Collision-Accidental Limit States Performance of Double-Hull Oil Tanker Structures: Pre-CSR versus CSR Designs

Abstract

To mitigate the impact of consequences of ship collisions in terms of health, safety, and the environment, it has been made mandatory that hull structures of all oil tankers have double sides and double bottoms. In recent years, International Association of Classification Societies (IACS) has developed Common Structural Rules (CSR) for structural design of double-hull oil tankers on the basis of limit states, together with the traditional approach using the allowable working stress that has been a basis of pre-CSR. The application of CSR may result in some differences in terms of structural performance, among other aspects. The main objective of the present paper is to investigate the structural performance of CSRdesigned tankers associated with ship collisions. This aspect might be interesting, although CSR are not intended specifically to improve collision performance. As an illustrative example, an AFRAMAX-class double-hull oil tanker structure with same deadweight designed by both pre-CSR and CSR methods is studied by comparing their collision energy-absorption capabilities as obtained by nonlinear finite element methods. It is found that the collision performance of the CSR design could be improved by 5% to 25% compared with that of the pre-CSR design, depending on the accidental limit state criteria. However, it is concluded that the strength performance of the CSR vessel is similar to that of the pre-CSR vessel in terms of collision-accidental limit states, considering the uncertainties involved in conjunction with collision scenarios and nonlinear finite element method modeling techniques. Although the present study deals with some very specific scenarios of collisions, the insights and conclusions developed will still be useful for recognizing a structural design trend related to collision-accidental limit states