Standard structural assessments of ship hulls include the evaluation of the elastic structural response. Elastic analysis neglects extreme and unpredicted loadings, which can produce catastrophic outcomes, such as the loss of the ship’s ultimate strength. Moreover, hull elements are considered unaffected by age-related degradation. Therefore, this study models and quantifies the effect of corrosion-induced structural degradation on the ultimate strength of a high-tensile-steel (HTS) cargo ship using progressive collapse and nonlinear finite element methods. Uniform and pitting corrosion are modeled through selected scenarios, which hull elements might encounter during exploitation, producing a total of 148 calculation models. The findings show that corrosion-induced degradation can significantly decrease the ultimate strength of the hull (up to 30% for the most severe scenarios assessed). Furthermore, ultimate strength decreases almost proportionally to the amount of wastage considered. It was found that stiffener corrosion has a significant effect on the total ultimate strength. This study’s aim is to emphasize the vast importance of including ultimate strength along with ageing effects in industry-standard structural assessments of large HTS ship structures, designed to last for several decades whilst exposed to excessive and unpredicted bending moments.

Although the International Maritime Organization (IMO) introduced the energy efficiency requirements for ships more than a decade ago, to date, inland navigation has not been affected by corresponding regulations at all. Therefore, inland waterway vessels are left with no mandatory requirements that could push their technology into more energy efficient design. Fortunately, there are certain pioneering attempts to define energy efficiency criteria for inland vessels. This paper tries to gather and provide a review of such methods. Moreover, a typical Danube cargo inland vessel’s data are used to evaluate their current energy efficiency levels with respect to provisional criteria. Consequently, two methods are found and used here. They are both based on IMO’s energy efficiency concept but modified for the inland waterway vessels. The methods delivered a significant difference in applicability and were difficult to compare. Moreover, shallow and deep-water effects are explored in the same regard but provided unsound conclusions. The final results displayed discrepancies in energy efficiency levels for the same vessels and so the methodology should be improved and harmonised, if it is to be introduced as mandatory for inland waterway vessels. The analysis provided a glimpse into the current condition of the traditional design of the Danube inland fleet, with respect to the emerging energy efficiency policies.

Inland waterways vessels (IWV) have no mandatory regulations regarding their energy efficiency, as sea-going ships have. So far, there are just two proposed design energy efficiency evaluation methods, both based on IMO EEDI approach and data on EU inland navigation. Operational indicators and real-time navigation measurements from available literature do not exist. Therefore, this paper aims to introduce the energy efficiency in operation (EEO), assessed for the typical Danube cargo vessel. Firstly, an operational profile is acquired by tracking the vessel’s voyages, and by identifying actual constraints of each sector the vessel has sailed during the designated time. Secondly, EEO is incorporated within two available methods and calculated based on acquired operational data considering different navigational conditions. The paper shows how the energy efficiency vastly depends on variables such as water depth, current speed, draught, deadweight, river constraints. Analysis is performed for the most employed month of the vessel navigation, and annually. Depending on water level scenarios and during the selected month of sailing, the total amount of CO2 emitted is estimated to be between 22.7 t and 29.9 t, while the necessary average speed reduction (i.e., slow steaming) per sectoral voyage for the requirement compliance is calculated to be in between 4.8%-26%. Slow steaming is assessed to extend the time of voyage for 6.1-10.7 hours on monthly basis and 49-87 hours annually.

This study presents a comprehensive approach to trim optimization as an energy efficiency improvement measure, focusing on reducing fuel consumption for one RO-RO car carrier. Utilizing Computational Fluid Dynamics (CFD) software, the methodology incorporates artificial neural networks (ANNs) to develop a mathematical model for estimating key parameters such as the brake power, daily fuel oil consumption (DFOC) and propeller speed. The complex ANN model is then integrated into a user-friendly software tool for practical engineering applications. The research outlines a seven-phase trim optimization process and discusses its potential extension to other types of ships, aiming to establish a universal methodology for CFD-based engineering analyses. Based on the trim optimization results, the biggest DFOC goes up to 10.5% at 7.5 m draft and up to 8% for higher drafts. Generally, in every considered case, it is recommended to sail with the trim towards the bow, meaning that the ship’s longitudinal center of gravity should be adjusted to tilt slightly forward.