Gap Analysis of Ship Design Approval Case Study: Key Plan Drawing Assessment for Dual Fuel Harbour Tugboat

Starting to build the ship, the ship’s designer or builder must prepare key plan drawings with an approval statement that comes from the Classification Society (CS) based on the conformity of key plan drawings to comply with the rules or sometimes do not comply with those rules in several cases, so this situation could be minimized by using a gap analysis technique prior to the approval of the ship design process. Gap analysis is the tool to evaluate whether the design has been conforming to comply with the rules of the classification society or not. This paper chooses some parts of the ship design of a Dual Fuel Harbour Tugboat (DF Tug) to show the level of conformity to the rules. The assessment process involves Biro Klasifikasi Indonesia (BKI) since the DF Tug will be classified by BKI as a competent national classification society. The findings gap is used to improve the design of DF Tug. Finally, the framework of corrections and improvements to the DF Tug design is proposed as part of the refinement of key plan drawings, and the final ship design complies with rules and gets full approval from the classification societ

A comparison of two wave models and their influence on fatigue damage in ship structures

In the maritime industry, fatigue failure is one of the most significant failure modes for ship structures. The fatigue damage in ship structures is mainly caused by the variation of wave loadings applied on ships, leading to variable structural stresses. Therefore, a reliable description of wave environments encountered during a ship’s service life is essential for accurate fatigue assessment of ship structures. Besides the wave scatter diagram provided by classification society rules, different statistical wave models have also been built up to model wave environments along arbitrary ship routes. The wave models could provide more specific wave environment for any chosen sailing routes of an individual ship. They may have the potential to be used for some practical applications, such as conceptual ship fatigue design, remaining fatigue life prediction when a ship plans to change its original trade region, and crack maintenance planning etc. Since the development of these models may be based on different sources, e.g. satellite measurements, hindcast data, buoys, etc., the reliability and consistence of wave generations from various wave models must be validated by the measured wave environments in order to be used for those practical applications. In this paper, waves generated from two different wave models, one based on hindcast data and one mainly on satellite data, are compared with measured wave environments encountered by a 2800 TEU container vessel on the North Atlantic route. These wave models are used in the calculation of the fatigue damage in the vessel. The results obtained using waves generated from the two wave models are compared with the fatigue damage calculated based on strain measurements in the ship. Recommendations for future development of the wave models and further investigation to make the applications more realistic for ship fatigue assessment are also presented

Analysis of crack retardation effects and crack path in ship structure members on different routes

The ship size has been rapidly increased in recent years. Consequently, many aspects of ship structural safety have been concerned, i.e. fatigue strength. Since fatigue cracks are found in the early stage of a ship’s service life, it might be that the classical cumulative fatigue rule is insufficient to consider the effects of many uncertain factors, such as variable wave environment loads. The wave load history hinges on the short-sea history. It means that the accuracy of fatigue assessment is affected by the used wave model. There are several established wave models, which could be used to simulate wave load history as in the real ocean conditions. In this paper, wave load histories of a 2800TEU container ship are generated by two different wave models. It is used for crack propagation analysis in the changing routes and trades. The result in the simulated crack propagation lives is examined and discussed