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©2012 Civil-Comp Ltd |
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A. Crisan1, V. Ungureanu1,2 and D. Dubina1,2
1Department of Steel Structures and Structural Mechanics, Laboratory of Steel Structures, "Politehnica" University of Timisoara, Romania
2Romanian Academy-Timisoara Branch, Romania
Keywords: erosion of critical bifurcation load, erosion coefficient, imperfection factor, rack, upright, finite element method.
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The present paper summarises a numerical investigation on two perforated pallet rack upright sections in the interactive buckling range using the erosion of critical bifurcation load (ECBL) approach [1]. The numerical models were calibrated against the results of an extensive experimental program carried out by the authors. The experimental program was based on the guidelines of the European design code [2] and comprises stub column tests, tests on upright sections with the length equal with the distance between two subsequent nodes, tests on upright sections having the critical length for distortional buckling and tests on uprights having the length (calibrated using the ECBL approach) in the interactive buckling range. It must be mentioned that, besides the experimental tests on the perforated sections, foreseen by EN15512 [2], un-perforated sections were tested in order to determine the influence of perforations on sectional capacity and on buckling resistance. Within the experimental program the mechanical properties of base material were determined, the mechanical properties of material extracted from cold-formed section, the residual stresses and the geometric imperfections, sectional and overall properties.
Numerical analyses were conducted in order to extend the experimental database and obtain more information regarding the behaviour of the studied sections. Using the calibrated numerical models, a sensitivity analysis was performed in order to identify the critical geometric imperfections based on the maximum erosion of the critical load. Further, based on the ECBL approach [1] and using the numerically obtained compression capacity for studied sections, the erosion was computed, and based on its design value the imperfection factor was calibrated. Based on the results of the analyses, it can be concluded that the interaction between the distortional and overall buckling in the case of this particular type of rack section has a negative influence on the upright buckling strength.
A design procedure based on EN1993-1-1 [3], coupled with the ECBL approach, applied to calibrate the value of the imperfection factor, can be used to determine the buckling strength of compressed pallet rack uprights in compression.
From the point of view of design procedure, the perforations can be treated as geometric imperfections. The presence of perforations increase the value of the imperfection factor. A rational sensitivity analysis, supported by reference test, is of paramount importance in order to determine the imperfections to be considered for the numerical model, when determining the erosion factor.
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- 1
- D. Dubina, "The ECBL approach for interactive buckling of thin-walled steel members", Steel & Composite Structures, 1(1), 75-96, 2001.
- 2
- EN15512:2009, "Steel static storage systems - Adjustable pallet racking systems - Principles for structural design", CEN, Brussels, 2009.
- 3
- EN1993-1-1, "Eurocode 3: Design of steel structures - Part 1-1: General rules and rules for buildings", CEN, Brussels, 2005.
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