The document discusses an experimental and analytical study on the bending capacity of 42 cold-formed channel steel sections according to European design standards. Tensile coupon tests found the steel's average yield strength was 541 MPa, with an average ultimate-to-yield strength ratio of 1.06. Pure bending tests were conducted on the sections, which ranged from simple to complex stiffened designs. The test results were compared to bending capacity calculations in Eurocode 3. While Eurocode 3 allows for inelastic capacity, specifications like AS/NZS 4600 do not. The test data showed some non-slender sections had significant inelastic behavior and capacity beyond yield. Therefore, modifications to Eurocode 3 may be needed for accurate design of

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Section classifications for cold-formed channel steel
Article in Structures & Buildings · October 2013
DOI: 10.1680/stbu.12.00019
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2. Proceedings of the Institution of Civil Engineers
http://dx.doi.org/10.1680/stbu.12.00019
Paper 1200019
Received 16/04/2012 Accepted 04/06/2013
Keywords: buildings, structures & design/codes of practice & standards/
steel structures
ICE Publishing: All rights reserved
Structures and Buildings
Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
Section classifications for
cold-formed channel steel
j1 Soheila Maduliat PhD
Research Fellow, Department of Infrastructure Engineering,
University of Melbourne, Melbourne, Australia
j2 Priyan Mendis PhD
Professor and Discipline Leader in Civil Engineering, Department of
Infrastructure Engineering, University of Melbourne, Melbourne,
Australia
j3 Tuan Duc Ngo PhD
Senior Lecturer, Department of Infrastructure Engineering, University
of Melbourne, Melbourne, Australia
j1 j2 j3
The inelastic reserve capacity, which is the additional capacity of a member beyond the first yielding, is very
important for limit-state design of frame structures. The aim of this work was to investigate the inelastic bending
capacity of cold-formed channel sections according to European standards and to propose revisions to current
design rules. An extensive experimental and analytical analysis of 42 cold-formed channel sections was conducted.
Material properties of the tested sections were examined using tension tests on metal coupons. The sections were
cold-formed from G450 steel with a nominal thicknesses of 1.6 mm, and varying theoretical buckling stresses
ranging between elastic and seven times the yield stress. The results from the pure bending experimental
investigations and the European design standards for steel structures were compared. It is concluded that the
section classifications defined in Eurocode 3 are not accurate for cold-formed channel sections. Therefore,
modifications to the section classifications that have been derived for hot-rolled sections are required in the case of
cold-formed sections to maintain accuracy (based on the presented test series). Design rules are developed to
account for such behaviour.
Notation
b width of section
be effective width
E Young’s modulus of elasticity
fu tensile strength
fy yield stress
Mc,Rd member moment capacity
MEC3 ultimate moment capacity based on Eurocode 3 design
rules
Mp plastic moment
Mtest ultimate moment capacity based on test result
My yield moment
Weff elastic bending modulus of the reduced effective
section
Wel elastic section bending modulus
Wpl plastic section bending modulus
ªM0 safety factor
åu ultimate strain
åy yield strain
ºe element slenderness ratio
ł stress ratio
1. Introduction
In cold-formed sections, geometric shapes, thinner plate elements
and imperfections are causes of local buckling failure prior to
yielding. These sections are called slender sections and are not fully
effective. Effective sections are the reduced design sections that are
used to calculate the ultimate capacity of a structural element.
The effective width method (EWM) was first introduced by Von
Karman et al. (1932). Following a series of experiments, Von
Karman et al. concluded that ultimate loads are independent from
the width and length of a plate. They assumed that buckled
portions of a plate do not carry any load, but unbuckled portions
can carry loads of up to the yield point. In their method, instead
of a non-uniform stress along the full width b, it is assumed that
a uniform stress, equal to the edge stress, is distributed along a
portion of the width, be.
According to AS/NZS 4600 (SA, 2005) and NASPEC (2007)
specifications for cold-formed steel, the ultimate section moment
capacity can be calculated by using the elastic EWM based on
the Winter (1947) formula. The design assumption for the EWM
1

3. is that the ultimate capacity of the cold-formed sections should
not exceed the yield capacity.
Bambach (2003) collected experimental results for I-sections and
channel sections in minor axis bending. The experimental data for
the I-sections came from work carried out by Chick and Rasmus-
sen (1999) and Rusch and Lindner (2001). The experimental
results from Beale et al. (2001) and Yiu and Pekoz (2000) were
used for the channel sections. These experimental results exhibited
some inelastic behaviour for some sections. For example, Yiu and
Pekoz (2000) anticipated that plain channel sections (sections with
no stiffeners) with a flange slenderness ratio of less than 0.859
would have inelastic behaviour. A number of authors have demon-
strated that some cold-formed sections cannot only behave
inelastically (Baigent and Hancock, 1981; Bambach and Rasmus-
sen, 2004; Reck et al., 1975; Yener and Pekoz, 1985) but may also
be suitable for full plastic design (Elchalakani et al., 2002; Hasan
and Hancock, 1988; Wilkinson and Hancock, 1998; Zhao and
Hancock, 1991). This is due to local plastic mechanism develop-
ment of the cold-formed (thin-walled) section, which causes
inelastic behaviour of the section (Ungureanu et al., 2010).
Maduliat et al. (2012) conducted pure bending tests on cold-
formed channel sections. They demonstrated that sections with
low slenderness values exhibit significant inelastic behaviour,
resulting in capacities significantly exceeding the first yield values.
The cold-formed steel specifications of SA (2005) (AS/
NZS 4600) and NASPEC (2007) do not allow the ultimate
capacity of the cold-formed section to exceed the yield capacity.
However, for fully effective sections, the European standard for
cold-formed sections allows a member moment capacity beyond
the yield moment. The inelastic design methods from Eurocode 3
(EC3) (CEN, 2006) are defined as follows.
For non-fully effective sections
Mc,Rd ¼ Weff f y=ªM01:
For fully effective sections
Mc,Rd ¼ f f y[Wel þ (Wpl À Wel 3 4 3 1
À ººemax=ººe0)]=ªM0g , (Wpl f y)=ªM02:
in which ªM0 is the safety factor, Weff is the elastic bending
modulus of the reduced effective section, Wel is the elastic section
bending modulus, Wpl is the plastic section bending modulus and
ºemax is the slenderness of the element, which corresponds to the
largest value of ººe=ººe0:
For double supported plane elements
ººe ¼ ººp3a:
ººp ¼
b=t
28:4å
ffiffiffiffiffiffi
kó
p
where kó is the buckling factor corresponding to the stress ratio
and boundary condition.
ººe0 ¼ 0:5 þ [0:25 À 0:055(3 þ ł)]1=2
3b:
where ł is the stress ratio.
For outstand elements
ººe ¼ ººp4a:
ººe0 ¼ 0:6734b:
For stiffened elements
ººe ¼ ººd5a:
ººd ¼
ffiffiffiffiffiffiffiffiffiffi
f y
ócr; s
s
where ócr,s is the elastic critical stress for the stiffener.
ººe0 ¼ 0:655b:
The European standard for hot-rolled steel, Eurocode 3 (CEN,
2006), classifies hot-rolled sections into four different classes (1,
2, 3 and 4) according to their applied internal force, steel grade
and width-to-thickness ratio of elements (which are totally or
partially in compression). The ultimate moment capacity is
calculated using the following Equations 6–8.
For class 1 and 2 sections
Mc,Rd ¼ f yWpl=ªM06:
For class 3 sections
Mc,Rd ¼ f yWel=ªM07:
2
Structures and Buildings Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution

4. For class 4 sections
Mc,Rd ¼ f yWeff =ªM08:
While the inelastic capacity of non-slender cold-formed steel
channel sections has been demonstrated, there is scarce literature
available on such sections’ classifications. In the past, most
investigations have been directed towards slender sections or hot-
rolled steel.
The purpose of this work was thus to perform experimental and
analytical investigations of such sections and accordingly develop
design rules for cold-formed channel sections using the approach
of hot-rolled steel specifications. The results of a series of
experiments are presented and compared with the current plastic
approach in Eurocode 3 (CEN, 2006) and modifications to this
standard, which are specifically applicable to cold-formed chan-
nels in bending, are developed.
2. Experimental set-up and test specimens
2.1 Material and mechanical properties of specimens
The channel sections were brake-pressed from four different
steel G450 sheets of 1500 mm length and a nominal thickness of
1.6 mm. From each sheet, two tensile coupons were cut.
To determine strain from the tests, in addition to strain gauges, an
extensometer was used to collect strain data after the strain gauges
of the coupons were detached. The tension tests were performed
using a 500 kN capacity Baldwin universal testing machine.
Table 1 shows the calculated values of Young’s modulus E,
yield strength fy, tensile strength fu, yield strain åy and
ultimate strain åu from the tension tests on the eight coupons.
As shown in the table, the average value of the yield stress is
541 MPa, the average ratio of the ultimate tensile stress over
the yield stress is 1.06 and the average ratio of the ultimate
strain over the yield strain is 14.51. These values do not
satisfy some of the plastic design limitations in AS 4100 (SA,
1998) and Eurocode 3 (CEN, 2006). For example, the plastic
design rules given in AS 4100 are as follows.
j The yield stress must not exceed 450 MPa.
j The ratio of ultimate tensile stress to yield stress must not be
less than 1.2.
j The steel must exhibit a strain hardening capacity.
Therefore, based on the Eurocode 3 and AS 4100 design rules,
the bending capacities of the tested sections cannot reach the
plastic moment. However, Gardner et al. (2010) showed that
plastic design is equally applicable to stocky hot-rolled and cold-
formed rectangular hollow sections.
The tested sections can be categorised into three different
geometric groups
j simple channel sections
j channel sections with simple edge stiffeners
j channel sections with complex edge stiffeners.
The dimensions, yield moment My and plastic moment Mp for
each section are shown in Table 2 and the geometry of the tested
section is shown in Figure 1. The channel sections were filled
with 50 MPa grout concrete at their ends where the sections were
in contact with the loading pins for a length of 500 mm, so that
no local crushing occurred at the loading pins.
2.2 Bending rig setup
The channel sections were tested using a large deformation
pure bending rig 3500 mm long and 460 mm wide (Figure 2).
The wheel rig is a more convenient technique of applying
large rotations than the traditional four-point bending setup
(Cimpoeru, 1992). The two wheels are rotated by hydraulic
pistons that contain load cells with a maximum capacity of
25 kN. The rotation of the wheels loads the specimen via
loading pins in the same manner as the traditional four-point
Coupon Thickness t:
mm
Yield stress fy:
MPa
Average fy for
each steel sheet
Tensile stress fu:
MPa
fu/fy åu: % åy: % åu/åy
G1 1.54 535.0 528.5 561.8 1.05 6.53 0.48 13.74
G2 1.57 522.0 563.5 1.08 6.69 0.49 13.54
H1 1.53 541.0 542.5 565.4 1.05 6.63 0.51 13.11
H2 1.53 544.0 581.0 1.07 6.57 0.49 13.43
I1 1.50 557.0 541.0 584.3 1.05 7.04 0.48 14.57
I2 1.51 525.0 559.3 1.07 8.46 0.47 17.85
J1 1.49 543.0 552.0 568.4 1.05 7.46 0.47 15.77
J2 1.49 561.0 595.7 1.06 6.81 0.48 14.09
Mean 1.52 541.0 572.2 1.06 (,1.1) 14.51 (,15)
Table 1. Tensile coupon test results
3
Structures and Buildings Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
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5. bending test. One end of the sample is simply supported and
the other end is roller supported.
3. Comparison of tests and design rules
The compression elements for each of the tested sections were
either unstiffened or stiffened with an edge stiffener. All the
sections were fully restrained against lateral/torsional buckling,
thus the member capacity was controlled by material yielding,
local or distortional buckling.
To avoid any lateral buckling prior to local or distortional buckling,
four restraining steel plates were installed on each loading wheel.
Section b4: mm b3: mm b2: mm b1: mm Thickness t:
mm
Length Leff:
mm
Yield stress
fy: MPa
My: kN m Mp: kN m
1 — — 47.40 161.22 1.54 500 541.00 9.52 11.39
2 — — 66.45 121.68 1.57 500 541.00 8.53 9.67
3 12.32 15.94 44.92 122.14 1.57 500 528.50 7.80 9.24
4 14.20 14.94 62.75 79.85 1.56 500 552.00 5.75 6.62
5 12.62 21.67 41.49 111.16 1.57 500 528.50 6.66 8.07
6 12.51 16.29 41.27 129.03 1.57 500 528.50 8.05 9.63
7 12.39 15.78 34.99 139.88 1.58 500 528.50 8.32 10.09
8 11.82 17.66 48.23 110.04 1.59 500 528.50 7.15 8.45
9 9.78 18.06 56.65 99.00 1.56 500 552.00 6.98 8.10
10 17.12 17.98 49.36 99.83 1.54 500 541.00 6.50 7.73
11 10.85 16.19 60.10 94.21 1.54 500 552.00 6.73 7.75
12 10.85 16.50 50.93 113.76 1.53 500 541.00 7.55 8.84
13 9.98 14.27 58.18 102.90 1.57 500 541.00 7.29 8.38
14 — 22.74 47.59 121.10 1.58 500 542.50 7.98 9.42
15 — 13.34 42.49 141.02 1.58 500 542.50 8.59 10.19
16 — 18.67 31.40 159.19 1.57 500 542.50 9.08 11.17
17 — 12.44 37.01 161.69 1.54 500 542.50 9.31 11.29
18 — 17.34 62.09 102.68 1.56 500 541.00 7.33 8.34
19 — 12.45 47.50 141.42 1.55 500 542.50 8.98 10.55
20 — 14.53 55.88 121.20 1.56 500 542.50 8.31 9.57
21 — 12.88 65.86 103.61 1.57 500 541.00 7.58 8.54
22 — 20.00 39.99 89.00 1.50 500 541.00 4.41 5.22
23 — 19.96 45.00 89.98 1.50 500 541.00 4.83 5.65
24 — 19.96 49.99 89.96 1.50 500 541.00 5.18 6.01
25 — 19.97 35.00 79.80 1.55 500 541.00 3.60 4.30
26 — 20.00 40.20 79.99 1.50 500 541.00 3.82 4.52
27 — 19.97 45.00 79.98 1.52 500 541.00 4.18 4.88
28 — 19.96 29.97 70.05 1.50 500 541.00 2.63 3.20
29 — 19.95 34.99 70.10 1.55 500 541.00 3.00 3.59
30 — 19.99 39.97 70.00 1.50 500 541.00 3.18 3.75
31 — 20.00 25.00 58.90 1.50 300 541.00 1.83 2.27
32 — 19.97 29.96 60.80 1.55 400 541.00 2.22 2.70
33 — 19.97 35.00 60.40 1.55 500 541.00 2.44 2.92
34 — 14.80 19.90 49.50 1.55 190 541.00 1.24 1.54
35 — 14.96 24.99 50.10 1.50 285 541.00 1.42 1.73
36 — 14.95 29.97 50.10 1.50 290 541.00 1.61 1.92
37 — 9.75 14.78 38.20 1.55 170 541.00 0.67 0.84
38 — 9.63 19.75 39.40 1.55 210 541.00 0.85 1.03
39 — 9.83 24.68 38.50 1.55 240 541.00 0.97 1.15
40 — 9.20 10.45 28.10 1.55 85 541.00 0.33 0.43
41 — 9.70 14.50 29.50 1.55 155 541.00 0.45 0.56
42 — 9.73 19.55 29.00 1.55 145 541.00 0.54 0.67
Table 2. Section properties
4
Structures and Buildings Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution

6. The steel plates were used to restrain all sections with a depth of
less than 210 mm (Figure 3). As with the pure bending rig, one of
the loading wheels could be moved horizontally and therefore the
effective length could be adjusted for each section.
Two different methods from Eurocode 3 were used to analyse the
nominal member capacity of the tested sections: one method for
cold-formed steel and the other for hot-rolled steel. In the first
method, the effective section should be determined. It is noted that
the methods to calculate the effective section in this standard are
not similar to the methods used in the North American (NASPEC,
2007) and Australian standards (SA, 2005). The ultimate moment
capacities of the tested sections based on Eurocode 3 design rules
are set out in Table 3. These are also compared with the test
results. Review of Table 3 and Figure 4 indicates that, for 81% of
the sections, the calculated ultimate moment capacities based on
Eurocode 3 design rules were in good agreement with the test
results. The predictions from the Eurocode 3 design rules were
compared with the values derived using the test results. Table 3
reports the mean and coefficient of variation (CoV) relating the
ratio of the ultimate bending capacity attained experimentally
(Mtest) to the corresponding analytical value derived according to
b2
b4
b1
b3t
Figure 1. Section dimensions
Hydraulic
pump
Manifold
Jack
Inclinometers
Support wheel Loading
pin
Specimen Loading wheel
Load cell
Figure 2. Schematic illustration of the pure bending rig
250 mm
Bolts and nuts to alter
plate lateral position
Front view of the loading wheel
(the rest are not shown for clarity)
Loading
wheel
View A–A
Section
A
ASteel plates to
restrain section
Figure 3. Restraining plates
5
Structures and Buildings Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution

7. Section Eurocode 3 Eurocode 3 inelastic
Mtest: kN m MEC3: kN m Mtest/MEC3 Mc,Rd: kN m Mtest/Mc,Rd
ªM0 ¼ 1.0 ªM0 ¼ 1.1 ªM0 ¼ 1.0 ªM0 ¼ 1.1
1 5.03 5.25 0.96 5.25 4.77 0.96* 1.05
2 4.45 4.16 1.07 4.16 3.78 1.07 1.18
3 7.90 7.72 1.02 7.72 7.02 1.02 1.13
4 4.85 4.96 0.98 4.96 4.51 0.98* 1.07
5 7.56 6.66 1.13 8.07 7.34 0.94* 1.03
6 8.17 8.05 1.01 8.05 7.32 1.01 1.12
7 8.60 8.17 1.05 8.17 7.43 1.05 1.16
8 7.45 6.97 1.07 6.97 6.33 1.07 1.18
9 6.80 6.33 1.07 6.33 5.75 1.07 1.18
10 6.76 6.18 1.09 6.18 5.62 1.09 1.20
11 6.09 5.92 1.03 5.92 5.38 1.03 1.13
12 7.48 7.13 1.05 7.13 6.48 1.05 1.15
13 6.60 6.57 1.00 6.57 5.98 1.00 1.10
14 7.97 7.69 1.04 7.69 6.99 1.04 1.14
15 8.76 8.38 1.05 8.38 7.61 1.05 1.15
16 8.57 8.25 1.04 8.25 7.50 1.04 1.14
17 8.73 8.52 1.02 8.52 7.75 1.02 1.13
18 6.38 6.38 1.00 6.38 5.80 1.00 1.10
19 8.37 8.37 1.00 8.37 7.61 1.00 1.10
20 7.82 7.60 1.03 7.60 6.91 1.03 1.13
21 5.78 6.42 0.90 6.42 5.83 0.90* 0.99*
22 4.98 4.40 1.13 4.40 4.00 1.13 1.24
23 4.97 4.67 1.06 4.67 4.24 1.06 1.17
24 4.91 4.81 1.02 4.81 4.37 1.02 1.12
25 3.95 3.60 1.10 4.30 3.91 0.92* 1.01
26 4.26 3.82 1.12 3.82 3.47 1.12 1.23
27 4.46 4.05 1.10 4.05 3.69 1.10 1.21
28 3.11 2.58 1.20 2.58 2.35 1.20 1.32
29 3.30 3.00 1.10 3.59 3.26 0.92* 1.01
30 3.40 3.17 1.07 3.17 2.88 1.07 1.18
31 2.24 1.80 1.24 1.80 1.64 1.24 1.37
32 2.50 2.19 1.14 2.19 1.99 1.14 1.26
33 2.72 2.44 1.12 2.92 2.65 0.93* 1.02
34 1.58 1.24 1.28 1.24 1.13 1.28 1.40
35 1.70 1.42 1.20 1.42 1.29 1.20 1.32
36 1.88 1.61 1.17 1.92 1.75 0.98* 1.08
37 0.91 0.67 1.36 0.84 0.76 1.09 1.20
38 1.07 0.85 1.26 1.03 0.94 1.04 1.14
39 1.22 0.97 1.26 1.15 1.05 1.06 1.17
40 0.52 0.33 1.59 0.33 0.30 1.59 1.75
41 0.64 0.45 1.44 0.56 0.51 1.14 1.25
42 0.73 0.54 1.35 0.67 0.61 1.10 1.21
Mean — — 1.12 — — 1.07 1.17
CoV — — 0.12 — — 0.11 0.11
Table 3. Ultimate moment capacities of the tested sections based
on Eurocode 3 (for cold-formed steel) design rules; values
marked with an asterisk are sections whose ultimate capacity
(based on Eurocode 3 design rules) is unconservative compared
with the test results
6
Structures and Buildings Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
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8. Eurocode 3 (Mc,Rd), both with a safety factor of 1.1 and without a
safety factor. The values indicated with an asterisk in this table are
the sections whose ultimate capacity (based on Eurocode 3 design
rules) is unconservative in comparison with the test results. How-
ever, it can be seen that the European standard gives mean values
of Mtest/Mc,Rd of 1.172 and 1.07 (with and without a safety factor
respectively), with a CoVof 0.11 for both cases.
In the second method, based on Eurocode 3 design rules for hot-
rolled steel, the tested sections were classified into four different
classes (class 1, 2, 3 and 4) based on their element’s width-to-
thickness ratio. The section classifications based on the test
results and Eurocode 3 design rules are shown in Table 4.
In many instances the section classifications calculated using
Eurocode 3 were different to those determined in the experiments
(these sections are marked with an asterisk in the table). The
results are plotted in Figure 5, where it is clear that this is
especially true for the classification of class 1 sections. There
were 13 sections that were classified as class 1, but the test results
showed that they did not satisfy the rotation requirement for such
classification. In Table 4, the test capacities are compared with
the design capacities (existing limit Mtest/MEC3): for many of
these sections, incorrect classification led to overprediction of
capacity. The slenderness limits (CEN, 2006) for class 2, 3 and 4
classifications are generally satisfactory, albeit with three, one
and two exceptions for classes 2, 3 and 4 respectively.
4. Proposed design modifications
In order to improve the classification of cold-formed steel
channel sections into the categories of class 1, 2, 3 and 4, new
width-to-thickness ratio limits are proposed in Eurocode 3 (CEN,
2006). A conservative approach was taken, whereby the limits
were designed to exclude class 4 sections from class 3, class 3
sections from class 2 and class 2 sections from class 1, as shown
graphically in Figure 6.
The proposed cold-formed channel section classifications accord-
ing to the width-to-thickness ratio (b/t) limits are as follows
[å ¼ (235=f y)1=2
].
Class 1
j internal element subjected to bending: b=t 22å
j internal element subjected to compression: b=t 5å
Class 2
j internal element subjected to bending: b=t 44å
j internal element subjected to compression: b=t 19å
Class 3
j internal element subjected to bending: b=t 130å
j internal element subjected to compression: b=t 40å
In general, the least favourable class of the section’s element is
defined as the section’s class.
According to Eurocode 3 (CEN, 2006), the section’s classification
depends on the width-to-thickness ratio of the elements that are
totally or partially in compression, the applied internal force and
the steel grade.
The moment capacities calculated with Eurocode 3 and the
revised width-to-thickness ratio limits are compared with the test
results in Table 4 (proposed Mtest/MEC3). With the new classifica-
tion, the unconservative capacity predictions derived with the
existing width-to-thickness ratio limits become conservative with
the proposed slenderness limits. The proposed slenderness limits
may thus be considered accurate for the design of cold-formed
steel channel sections in bending.
The ultimate moment capacities of the tested sections based on
existing and proposed classifications are compared with the test
results in Figure 7. By reviewing Figure 7 and Table 4, it is evident
that the ultimate moment capacities of the sections based on the
proposed method have not changed considerably compared to the
existing method. However, the plastic behaviour of these sections
as a member of a structural assembly (such as portal frames) is not
predicted accurately according to the existing classification.
5. Conclusion
By reviewing a range of literature on the study of designing cold-
formed channel sections, a number of conclusions are evident.
j The design methods for cold-formed sections in Australian
and North American standards do not include any inelastic
reserve capacity for cold-formed channel sections with edge
stiffeners. The assumption in the Australian and North
American standards is that the maximum moment capacity is
the yield moment. However, the European standard allows a
capacity beyond the yield moment for fully effective sections.
j The plastic design method is based on studies for hot-rolled
steel and is mainly applicable to hot-rolled sections. Only a
0
1
2
3
4
5
6
7
8
9
10
11
0 1 2 3 4 5 6 7 8 9 10 11 12
Mc,Rd
Mtest
Ultimate capacity
Ultimate capacity
with safety factor
Safe
Unsafe
Figure 4. Comparison of test results with Eurocode 3 for
cold-formed steel (with and without safety factor)
7
Structures and Buildings Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
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9. Section Rotation
capacity
R ¼ k/kp À 1
Classification Mtest/MEC3
Test Standard Existing limit Proposed
limit
1 — 4 4 0.96 0.96
2 — 4 4 1.07 1.07
3 — 3 3 1.01 1.01
4 — 4 4 0.98 0.98
5 — 3 3 1.13 1.13
6 — 3 3 1.01 1.01
7* — 3 4 1.05 1.03
8 — 3 3 1.04 1.04
9 — 4 4 1.07 1.07
10* — 3 4 1.09 1.09
11 — 4 4 1.03 1.03
12 — 4 4 1.05 1.05
13 — 4 4 1.00 1.00
14* — 4 3 1.00 1.00
15 — 3 4 1.05 1.02
16 — 4 4 1.04 1.04
17 — 4 4 1.02 1.02
18 — 4 4 1.00 1.00
19 — 4 4 1.00 1.00
20 — 4 4 1.03 1.03
21 — 4 4 0.90 0.90
22 — 3 3 1.13 1.13
23 — 3 3 1.03 1.03
24 — 4 4 1.02 1.02
25* — 3 2 0.92 1.10
26* — 3 2 0.94 1.11
27 — 3 3 1.07 1.07
28* — 3 1 0.97 1.18
29* — 3 1 0.92 1.10
30* — 3 2 0.91 1.07
31* — 3 1 0.99 1.22
32* — 3 1 0.93 1.13
33* — 3 1 0.93 1.12
34* 0.65 2 1 1.03 1.03
35* — 3 1 0.99 1.20
36* — 3 1 0.98 1.17
37* 1.50 2 1 1.09 1.09
38* 1.30 2 1 1.04 1.04
39* 0.70 2 1 1.06 1.06
40 4.30 1 1 1.21 1.21
41* 2.10 2 1 1.14 1.14
42* 2.45 2 1 1.10 1.10
Mean — — — 1.02 1.07
CoV — — — 0.07 0.07
Table 4. Test results and comparison with Eurocode 3 (for hot-rolled steel)
8
Structures and Buildings Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution

10. few studies have been conducted on the behaviour of cold-
formed closed sections in the plastic range.
This paper examined the material properties of test sections by
performing tension tests on coupons from different metal sheets.
The outcomes of the tension tests revealed that the material
properties of the tested sections were not in a range to satisfy some
of the plastic design limitations in Eurocode 3 (CEN, 2006).
The bending behaviour of 42 cold-formed channel sections was
explored and analysed by means of pure bending tests. The
experimental results were compared with results from Eurocode 3
design methods, which led to a number of conclusions.
j The European standard for cold-formed steel was accurate for
calculating the cold-formed channel section’s ultimate
moment capacity with a safety factor of 1.1.
j Sections that are classified as compact sections do not have
the appropriate rotation capacity for plastic design. Therefore,
the section classifications defined in Eurocode 3 are not
accurate for cold-formed channel sections. It can also be
concluded that the proposed section classifications in
0
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120
140
160
0 10 20 30 40 50 60 70 80 90 100
(/)/btεweb
( / )/b t εflange
Class 4 (test result)
Class 3 (test result)
Class 2 (test result)
Class 1 (test result)
Class 3 limits (existing
classification)
Class 2 limits (existing
classification)
Class 1 limits (existing
classification)
Figure 5. Comparison of test results with existing Eurocode 3
classification
0
20
40
60
80
100
120
140
160
0 10 20 30 40 50 60 70 80 90 100
(/)/btεweb
( / )/b t εflange
Class 4 (test result)
Class 3 (test result)
Class 2 (test result)
Class 1 (test result)
Class 3 limits (proposed
classification)
Class 2 limits (proposed
classification)
Class 1 limits (proposed
classification)
Figure 6. Comparison of test results with proposed Eurocode 3
classification
9
Structures and Buildings Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution

11. Eurocode 3 provide a more conservative result than the
existing classification, noting that the existing section
classifications are not accurate.
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Figure 7. Comparison of test results with Eurocode 3 for
hot-rolled steel
10
Structures and Buildings Section classifications for cold-formed
channel steel
Maduliat, Mendis and Ngo
Offprint provided courtesy of www.icevirtuallibrary.com
Author copy for personal use, not for distribution
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