Um sistema computacional para a análise de cascas de revolução com irregularidades localizadas

Abstract

This work presents the development of a finite element computer program, which is presently intended for the analysis of shells, and particularly of shells of revolution with local irregularities. In the analysis of these shells, the "classic" approach would be either to analyse the entire structure with 3-D shell elements, or else, for preliminar studies, to ignore the non-axisymmetric portions, thus obtaining an approximate solution with the use of shell-of-revolution elements. The development of a third approach is presented here, which utilizes the economical advantages of axiymmetry, while maintaining the accuracy for the non-axsymmetric portion: rotational shell elements are used in the axisymmetrical region of the shell, while 3-D shell elements are used in the regions where deviations (attachments, cut-outs) are found. The transition between these regions is accomplished by a "transitional element". The finite elements used in the computer program are derived from isoparametric formulation. The development for the determination of their stiffness matrices is presented. Considerations about the computer program are also presented, including details of the techniques employed to assemble and solve the system of equations, and the facilities provided for the description of the structural model in terms of a problem-oriented language. Finally, numerical examples are shown, which verify the results presented by the implemented elements, and the behaviour of the "quasi-axisymmetric" model.