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Experimental investigations of cold-formed steel beams of corrugatedweb and built-up section for anges

Dan Dubina a,b, Viorel Ungureanu a,b,n, Lucian Glia c

a Department of Steel Structures and Structural Mechanics, Politehnica University of Timisoara, Timisoara, Romaniab Laboratory of Steel Structures, Romanian AcademyTimisoara Branch, Timisoara, Romaniac Technical University of Cluj-Napoca, Cluj-Napoca, Romania

a r t i c l e i n f o

Article history:Received 13 January 2015

Received in revised form

18 January 2015

Accepted 19 January 2015Available online 11 February 2015

Keywords:

Corrugated web beam

Cold-formed steel solution

Discrete fasteners

Self-drilling screws

Experimental investigation

a b s t r a c t

The steel beams of corrugated web represent a relatively new structural system which emerged in thepast two decades. The thin corrugated web affords a signicant weight reduction of these beams,

compared with hot-rolled or welded ones. In the solutions existing on the market, the anges are made

ofat plates welded to the sinusoidal web sheet, requiring a specic welding technology. A new solution

is proposed in this paper, in which the beam is composed by a web of trapezoidal cold-formed steel

sheet and anges of built-up cold-formed steel members (e.g. back-to-back lipped channel sections or

angles with turn lips). The connections betweenanges and web can be done by self-drilling screws or

by spot welding. The rst part of the study, summarised in this paper, is devoted to the evaluation and

validation of technical solution, including experimental investigations, carried out at the CEMSIG

Research Centre of the Politehnica University of Timisoara ( http://www.ct.upt.ro/en/centre/cemsig). In

a subsequent paper, numerical investigations aiming to optimise the solution and estimate its technical

limits for applications will be presented.

& 2015 Elsevier Ltd. All rights reserved.

1. Introduction

Corrugated web girders represent a relatively new structural

system emerged in the past two decades especially in Germany

and Austria, used in a large number of applications. Increased

interest of this solution was observed for the main frames of

single-storey steel buildings and in steel bridges. In 1988 the rst

machines for the production of SIN-beams were developed by

Zeman[1]. These semi-automatic machines of the rst generation

were able to produce SIN-beams with parallel anges and web

thicknesses of 2.0 mm, 2.5 mm or 3.0 mm. The machines of latest

generation are able to produce SIN-beams by a fully automated

process. A more variable design of cross-sections, a variety of web

thickness, lower beam heights and smaller ange dimensionsbecame possible. Furthermore tapered beams and machine-made

web openings can be produced.

In Japan has been developed a roll forming process to produce

corrugated web I-beams and partially corrugated webs which

were used in mobile-modular home construction[2]. In the United

States, beams with corrugated webs are more and more widely

used and many bridges and large span buildings are built using

corrugated web I-beam.

The main benets of this type of beams are that the corrugated

webs increase the beams stability against buckling, which may

result in a very economical design via the reduction of web

stiffeners. Due to improvements of the automatic fabrication

process corrugated webs up to 6 mm thickness became possible.

Furthermore, the use of thinner webs results in lower material

cost, with an estimated cost savings of 1030% in comparison with

conventional fabricated sections and more than 30% compared

with standard hot-rolled beams. The buckling resistance of used

sinusoidal corrugated sheet used for webs is comparable with

plane webs of 12 mm thickness or more.

In the existing solutions the anges are at plates, welded tothe sinusoidal web sheet, requiring a specic welding technology

and highly automated manufacturing process. The anges mainly

provide exural strength to the beam with low contribution from

the corrugated web, which provides the shear capacity. Failure of

the web occurs by steel yielding or web buckling. Lateral-torsional

buckling of the girder and local ange buckling, separately or in

interaction, represents other possible failure modes.

The paper presents a new technological solution of such a

system, composed by webs made of trapezoidal cold-formed steel

sheets and anges of built-up cold-formed steel members (e.g.

back-to-back lipped channels, back-to-back angles with turn lips

Contents lists available at ScienceDirect

jo ur nal ho me pa ge: www.elsevier.com/locate/tws

Thin-Walled Structures

http://dx.doi.org/10.1016/j.tws.2015.01.018

0263-8231/&2015 Elsevier Ltd. All rights reserved.

n Corresponding author at: Department of Steel Structures and Structural Mechanics,

Politehnica University of Timisoara, Timisoara, Romania.

E-mail address:[email protected](V. Ungureanu).

Thin-Walled Structures 90 (2015) 159170
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or hat omega). The connections between anges and web are

made with self-drilling screws or by spot welding. It is easy to be

observed that the new solution, as a whole, is 100% composed by

cold-formed steel elements, avoiding the combination of two

types of products, i.e. cold-formed for webs and hot-rolled for

anges. High protection to corrosion due to the fact that all

components are galvanized is a major advantage. On the other

hand, if the fabrication might adopt an automotive fastening

technology such as spot welding, the production of some standar-

dised beam series can be highly automated.

2. Literature review

There are several types of built-up cold-formed steel beams onthe market, prepared for industrialised fabrication, for which bolts,

screws or spot welds are used for anges-to-web connection.

Zhao [3] at Queensland University of Technology initiated a

research program to investigate the structural behaviour and

design of hollow ange members in compression. The study was

focus on members with rectangular hollow anges, where the

sections are formed from a single steel strip, with various

manufacturing methods such as spot welding, self-pierced riveting

and screw fastening foranges-to-web connections. He found that

the type of fastening and spacing does not affect the member

compression capacity signicantly. Wanniarachchi [4] extended

the work of Zhao[3]and developed a new cold-formed steel beam

with two rectangular hollow anges, rigid in torsion, and a slender

web, cross-section assembled using intermittent screw fastening.He has found that intermittent screw fastening method appears to

be structurally adequate and minimises the fabrication cost.

Landolfo et al. [5] evaluated the applicability of built-up cold-

formed steel beams assembled by laser welding and assessed the load

bearing capacity of the assembled beams. The I-section with hollow

anges is fabricated from two back-to-back special C-proles. The two

proles are joined with connections which are located on the web

and on the anges. Two reinforcing plates are placed inside the top

and bottom hollow anges of the I-section, providing an additional

connection system between the two C-proles.

BEN-VAUTIER S.P.A.[6], patented a modular H-beam comprises

one or more modules, each formed of two half-structural parts of

two pieces of structural steel, forming each a thin sheet, compris-

ing a central part or core, and lateral half-anges. The half-anges

form gaps, inside which plates are introduced in order to

strengthen the anges of the beam, which constitute the regions

more subjected to bending stresses.

Table 1

Types of specimens.

CWB-1 Standard solution:ange-to-web connection in every corrugations and uniformly distributed seam fasteners (see Fig. 1)

CWB-2 Standard solutionsupplementary lipped channel sections under the load application points (see Fig. 2)

CWB-3 Optimized solution by adapting the ange-to-web connections according to the distribution of shear stresses (connections at each second corrugations where

the shear force decreases) (seeFig. 3)

CWB-4 Standard solution by eliminating shear panels and doubling of corrugated webs in the zones with high shear forces (seeFig. 4)

CWB-5 Optimized solution by adapting both the ange-to-web connections and seam fasteners to the distribution of shear stresses (see Fig. 5)

Fig. 2. Conguration of the specimens CWB-2.




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Signicant work on girders with corrugated web was devoted to

study the shear capacity. A summary of the research and development

in beams with corrugated webs was reported by Elgaaly and Dagher

[7]. Smith [8] performed four tests on two girders with corrugated

webs, which were welded to the anges using intermittent welding.

He found that the connection between the ange and the web is

critical for the shear strength as the weld used in the test was

subjected to high strength and web was easily ruptured at this point

before it reached its buckling strength. He suggested that intermittent

welding of the corrugated webs to the ange is not advisable.

Hamilton[9]performed 42 tests on 21 beams, which used four

different corrugation congurations and two thicknesses. Unlike

Smiths[8] specimens, the webs were continuously welded to the

anges from one side. It was found that the failure of all specimens

was initiated by local buckling of one of the corrugation folds.

Another conclusion was that dense corrugation proles are more

likely to fail in global shear buckling. Elgaaly et al.[10]veried the

test results done by Smith [8] and Hamilton [9] using nonlinear

FEM and found that the results of the nite element analysis were

very close to the test results.

Luo and Edlund[11]used non-linear nite element analysis to

perform a geometrical parametric study and compared the numer-

ical results with existing empirical and analytical formulae. Within

the parametric range studied, they have found that the ultimate

shear capacity increases proportionally with the girder depth and

does not seem to be dependent on the ratio of girder length over

girder depth, while the post-buckling shear capacity not only

increases with the girder depth, but also appears to be dependent

on the ratio of girder length over girder depth. They have also

found that the corrugation depth did not seem to have much effect

on the ultimate shear capacity but affected the degree of the

localization of the buckling mode.A lot of work has been done on the bending behaviour of steel

girders with corrugated web. It was observed that the contribution

of the web to the ultimate moment capacity of a beam with

corrugated web is negligible, and the ultimate moment capacity

will be based on the ange yield stress.

Elgaaly et al.[12]have performed a series of experimental and

analytical studies. They have experimentally tested six specimens

that had corrugated webs in the centre panel and at panels

adjacent to the support. They cross braced theat panels to ensure

that the failure would occur in the centre panel. All the specimens

failed due to ange yielding followed by vertical buckling of the

compression ange into the web. They found that the web did not

contribute much to the bending capacity of the beam and its

contribution could be neglected.Chan et al. [13] studied the effect of web corrugation on the

bending capacity of the beam using FEM. Beams with plan web,

horizontally corrugated web and vertically corrugated web were

studied. They found that the vertically corrugated web provides a

stronger support against the ange buckling than those with hor-

izontally corrugated and at webs. Also, the corrugation radius was

investigated and found that larger corrugation radius could sustain

higher bending moment. It was also found that, the vertically

corrugated beam had a 10.6% reduction in weight when compared

with the beam with at web.

Johnson and Cafolla[14]have studied the effect of the vertically

corrugated webs on the local buckling of the compressive ange and

the exural behaviour of beams with corrugated webs via numerically

and in experimental tests. They found that, depending on the shape of


Fig. 6. Experimental arrangement.

Fig. 7. Samples cut from at regions and corners.

Table 2

Yield and ultimate strengths.

Type fyM[N/mm2] fuM[N/mm

2] sfy sfu fyk [N/mm2] fuk [N/mm

2]

BM-CF 438.74 517.06 5.69 2.46 425.48 511.33

BM-CW 441.65 521.86 25.53 3.48 382.16 513.05

CM-CF 521.64 585.07 9.89 9.69 498.60 562.49

BM-CW 349.41 394.75 12.67 10.89 319.89 369.37

BM-SP 358.42 419.59 4.09 2.48 348.90 413.81

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the corrugations, the slenderness should be based on the mean or on

the maximum outstand, which means the distances from the hor-

izontal fold to the edges of the ange. Also, they found that the

contribution of the web to exural capacity was small.

Lindner[15]studied by experimental tests the lateral-torsional

behaviour of steel girders with corrugated webs and found thatthe torsional section constant ITfor a beam with corrugated web

doesnt differ from that of a beam with at web, but the warping

section constant Iwis different.

The effect of the corrugation proles of the web on the lateral-

torsional buckling strength of I-girders was also studied [16,17].

Pasternak et al. [18,19]presented a new proposal for Annex D of

EN 1993-1-5:2006[20].

Moon et al. [21] investigated the lateral-torsional buckling

strength of an I-girder with corrugated steel webs under linear

moment gradient by using nite element analysis. It was found

that the buckling behaviour of the I-girder with corrugated steel

webs differed depending on the number of periods of the

corrugation. Simple equation for the moment gradient correction

factor for these types of beams was suggested.

In what concerns girders with trapezoidal corrugated webs

under patch loading, Leiva-Aravena and Edlund[22]performed six

tests, in which three parameters were considered, i.e. the load

patch width, the load path location and the web thickness. From

the comparison between the test and nite element analysis

results, it can be concluded that the FE model is able of depicting

the behaviour of girders with corrugated webs subjected to in

plane compressive patch loading and of calculating the failure load

to a good degree of accuracy.

Elgaaly and Seshadri [23] performed ve tests on four different

corrugation proles. Two distinct modes of failure were observed: web

crippling and web yielding. They also studied, using FEM, the interac-

tion between partial compressive edge loading and bending or shear.

Luo and Edlund [24] performed nonlinearnite element analysis to

study the effect of four factors that inuence the buckling strength of

the beams, i.e.: (1) strain hardening model; (2) corner effect; (3) initial

imperfections; (4) loading position. They used elastic-perfectly plasticand RambergOsgoods models and found that with a Ramberg

Osgood strain-hardening model for webs, the ultimate strength of the

girder is about 812% higher than using an elastic-perfectly plastic

model. Also, the effect of the corners due to cold-forming does not

have any signicant effect on the ultimate strength.

Nguyen et al.[25]investigate the moment modication factors of

I-girder with trapezoidal web corrugations under moment gradient

and various end restraint conditions and proposed closed-form

expressions for the moment modication factors.

Tahir et al. [26]investigated the performance of the strength, the

rotational stiffness, and the ductility of the composite and non-

composite connection using trapezoidal web proled steel sections.

Eight full scales testing of beam-to-column connections comprised of

four specimens for composite and four for non-composite connectionwith different geometrical congurations have been carried out. The

tests results showed good agreement between the experimental and

the predicted values. The test also concluded that composite connec-

tions have higher moment resistance, higher stiffness, and less ductile

compared with the non-composite connections.

Kvesdi et al. [27] investigated of the stress distribution in the

ange of the girders with corrugated webs. During the experimental

tests the stress distributions on different locations (i.e. anges and

web) were measured as a basis for parametric analyses.

Probably, the rst built-up steel girder using corrugated sheets as

web elements and cold-formed sections for anges is the Macomber

Panlweb girder, patented in 1967. The Macomber Panlweb girder

consists of 1.9 mm to 3.8 mm thickness of the corrugated web for

depths of 0.51 to 1.02 m [28,29]. This solution applies shallow

Fig. 8. Failure modes of (a) coupons cut from BM-CW, BM-SP, BM-CW and BM-SP; (b) coupons cut from CM-CF.

Table 3

Types of tested connections.

Name t1[mm] t2 [mm] No. of tests dnom[mm]

T1-1.4 0.7 0.7 6 4.8

T2-1.7 1.0 0.7 5 4.8

T3-3.7 2.01.0 0.7 6 6.3

T4-9.0 1.0 8.0 5 5.5

T5-11.0 2.01.0 8.0 5 M12

T6-2.7 2.0 0.7 10 6.3

T

3

T4-9.0

1.0

T

T2-1.7

3.7

T1-1.4

22.7

Fig. 9. Location of tested connections.


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VV-section for anges, which make difcult enough the installing of

ange-to-web fasteners. On these system the rst research activities

were carried out in the 70s by Harrison[30].

The rst attempt of the authors of this paper related to this

type of beams 100% composed by cold-formed steel elements was

a numerical study [31] in order to prove the efciency of such

solution against cold-formed steel trusses.

A similar solution has been proposed and analysed in the frame

of PRECASTEEL project [32], but using blind rivets as seam

fasteners for the corrugated web and bolts for web-to-ange

connections. For anges, back-to-back lipped channel or two typesof hat-sections have been used. Deep corrugation web sheeting of

longitudinal intermediate stiffeners have been applied in this

solution. However, looking to the test results, one observes the

sensitivity to distortion of corrugation still remain high.

Another very important aspect related to the cold-formed steel is

the connecting technique. Briskham et al. [33]performed a compara-

tive study on of self-pierce riveting, resistance spot welding and spot

friction joining for aluminium automotive sheet. Quantitative compar-

isons have been made on the basis of tensile strength (shear and peel),

process time, equipment price and running cost. The results identied

resistance spot welding as a more economically favourable option

than self-pierce riveting or spot friction joining for the task of

producing the majority of the joints. The analysis indicates that it is

the ongoing cost of the rivets that makes self-pierce riveting the most

expensive process. For resistance spot welding, the largest cost factors

identied were energy consumption and frequency of electrode

replacement. Even the material is aluminium, similar conclusions

can be drawn for steel too.

Guenfoud et al. [34] tested welded specimens fabricated

through one, two or four layers of steel sheets with thicknesses

ranging from 0.76 mm to 1.52 mm. A total of 72 tension tests and

107 shear tests were completed. The idea was the initiation of a

research program on the shear resistance and tension resistance of

multi-layer arc spot welds. They found that the type of electrode,

high current setting and proper welding technique affect thequality of arc-spot welds in multi-layer connections, and a lower

limit for the net effective weld diameter was proposed.

Snow [35] conducted a similar research in order to establish a

relationship between arc spot weld shear strength and the arc time

used while forming the weld. In this case the arc times were broken

down into three separate categories. The rst category consisted of

full-time welds, the second 2/3-time welds, and the third 1/3-time

welds. Testing was performed on steel gauge sheets of 0.85 mm,

1 mm, 1.3 mm and 1.6 mm. Each gauge material was tested in single-,

double- and four-layer congurations. Two types of diameter arc spot

welds were tested. Comparisons were made between shear strength

and weld geometry, including average diameter, effective diameter

and penetration. The research has proven that arc time has a

tremendous inuence on arc spot weld shear strength.

Fig. 10. Forcedisplacement curves for the tested connections.


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As a nal remark, a beam with corrugated web behaves similarly

to a lattice girder, in which the bending moments and applied forces

are transferred via anges only, while the transverse forces are

transferred through the diagonals and verticals of the lattice girder,

in this case the corrugated web. The dimensioning of corrugated web

beams is ruled by Annex D of the EN 1993-1-5:2006[20], together

with specic aspects of EN 1993-1-1:2006 [36] and EN 1993-1-

3:2006 [37]. At the end, on the purpose of nding an analytical

approach for designing such beams with corrugated web intermit-

tently connected to the anges, the procedure used for calculation

sheathing acting as a diaphragm could be adapted[38]. The experi-

ence, in this case, has shown the most contributing factors, both to

Fig. 11. T3-3.7 connection: (a) at 3 mm displacement corresponding to SLS; (b) at 6 mm; (c) at 12 mm; (d) at failure.

Fig. 12. Deformed shape of the beam end shear panel.

Fig. 13. Deformed shape of CWB-1 beam at failure.


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strength and stiffness are the distortion of sheeting corrugations and

seem fasteners[39].

3. Technical solution: Specimens, material and connection

properties

3.1. Description of technical solution

The new technological solution proposed by the authors is

composed by webs made of trapezoidal cold-formed steel sheets

and anges of built-up cold-formed steel members (e.g. back-to-

back lipped channels, back-to-back angles with turn lips or hat

omega). As connecting technique self-drilling screws or spot weld-

ing both for the connections betweenanges and web and as seam

fasteners to ensure the continuity of the web can be used.

Fig. 15. Deformed shape of the beam end shear panel and distortion of the web corrugation.

Fig. 16. Evolution of shear yield lines for beam end shear panel: (a) at 44 mm; (b) at failure.

0

50

100

150

200

250

0 10 20 30 40 50 60

Force

[kN]

Displacement [mm]

CWB - 1

buckling of the shear panel (BSP)

distortions of the corrugated web (DCW)

collapseFig. 12(a)

Fig. 12(b)

Fig. 12(c)

Fig. 14. Loaddisplacement curve for CWB-1 beam.



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In this paper only the solution considering back-to-back lipped

channels for anges and self-drilling screws is investigated. Some

other particularities of this solution compared to the ones pre-

sented in[28]and [32]are:

Small corrugation depths and the thicknesses for corrugated

web in order to reduce the distortion of the corrugation; Reinforcing shear panels where the shear force is maximum;

Trapezoidal or parallel anges sloped beams.

3.2. Specimens and test procedure

The experimental program was carried out at the CEMSIG

Research Centre (http://www.ct.upt.ro/en/centre/cemsig) of the

Politehnica University of Timisoara. Five beams with corrugated

webs with a span of 5157 mm and a height of 600 mm have been

tested, as shown inTable 1, considering different arrangements for

self-drilling screws and shear panels [40,41].

Fig. 1 presents the components of the CWB-1 beam with

corrugated web, the so called standard solution, i.e.:

back-to-back lipped channel sections for anges2C120/2.0

(grade S350GDZ); corrugated web with the corrugation depth of 43 mm and the

thickness of 0.7 mm

A45/0.7 (grade S320GDZ); reinforcing shear panelssupplementary plates of 1 mm thick-

ness and 830 mm length, at the beam ends where the shear

force is maximum (doubling the corrugated web) (grade

S320GDZ); reinforcing U150/2.0 proles used under the load application

points, to avoid excessive local deformations (grade S350GDZ); self-drilling screws for ange-to-web connectionSTP-6.325; self-drilling screws for shear plates to end support with a

nominal diameterSTP-5.525; self-drilling screws as seam fasteners for corrugated webs with

a nominal diameterSTT-4.820; bolts M12 class 8.8 for anges to the end support connection.

Fig. 6 presents the experimental arrangement. Six pointsbending tests, monotonically conducted, were applied for each

specimen with a loading velocity of 2 mm/min.

The full-scale testing program was completed with tensile tests

to determine both the material properties for beam components

and the behaviour of connections.

3.3. Material and connections properties

In order to determine the mechanical properties of the CWB

components, a set of samples were cut out from the lipped

channels, corrugated sheet, both from the at regions and corners

0

50

100

150

200

250

0 10 20 30 40 50 60

Force

[kN]

Displacement [mm]

CWB - 2

BSP + DCW

DCW+ pull out of the screws

increasing of yield lines on SP

collapse

Fig. 15(a+b)

Fig. 15(c)

Fig. 16(a) Fig. 16(b)


Fig. 19. Distortion of the web corrugation at different levels of the load.



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and reinforcing shear panels, according to EN ISO 6892-1:2009

[42] specications, as shown in Fig. 7. A total number of 30

specimens have been tested, 5 for each type of specimen.

Table 2presents the mean values of tensile testes (i.e. yield and

ultimate strengths, fyM, fuM), the corresponding standard devia-

tions (i.e. sfy, sfu) and the characteristic values for yield and

ultimate strengths (i.e. fyk, fuk) for the above samples [40]. The

following abbreviations for coupons have been used: BM-CF

coupon cut from the ange of the lipped channel; BM-CW couponcut from the web of the lipped channel; CM-CF coupon cut from

the ange-web corner of the lipped channel; BM-CW coupon cut

from the at region of the corrugated web; BM-SP coupon cut

from the shear panel. Fig. 8 presents the failure modes for the

tested coupons.

Six types of connections were tested according to ECCS pub-

lication No. 124 [43] in order to determine their behaviour, at a

loading velocity of 1 mm/min, i.e.:

(1) T1-1.4 seam fasteners for corrugated sheets;

(2) T2-1.7, seam fasteners for shear plates and corrugated sheets;

(3) T3-3.7, self-drilling screws for shear plates and anges;

(4) T4-9.0, self-drilling screws for shear plates and end supports;

(5) T5-11.0, bolts for anges to end-supports;(6) T6-2.7, self-drilling screws for anges to corrugated webs at

mid-span,

in order to determine the behaviour of all types of connections

found in the beam[38].Table 3presents the tested specimens and

0

50

100

150

200

250

0 10 20 30 40 50 60 70

Fo

rce

[kN]

Displacement [mm]

CWB - 3

Fig. 19(a)

BSP + DCW

DCW+ tilting of the screws

collapse

Fig. 19(b) Fig. 20


Fig. 22. Distortion of the web corrugation.


0

20

40

60

80

100

120

140

160

180

200

0 20 40 60 80 100 120 140 160

For

ce

[kN]

Displacement [mm]

CWB - 4


shear failure of the fastners

collapse

Fig. 22(a)

Fig. 22(b)

Fig. 23



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the number of tests done for each typology, while Fig. 9presents

the location of these types of connections.

Fig. 10presents the forcedisplacement curves for the six types

of tested connections presented above, with corresponding mean

values, to be used for relevant models in numerical simulations.Very good ductility can be observed in all the cases that being one

of the causes for the signicant redundancy of tested beams.

Fig. 11 presents one of the T3-3.7 tested connections in four

different stages.

4. Testing of specimens. Main results and interpretation

Therst tested specimen was CWB-1 beam and its conguration

has been presented in Fig.1. In this case the rst deformation, which

corresponds to the buckling of shear panel (BSP), appears for a

displacement of 10 mm at 52 kN (see Fig. 12a). At 11 mm small

distortions of the corrugated (DCW) web have been recorded, asshown inFig. 12b.Fig. 12c presents a detail of the shear panel at

failure.

The behaviour was ductile, with an initial stiffness ofK0-Exp

6862.2 N/mm and the maximum load is reached at Fmax

218.9 kN. The collapse appears for a displacement of 58 mm.

Fig. 13presents the deformed shape of the beam at collapse, while

inFig. 14the loaddisplacement curve is drawn.

In case of CWB-2 beam, detailed in Fig. 2, i.e. standard solution

(CWB-1) and supplementary lipped channel sections under the load

application points, the rst deformations correspond to the buckling

of shear panel combined with the distortion of the corrugated web,

and appear for a displacement of 14 mm (see Fig. 15a and b). At

29 mm displacement the distortion of the corrugated web increase

simultaneously with the pull out of the screws (see Fig. 15c).

Fig. 16a presents a detail of the shear panel for a displacementof 44 mm and at failure (seeFig. 16b).

The behaviour was ductile, with an initial stiffness ofK0-Exp

7831.5 N/mm and the maximum load is reached atFmax231.3 kN.

The collapse appears for a displacement of 54 mm. Fig. 17 shows

the deformed shape of the beam at collapse, while in Fig. 18 the

loaddisplacement curve is plotted.

Beam CWB-3 beam is the optimized solution by adapting the

ange-to-web connections according to the distribution of shear

stresses (connections at each second corrugations where the shear

force decreases), as shown in Fig. 3. For this beam the rst

deformation appears for a displacement of 15 mm, which corre-

sponds to the buckling of shear panel and distortion of the

corrugated web (seeFig. 19a). At 44 mm displacement the distor-

tion of the corrugated web is accompanied by the tilting of the

Fig. 25. (a) Distortion of the web corrugation; (b) buckling of shear panel.


0

50

100

150

200

250

0 10 20 30 40 50 60 70 80 90 100

Force

[kN]

Displacement [mm]

CWB - 5


buckling of the shear panel (BSP)

collapse

Fig. 25(a)

Fig. 25(b)

Fig. 26



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screws (see Fig. 19b), in the regions where the shear force is

signicant, but the number of screws is optimised.

The behaviour is ductile, with an initial stiffness of K0-Exp

7184.9 N/mm and the maximum load is reached at Fmax

209.5 kN. The collapse appears for a displacement of 62 mm.

Fig. 20 presents the deformed shape of the beam at collapse,

whileFig. 21shows the recorded loaddisplacement curve.

Beam CWB-4 is the standard solution, i.e. CWB-1, but eliminat-

ing shear panels and doubling of corrugated webs in the zones

with high shear forces, i.e. ends of the beam (see Fig. 4). In case of

this beam, the rst deformation, which corresponds to the distor-

tion of the corrugated web near supports, appears for a displace-

ment of 21 mm, as shown in Fig. 22a. At 74 mm displacement

shear failure of the fasteners was recorded followed by 10%

reduction of the beam capacity (seeFig. 22b).


3985 N/mm and the maximum load is reached at Fmax181.9 kN.

The collapse appears for a displacement of 164 mm. Fig. 23

presents the deformed shape of the beam at collapse, while

Fig. 24shows the recorded loaddisplacement curve.The last beam is CWB-5, and represents the optimized solution

by adapting both the ange-to-web connections (i.e. CWB-3) and,

supplementary, seam fasteners to ensure the continuity of corru-

gated web, according to the distribution of shear stresses (see

Fig. 5). The rst deformation corresponds to the distortion of the

web corrugation in the region with the reduced number of screws

for a displacement of 21 mm (see Fig. 25a), while at 35 mm

buckling of shear panels appears (Fig. 25b).


5516.2 N/mm and the maximum load is reached atFmax214.6 kN.

The collapse appears for a displacement of 88 mm. Fig. 26presents

the deformed shape of the beam at collapse, while Fig. 27shows

the recorded loaddisplacement curve.

Finally, Fig. 28 shows comparatively, for all the ve testedspecimens, the loaddisplacement curves and the ultimate (ULS)

and serviceability limit state (SLS) levels.

5. Conclusions

A large experimental program carried out at the CEMSIG

Research Centre (http://cemsig.ct.upt.ro) of the Politehnica Uni-

versity of Timisoara on ve beams with corrugated webs with

different arrangements for self-drilling screws and shear panels

was presented.

Very good agreement can be found between beams CWB-1 and

CWB-3, both in terms of initial stiffness and ultimate force. A

slightly increase in stiffness can be observed in case of CWB-2

beam, due to the supplementary lipped channel sections added

locally at the load application points. CWB-4 beam is the most

exible solution compared to the other four and has half initial

stiffness compared to CWB-2 beam. At this level, CWB-5 beam

represents the best solution in terms of optimisation.

Finally, even the results looks promising, signicant work has

to be done in order to investigate, validate and optimise such a

solution for mass production, i.e.:

numerical models for calibration and validation of experimen-

tal models[44];

to optimise the number of self-drilling screws used for connections;

tests using spot welding are the next step of research; there are

no differences expected at the level of global behaviour, but

some are estimated in terms of strength and stiffness;

numerical simulation of large span beams in order to study the

sensitivity to lateral-torsional buckling of such elements[44].

Based on that, standardized beams can be designed, calibrated

for series of vertical loading intensities, accounting or not for

lateral-torsional effects and the potential of this solution for

industrialized fabrication has to be, once more, emphasized.

It has to be notice that, by extending the application of thetechnical solution described within present paper for parallelanges girders, promising experimental results have been very

recently obtained in a PhD study on trapezoidal beams made of

cold-formed steel proles and corrugated web[45].

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0

50

100

150

200

250

0 20 40 60 80 100 120 140 160 180

Force

[kN]

Displacement [mm]

CWB - 1

CWB - 2

CWB - 3

CWB - 4

CWB - 5

Fig. 28. Loaddisplacement curves for the tested specimens.

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