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Interactive Buckling Analysis of Thin-Walled Cold-Formed Steel Members via Critical Load Erosion Theory

  • D. Dubina
Conference paper
Part of the CISM International Centre for Mechanical Sciences book series (CISM, volume 379)

Abstract

The European buckling curves actually enclosed in EUROCODE 3 — Part 1.3, used for the stability analysis of cold-formed steel members, have resulted by means of statistical processing of the experimental data carried out on hot-rolled steel profiles.

Due to the nature of imperfections of thin-walled in cold-formed steel profiles, which are different from that of hot-rolled ones, and taking into account to the interaction between the overall and local buckling, the present European buckling curves cannot appropriately describe the behaviour of cold-formed members.

In this case, both the imperfections and wall slenderness influence the buckling of the member in compression and/or bending.

Starting from the Ayrton-Perry formula of European buckling curves, and based on the Erosion of Critical Bifurcation Load — ECBL — theory, a new approach for the interactive buckling of cold-formed steel members is proposed. In fact, the general format of European buckling curves is still valid, and only the α imperfection coefficient must be calibrated in terms of both the erosion factor and effective area of the member cross-section. The erosion of critical load is evaluated by statistical processing of some selected series of cold-formed steel specimens. The DATACOST experimental database was built to be used in this reason.

A large number of numerical and experimental comparative results demonstrate the validity of the proposed approach.

Keywords

Local Buckling Torsional Buckling Compression Member Erosion Coefficient Distortional Buckling 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notation

A

gross cross-section area

Aeff

effective cross-section area

C1, C2, C3

factors depending on the loading and end restraint conditions

Cb

bending coefficient

Cm

coefficient for unequal end moment

Cs

coefficient for moment causing compression on the shear centre side of the centroid

E

Young Modulus

fy

yield stress

G

shear modulus

Iy

second moment of area of the cross-section about the y-axis

Iz

second moment of area about the minor axis

It

St. Venant torsion constant of the cross-section

Iw

warping constant of the cross-section

k, kw

effective length factors for bending about z-axis and for twisting

L

is the length of the beam between points which have lateral restraint

lz, lx

effective lengths for bending about the z-axis and for twisting

Lz, Lt

unbraced lengths of compression member for bending about the z-axis and for twisting

LeY

member effective length in flexural buckling about y-y axis

LeT

member effective length in torsional buckling

Mb,Rd

bending moment resistance of the section

Mcr

the elastic critical moment for lateral torsional buckling for the gross cross-section

Mex

the experimental failure moment

Mpl

the full plastic resistance of the beam

N

axial load

Ncr

Euler critical buckling load

Nexp

experimental failure load

Npl

full plastic resistance of the column

Npl,eff

effective cross-section plastical strength

NSd

compressive force due to design load

Nb,Rd

design buckling resistance

Ncr,FT

critical flexural-torsional load

Ncr,T

critical torsional load

Ncr,y

flexural torsional load with respect to the major inertia axis, y-y

Q

reducing factor of area in interactive local-overall buckling

QLT

the reducing factor of section modulus in interactive local-lateral torsional buckling

ro

polar radius of gyration of the cross-section about the shear centre

ry, rz

radius of gyration of the cross-section about the y- and z-axes, respectively

Weff,y

section modulus of the effective cross-section when subject only to moment about relevant axis

Wpl,y

the full plastic section modulus of the cross-section

yo

distance from the shear centre to the centroid along the principal y-axis, taken as negative

za

the coordinate of the point of load application

zs

z coordinate of the shear centre

χ

reduction factor for the buckling of compression members

χLT

reduction factor for the buckling of bending members

α

imperfection coefficient for compression members

αLT

imperfection coefficient for bending members

βy

mono-symmetry section constant about the y-axis

γMI

partial safety factor

λ

member slenderness for the relevant buckling mode

\(\bar \lambda \)

relative member slenderness for compression members

\(\bar \lambda \)LT

relative member slenderness for bending members

η

generalised imperfection factor for compression members

ηLT

generalised imperfection factor for bending members

ψ

erosion factor for compression members

ψLT

erosion factor for bending members

σez

elastic buckling stress in an axially loaded compression member for flexural buckling about the z axis

σt

elastic buckling stress in an axially loaded compression member for torsional buckling

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Copyright information

© Springer-Verlag Wien 1998

Authors and Affiliations

  • D. Dubina
    • 1
  1. 1.Technical University of TimisoaraTimisoaraRomania

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