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The authors are developing the simple and easy structural design system which investigates rapidly the design spiral in the stage of early design. In this system, initial scantlings and dimensions are determined through the total strength analysis system before performing FE analysis. The shear flow analysis is carried out by identifying the cross-section shape of hull girder using the number of representative points in a cross-section, the shape of closed circuits and the property of the shear flow on each member.The coefficients of the expression to shear flow distribution are automatically calculated. However, to apply this analysis to more complicated and various cross-sections within fore and aft portion of ships, it is important to develop a more generalized shear flow analysis method.In this paper, the authors propose a new shear flow analysis method using the basic concept of graph theory, where a pattern of networks is expressed by connections between points and edges, mainly applied to electric circuit network.In this first report, the authors give a concrete description for the formulation of the new analysis and the analytical procedure using a cross-section with three closed circuits.

Shear lag in the cross section of a bulk carrier will be discussed in this paper. The hull girder of a bulk carrier consists of multi-cellular box girder. As to the single cell box girder, the approximate methods of calculation were proposed by Kuranishi M. and Miyashita M. and by Reissner E., independently.To apply these methods to the hull girder of a bulk carrier, the former is preferable to the latter because of the flexibility in the mathematical formulation of its warping function.At first, authors developed the former method to the multi-cellular box girder. And then, after some numerical calculations on the bulk carrier of 60 thousands Dead Weight tons, in the condition of loading alternatively in every other hold, the following results were obtained : (1) In girthwise, the warping and the warping normal stress due to shear lag become greater in the bilge part and in the double bottom plates near the ship centre line than other part, mainly. As to the warping. shear flow, it acts so as to decrease the maximum value of shear flow and to make smooth the 'distribution pattern in the side shell.(2) In spanwise, the warping and the warping normal stress and shear flow due to shear lag are much affected by the magnitude and distributing pattern of the shearing force acting on the hull girder.