Capsizing of ships : static and dynamic analysis of wind effect and cost implications

Abstract

Capsizing of small vessels, such as commercial fishing vessels, is a frequent event. This phenomenon is generally associated with the combined action of storm seas, inadequate design parameter regulations, and dangerous operational procedures. In contrast, the capsizing of large ships is rare, but does occur. For these large vessels, more strict regulations exist to ensure safe operational procedures. While the storminess of the sea cannot be controlled, the navigation procedure can. Large offshore ships tend to navigate in a path to avoid forecasted severe weather, and in cases of stormy seas they temporarily operate at safe speeds and in the direction parallel to the waves. The work presented in this thesis investigates the effect of the wind in rolling and finally capsizing a ship. For the purposes of mechanical analysis, realistic hull forms are used and fundamental issues associated with moments and forces imposed by the wind, are applied. The platforms are examined for several wind speeds that strike the ship at different angles. Both static and dynamic cases were examined. Under the assumption of general conditions, the angles of heeling in each case and the wind speeds that caused the ship to capsize are calculated.

(cont.) Furthermore, a cost analysis associated with the total loss of the ship due to capsize is also reviewed. An existing worldwide database of vessel total losses, dating from 1960 to present, is used to calculate the costs per ship capsize. Some simplifications are inevitably used, because the cost implications of total ship losses have both direct and indirect portions that are difficult to quantify. In addition, the actual numbers that result from such a catastrophe are not generally available to the public and are not found in the open literature. Given these limitations, a preliminary analysis of the capsize-associated costs is performed for several types of commercial vessels.