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ABSTRACT To make optimal design decisions regarding structural safety and economical efficiency, it is very important to be able to assess the influence of damages on the performance of damaged structural members. In this paper, the ultimate strength characteristics of dented tubular members under various loads are investigated by using the ANSYS nonlinear finite element code. The effects of dent depth on the ultimate strength behavior under various loads are studied. And the results of analysis are compared with experiment results. INTRODUCTION Cylindrical tubular members are widely used for leg and bracing of offshore structures. Generally, these members experience axial, bending and shear force, therefore it should be designed to withstand the extreme environmental loads of ocean. Actually they undergo local damages frequently due to the collision of supply vessels or falling heavy objects from deck. Unfortunately, such damages reduce the load carrying capacity of the each members and collapse load of the overall structures (Ellinas, CP et al, 1985). Moreover, inevitable initial imperfections and welding residual stresses caused by the construction process are also considered to decrease the strength of structural systems. Hence, when the effect of damages to the strength of overall structural system is considered to be not negligible, partial repair or replacement of members would be necessary. To make a decision whether we should repair a damaged member or not, it is necessary to investigate the economic aspect and effects of damages on the safety of structure carefully. If we can estimate the safety of structures with damaged members in the earlier structural design stage, it could be applied to optimizing the construction cost including the repair and maintenance. To estimate the effects of damages precisely, nonlinear structural analysis techniques considering the material and geometrical non-linear ties can be applied.
A Study On the Structural Design And Analysis of Unmanned Underwater Vehicle
Joung, Tae-Hwan (Dept. of Naval Architecture and Ocean Engineering, Chungnam University) | Nho, In Sik (Dept. of Naval Architecture and Ocean Engineering, Chungnam University) | Lee, Pan-Mook (Korea Research Institute of Ships and Ocean Engineering, KORDI)
ABSTRACT This paper discusses the structural design and analysis of a 6,000 meters depth-rated capable deep-sea unmanned underwater vehicle (UUV) system. The UUV system is currently under development by Korea Research Institute of Ships and Ocean Engineering (KRISO), Korea Ocean Research and Development Institute (KORDI). The UUV system is composed of three vehicles - a Remotely Operated Vehicle (ROV), an Autonomous Underwater Vehicle (AUV) and a Launcher - which include underwater equipment. The dry weight of the system exceeds 3 tons; hence it is necessary to carry out the optimal design of structural system to ensure the minimum weight and sufficient space within the frame for the convenient use of the embedded equipments. In this paper, therefore, the structural design and analysis of the ROV and launcher frame system were carried out, using the optimizing process. The cylindrical pressure vessels for the ROV were designed to resist the extreme pressure of 600 bars, based on the finite element analysis. INTRODUCTION In the past, ROV (Remotely Operated Vehicles) started to be developed in order to accomplish minor roles in places where diver's work was impossible or just for general scientific research. Recently, however, such vehicles have various uses in the development of deep-sea resources, the installation or repair of communication lines or rescue work, etc. An ROV is composed of a frame, buoyant material, control and navigation devices, manipulators and pressure vessels which are able to protect the various electronic devices. Among the structural elements of ROVs, especially, the frame and the pressure vessels must have thorough safety investigation through structural analysis before construction, because the structural safety of ROV is affected by the weight of the electronic devices, their location, their size, static or kinetic loads and deep-sea pressure.