6. Fundamental Study of Wave Impact Loads on Ship Bow

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Three-dimensional semi-cylindrical 1/3-scale bow models were subjected to drop test in a water impact generating tower in order to evaluate the characteristics of wave impact pressure acting on the bows of very large ships and to investigate their structural response. The models were dropped on the still water surface from various heights (5 m at the maximum) at small relative angle (0°, 5° and 15°). The total drop weight was 10 tons each time. From the results of the drop test, the relations among the maximum impact pressure P_<max>, the relative bow・wave impact velocity V_0, the relative stem-wave angle a and the, radius of bow curvature R were obtained. It was found that the maximum impact pressure would be affected by the relative stem-wave angle more strongly than the radius of bow curvature. The maximum impact pressure as measured on the surface of one rectangular section of the curved model plating were not distributed uniformly and simultaneously and were not considered to directly contribute to the structural response of the plating. Accordingly, the equivalent static pressure P_<eq>, which was converted from the maximum transient strain of the panel into uniformly distributed static pressure was defined. In the severest impact condition, the magnitude of P_<eq> was of the order of one third of P_<max>. The relationship between the relative angle α and P_<eq> for a panel located at the center of the model was obtained. Furthermore, the quasi-static response of a rectangular plate panel to impact pressure was obtained by applying Wagner's theory on wedge models to the cylindrical body. It was found that such numerical analysis would be useful in estimating the approximate magnitude of equivalent pressure P_<eq> and that P_<eq> was affected considerably by an area of a panel and its position. It was also confirmed that the same bow damage could be reproduced in the models as in the actual bows of the large full ships under repeated impacts with stem-wave angle α of 0 deg. at impact velocity V_0 of 8 m/s. And it was estimated that the impact pressure that could be expected at the bow plating during wave impacts were of the order of 330 t/m^2 in terms of uniform static pressure.
社団法人日本船舶海洋工学会の論文

6. Fundamental Study of Wave Impact Loads on Ship Bow

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