Abstract
In the case of a grounded ship, tears longer than half the ship's length may be found in its bottom. For this reason, a grounded tanker leaking heavy pollutants poses a serious threat to sea environments. Although researches on collision are intensive, very little is known about structural damage in the event of grounding.
This paper aims to contribute to the theoretical prediction of failures of bottom structures. The scenario under consideration is bottom raking. A method considering primary energy absorbing mechanisms is proposed to predict the structural strength against this kind of damage. Along the longitudinal direction, periodic structures extend nearly all the way from collision bulkhead at bow down to stern, so the resistance of bottom structures is assumed also to be periodic, with tearing and denting failures being predominant in the damage process, occurring alternately.
If a seabed reef impacts on a transverse structure, the bottom plate immediately behind the transverse structure tends to bulge out of its original plane, causing the denting of plate. Emphasis of this paper is on introducing and analyzing this failure mode. Through application of plasticity theory, a closed-form solution is derived for predicting the strength of a dented plate. By checking against existing experimental researches, the proposed kinematic models and the obtained formulas can be verified.
It is found that resistance of bottom plate is proportional to t1.67 when it is dented, and proportional to t1.5 when it is torn.
