Short Term Statistics of Hydroelastic Loads of a Containership in Head and Oblique Seas

Abstract

Vertical bending moment (VBM) is an important parameter for the structural safety of any sea going ship. Generally, it is expected that ships encounter largest VBM in head seas. However, when it comes to flexible ships, it is not necessary that the largest VBM always occurs in head sea. It can also occur in oblique waves and high frequency response in waves with shorter period can be as large as the wave frequency response or can be even larger. Studies conducted in the recent past by other researchers has shed some light into this peculiar characteristics of VBM of flexible hulls. Therefore, it will be worthwhile to further investigate to check whether the nonlinear design load calculation of the flexible hull in head seas will lead to conservative results or should be tested for a range of headings with different combinations of wave period in order to estimate the largest VBM acting on the hull. In this paper, the numerical and the measured VBM of an ultra large container ship (ULCS) in low to severe sea states are analyzed and compared. The effect of speed, significant wave height, springing and bow flare slamming on the response is studied. The measured VBM in head and oblique waves are compared and interesting findings are observed.