City Research Online

Abstract

This work relates to the finite element analysis of three dimensional stiffened plate structures and introduces the idea of a self contained stiffness vector. Such a vector is assembled for each degree of freedom in turn rather than an overlapping stiffness matrix for each element. Using this vector concept and a continuous partial inversion routine, the intermediate version of the stiffness matrix never occupies a space larger than its fined, size when it is then expressed only in terms of those degrees of freedom which are either automatically or manually nominated to remain active. As a result there is a saving in core space over conventional assembly and wavefront techniques. By this method the wavefront is minimized and goes where it is required at the best time to suit the efficient running of the program. For faster running the offloading of coefficients to disc is delayed until all available core space is exhausted, whereupon a selective clearing of core space is initiated. Since rows of the stiffness matrix corresponding to inactive degrees of freedom are eliminated and finally reformed in their natural order there is a need for only limited housekeeping routines.

This process of a continuous partial inversion shows quite remarkable savings in the time taken for inversion in the analysis of large structures having a few degrees of freedom whose stiffness terms may change or vanish depending upon their deflections during the solution stage and thus require their inversion phase to be within an iterative loop.

The plate contribution to the stiffness matrix employs a little used element whose proof was not available for this work. A derivation of its formulation based on the modes of inplane distortion to which a rectangular plate can be subjected is made and included in the text.

Advantage is taken of the repetitive nature of details in many large structures to take the minimization of hand prepared input data to an extreme. At the same time facilities are available to input information for awkward structures not lending themselves to such a routine. A comprehensive list of error detecting checks monitor each stage of the package. Hydrostatic, thermal and gravity loads are generated by built in routines as are those caused by accelerations of the structure and cargo. Automatic evaluation of stiffness terms is made to prevent singularities associated with floating bodies.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QA Mathematics > QA76 Computer software T Technology > TA Engineering (General). Civil engineering (General) V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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