Author(s)

U. Klanšek & S. Kravanja

Abstract

This paper presents standard optimization of unbraced steel plane frames with rigid beam-to-column connections. The optimization has been performed by the Mixed-Integer Non-linear Programming (MINLP) approach. The MINLP performs a discrete optimization of different standard dimensions, while continuous parameters are simultaneously calculated inside the continuous space. As the discrete/continuous optimization problem of steel frames is non-convex and highly non-linear, the Modified Outer-Approximation/Equality-Relaxation (OA/ER) algorithm has been used for the optimization. 1 Introduction The paper deals with standard dimension optimization of unbraced steel plane frames with rigid beam-to-column connections. The optimization of frames is performed by the Mixed-Integer Nonlinear Programming, MINLP. The MINLP is a combined discrete-continuous optimization technique. This way, the MINLP performs the discrete optimization of standard dimensions (i.e. cross-section sizes of columns and beams) simultaneously with the continuous optimization of parameters (e.g. internal forces, deflections, etc.). The MINLP discrete/continuous optimization problems of frames are in most cases comprehensive, non-convex and highly non-linear. This optimization approach is proposed to be performed through three steps. The first one includes the generation of a mechanical superstructure of different standard dimension alternatives, the second one involves the development of an MINLP model formulation and the last one consists of a solution for the defined MINLP optimization problem. The Modified Outer-Approximation/Equality-Relaxation algorithm [1], [2] and [3] is used to perform the optimization. The two-phase MINLP optimization

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