Abstract
The optimal layout for structures of self-supporting truss-towers is found by comparing the different minimum weight design topologies under geometric, structural, assemblage and maintenance aspects with respect to static and dynamic effects. The basic idea concerning the geometry of the structures was to determine a design with a minimum of different elements with respect to length, cross-sectional area, etc.
A modified Newton-Raphson iteration is used to consider the effects of non-linearity in the static analysis. Dynamic investigations applying Stodola's method are necessary because the first frequencies in bending and torsion have to be examined. The present optimization problem is nonlinear with the cross-sectional areas of the truss elements as design variables. The problem is solved by formulating optimality criteria derived from the different restrictions. The strongest restriction is the one concerning the eigenfrequencies, followed by the warping stiffness and stability restrictions. Extensive studies, done by a computer program, showed that the differences in weight are negligible; only design aspects are of significance for the optimal truss tower. Therefore, a new and simple nodal point construction is developed using sheets prefabricated very easily in one piece out of a flat panel.
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