshing becomes more complicated than sinusoidal excitation. To simplify this complicated phenomenon, we proposed a concept of equivalent growth wave number. This number represents the magnitude of the increase in the peak of liquid surface level during seismic wave excitation. We proposed a method to quantitatively evaluate this number from seismic response analysis. In addition, we proposed a method to evaluate the vertical load on the roof during seismic wave excitation, by introducing this number into the predictive evaluation method. 
We evaluated the vertical load on the roof by using this proposed evaluation method, and we compared the evaluation results with the test results of seismic wave excitation. The evaluation results were more than 0.5 times higher than the test results under the low roof height condition. On the other hand, as the roof height increased, the test results tended to be extremely larger than the evaluation results. We carried out CFD analysis to investigate the cause of this extremely large load. The CFD analysis result indicates that the weak roof collision deformed the liquid surface in a flat shape, and this flat liquid surface caused the extremely large load on the roof. From this result, we clarified that the history of roof collision and the liquid surface shape have a large influence on the vertical load acting on the roof, not only in sinusoidal excitation but also in seismic wave excitation.

Presenting Author: Shunichi Ikesue Mitsubishi Heavy Industries, Ltd.

Presenting Author Biography: Academic Background
Graduated Kyoto Univ. in 1997 (Faculty of Engineering, Division of Civil Engineering)
Graduated Kyoto Univ. in 1999 (Master's Program, Graduate School of Engineering, Department of Civil
Engineering)
Doctoral Degree (Dissertation), Kyoto Univ. in 2007

Career
(1999-2005) Steel Structure & Civil Engineering Laboratory, Hiroshima R&D Center, Mitsubishi Heavy Industries,
Ltd.
(2005-2014) Fluid Dynamics Laboratory, Nagasaki R&D Center, Mitsubishi Heavy Industries, Ltd.
(2014-2015) Fluid Dynamics Laboratory, Nagasaki R&D Center, Mitsubishi Heavy Industries, Ltd.
(2015-present) Fluid Dynamics No.1 Laboratory, Fluid Dynamics Research Department, Mitsubishi Heavy Industries, Ltd.

Authors:

Shunichi Ikesue Mitsubishi Heavy Industries, Ltd.
Akihisa Iwasaki Mitsubishi Heavy Industries, Ltd.
Hiromi Sago Mitsubishi Heavy Industries, Ltd.
Shinobu Yokoi Mitsubishi Heavy Industries, Ltd.
Tomohiko Yamamoto Japan Atomic Energy Agency