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PROCEEDINGS OF THE SEVENTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY
Edited by: B.H.V. Topping and C.A. Mota Soares
Large Deformation Elastic-Plastic Analysis of Uprights of Steel Racks
A. Fadel+, N. Abdel-Rahman*, M. El-Sadaawy+ and S.A. Mourad#
+Housing and Building Research Center, Cairo, Egypt
A. Fadel, N. Abdel-Rahman, M. El-Sadaawy, S.A. Moura, "Large Deformation Elastic-Plastic Analysis of Uprights of Steel Racks", in B.H.V. Topping, C.A. Mota Soares, (Editors), "Proceedings of the Seventh International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 149, 2004. doi:10.4203/ccp.79.149
Keywords: steel racks, upright, cold formed, elasto-plastic analysis, finite element, nonlinear, buckling.
This research describes the numerical modeling to obtain the buckling load of cold-formed column profiles with rear flanges and additional lip stiffeners used in storage rack systems for unperforated and perforated sections. Pallet racking is one of the most widely used systems, where the racking consists of thin walled compression members and beams with hook-on connectors. Columns of individual steel storage racks are generally made of cold-formed steel lipped channels. The columns are braced into upright frames by connecting inclined bracing between the channel lips of opposing channels using either welded or bolted connections. If welding is used, the braces are welded directly to the flange stiffening lips. If bolting is used, additional elements parallel to the channel flanges are located at the ends of the flange stiffening lips, and are often used to permit the braces to be bolted to the channel column. These additional elements, called "Rear Flanges", are often wide and may require additional lip stiffeners. Perforations in these special lipped channel sections are not a result of punched holes in the cross-section. However, the perforations are formed by displacing the material of the cross-section by 6 mm.
Two kinds of sections are used: Unperforated and perforated sections, having two thicknesses of 2mm and 3mm. The analysis has been carried out for two end conditions : pinned-pinned and fixed-pinned. The ranges of the slenderness ratio are between 31.55 and 200. The sections considered in the study are the commercial sections produced by an Egyptian Company. The columns are covered by end plates with thickness equal 20mm at both ends. The load is assuned to be acting at the centroid of the section . The steel used is steel (37/2) with = 2400 Kgm/cm, the modulus of elasticity = 2100 t /cm and the tangent modulus = 20 t/cm.
A nonlinear 3-D finite element model is developed to investigate the buckling modes and ultimate strength of uprights of steel racks shaped as channel sections with multiple perforations and rear flanges. The model utilizes a 4-node shell element with membrane, bending, and shears deformation capabilities. Geometric nonlinearity is considered by using large displacement analysis, while material nonlinearity is considered by using a bi-linear stress-strain relationship for the steel material.
The main conclusions from the current study can be summarized as follows: