Study on Vibration of a Floating Roof of an Oil Storage Tank Due to Nonlinear Sloshing

In a previous paper, it was shown that stresses arising in a floating roof subjected to sloshing are significantly underestimated if the nonlinearity of the sloshing is neglected. In this paper, dependence of the nonlinear responses of the stresses on the slope of the pontoon is examined. Numerical results show that the decrease in the slope of the top and bottom of the pontoon results in decrease of the out-of-plane stresses and increase of relatively small in-plane stress components. Furthermore, the validity of the present nonlinear sloshing analysis is confirmed by conducting numerical calculations for the cases in which the pressure under the pontoon becomes negative and the free liquid surface oscillates with finite amplitude. It is confirmed that the results for the negative pressure and the surface displacement are in good agreement with results presented in past works.