벌크선의 積載狀態에 따른 航海安全性 評價에 관한 硏究

A Study on the Navigational Safety Evaluation in accordance to Loading Condition in Bulk Carrier

A method for quantitative evaluation of the navigational safety of a bulk carrier according to different loading conditions is presented here. Generally, the navigational safety of a ship in various loading condotions is evaluated by a loamanual. However, the loading manual of ship handles only statical factors such as weight and buoyancy of ship without including any wave conditions. Practically ship's safety is much concerned with ship's actions on the rough sea as propeller racing, rolling, deck wetness, vertical acceleration, lateral acceleration, and slamming. These phenomenonena are occurred not by wave or ship's conditions independently but by coreactions of wave and ship's conditions. Response amplitude of ship's motion is manipulated by ordinary strip method(OSM) on a given bulk carrier of 170,000 deadweight tonnage under 6, 7, 8 and 9 Beaufort scale of sea states. Author applied each response amplitude of ship's motion induced by OSM to short-crested and irregular waves for stochastic process of phenomenonena on navigational safety of the bulk carrier. And the occurrence probability of the phenomenon is caculated by Rayleigh's joint probability density function according to different speed and loading conditions of the ship. Utilizing the evaluation indicies, the dangerousness, the maximum dangerousness and the evaluation diagram on the results, author depicted the general safety evaluation diagram. In order to make evaluation simple and effective, author adopted propeller racing and ship's rolling as the representative factors on navigational safety in bulk carrier through clarifying the correlation of factors of stochastic process. The simulation model of the study is 259.00m Lpp, 170,000 d.w.t, single screw, diesel engine operated bulk carrier. And the loading conditions adopted are four, homogeneous full loaded, half loaded, heavy ballast loaded, and normal ballast loaded conditions. This study has presented some different results of dangerousness on ship's varied loading conditions. By applying the evaluation diagrames, navigators are able to avoid dangerousness by keeping away of the danger encountering angle of wave direction which the diagram showes. This evaluation method may be useful for developing the practical safety evaluation system of ships as well as human beings and cargoes at sea.