International Shipbuilding Progress - Volume 66, issue 3

Authors: Shabani, Babak | Lavroff, Jason | Holloway, Damien S. | Davis, Michael R. | Thomas, Giles A.

Article Type: Research Article

Abstract: Background: The wet-deck height and centre bow configuration in wave piercing catamarans are critical design factors which influence slamming occurrence and severity. Objective: In this paper, the wet-deck slamming loads and pressures acting on a 112 m catamaran with a centre bow were investigated in regular waves in two wave heights. Methods: A 2.5 m hydroelastic model with three alternate configurations of wet-deck vertical clearance was tested at a speed of 2.89 m/s (38 knots full-scale equivalent). Results: The results showed that at the instant of slamming the centre bow immersion depth relative to the undisturbed incident …wave elevation was less than two thirds of the maximum immersion depth during the wet-deck slam event. The location of maximum slamming pressure was found to be in the range between 77% and 80% of the overall length from the transom. The relationship between the relative velocity at impact and slamming force indicated that slamming loads in the order of the vessel weight can occur for the parent design when the relative velocity at slam is about a quarter of the forward speed. Conclusions: Overall, increasing the wet-deck height was more beneficial for reduction of slamming loads and pressures in smaller waves than in large waves. Show more

Keywords: Wave piercing catamaran, hydroelastic segmented model, center bow, wet-deck height, slamming loads, slamming pressures, relative velocity

DOI: 10.3233/ISP-180247

Citation: International Shipbuilding Progress, vol. 66, no. 3, pp. 201-231, 2019

Authors: Taheri, Abdolrahim | Alizadeh, Mohamad

Article Type: Research Article

Abstract: Today’s oil and gas industry is facing deeper waters and harsher environmental conditions. Offshore platforms and marine risers, as the main parts of this industry, have many challenges and design issues. Steel Catenary Riser (SCR) connected to Floating, Production, Storage, and Offloading unit (FPSO), is a preferred and commonly used solution to the challenges. It is needed to have more understandings of SCR behavior. So in this study, the significance of SCR-seabed interaction is investigated. Also, the effect of seabed stiffness on the structural behavior of the SCR is studied. Results show that the seabed stiffness makes considerable differences in …dynamic and fatigue responses of SCRs in the touch down zone (TDZ) and reveal the importance of proper seabed stiffness modeling. Model (I), which represents weak soils with very low stiffness, could resist on continuously applied harsh environmental condition for 139.6 days. Model (IV) which represents a very stiff seabed, had a minimum fatigue life of about 6.5 percent of the model (I). The results indicated that the SCR responses were highly separated in terms of fatigue performance especially for weak to normal soils. Show more

Keywords: Riser, seabed, fatigue, random waves, soil stiffness

DOI: 10.3233/ISP-180249

Citation: International Shipbuilding Progress, vol. 66, no. 3, pp. 233-246, 2019

Authors: Antão, P. | Hoogeland, M. | Vredeveldt, A.W. | Santos, F.P.

Article Type: Research Article

Abstract: Crewmembers are exposed to high work pressure. Pressure on freight tariffs motivates cost reduction in manning and maintenance, whilst societal developments show decreasing tolerances towards incidents. In conjunction with the developments towards autonomous shipping, the need for continuous and unmanned inspection increases. Considerable progress had been made with respect to monitoring machinery condition, however, the hull structure is as relevant for inspection and maintenance. This will require enhanced inspection, i.e., E-inspection. For hull structure corrosion and fatigue are of main interest. The application of E-inspection, directs the work effort from the crew to the location of interest, at the right …time. It gives also the option to monitor the health status of a ship from shore. This paper summarizes the E-inspection methods, as identified in the SAFEPEC European project, and how they will help the crew reducing inspection workload. Show more

Keywords: E-inspection, workload, hull structure, inspection

DOI: 10.3233/ISP-190263

Citation: International Shipbuilding Progress, vol. 66, no. 3, pp. 247-270, 2019