STRUCTURAL OPTIMIZATION OF TRUSSES UNDER ELASTIC AND INELASTIC BUCKLING CONSTRAINTS

Resumo

It is well known in the literature and practice of structural optimization that optimal struc-
tural configurations are highly dependent on the constraints applied to the problem or, in other words,

on the definition of what is feasible or not. Results obtained under a certain type of constraints may
be not optimal, or even not acceptable, if other types of constraints are considered. Discussions related
to constraints and their effects on structural optimization are found in many papers, but only a few of
them directly address this subject. In the specific case of optimization of trusses, it is common to find
applications involving two different scenarios, where stress-based constraints are combined with elastic
buckling or with inelastic buckling constraints, respectively. The first scenario is much more common,
and the differences between results related to each of these combinations are hardly ever discussed or

emphasized. The present paper focus on the comparison of structural optimization of trusses, consid-
ering these two scenarios, in an attempt to identify in which cases similar results are obtained and how

different the results can be. The paper also proposes a simple multistart optimization scheme combined

with sequential quadratic programming, so that the optimization problems are solved in a global and ef-
ficient manner, and the comparisons are not significantly compromised by local minima. Two trusses are

evaluated, for some different cases of boundary conditions, and the results indicate that the optimal con-
figurations may be significantly different in the cases where a sufficient number of compressed slender

bars is present.