Original Article Proc IMechE Part M: J Engineering for the Maritime Environment 226(3) 222–234 Ó IMechE 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1475090212436606 pim.sagepub.com Application of a ship-routing fatigue model to case studies of 2800 TEU and 4400 TEU container vessels Wengang Mao 1 , Zhiyuan Li 1 , Jonas W Ringsberg 1 and Igor Rychlik 2 Abstract Ship structures will always be subjected to and suffer from fatigue damage and fracture. However, we can become better at utilizing the materials and the structures and operating them more wisely, leading to less maintenance, extended ser- vice life and enhanced safety if we can improve the fatigue damage prediction. In this study, a fatigue model useful for ship routing is presented. Similar to the ship-routing design for the expected time of arrival and fuel reduction, the objective here is to demonstrate the possibility and benefits of ship route planning which lead to a reduction in fatigue damage accumulation. In the context of ship fatigue route planning, uncertainty analysis of the fatigue assessments of container ships is discussed. The proposed ship-routing fatigue model is employed in case studies on two container vessels to illustrate the possible benefits to the fatigue safety of ship structures. Sea environments in the application are obtained from hindcast wave data and a spatiotemporal wave model. The results show that the fatigue damage of the studied con- tainer ship structures could be decreased by more than 50% if awareness and knowledge of fatigue in ship route planning are employed. Keywords Container vessels, fatigue, ship routing Date received: 19 December 2011; accepted: 4 January 2012 Introduction Fatigue damage accumulation in a ship structure is a continuous random process, which is a great challenge to assess and take into account in the design procedure. There are several sources of uncertainties such as loads, material and fabricated-related issues which, using today’s commonly used fatigue design procedures pro- posed by classification societies such as Det Norske Veritas (DNV), 1 make the fatigue life estimation demanding but often too inaccurate. Thus, even if a ship is ‘correctly’ designed according to classification rules, experience shows that it can be seriously dam- aged already after a very short time in operation. Figure 1 shows examples from two different vessels sailing on the North Atlantic trade route where fatigue cracks were found after operation for less than 5 years. With today’s knowledge of material mechanics, compu- tational mechanics, hydrodynamic load analysis and mathematical statistics, it ought to be possible to iden- tify more accurately and to prevent fatigue damage too early in ship structures. The occurrence and presence of fatigue cracks always increase the risk of the ship’s structural failure, leading to large casualties, such as the MSC Napoli accident in 2007. 3 The uncertainties in fatigue assessment of a ship ori- ginate from the random properties of construction materials (represented by S–N curves, where S is the stress cycle range and N is the number of cycles to failure), fatigue failure criteria, models for fatigue assessments and variable wave environments, opera- tional profiles, etc. The uncertainty in fatigue damage assessment could be reduced by carefully designed ship routes that also reduce the fatigue damage accumula- tion in total; this can be achieved by, for example, choosing less severe wave environments and more 1 Chalmers University of Technology, Department of Shipping and Marine Technology, Division of Marine Design, Gothenburg, Sweden 2 Chalmers University of Technology, Department of Mathematical Sciences, Gothenburg, Sweden Corresponding author: Jonas W Ringsberg, Chalmers University of Technology, Department of Shipping and Marine Technology, Division of Marine Design, SE-412 96 Gothenburg, Sweden. Email: Jonas.Ringsberg@chalmers.se at Chalmers Univ of Technology on March 19, 2015 pim.sagepub.com Downloaded from