RISK ASSESSMENT OF ARCTIC NAVIGATION BY USING IMPROVED FUZZY-AHP APPROACH

In this study, navigational risk factors of the Arctic Ocean are defined and numerical weights of each risk are obtained by using Improved Fuzzy Analytical Hierarchy Process (IF-AHP) method after conducting expert consultations. The Northern Sea Route shortens the maritime distance approximately 7000 nautical miles comparing to the conventional Suez Canal route. Therefore, it takes a significant role of being economic and time advantage for global logistics. Its geographical position, presence of ice, heavy weather conditions, strong currents and winds are some risks for Arctic transportation. There always have the possibility of unpredictable catastrophes such as a collision, grounding, hull damage and etc. in this region. Reflections of such unwanted incidents might be very costly for economic, political, environmental and safety concerns. Due to there are limited academic studies regarding to analytical and systematical risk identification and determination of risk levels, this study contributes to complete this academic gap.

Pengaruh Salinitas Air Laut Terhadap Laju Korosi Pada Plat Lambung Kapal Bobot 1500 DWT

Ships are a means of transportation over the sea, where ships play a vital role in the socio-economic aspect through their distribution function between regions. One part of the ship that is often damaged is the hull of the ship. The cause of hull damage is corrosion. The aspect of high and low level of corrosion on the hull is the salinity content in seawater. This study aims to determine the effect of salinity in seawater on the rate of corrosion on the hull plate with seawater media taken from the waters of the port of Tanjung Emas Semarang. This study used an experimental test method of weight loss (weight loss) referring to the ASTM G31-72 standard. With specimens made coupons to calculate the weight before immersion and weight calculation after soaking. Soaking is carried out for 7 days in the prepared corrosion installation. The results of this study indicate that seawater which has a higher salinity content than brackish water and fresh water has a higher corrosion rate than other coupon specimens.

Numerical Study on Seakeeping Performance of a Damaged Ship

Ships sailing in the sea may encounter collision, grounding or projectile impacting accidents, which may cause hull damage and subsequent compartment flooding. Due to the effect of the flooding water induced moment and the restoring moment, the damaged ship may have inclination and rolling motion. When the inclination or the rolling motion is too large, it may affect the safety and survivability of ship in navigation and cause severe casualties and property losses. In order to increase the navigation safety and survivability of the damaged ship, a numerical model is established based on the potential flow theory to investigate the seakeeping performance of the damaged ship in two scenarios, i.e., the case before ship damaged, and the case when the damaged ship reaching a relatively stable floating state. The heave, pitch and roll motion responses and corresponding wave-induced loads acting on the ship are analyzed in regular waves. In addition, the effects of the navigation speed and the wave direction on the seakeeping performance are also investigated.

A Zero-Inflated Negative Binomial Regression Model to Evaluate Ship Sinking Accident Mortalities

Sinking accidents are a seafarer’s nightmare. Using 10 years’ of worldwide sinking accident data, this study aims to develop a mortality count model to evaluate the human life loss resulting from sinking accidents using zero-inflated negative binomial regression approaches. The model results show that the increase of the expected human life loss is the largest when a ship suffers a precedent accident of capsizing, followed by fire/explosion or collisions. Lower human life loss is associated with contact and machinery/hull damage accidents. Consistent with our expectation, cruise ships involved in sinking accidents usually suffer more human life loss than non-cruise ships and there is be a bigger mortality count for sinking accidents that occur far away from the coastal area/harbor/port. Fatalities can be less when the ship is moored or docked. The results of this study are beneficial for policy-makers in proposing efficient strategies to reduce sinking accident mortalities.

DEVELOPMENT OF STRUCTURAL SOLUTIONS FOR PREVENTION OF WAVE RUN-UP OF THE BOW

One of the most dangerous situations for seagoing ships is wave run-up in a head sea. In such a case, significant hydrodynamic forces appear resulting in stability loss or ship hull damage. The paper presents structural solutions that contribute towards navigation safety by means of decreasing probability of wave run-up of the ship bow in a head sea. A design has been developed of a ship stabilizer in the form of hinge-mounted stabilizing wings which deflect from the hull when the bow submerges in water and then cling to it when it emerges. The paper presents a new design of the bulwark with rotating sections able to rotate in the direction from the deck to the board. These designs can reduce dipping in a wave and reduce hydrodynamic impact on the bow. Apart from this, a hull structure has been proposed with a detachable bow to prevent capsizing of a ship. If the hydrodynamic force reaches a critical value, destruction of a permanent joint will happen in the proposed design, resulting in the situation when leak-proof aft and bow parts detach and remain afloat, which will allow the crew to evacuate. The proposed designs will increase navigation safety in storm conditions.

Stochastic Characterisation of Ship Hull Damage in Collisions

This paper presents the probabilistic characterisation of basic variables of ship structures and their application in characterising ship hull response during collisions. 83 dog-bone samples from mild steel are tested until fracture by axial displacement and basic strength variable data are collected from their resulting stress-strain relations. The data are fitted with suitable probability density functions (PDFs), with the two best PDFs identified from Goodness-of-Fit (GoF) test results. In order to analyse response variability from ship hull collisions, indentation tests are done on six hull plate models by penetrating them with two bulbous bow models. A sampling technique is then used to select probable input design sets from the probabilistic characteristics derived for basic variables. These design sets are propagated through an automated nonlinear finite element (FE) simulation of the hull plate indentation to characterise hull plate response at the onset of rupture.

A FORMULA PROPOSED FOR ESTIMATING THE LONGITUDINAL EXTENT OF RAKING DAMAGE TO THE HULL OF A HIGH-SPEED VESSEL

The old and new requirements of the High Speed Craft Code, and the methods used by some researchers for calculating the damage length for a ship’s hull, are considered in this paper. Damage occurs more often in small vessels than in large vessels. Collisions between ships and ship grounding are two of the main reasons for the loss of ships. The damage to a vessel is determined for the worst case scenario. Long and narrow ("raking") damage, which absorbs the kinetic energy of the vessel, is the worst-case scenario. Small high speed craft were selected for analysis. This paper describes the requirements of the High Speed Craft Code related to high-speed vessels. Small semi planing vessels are a category of high-speed vessels, operated at volume Froude numbers between 1 and 3. The formula for calculating the length of the possible hull damage should take into account the material, the thickness of the plating, the width of the damage, the vessel's speed and its displacement. This paper proposes such a formula for the maximum possible length of the hull damage, which has been calculated using different methods. The formula is proposed for small high speed vessels, but it is possible to use the same formula for other types of ships.