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Fukuyama, Japan

Tanaka S.,Hiroshima University | Yanagihara D.,Ehime University | Yasuoka A.,Hiroshima University | Harada M.,Nippon Kaiji Kyokai | And 3 more authors.
Marine Structures

A series of collapse analyses is performed applying nonlinear FEM on stiffened panels subjected to longitudinal thrust. MSC.Marc is used. Numbers, types and sizes of stiffeners are varied and so slenderness ratio as well as aspect ratio of local panels partitioned by stiffeners keeping the spacing between adjacent longitudinal stiffeners the same. Initial deflection of a thin-horse mode is imposed on local panels and that of flexural buckling and tripping modes on stiffeners to represent actual initial deflection in stiffened panels in ship structures. On the basis of the calculated results, buckling/plastic collapse behaviour of stiffened panels under longitudinal thrust is investigated. The calculated ultimate strength are compared with those obtained by applying several existing methods such as CSR for bulk carriers and PULS. Simple formulas for stiffened panels, of which collapse is dominated fundamentally by the collapse of local panels between longitudinal stiffeners, are also examined if they accurately estimate the ultimate strength. Through comparison of the estimated results with the FEM results, it has been concluded that PULS and modified FYH formulas fundamentally give good estimation of the ultimate strength of stiffened panels under longitudinal thrust. © 2013 Elsevier Ltd. Source

Pei Z.,Wuhan University of Technology | Iijima K.,Osaka University | Fujikubo M.,Osaka University | Tanaka Y.,Japan National Maritime Research Institute | And 3 more authors.
International Journal of Offshore and Polar Engineering

For a bulk carrier in alternate heavy loading conditions, it is noted that the double bottom of an empty hold is subjected to both longitudinal thrust due to hull girder bending in hogging and local bending caused by high pressure loads on bottom plating. In order to examine the influence of local bending of the double bottom on the ultimate hull girder strength, a series of nonlinear calculations is performed applying three different methods. The first method is Smith's method using in-house code, HULLST, to evaluate ultimate hull girder strength under pure bending. The second is the application of a new system recently developed by the authors. This method is a combination of load/motion analysis by Singularity Distribution Method and progressive collapse analysis by ISUM/FEM. The third is nonlinear FEM analysis using a commercial code, MSC.Marc. It has been found that bending deformation is produced not only in the double bottom but also in the bilge hopper tank, and the ultimate hull girder strength is reduced by roughly 20% due to this local bending. © by The International Society of Offshore and Polar Engineers. Source

Yamamoto M.,Hiroshima University | Shinozaki K.,Hiroshima University | Kadoi K.,Hiroshima University | Fujita D.,Tsuneishi Shipbuilding Co. | And 3 more authors.
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society

In this study, hot-wire laser welding was used to develop the welding method for the lap joint of 980MPa class high-strength steel sheets (thickness: 1 mm) with a wide gap. Detailed phenomena of wire melting and bead formation during welding were understood using the high-speed camera, and then the optimum welding condition and the mechanical properties of weld joints were investigated. The fiber laser with hot wire was used for welding the lap joint with the gap of 1 mm. The welding parameters such as the laser output of 3kW, spot diameter of 1.5mm ø, welding speed of 1.5m/min and the wire feeding speed of 3.8 m/min were fixed. The welding parameters of hot wire such as wire insertion angle, wire insertion position, and current of wire were varied. Moreover, shear test of the weld joints were done. As a result, upper and lower sheets with gap of 1 mm were well joined without weld defects in the welding parameters such as the wire insertion positions (from the laser spot center) of 3mm and the wire insertion angle of 70° and the wire currents of 102∼116A. Moreover, the tensile shear strengths of weld joints were 500∼600MPa regardless of the wire current. Source

Pei Z.,Wuhan University of Technology | Iijima K.,Osaka University | Fujikubo M.,Osaka University | Tanaka S.,Hiroshima University | And 2 more authors.
Marine Structures

To ensure the safety of navigating ship, working loads and structural load-carrying capacity are two important aspects. In the present paper, a total simulation system combing load calculation and structural collapse analysis is applied to simulate progressive collapse behaviour of a single-hull Kamsarmax type bulk carrier. A three dimensional singularity distribution method is adopted to calculate pressure distribution with time history. A mixed structural model, collapse part simulated by ISUM elements and remaining part by elastic FEM elements with relative coarse mesh, is proposed for collapse analysis. Progressive collapse behaviour obtained by ISUM is good agreement with that by nonlinear software package, MARC. However, the calculation time of ISUM analysis is about 1/70 of MARC analysis. The applicability to structure system, high accuracy and sufficient efficiency of ISUM had been demonstrated. © 2014 Elsevier Ltd. Source

Abe R.,Kokusai Kogyo Co. | Hamada K.,Hiroshima University | Hirata N.,Hiroshima University | Tamura R.,Hiroshima University | Nishi N.,Tsuneishi Shipbuilding Co.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives

As well as the BIM of quality management in the construction industry, demand for quality management of the manufacturing process of the member is higher in shipbuilding field. The time series of three-dimensional deformation of the each process, and are accurately be grasped strongly demanded. In this study, we focused on the shipbuilding field, will be examined three-dimensional measurement method. The shipyard, since a large equipment and components are intricately arranged in a limited space, the installation of the measuring equipment and the target is limited. There is also the element to be measured is moved in each process, the establishment of the reference point for time series comparison is necessary to devise. In this paper will be discussed method for measuring the welding deformation in time series by using a total station. In particular, by using a plurality of measurement data obtained from this approach and evaluated the amount of deformation of each process. © 2015, Copernicus. All rights reserved. Source

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