![]() |
Computational & Technology Resources
an online resource for computational,
engineering & technology publications |
||
Civil-Comp Proceedings
ISSN 1759-3433 CCP: 81
PROCEEDINGS OF THE TENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: B.H.V. Topping
Paper 152
Analysis of Local-Plate/Distortional Mode Interaction in Cold-Formed Steel Lipped Channel Columns P.B. Dinis, N. Silvestre and D. Camotim
Department of Civil Engineering and Architecture, Instituto Superior Técnico, Technical University of Lisbon, Portugal Full Bibliographic Reference for this paper
P.B. Dinis, N. Silvestre, D. Camotim, "Analysis of Local-Plate/Distortional Mode Interaction in Cold-Formed Steel Lipped Channel Columns", in B.H.V. Topping, (Editor), "Proceedings of the Tenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 152, 2005. doi:10.4203/ccp.81.152
Keywords: cold-formed steel lipped channel columns, distortional buckling, local-plate buckling, local-plate/distortional mode interaction, elastic post-buckling, elastic-plastic post-buckling, shell finite element analysis, GBT-based analysis.
Summary
Most cold-formed steel members display very slender thin-walled open cross-sections,
a feature making them highly susceptible to local instability phenomena, namely (i)
local-plate and (ii) distortional buckling. Moreover, since several commonly used
members exhibit cross-section geometries (shape and/or dimensions) associated with
rather similar local-plate and distortional bifurcation stresses, their overall structural
behaviour is likely to be affected by the occurrence of mode interaction phenomena
involving the above two (local) buckling modes.
The aim of this paper is to present and discuss the results of a numerical investigation
dealing with the influence of local-plate/distortional buckling mode interaction on the
elastic and elastic-plastic post-buckling behaviour and strength of lipped channel
cold-formed steel columns. The columns analysed exhibit (i) cross-section dimensions and
length values that ensure equal local-plate and distortional critical stresses, (ii) several
yield-to-critical stress ratios and (iii) locally/globally pinned free-to-warp end sections.
Moreover, since the main goal of this work is to assess the local-plate/distortional mode
interaction effects, one must determine the post-buckling behaviour of columns with
a wide variety of critical-mode initial imperfection shapes, all sharing the same overall
amplitude. In this work, the initial imperfection shapes combine the three-wave local-plate
and single-wave distortional critical buckling modes, multiplied by amplitudes The analyses were performed using mostly the finite element method (code ABAQUS with columns discretised by means of fine meshes of 4-node shell elements), but also a recently developed and numerically implemented generalised beam theory (GBT) formulation, which includes shear and transverse extension deformation modes (only elastic results). The results presented and discussed consist of (i) elastic and elastic-plastic post-buckling equilibrium paths, (ii) curves describing the evolution, along the elastic paths, of the column deformed configurations and (iii) figures providing information about the effect of the initial imperfection shape on the spread of plasticity and column elastic-plastic failure mode (see Figure 152.2).
Among the conclusions drawn from this investigation, it is worth mentioning: (i) in
the advanced post-buckling stages, all the elastic and elastic-plastic equilibrium paths
"merge" into two curves, associated with predominantly distortional coupled modes; (ii)
when the imperfection is predominantly local-plate, a "snap-through" occurs along the
column elastic equilibrium path; (iii) in the GBT-based post-buckling analyses, it is more
meaningful to view the initial imperfections as combinations of deformation modes; (iv)
in spite of the fairly good qualitative agreement between the finite element method (FEM) and GBT-based
elastic post-buckling results, some quantitative differences remain to be explained; (v)
the elastic-plastic failure may be triggered by the onset of yielding (low-to-moderate
purchase the full-text of this paper (price £20)
go to the previous paper |
|||