PSI - Issue 27

Aditya Rio Prabowo et al. / Procedia Structural Integrity 27 (2020) 171–178 Prabowo et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Phenomenon of actual collision accident The phenomenon of the collision on the sea is an event with a limitless possibility of its scenario. The collision can happen between many objects, for example, between ships, ships with containers, ships with platform peers, ships with jetties, etc. The damage will become different if collisions happen in different locations, such as near the main deck, middle deck, and car deck. The region of the target point, such as the fore-end, middle, and after end structure also contributes significantly since the shape and pattern of the structure is different in these regions. The mass, velocity, and angle contributed considerably to this phenomenon (Zhang et al., 2019). Lützen (2002), from Denmark in her previous work, described that instrumentation, ship management, and human factors were involved in collision phenomena. This condition makes collision accidents a research field with complex parameters but also a wide range, which becomes an excellent research potential and source. The focus on this phenomenon is given because casualties after the process are too remarkable to be ignored. The environmental damage caused by the Exxon Valdez accident forced the USA to make the law of The Oil Pollution Act 1990 (OPA-90). The tragic losses of several Ro-Ro passenger ships: the European Gateway in 1982, the Herald of Free Enterprise in 1987, and particularly the catastrophe of the Estonia in 1994 with the loss of more than 800 lives, led to a reassessment of the safety of passenger ships in many countries. The collision accident also happened in the Republic of Indonesia approximately one year ago. The collision occurred between Indonesian Roll on - Roll off (Ro-Ro) passenger Marisa Nusantara and Cambodian cargo reefer Qi Hang. The Ro-Ro passenger, which during the sailing process from Java Island to Sumatra Island, was struck by a cargo reefer from the north direction. The casualties of the striking ship are unknown because cargo reefer fled after the collision, and the Ro-Ro passenger experienced severe damage on its side hull. The estimation of damage was 7 meters in length and 5 meters in width on the side shell area between the middle and main decks. 4. Review on the collision study 4.1. Accident case As stated previously by Kitamura (2002), the reliable and confident result from the study of ship collision can be obtained if the analysis is conducted based on real accident, experiment, and using finite element approach. Therefore, in this research, ship collision accidents and finite element methods were taken as consideration. The collision accident for this study took the collision case between two ships in the Sunda Strait, Republic of Indonesia. In this collision event, the Cambodian ship struck the Indonesian Ro-Ro with a predicted velocity of 12 knots. The field survey and the direct measurement of the damage were performed to the Ro-Ro passenger. The damage approximately reached 7 meters in length, 5 meters in width, and 2 meters in depths and occurred on the side hull. The damage was located on the side hull area between the main and middle deck. Nonlinear finite element methods would be deployed to produce calculation results in the form of damage pattern, dimension as well as collision energy. These results were compared with data from real accidents in terms of damage patterns and dimensions. The collision energy in a real accident case could not be provided because it is almost impossible to record the energy when the accident is in process. The empirical formula from Zhang et al. (2019) would be used to calculate the energy based on damage from the FEM analysis. The formulae are presented in Eqs. 1 and 2. These energy equations are implemented based on damage type, i.e., folding and tearing damage. E = 3.50 ( t 1 / d ) 0.67 σ 0 R T (1) E = 3.21 ( t 1 / l ) 0.6 σ 0 R T (2) where t 1 is the average thickness of the crushed plate, d is the average width of the plates in the crushed cross-section, σ 0 is the flow stress of the material, and R T is the destroyed material volume of materials. In order to obtain practical failure strain definitions in consideration of many parameters, e.g., element size, stress state, and manufacture influence many full-scale thickness measurements on the prototype-damaged structure 4.2. Investigation procedures