scholarly journals STRENGTH EVALUATION OF COLD-FORMED STEEL COLUMNS USING THE RESULTS OF FINITE STRIP AND FINITE ELEMENT LINEAR STABILITY ANALYSIS

2009 ◽  
Vol 1 (1) ◽  
pp. 40-43 ◽  
Author(s):  
Luís C. Prola ◽  
Igor Pierin
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Steel Columns ◽  
Finite Strip ◽  
Strip Method ◽  
Finite Strip Method ◽  
Global Buckling ◽  
Cold Formed Steel ◽  
Thin Walled

Most cold-formed steel columns display open and rather thin-walled cross-sections which mean that their structural behaviour is strongly affected by local and global buckling. Th e local mode, that occurs for shorter profi les, is characterized by (i) the local plate mode (LPM) characterized by the simultaneous flexural buckling of the web and fl anges and (ii) by the distortional mode (DM) characterized by the displacements of flange-stiff ener edges (that remain plane). The global mode occurring for long profi les is characterized by (i) the fl exural mode (FM) characterized by the translation of the whole section in the direction of the major principal axis and (ii) by the fl exural-torsional mode (FTM) characterized by the simultaneous translation and rotation of the whole section. Th e possibility of using the results of linear stability analysis in the national codes of thin-walled cold-formed steel structural elements (for instance, European and Brazilian Codes) arises, i.e. local and global buckling instability modes and corresponding bifurcation stresses determining the ultimate strength of members. Two powerful numerical methods are chosen to perform a linear stability analysis of a cold-formed steel structural member: (i) the Finite Strip Method, (i1) the Semi-Analytical Finite Strip Method (trigonometric functions are used in the approximation of displacement) used for simply supported boundary conditions, (i2) the Spline Finite Strip Method (‘spline’ functions are used in the approximation of displacement) used other boundary conditions and (ii) the Finite Element Method. The linear local and global stability results of for Z, C and rack cold-formed columns are used to obtain ultimate strength through the procedures adopted in the Eurocode 3, Part 1.3 and in the Brazilian Code (NBR 14.762/2001). The obtained numerical estimates by specifi cations are compared with experimental results available in literature.

scholarly journals Constrained Finite Strip Method with Rigid Corner Element for the Buckling Analysis of Thin-Walled Members with Rounded Corners

2019 ◽  
Author(s):  
Zoltán Beregszászi ◽  
Sándor Ádány
Keyword(s):  
Buckling Analysis ◽  
Structural Members ◽  
Distortional Buckling ◽  
Modal Decomposition ◽  
Buckling Mode ◽  
Finite Strip ◽  
Strip Method ◽  
Finite Strip Method ◽  
Cold Formed Steel ◽  
Thin Walled

In this paper modal decomposition of the deformations of thin-walled structural members are discussed. Modal decomposition is a process which separates the characteristic behavior modes. If applied in buckling analysis, modal decomposition makes it possible to analyze pure global or pure distortional buckling or pure local-plate buckling. Ability to calculate critical loads to a pure buckling mode is highly useful in the design of thin-walled structural members, such as cold-formed steel beams or columns. Cold-formed steel profiles are always produced with rounded corners, and earlier studies showed that the now-used modal decomposition techniques of the constrained finite element method and generalized beam theory fail to lead to reasonable results if the rounded corners are directly modelled in the analysis. An extension to the constrained finite strip method is proposed and discussed. The proposal introduces rigid corner elements, which make it possible to perform the modal decomposition by the same process used for members with sharp corners, even if the rounded corners are directly modelled. The formulation of the proposal is summarized, then the rigid-corner approach is studied by an extended parametric study.

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