A Study on the Strength of Ships Collision

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The strength of ship structure in collision is one of the important matters in the term of saving crews lives and preventing heavy disasters from the economic point of views, in the cases of which the collided ships are carrying dangerouse articles such as liquided natural gas and so on.1. In this research, time history of collision forces were correctly calculated by introducing mass, spring dash-pot system in the substructure where locally striked and by considering ship motions and ship hull vibrations of laterally collided ship in order to avoid over-estimation for collision forces. And extending this method, penetrations of the collided ship were approx mately estimated by using static destructive test result.2. In order to improve accuracy for the estimations by this method, the following fundametal researches were carried on :1)Added mass and hydrodynamic damping force were strictly calculated by solving equations of motions both for striked sub-structure and collided shib. It was cleared that the effect on collision phenomena owing to hydrodynamic damping force was more important than to added mass, especially for the heavy collision.2)An experimental method to estimate constructive damping for beam element, cross-beam element and plate element was developed and improved. And relations between damping coefficients and frequencies were obtained.3. The validity of this method was confirmed by analyzing an accidents of a high speed passenger ship longitudinally collided with break water at Awail Island in 1989.4. Design charts to estimate penetration on laterally collided Panamax bulkcarriers were presented.