Algorithms for the Recognition of the Hull Structures’ Elementary Plate Panels and the Determination of Their Parameters in a Ship CAD System

Abstract

The article deals with some issues of geometric modeling of ship hull structures in specialized CAD system. Stiffened shells and platings should be idealized as a set of elementary plate panels for the purpose of structural design using local strength and buckling requirements. In the process of geometric modeling and creating the database for calculation, a special searching algorithm for closed loops of every panel should be used. This algorithm is to have good performance and versatility. In this paper, the authors suggest an original algorithm used in CADS-Hull software developed in SMTU. It is based on a regular field of points generation within the large contour of the considered structure. A series of rays is built from every point to find intersections. It is shown that this algorithm is quite good for structures (expansions, decks, bulkheads, etc.) with non-orthogonal boundaries. Some tasks for logical operations with found panels are also discussed. One of them is the clipping of a panel or plate polygon by boundaries of a considered structure (expansion contour, hull lines). The authors developed a generic method of polygons clipping. It is based on a rotation of clipping convex polygons together with the clipped polygons. All faces of the latter that are in the negative half-plane are removed. Some problems of collecting data for every found panel are discussed. An original algorithm of smaller and larger size definition for irregular and triangular panels is also given in this paper.