Cold-formed steel channel sections have been widely applied in structural buildings. This type of section is then added stiffeners in the web to form the new section called SupaCee. The capacities of these sections have been investigated due to shear actions paralleling their webs. Shear forces are assumed to be resisted by the web, but the presence of the flanges and lips also have specific impacts on the shear capacities of these sections. This paper, therefore, investigates the effects of the flange widths and lip lengths on the shear capacities of the channel and SupaCee sections. Also, the shear capacities of SupaCee sections are studied to illustrate their strength improvements compared to those of channel sections. Shear capacities of the investigated sections are determined according to AS/NZS 4600:2018. The study demonstrated the innovation of SupaCee sections in shear strength improvements in comparison with those of channel sections.
Cold-formed steel channel sections have become a common product in structural buildings with numerous applications . They can be subjected to compression, bending or shear. In terms of compression or bending, buckling modes such as local, distortional, flexural, or flexural-torsional buckling have been investigated in many research studies and are deeply understood . In the case of shear, shear buckling of channel section was investigated with the consideration of the web alone, but the flanges and the lips were ignored in the behavior. There was not any consistent theory for shear buckling of full thin-wall sections. The channel sections have then added web stiffeners to increase the stabilities. These such sections termed as SupaCee sections have a variety of advantages compared to the traditional channel ones, as discussed in Pham and Vu . The recent development of the DSM method for thin-wall sections in shear required the elastic buckling loads of the whole section in pure shear. Pham and Hancock [3-6] carried out a series of the channel and SupaCee section beams under shear to provide deep understandings of their strengths and behaviors. Also, Hancock and Pham [7,8] used the complex Semi-Analytical Finite Strip Method proposed by Plank and Wittrick  to develop the signature curve for channel sections under shear actions with the assumption of unrestraint at end conditions. Pham and Hancock  used a spline finite strip analysis to investigate the shear buckling of whole channel sections restrained at their ends. The spline finite strip analysis was developed by Lau and Hancock . To reduce computer resources in analysis, Hancock and Pham  developed a new version of the semi-analytical finite strip analysis called reSAFSM that allows considering restrained ends in the analysis of thin-walled sections under shear actions. Channel sections with intermediate web stiffeners have been also investigated by Pham [13-14] using Semi-Analytical Finite Strip Method. This method was subsequently incorporated into the Thin-Wall-2  in the analysis of the buckling loads under shear . Thin-Wall-2 has been allowed to use for elastic buckling analysis of thin- wall sections according to the AS/NZS 4600-2018 .
The paper, therefore, is aimed to investigate the shear capacities of the channel and SupaCee sections with the variations of dimensions of the flanges and lips. The effects of the flanges and lips on the elastic shear buckling loads of thin-walled channel sections can be accounted for as presented in Appendix D3, but the intermediate web stiffeners are not included. Thin-Wall-2 software program , therefore, can be used for the elastic shear buckling analyses in this investigation. The shear capacities of commercial SupaCee sections are also investigated to illustrate their innovation in strength improvements based on comparing the shear capacities between SupaCee and channel sections.
The investigated sections are commercial sections provided by
BlueScope Lysaght . The THIN-WALL-2 software program
 is used for elastic bucking analysis under shear actions, and
the shear capacities are determined according to the AS/NZS
4600: 2018 .
The nominal shear capacity of beams without transverse
web stiffeners can be calculated determined according to AS/NZS
4600-2018  as follows:
are the yield shear force and the elastic shear
buckling force of the section;
is the non-dimensional slenderness,
The yield shear force , can be calculated as
, where is the area of the web element; y f is the design yield
stress. The elastic shear buckling force can be determined
according to Appendix D, AS/NZS 4600-2018  or a rational
elastic buckling analysis. THIN-WALL-2 software program 
will be used for this elastic buckling analysis in this investigation.
This software program was developed at the University of Sydney
using the finite strip method. One of the outputs of buckling
analysis is a signature curve performing the relationship between
the elastic buckling stress and the half-wavelength of each
buckling mode. This program can be used for buckling analysis
under compression, bending, shear, localized loading or combined
actions. (Figure 1 (a)) shows the signature curve of a channel
section under the shear actions paralleling the web. The elastic
shear buckling stress is the minimum point in the curve with the
buckling mode demonstrated in (Figure 1(b)).
The geometry of the unlipped, lipped channel and SupaCee
sections are demonstrated in (Figure 2). The section depths (D)
are 250 mm, the flanges (B) vary from 0.1 to 0.9 times of the depth
(D). The sectional thicknesses (t) are 1.5 mm, 1.9 mm and 2.4 mm,
and the inner radii at corners (r1 or r2) are 5 mm. The elastic shear buckling stresses are determined with the support of the THINWALL-
2 software program . The buckling stresses are listed
in (Table 1) with the variation of the dimensions of the flanges
and the lips. The shear capacities are then calculated with the
design yield stress of 450 MPa, as presented in Section 2. The
nominal shear capacities are listed in (Table 2) and demonstrated
in (Figure 3).
Based on the results in (Table 2), the shear forces are
maximum at the ratio B/D of 0.5 for unlipped channel sections,
whereas the maximum of shear forces are obtained at the lower
ratio B/D varying from 0.2 to 0.4 depending on the lip lengths for
lipped channel or SupaCee sections. In terms of lipped channel and SupaCee sections, as the ratio B/D increases from 0.1 to 0.2,
the shear force goes up rapidly. This illustrates the significant
contribution of the flange on the shear capacities of the channel
sections. The ratio B/D subsequently increases, the shear
capacities improve slowly to the maximum values, subsequently reducing gradually as the flange width increase to 0.9. These
results can be explained due to the effects of flange slenderness
(Figures (4&5)). With the small flange, there is very little effect of
flange slenderness on the shear buckling capacity. This effect is
significant when the flange dimensions increase resulting in the
reduction of the shear capacities. In terms of the unlipped channel
section, as the increase of the ratio B/D, the shear capacities have a slow increase trend to the maximum values, and then have a
gradual reduction. When the ratio B/D increases to 0.8 and 0.9,
shear buckling occurs in the flanges (Figure 6), this leads to the
significant reductions of elastic buckling stresses. The lips are
then added, shear buckling is prevented in the flanges, and the
elastic shear buckling stresses are significantly improved as
presented in (Table 1).
The channel and SupaCee sections for this investigation are
taken from the catalogue provided by BlueScope Lysaght .
Their dimensions are presented in (Table 3) with the nomenclature
demonstrated in (Figure 2). The elastic shear buckling stresses
are determined using the Thin-Wall-2 software program  and
are listed in (Table 3). These buckling stresses are then used to determine shear capacities of the investigated sections according
to AS/NZS 4600-2018  as presented in Section 2. The design
yield stress of 450 MPa is used for this investigation. Shear
capacities of channel and SupaCee are summarized in (Table 3).
The results of shear capacities are plotted in percentage diagrams,
where the shear capacities of channel sections are shown in the
horizontal axis and the vertical axis is for the shear capacity
deviations (in %) between SupaCee and channel sections, as
illustrated in (Figure 7).
The SupaCee sections have demonstrated their innovation
in shear capacities compared to those of channel sections due to
the effects of the intermediate web stiffeners with the increase
of shear capacities reaching 22%. The web stiffeners become
more beneficial effects with the smaller thicknesses in all
investigated sections. This conclusion can be seen as the strength improvements of the SC250 section decrease from 11.54% to
4.48% when the thicknesses increase from 1.5mm to 2.4mm as
presented in (Table 4). This trend is also observed in the other
sections. For small sections (SC150 and SC200 sections), the shear
strength improvements are more noticeable for the small section.
This result is illustrated as the higher strength improvements of SC150 section compared to those of SC200 section in almost
investigated thicknesses. For large sections (see SC250 to SC400
sections), the strength improvements become more significant
as the increase of web slenderness. This conclusion is based on the increasing trend of strength improvements from 7.29% to
9.14% corresponding to the increase of web slenderness from
SC25019 to SC40019 sections. This trend is also seen for the other
Note: the inner radius r1 = r2 = 5mm; t, D, B, L1, L2, GS, S (mm); α1, α2(0)
Note: Δ (%) is the nominal shear capacity deviation between SupaCee and Lipped channel sections (in %)
The paper investigated the effects of flange widths and lip
lengths on the shear capacities of unlipped channel, lipped channel
and SupaCee sections. The investigated results have demonstrated
the role of the flanges and lips on the shear capacities with the
significant increase of shear forces as the ratio of B/D increase
from 0.1 to 0.2, but then observe a gradual reduction due to the
effects of flange slenderness. Also, the lips can prevent the shear
buckling from occurring in the flanges with the large ratio of B/D.
The paper subsequently investigated the innovation in shear
capacities of SupaCee sections compared to those of traditional
channel sections with significant shear strength improvements.
Pham CH, Hancock GJ (2010) Finite element analyses of high strength Cold- Formed SupaCee® Sections in Shear, Proceedings of SDSS Rio. International Colloquium Stability and Ductility of Steel Structures Volume 2, 1025-1032.
Pham CH and Hancock GJ (2012) Direct strength design of cold-formed sections for shear and combined actions. Journal of Structural Engineering Volume 1, 759-768.
Hancock GJ, Pham CH (2011) A signature curve for cold-formed channel sections in pure shear. Research Report R919.
Hancock GJ, Pham CH (2012) Direct method of design for shear of cold-formed channel sections based on a shear signature curve. in 21st international specialty conference on cold-formed steel structures pp: 207-221.
Nguyen VV, Hancock GJ, Pham CH (2015) Development of the Thin-Wall- 2 for Buckling Analysis of Thin-Walled Sections Under Generalized Loading. in Proceeding of 8th International Conference on Advances in Steel Structures.
Hancock GJ, Pham CH (2022) Finite strip methods for stability analysis of thin- walled members with applications to the Direct Strength Method of design LTD.
(2018) AS/NZS 4600-2018, Australian / New Zealand Standard TM Cold-formed steel structures. The Council of Standards Australia.
(2014) BlueScope Lysaght, Supapurlins Supazeds & Supacees. Blue Scope Lysaghts.