Storage rack systems are structures composed of cold-formed steel structural members that are needed as columns, beams and bracing. The rack columns present peculiar features in their design like they have perforations to facilitate assemblage within the system, which makes them more not easy to analyze by cold-formed steel structures design codes. There are plenty design codes proposed from manufacturers associations, as the specifications of Rack Manufacturers Institute (RMI), applied in the usa along with the specification of your American Iron and Steel Institute (AISI). These codes propose experimental stub columns tests for the determination of their resistance. In this work, industry software, ANSYS, is used for material and geometric non-linear analysis of these columns, as well as the results are compared with experimental data obtained by stub column tests, to get a typical part of racks made in Brazil.

Introduction
Cold-formed steel sections are usual inside kinds of structures, and thus much research has been performed on understand their behaviour and to develop design procedures. Among these structures, a couple of the storage systems, usually called racks, widely used throughout planet for storing materials in distribution employers. These systems provide high storage density, allowing the storage of an abundance of products in reduced areas, due for their vertical character. Besides, they also allow great accessibility on the stored resources. Many companies are using scalping strategies to store their product in large scale.

There are a few commercial models that fit to the stipulations demanded for each product with regard to stored the actual world available space in your home. These models vary from simple shelves to automated structures of more than 30 m height. Among these several models, it is worth mentioning the Pallet and Drive-in Sources. The Pallet rack is the most common storage rack used in Brazil. The Drive-in model presents peculiar structural concepts: the shortage of transversal beams to allow trucks to move inside brand new and arsenic intoxication perforations with a columns to facilitate montage. Fig. 1 shows a Pallet and a Drive-in rack in operation [1].

The Brazilian Association of Handling and Logistic provides some recommendations for designing rack systems that, in the future, will be used in a Brazilian discount code. This work presents an analysis of typical columns of commercial Brazilian racks, using industry finite element software ANSYS [2]. The effects are fairly experimental data, based on prescriptions of RMI [3] and from previous work (Oliveira [4]). The influence of the perforations and geometric imperfections on the resistance from the columns is also assessed.

Section snippets
The rack column
The analyzed column is made of cold-formed steel [5], the place that the cross-section shape is a thin-walled "rack". One worth mentioning cross sections and the nomenclature used in the identification of its parts are presented in Fig. associated with. It has as particularity rear flanges that allow fitting the braces, making it simpler to assemble the construct.

The main characteristic from the column, however, is the presence of perforations along its height that allows fitting the connections of braces various other structural

Design concept
The utilization of thin-walled sections can result in specific design problems due to the failure modes such as local buckling and distortional buckling [6]. The rack sections usually contain perforations and imperfections that lessen the resistance of these members. You should rules aimed at these members use minimum geometric properties and experimental results to calculate the behaviour of framework.

For the evaluation among the load capacity of the column by the RMI specification it is

Finite element analysis
This item presents the constructional procedures of the finite element model for your proposed non-linear analysis using the software ANSYS. The prototype of the cold-formed steel column and the cross section presented in Fig. 2 can be simulated the shell . To consider the shape of the perforations in mesh, a triangular mesh was used, with automatic adjust and fine rate, generating small elements may easily be avoided exactly contour the perforations. Fig. 5 presents the finite element meshes

Experimental results
Ultimate compressive strength was evaluated. The experimental program consisted of four specimens tested by the "stub column test", described in Section 3. Fig. 6 shows the average actual size of the cross sections tested and the gravity center of minimal net area,
. Table 2 shows the experimental results of this ultimate axial load,
. As prescribed via the stub column test just ultimate compressive load was measured.

By using Eq. (3) and the experimental results the form factor

Conclusions
A finite element analysis has been developed to examine the influence of imperfections, perforations and material properties on the roof mode and supreme strength of rack cold-formed steel sections submitted to axial pressure. In the model, shell, solid and contact finite elements were acquainted with represent the stub column analyzed by the experimental device. The finite element model also used nominal and experimentally derived stress–strain relationships and geometric imperfection

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