In this study, compressive strength, modulus of elasticity and steel tensile coupon tests are performed to determine material properties. Sixteen hollow cold formed steel tubes and 48 concrete filled steel tube specimens are used for axial compression tests. The effects of width/thickness ratio (b/t), the compressive strength of concrete and geometrical shape of cross section parameters on ultimate loads, axial stress, ductility and buckling behavior are investigated. Circular, hexagonal, rectangular and square sections, 18.75, 30.00, 50.00, 100.00 b/t ratio values and 13, 26, 35 MPa concrete compressive strength values are chosen for the experimental procedure. Analytical models of specimens are developed using a finite element program (ABAQUS) and the results are compared. Circular specimens are the most effective samples according to both axial stress and ductility values. The concrete in tubes has experienced considerable amount of deformations which is not expected from such a brittle material in certain cases. The results provide an innovative perspective on using cold formed steel and concrete together as a composite material.

Structural behavior of concrete filled steel tubular sections (CFT/CFSt) under axial compression

A research study on the structural behaviour of cold formed steel beams with C-, I-, R- and 2R-shaped cross-sections at ambient temperature is presented, based on the results of a large programme of experimental tests and numerical simulations. Firstly, several four-point bending tests were carried out in order to assess mainly the failure loads and failure modes of the beams. Secondly, a suitable finite element model was developed to compare with the experimental results, and finally, a parametric study was undertaken in order to investigate the influence of the thickness, height and length of the beams on its structural behaviour.

Experimental and numerical analysis on the structural behaviour of cold-formed steel beams

Non-linear behaviour and load-carrying capacity of CFRP-strengthened lipped channel steel columns

The paper is devoted to cold-formed thin-walled channel beams with open or closed flanges. The global–local buckling and optimization of these beams are described. The review includes simple analytical description and calculations, numerical analysis, and the laboratory tests of selected beams. The buckling problems for flanges and webs of thin-walled beams are described in detail. Additionally, an objective comparison of the beams of different cross sections is presented. A quality measure of thin-walled beams is proposed. Comparison of selected thin-walled beams with use of the quality measure is presented in figures.

Buckling and optimal design of cold-formed thin-walled beams: Review of selected problems

This paper reports a detailed investigation concerning the local-plate and distortional elastic postbuckling behaviors of cold-formed steel lipped channel columns with web and flange intermediate stiffeners (the corresponding unstiffened lipped channel column postbuckling behaviors are often used as reference) This investigation relies on results obtained through geometrically nonlinear analyses based on a recently developed and numerically implemented generalized beam theory (GBT) formulation that incorporates (1) conventional (no shear deformation), (2) shear (nonlinear warping), and (3) transverse extension deformation modes The numerical results shown provide the evolution, along a given local-plate or distortional postbuckling equilibrium path, of the column (1) deformed configuration and (2) relevant displacement profiles and/or stress distributions—mostly for validation purposes, some of them are compared with values yielded by shell finite element analyses performed by means of the code ABAQUS 

/pdf/local-plate-and-distortional-postbuckling-behavior-of-cold-1ytdwu11zu.pdf

Local-Plate and Distortional Postbuckling Behavior of Cold-Formed Steel Lipped Channel Columns with Intermediate Stiffeners

http://eprints.qut.edu.au/7620/1/7620.pdf

Ultimate capacity of innovative cold-formed steel columns

This paper describes the distortional buckling behaviour of a series of innovative cold-formed steel columns. More than 15 laboratory experiments were undertaken first on these innovative steel columns of intermediate length under axial compression. All of these columns failed by distortional buckling with very little post-buckling strength. The section and buckling properties of the columns were determined using the finite strip analysis program THINWALL. The distortional buckling and nonlinear ultimate strength behaviour of the columns was investigated in detail using finite element analyses (ABAQUS). The finite element analyses included relevant geometric imperfections and residual stresses. The deflection and strain results from the experiments compared well with those from the analyses. The ultimate design load capacities were evaluated using the provisions of Australian Cold-formed Steel Structures Standard AS/NZS 4600-1996, and were compared with those from experiments and finite element analyses. A series of parametric studies was also carried out by varying the yield strength, thickness and column length. Details of this investigation and the results are presented in this paper.

Shane Narayanan

Papers

Ultimate capacity of innovative cold-formed steel columns

Predicting the Ultimate Capacity of Innovative Cold-formed Steel Columns

Distortional Buckling Behaviour of Innovative Cold-formed Steel Columns