Fatigue analysis is an important part of the structural design of weight-optimised naval ships, because they are often constructed from aluminium alloys or high tensile steel. Due to the low fatigue strength of these metals, the welded joints are vulnerable to cracking. Furthermore, naval ships can be required to operate in demanding environments, and remain in service longer than assumed during design. Thus, ship designers and in-service managers require efficient fatigue evaluation approaches. One industry-accepted and relatively quick method, documented in design codes, to assess the fatigue strength of welded joints is the nominal stress or S-N curve approach. However, there are uncertainties associated with using a design code; if all of the conditions for its applicability are not met, the analyst must reliably interpret the code. Further, different specifications for the use of S-N curves leads to different fatigue life estimates. In this paper, a refinement of the nominal stress approach for joints, typical of aluminium welded ship details, is proposed. The goal is to inject rigour and practicality into the fatigue analysis of naval ships. The refinement process leverages both in-service maintenance information and long-term strain measurements of a 56 m aluminium patrol boat. The sensitivity of the predicted fatigue life of welded details to the choice of S-N curve, available from a structural design code, and stress parameter extraction is investigated. Finally, recommendations for future work are provided.

When a ship enters service it has an implied or calculated design fatigue life. Factors including construction quality, loads, material performance, and operational profile are assumed. However, these factors vary through life. Failure of structural items due to fatigue cracking can lead to increased cost of ownership and reduced capability. Therefore, to allow informed decision-making, it is necessary to monitor the variables that influence a ship's fatigue life. This paper presents a new method whereby in-service data, fleet maintenance reports, and Finite Element Analysis are incorporated to predict the fatigue life and hence support the management of the remaining service life of a ship. The method is applied to a naval High Speed Light Craft to demonstrate its merit. The fatigue lives of different welded details are predicted using a practical implementation of the S-N curve approach, employed with strain and operational data acquired from an on-board hull monitoring system.

Ship maintenance was initially considered as more of a financial burden than as a way to preserve safety, environment and quality transportation. The benefits from applying a sound and systematic maintenance policy are emerging both in the minimisation of unnecessary downtime as well as in the increase of operational capability. In this paper, a novel predictive maintenance strategy is demonstrated, combining the existing ship operational and maintenance tasks with the advances stemming from new applied techniques. The initial step for the application of the above-mentioned strategy is also shown regarding the machinery space of a cruise ship. Well-known tools are applied such as Failure Modes, Effects and Criticality Analysis (FMECA) and Fault Tree Analysis (FTA). Outcomes of this study are the identification of the critical components of the system, the estimation of the reliability of the overall system and sub-systems, the prioritisation of the maintenance tasks and finally the availability of the specific end events/items.

The study investigates the experimental and numerical analysis of the occurrence of auto-parametric rolling for large, high-speed pod-driven ships in waves. Considering unique design and performance targets, the aim here is to exploit susceptibility to auto-parametric rolling behaviour and to identify probable design and operational precautions. In order to achieve this aim, an existing non-linear time-domain software to simulate capsizing and other critical manoeuvring behaviours of slow- to medium-speed conventional and podded ships in waves is being enhanced for fast pod-driven vessels and then compared against the dedicated model test conducted in long-crested regular and random waves for a large, pod-driven containership model. This paper includes the presentation of current numerical modifications for pod-driven ships and the verification analysis.

This paper presents a summary of the recent advances on Quasi-static response of ship and offshore structures as discussed by the Technical Committee II.1 - Quasi-Static Response of International Ship and Offshore Structures Congress (ISSC), 2006. The technical committee’s mandate was concern for the quasi-static response of ship and offshore structures, as required for safety and serviceability assessments. Attention was given to uncertainty of calculation models for use in reliability methods, and both exact and approximate methods for the determination of stresses appropriate for different acceptance criteria were considered.

The application of pod propulsion in a number of vessel types has been increasing steadily over the last two decades. This increase is attributed to the great advantages being offered by pod propulsion systems such as high manoeuvring capability, low noise and vibration, low fuel consumption, etc. Despite these advantages, operators are cautious due to the encountered teething problems, especially in the very competitive passenger ship market, where reliability and the maintainability of the service are crucial. This paper presents a reliability assessment methodology and its application to a combined four‐pod propulsion system on a vessel equipped with two fixed‐ and two rotating‐pod units. The assessment methodology made use of Failure Mode and Effect Analysis, Fault Tree Analysis (FTA) and Markov Analysis complementarily. In the FTA, minimal cut set, reliability importance measure and availability analyses were also considered. From the quantitative reliability assessment, the calculated reliabilities of each fixed‐ and rotating‐pod unit, their components' reliabilities as well as the reliability of the combined four‐pod propulsion system showed good agreement with the acceptable reliability criteria suggested by the pod manufacturers/operators based on the service experience. Copyright © 2006 John Wiley & Sons, Ltd.