Content area
Full text
In design of ships and ship-shaped offshore units, issues related to impact pressure actions arising from sloshing, slamming, green water, or explosion are of particular concern. The structural response under impact pressure actions is quite different from that under static or quasi-static actions. It has been recognized that the limit state approach is a more rational basis for structural design and safety assessment where both "demand" (loads) and "capacity" (strength) must be accurately defined. For impact pressure action cases, the demand is associated with hydrodynamics areas, taking into account the characteristics of impact pressure-time history, and the structural capacity is associated with structural mechanics areas, considering geometric and material nonlinearities together with strain rate sensitivity. This paper reviews recent advances and trends toward future limit state design of ships and offshore structures under impact pressure actions.
(ProQuest Information and Learning: ... denotes formula omitted.)
1. Introduction
SHIPS and offshore structures are often subjected to impact pressure actions arising from sloshing, slamming, green water, or explosion. The accelerations arising from the motions of a ship in a seaway produce sloshing loads, that is, inertial reactions, on liquid cargo tank structures of the ship. Motions of liquid cargo vessels, such as LNG (liquefied natural gas) carriers and double-hull tankers, often produce severe sloshing loads. Tanks of moored floating production, storage, and off-loading units (FPSOs) are continuously loaded and unloaded, and sloshing in the tanks is unavoidable. Recently, there is a trend in double-hull very large crude oil carriers (VLCCs) or ultra-large crude oil carriers (ULCCs) to adopt large wide tanks and also to reduce the number of their tanks, resulting in larger tanks with longer natural periods. There is a similar trend to increase the cargo hold size of large LNG carriers. These trends will make fluid motions in liquid tanks more sensitive to sea wave excitations.
Three trends on present-day types of vessels can be identified as contributing to the advent of sloshing as a more serious problem (Hamlin 1999), namely,
1. Most tank vessels carrying crude oil or petroleum products nowadays generally tend to have a smaller number of large tanks than in the past. Therefore, the natural period of waves at the free surface of the tank has been lengthened and is likely...