Comparison of rectangular and square box columns composed from cellular plates with welded and rolled stiffeners

Abstract

A cantilever column is loaded by a compression force and a bending moment caused by a horizontal force. It can be derived that, in the case of uniaxial bending, the rectangular cross section is more economic than the square one. In the given numerical case, the plate thicknesses are too large for enabling fabrication. Therefore stiffened plates should be used. Thus, the aim of the present study is to elaborate the minimum cost design of a column with rectangular cross-section and cellular plate walls. Cellular plates are constructed from two plates and longitudinal stiffeners welded between them. Previous studies have shown that welded T-stiffeners are more economic than the halved rolled I-section stiffeners, thus, welded T-stiffeners are used.Stress and horizontal deformation constraints are formulated. In the stress constraint, face plate buckling is taken into account by using effective widths. Local buckling constraint is used for the web of T-stiffeners.Variables are as follows: heights of welded T-sections, thicknesses of stiffener webs and flanges, number of stiffeners in both directions, main dimensions of the rectangular box section, thicknesses of outer and inner face plates in smaller and larger walls.The cost function is formulated according to the fabrication sequence and consists of cost of material, welding and painting. The constrained function minimization is performed by using an effective mathematical optimization method.