Optimization of cold-formed lipped C-section under bending using prediction equations as objective functions

Abstract

The use of cold-formed sections (CFS) in construction is growing quickly in spite of the difficulty facing the designer in choosing the optimum sections’ proportions of any CFS in order to acquire the most economical section. In this paper, the optimization of CFS C-lipped channel beam will be carried out with respect to their flexural strength calculated using the direct strength method (DSM) given by the American specifications (AISI). The optimization will be carried out by developing an accurate and effective optimization code using particle swarm optimization (PSO). The mathematical model and the optimization technique used in this paper will help in finding the most optimum ratios between the different elements of the C-lipped channel beam that are studied in three groups. Nonlinear regression analysis is performed to obtain proposed equations that predict the flexural capacity of the cross section in two modes of failure: the local buckling mode and the distortional buckling mode. These proposed equations are used as objective functions in the optimization process as they showed that they are capable of predicting the moment capacity of the C-lipped channel effectively. It was found that the most suitable group of the three studied groups is the ratios between different elements of the cross section lies between 15 and 50%.