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Structural Engineering and Mechanics
  Volume 64, Number 5, December10 2017, pages 621-640
DOI: http://dx.doi.org/10.12989/sem.2017.64.5.621
 


Post buckling mechanics and strength of cold-formed steel columns exhibiting Local-Distortional interaction mode failure
Hareesh Muthuraj, S.K. Sekar, Mahen Mahendran and O.P. Deepak

 
Abstract
    This paper reports the numerical investigation conducted to study the influence of Local-Distortional (L-D) interaction mode buckling on post buckling strength erosion in fixed ended lipped channel cold formed steel columns. This investigation comprises of 81 column sections with various geometries and yield stresses that are carefully chosen to cover wide range of strength related parametric ratios like (i) distortional to local critical buckling stress ratio (0.910.91<=FCRD/FCRL<=4.05) (ii) non dimensional local slenderness ratio (0.88<=tL<=3.54) (iii) non-dimensional distortional slenderness ratio (0.68<=tD<=3.23) and (iv) yield to non-critical buckling stress ratio (0.45 to 10.4). The numerical investigation is carried out by conducting linear and nonlinear shell finite element analysis (SFEA) using ABAQUS software. The non-linear SFEA includes both geometry and material non-linearity. The numerical results obtained are deeply analysed to understand the post buckling mechanics, failure modes and ultimate strength that are influenced by L-D interaction with respect to strength related parametric ratios. The ultimate strength data obtained from numerical analysis are compared with (i) the experimental tests data concerning L-D interaction mode buckling reported by other researchers (ii) column strength predicted by Direct Strength Method (DSM) column strength curves for local and distortional buckling specified in AISI S-100 (iii) strength predicted by available DSM based approaches that includes L-D interaction mode failure. The role of flange width to web depth ratio on post buckling strength erosion is reported. Then the paper concludes with merits and limitations of codified DSM and available DSM based approaches on accurate failure strength prediction.
 
Key Words
    lipped channel columns; Local-Distortional interaction; secondary bifurcation; cold formed steel; Direct Strength Method (DSM); numerical simulation; Finite Element Analysis (FEA); Generalized Beam Theory (GBT)
 
Address
Hareesh Muthuraj : School of Civil and Chemical Engineering, VIT University, Vellore, TamilNadu-632014, India

S.K. Sekar : School of Civil and Chemical Engineering, VIT University, Vellore, TamilNadu-632014, India

Mahen Mahendran : School of Civil and Built Environment, QUT, Brisbane, Australia

O.P. Deepak : School of Civil and Chemical Engineering, VIT University, Vellore, TamilNadu-632014, India
 

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