IMPROVEMENT OF THE METHODOLOGY FOR SPECIFYING TOPOLOGY VARIANTS OF STEEL BAR STRUCTURES FOR STRUCTURAL AND PARAMETRIC OPTIMIZATION PROBLEMS

Abstract

A structural and parametric optimization problem for steel bar structures is formulated as searching for optimum values of bar cross-section dimensions and parameters of structural geometrical scheme, as well as for optimum structural topology. The optimization problem is solved using the harmony search method.

The article proposes an improved methodology for specifying topology variants for the bar structures. The methodology is based on excluding bars from the structural design scheme in order to describe a set of topology variants of the bar structure. Additionally, a discrete design variable is used to select specific topology variants in the optimization process.

For a particular topology variant, the redundant bars are determined by using a logical expression. Because of the exclusion of some bars from the bar structure, some nodes may turn out to be unconnected to the bars or support. These nodes should be fixed by adding supports for each possible displacement direction using specified logical expressions.

The implementation of the proposed methodology in the OptCAD software intended to the optimal design of bar structures is described. As an example, a structural and parametric optimization problem of a steel truss is formulated. Conditions of exclusion nodes and bars for the considered truss structure are also presented. The results obtained were compared against solutions from an alternative methodology.

Excluding the bars from the bar structure allows us to transform the considered structural and parametric optimization problem into the set of parametric optimization problems formulated for each topology variant of the bar structure. Additionally, the number of analyses by the finite element method is decreased compared to the alternative methodology where the redundant bars remained in the bar structure. The proposed methodology simplifies setting the topology variants, because it does not require preserving the case of unstable structure which can occur due to the bar excluding. Unlike the alternative methodology where the excluded bars are transferred to an additional structure, the proposed approach provides more flexible process of designing topology variants.