The University of Sydney
Department of Civil Engineering
Sydney NSW 2006
AUSTRALIA
http://www.civil.usyd.edu.au/
Strength of Butt Welded Connections
between Equal-width Rectangular
Hollow Sections
Research Report No R817
By
Lip H Teh, BE PhD
Kim JR Rasmussen MScEng PhD
April 2002
The University of Sydney
Department of Civil Engineering
Centre for Advanced Structural Engineering
http://www.civil.usyd.edu.au
Strength of Butt Welded Connections between
Equal-width Rectangular Hollow Sections
Research Report No R817
Lip H Teh BE, PhD
Kim JR Rasmussen, MScEng, PhD
April 2002
Abstract:
The report describes a series of experimental tests on tensile coupons cut from the butt
welded brace-to-chord connections (T-joints) between rectangular hollow sections of
equal width. The aims of the tests are to investigate whether there are any serious
difficulties in producing satisfactory butt welds in the large root gaps resulting from
the rounded corners of chord sections, and to establish the welding procedures that
enable such connections to be pre-qualified. Rectangular hollow sections of various
thicknesses and corner radii are used, resulting in root gaps ranging from 0.8 mm to
9.4 mm. Four different types of joint preparations involving the use of backing strips,
fill bars, purging gas or no preparations at all are experimented with. The connections
are fabricated using the Gas Metal Arc Welding (GMAW) and the Manual Metal Arc
Welding (MMAW) processes. In general the GMAW process results in better quality
butt welds, whether the root gap is narrow or large. A narrow root gap may present a
problem if the MMAW electrode is not small enough and the brace edge is not
bevelled. It is concluded that SP (Structural Purpose) butt welded connections between
equal width cold-formed rectangular hollow sections which are fabricated using the
GMAW and MMAW processes may be pre-qualified provided the root gap is at least
3 mm and 4 mm respectively. The prequalification applies to the horizontal and flat
positions for the following weld preparations: no specific preparation, the use of
backing strip and the use of purging gas on the inside of the tube. The prequalification
does not apply to joints welded using fill bars.
Keywords:
Butt welds, welded connections, rectangular hollow sections, welding, pre-qualification
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Copyright Notice
Department of Civil Engineering, Research Report R817
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow
Sections
© 2002 Lip H Teh and Kim JR Rasmussen
k.rasmussen@civil.usyd.edu.au
This publication may be redistributed freely in its entirety and in its original
form without the consent of the copyright owner.
Use of material contained in this publication in any other published works must
be appropriately referenced, and, if necessary, permission sought from the
authors.
Published by:
Department of Civil Engineering
The University of Sydney
Sydney, NSW, 2006
AUSTRALIA
April 2002
http://www.civil.usyd.edu.au
Department of Civil Engineering
Research Report No R817
2
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Table of Contents
Introduction ................................................................................................... 4
1
2
Specimen configurations and joint preparations........................................... 5
3
Buttering technique to bridge large gaps .................................................... 10
4
Material properties of RHS specimens ....................................................... 10
5
Butt welded coupons: test results and discussions...................................... 10
6
Macro inspection ......................................................................................... 20
7
Recommendations ....................................................................................... 21
8
Reliability analysis ...................................................................................... 21
9
Conclusions ................................................................................................. 25
10 Acknowledgements ..................................................................................... 26
Appendix I. Chemical composition requirements of RHS specimens................ 27
Appendix II. Welding procedures ..................................................................... 28
Appendix III. Macros of welds with incomplete penetration ............................. 57
Appendix IV. Macros of welds with complete penetration ................................ 65
Appendix V. Proposed changes to AS/NZS1554.1........................................... 71
References ...................................................................................................... 81
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
1
April 2002
Introduction
Rectangular hollow sections are frequently used in steel frameworks, most notably in 2D and
3D triangulated truss girders. The joints are usually welded and may include one or several
brace (or web) members connected to a continuous chord. Typical joints include K-, N-, T-,
X- and Y-joints. Substantial research efforts have been made over the last 30 years to
determine the strength and behaviour of welded tubular joints (Wardenier 1982, CIDECT
1986, Packer and Henderson 1997).
It is common practice to use brace members that are smaller than the chords in welded
tubular construction. However, in some cases, particularly when the aesthetics of the structure
is to be highlighted, the brace members have the same width as the chord. This type of joints
presents a challenge to the fabricator because the weld between the end of the brace and the
side of the chord may become difficult to lay.
A number of methods exist for detailing equal-width RHS T-joints where the chord has a
large corner radius. A good practice is to profile the brace member to fit the chord, as shown
in Fig. 1a. In this case, the chord can serve as backing for the weld in the sidewall and good
penetration can usually be obtained. However, profiling is time consuming and hence the
brace is often cut square to obtain a lower cost detail, as shown in Fig. 1b. This solution may
produce large root gaps (G), which can be difficult to bridge, and inferior weld quality may
result. Cold-formed tubes in particular may have large root gaps because of their larger corner
radii compared to hot-formed tubes.
G
(a) Profiled brace
(b) Square cut brace
Fig.1 Profiled and square cut braces
Despite the extensive research work on welded connections between rectangular hollow
sections that has been carried out in the past (Wardenier & De Koning 1974, Mang et al.
1979, Davies et al. 1981, Packer 1983, Davies & Panjehshahi 1984, De Koning & Wardenier
1985, Zhao & Hancock 1991, Lu et al. 1994, Zhao 2000, Rasmussen & Young 2001), there
appears to be little if any experimental investigation whether and under what conditions a full
butt weld can be deposited in the large root gap of a brace-to-chord connection between two
cold-formed rectangular hollow sections of equal width. The investigations of Wardenier &
De Koning (1974) and Davies et al. (1981) involved rectangular hollow sections of sharp
corner radii, which result in narrow root gaps. The brace edges of such sections were bevelled
prior to welding in order to obtain good quality welds.
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
CIDECT (1984, page 184) recommends that the maximum root gap between a rectangular
hollow section member and a haunch cut from another rectangular hollow section of the same
width be set at 3 mm. This recommendation, however, appears to be a “rule of thumb” which
is not based on laboratory test results. On the other hand, Syam & Chapman (1996, page A-2)
recommends that arc welded brace-to-chord connections between rectangular hollow sections
of equal width be avoided as “difficulties may arise in depositing the weld between the brace
member and the large corner radii of thick chord members”. The present report therefore aims
to investigate whether there are any serious difficulties in producing satisfactory butt welds in
the large root gaps of brace-to-chord connections between rectangular hollow sections of
equal width where the brace is cut square, and if there are, establish the welding procedures
which enable such connections to be pre-qualified. A pre-qualified joint configuration has the
economic benefit of dispensing with qualification tests.
For the purpose of the present report, tension coupons are cut from the sides of T-joints
between rectangular hollow sections of equal width which contain the butt welds. The test
results of these butt welded coupons are compared with those of the corresponding unwelded
coupons. The T-joints have variable root gaps resulting from variable gaps between the flat
ends of the braces and the chord flanges, and/or different section thicknesses of the braces.
These joints are fabricated using GMAW (Gas Metal Arc Welding) and MMAW (Manual
Metal Arc Welding) processes, with four types of joint preparations as described later. Macros
are also cut to enable section examination of the butt welds.
In the course of the present work, difficulties in depositing a full butt weld in a narrow
gap between the brace and the sharp corner of the chord (without bevelling) are also
investigated.
2
Specimen configurations and joint preparations
The size of a root gap G is a function of the gap g between the flat end of the brace and
the chord flange (see Fig. 2 for definition), the outside corner radius R of the chord, and the
wall thickness t of the brace,
G=
( R + g )2 + ( R − t )2
−R
(1)
t
Brace section
g
G
R
Chord section
Fig. 2 Root gap due to rounded corner of RHS
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
The root gap G as defined in Fig. 2, which is the shortest distance between the brace and
the chord, becomes irrelevant when a backing strip (see Fig. 3) is used. In such a case, the
question concerning the bridging of a large root gap in butt welding also vanishes. The
possible advantage of using backing strips is therefore investigated in this report. In addition,
this report also investigates the use of fill bars (see Fig. 4) and the use of purging gas (see Fig.
5).
Fig. 3 Use of backing strips
Fig. 4 Use of fill bars
Fig. 5 Use of purging gas
The positioning of the fill bars from the inside, as illustrated in Fig. 4, may not be as
common as that illustrated in Fig. 6 quoted from Packer & Henderson (1997), where the rod is
inserted from outside the tubes after the brace and the chord are aligned to their position.
However, the joint preparation illustrated in Fig. 6 is likely to be detrimental rather than
helpful to the butt weld penetration.
The use of purging gas as illustrated in Fig. 5 may not be feasible when a brace is to be
connected to a top chord and a bottom chord, but this type of joint preparation has been
included in this report for research purposes. It may also be useful for certain applications.
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
The gases used are the same as the shielding gases for GMAW process.
butt weld
R
Fig. 6 Fill bar inserted from outside (Packer & Henderson 1997)
Table 1 shows the nominal root gaps G of the specimens fabricated in the present work,
computed using Equation (1) with the measured corner radii R of the chords rounded to the
nearest 1 mm.
Table 1. Nominal root gaps G of specimens
Chord
Brace
R
(mm)
g=0
g = 1.0 mm g = 1.5 mm g = 2.0 mm
125 × 125 × 6P
125 × 125 × 6P
10
0.8
1.7
2.2
2.6
125 × 125 × 6
125 × 125 × 6
15
2.5
3.4
3.8
4.2
125 × 125 × 6
125 × 125 × 4
15
3.6
4.4
4.8
5.2
250 × 150 × 9
150 × 150 × 9
27
5.4
6.3
6.7
7.1
250 × 150 × 9
150 × 150 × 5
27
7.8
8.6
9.0
9.4
The 125 × 125 × 6P RHS listed in the second row of Table 1 was supplied by Palmer Tube
Mills, Melbourne, and is of grade C450 with a nominal yield strength of 450 MPa and a
nominal tensile strength of 500 MPa. All the other sections were supplied by OneSteel Market
Mills, Pipe & Tube, Newcastle, and are of grade C350 with a nominal yield strength of 350
MPa and a nominal tensile strength of 430 MPa. These sections are manufactured to AS 1163
(SA 1991a) and their design capacities may be determined in accordance with either AS 4100
(SA 1998) or AS/NZS 4600 (SA/SNZ 1996a). The 125 × 125 × 6P RHS supplied by Palmer
Tube Mills has a smaller corner radius (R = 10 mm) than the corresponding section supplied
by OneSteel Market Mills (R = 15 mm).
Appendix I shows the limits of the chemical compositions of the C350 and C450 steels as
specified in AS 1163 (SA 1991a).
As mentioned in the Introduction, tension coupons are cut from the sides of T-joints
which contain butt welds, as illustrated in Fig. 7. The definitions of “adjacent” and “opposite”
faces, which are based on the location of the electric resistance weld (ERW) of the tube, are
given in Fig. 8. Thus the arrangement shown in Fig. 7 avoids the butt welds being deposited
along the side containing the ERW of the brace. Although the ERW of a 250 × 150 × 9 RHS
Department of Civil Engineering
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
chord (to which a 150 × 150 × 9 brace is connected as illustrated in Fig. 9) is located in the
longer side, the butt weld is only produced on the side where the ERW is not located.
The arrangement shown in Fig. 7 applies to all specimens. An unintended consequence of
such an arrangement is discussed in the next section.
Adjacent face
Brace
Tensile
coupon
Butt weld
Chord
Opposite face
Fig. 7 Butt welded tensile coupon
Opposite
Corner
Adjacent 1
Adjacent 2
ERW
R
Fig. 8 Adjacent and opposite faces of a rectangular hollow section (after Wilkinson 1999)
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April 2002
9
9
9
250
150
Fig. 9 150 × 150 × 9 brace to 250 × 150 × 9 chord
Table 2. Tensile coupon test results
Section
Grade
Direction of
Loading
fu
(MPa)
fun
(MPa)
125 X 125 X 6Pb
C450
Longitudinal
522
500
125 X 125 X 6Pc
C450
Transverse
512
500
125 X 125 X 6b
C350
Longitudinal
484
430
125 X 125 X 6c
C350
Transverse
477
430
125 X 125 X 4b
C350
Longitudinal
503
430
125 X 125 X 4c
C350
Transverse
486
430
150 X 150 X 9b
C350
Longitudinal
476
430
150 X 150 X 9c
C350
Transverse
479
430
250 X 150 X 9b
C350
Longitudinal
449
430
250 X 150 X 9c
C350
Transverse
435
430
150 X 150 X 5b
C350
Longitudinal
495
430
150 X 150 X 5c
C350
Transverse
491
430
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
3
April 2002
Buttering technique to bridge large gaps
In fabricating T-joints without using backing strip or fill bar, the root gap could not be
bridged when exceeding a certain limit which in the present investigation was 3 mm for the
MMAW (4 mm electrodes) and GMAW welding processes, and 2.5 mm for the MMAW
process when using 3.25 mm electrodes. For joints with root gaps exceeding these limits,
successive runs of weld were deposited (referred to as “buttering”) along the corner of the
chord until the root gap was sufficiently reduced to bridge the gap.
4
Material properties of RHS specimens
Table 2 shows the measured tensile strengths fu in the longitudinal direction (the rolling
direction) and in the transverse direction of the coupons cut from the rectangular hollow
sections listed in Table 1, obtained using a strain rate of about 5 × 10 −4 per second. The
coupons were cut from the same lengths of tube as those used for the T-joints. The coupons
did not contain butt welds and were used to obtain the material properties of the tube material.
Due to the section sizes which limit the length of the transverse coupons, all the coupons were
cut to a parallel width of 6 mm and a parallel length of 30 mm. The suffix ‘b’ in the label
denotes the longitudinal direction and may correspond to the brace member in a tensile test of
the butt welded coupons, as illustrated in Fig. 7. The suffix ‘c’ denotes the transverse
direction and may correspond to the chord member. Table 2 also shows the nominal value
(fun) of ultimate tensile strength.
It can be seen from Table 2 that the measured tensile strengths fu of the C350 and C450
steel sections tested in the present work are invariably higher than the nominal values fun of
430 MPa and 500 MPa, respectively. It can also be seen that in general the tensile strengths in
the longitudinal direction are somewhat higher than those in the transverse direction. In this
regard, it is noteworthy that for a given loading direction, the tensile strength in the opposite
face is generally higher than that in the adjacent faces of the same section (Key & Hancock
1985, Wilkinson 1999). Thus the orientations of the opposite and the adjacent faces of the
specimens tested in the present work, depicted in Fig. 7, minimise the differences in tensile
strength between the braces and the chords.
5
Butt welded coupons: test results and discussions
As mentioned in the Introduction, the brace-to-chord connections between the rectangular
hollow sections listed in Table 1 were fabricated using GMAW and MMAW processes. In
either process, only electrodes which are manufactured to AS/NZS 2717.1 (SA/SNZ 1996b)
and which are pre-qualified to AS/NZS 1554.1 (SA/SNZ 2000) for the C350 and C450 steels
were used. The nominal tensile strength of the GMAW wire is 500 MPa, while that of the
MMAW stick is 480 MPa. The detailed welding procedures for some of the butt welded
connections are given in Appendix II. The specimen numbers cited in Appendix II correspond
to the specimen numbers given in the following tables. Unless stated otherwise, the welding
position of all specimens is flat (1F), as shown in
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. 10 Flat welding position (1F)
It can be seen from Appendix II that for a given pair of section sizes listed in Table 1, the
voltage, the current and the heat input are not affected by the joint preparations used in the
present work. Importantly, the electrode stick-out, the gas flow rate and the shielding gases
have not been deliberately selected for the present specimens, but were left unchanged from
the previous operations and were used for all specimens fabricated using the GMAW process.
In trying to produce a visually acceptable and “smooth” weld, the welder would experiment
with the voltage, the current, the wire speed and the wire size, the latter limited to 0.8 mm,
0.9 mm and 1.2 mm available to the welder. For MMAW, common electrode sizes of 3.25mm and 4.0-mm were used. The welding speed depends on how the weld deposition is
perceived by the welder during welding and therefore on the welder’s skills.
As mentioned in the preceding section, the design capacities of arc welded connections in
sections thicker than 3 mm may be determined in accordance with AS 4100 (SA 1998).
Clause 9.7.2.7 of AS 4100 specifies that the design capacity of a complete penetration butt
weld shall be taken as the nominal capacity of the weaker part of the parts joined. In this
report, the predicted failure load Pp of a butt welded coupon is thus computed using the
appropriate measured tensile strength fu listed in Table 2 rounded to the nearest 5 MPa in
accordance with AS1391 (SA 1991b), the average measured thickness t of the weaker section
rounded to the nearest 0.05 mm, and the average measured width w within the parallel portion
of the weakest section rounded to the nearest 0.1 mm,
Pp = f u t w
(2)
The nominal failure load Pn of a coupon is similarly computed using the nominal tensile
strength of the weaker section, the nominal thickness of the weaker section, and the assumed
gauge width of 12.5 mm.
Tables 3 and 4 list the tensile test results of the butt welded coupons cut from the T-joints
between 125 × 125 × 6P RHS supplied by Palmer Tube Mills, fabricated using MMAW and
GMAW processes, respectively. The variable Pt denotes the ultimate test load. For these
coupons, the predicted failure loads Pp were computed using a tensile strength fu of 510 MPa,
which corresponds to the transverse tensile strength of 512 MPa (assuming failure in the
chord) listed in Table 2.
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Table 3. 125 × 125 × 6P brace to 125 × 125 × 6P chord (Palmer Tube), MMAW
g
G
(mm) (mm)
Special preparation
Electrode
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
1
0
0.8
None
3.25
1
0.62
0.61
Weld
2
0
0.8
None
4.00
1
0.84
0.81
Weld
3#
1.0
1.7
None
3.25
1
0.59
0.58
Weld
4
1.0
1.7
None
4.00
1
0.79
0.77
Weld
5#
1.5
2.2
2.5-mm fill bar
3.25
1
0.52
0.50
Weld
6
1.5
2.2
2.5-mm fill bar
4.00
1
0.65
0.63
Weld
7
£
2.0
2.6
None
3.25
3
1.08
1.05
Chord
8
2.0
2.6
None
4.00
1
0.94
0.91
Weld
2.0
2.6
2-mm backing strip
3.25
3
1.06
1.03
Chord
2.0
2.6
2-mm backing strip
4.00
1
0.71
0.69
Weld
9
10
#
# Macro shown in Appendix III
£ Macro shown in Appendix IV
Table 4. 125 × 125 × 6P brace to 125 × 125 × 6P chord (Palmer Tube), GMAW
g
(mm)
G
(mm)
Special preparation
Wire
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
11£
0
0.8
None
0.9
3
1.04
1.01
Chord
12
0
0.8
Purged
0.9
3
1.04
1.01
Chord
13
1.0
1.7
None
0.9
3
1.06
1.03
Chord
14
1.0
1.7
Purged
0.9
3
1.05
1.02
Chord
15
1.5
2.2
2.5-mm fill bar
0.9
3
1.00
0.97
Weld
16
2.0
2.6
None
0.9
4
1.03
1.00
Weld
17
2.0
2.6
2-mm backing strip
0.9
3
1.06
1.03
Weld
18
2.0
2.6
Purged
0.9
4
1.06
1.03
Chord
£ Macro shown in Appendix IV
It can be seen from the ratios of ultimate test load Pt to predicted failure load Pp shown in
Table 3 that all the MMAW coupons with gap g less than 2 mm failed in the welds at loads
significantly below the predicted failure loads. This result indicates that full butt weld
penetration was not achieved for these specimens, apparently due to the narrow root gaps
resulting from the relatively sharp corners of Palmer Tube Mills sections coupled with the use
of 3.25-mm and 4.0-mm electrodes. In fact, Fig. 11 shows that the butt weld of Specimen 10,
Department of Civil Engineering
Research Report No R817
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
which was produced with 2-mm gap and 4.0-mm electrode, has not fused with the backing
strip (not shown) which was supposed to facilitate the production of a full butt weld in a
“large gap”.
Fig. 11 Lack of full penetration in Specimen 10 due to oversize electrode (narrow gap)
It is noteworthy that in general the ultimate test loads Pt of the MMAW coupons failing in
the weld are also lower than the nominal failure load Pn, as evidenced from the ratios of these
values listed in Table 3.
It can also be seen from Table 3 that satisfactory butt welds were produced only when the
gap g was increased to 2.0 mm and the MMAW electrode size was limited to 3.25 mm, as
with Specimens 7 and 9. Three passes were required to obtain “visually acceptable” butt
welds in these specimens. Such specimens failed in the chord member as indicated in the last
column of Table 3.
Table 4 shows that in contrast to the MMAW process, the GMAW process resulted in
largely satisfactory butt welds irrespective of the joint preparations and welding procedures
used in the present work. Even when the coupon failed in the weld, the ultimate test load Pt
was found to be close to the predicted failure load Pp. For these Palmer Tube Mills specimens,
the GMAW process is superior to the MMAW process owing to the much smaller size of the
GMAW wire which enables full penetration of the butt welds in narrow gaps. Figure 12
shows that even for Specimen 11, which was welded with no gap and without the aid of
purging gas, full butt weld penetration was achieved. The coupon failure in the chord was
therefore not due to significant strength over-matching of the weld metal.
The fact that the 125 × 125 × 6P RHS coupons failed in the chord rather than the brace is
caused by the higher tensile strength of the sections in the longitudinal direction than in the
transverse direction, as indicated in Table 2. These results justify the use of the transverse
tensile strength value (510 MPa) to compute the predicted failure loads of the welded
coupons.
Fig. 12 Full penetration in Specimen 11
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
It appears from the ratios of ultimate test load Pt to predicted failure load Pp of the
coupons failing in the chord that the heat-affected-zone in the Palmer Tube Mils RHS, which
is of grade C450, is not weakened by the welding heat input incurred in the present work.
Appendix II shows the arc energy used in the production of Specimens 11 and 17. It can also
be seen in Fig. 13 that the failure of Specimen 18 took place at some distance away from the
butt weld.
Fig. 13 Failure of Specimen 18 away from weld
Tables 5 and 6 list the tensile test results of the butt welded coupons cut from the T-joints
between 125 × 125 × 4 RHS braces and 125 × 125 × 6 RHS chords supplied by OneSteel
Market Mills, fabricated using MMAW and GMAW processes, respectively. For these
coupons, the predicted failure loads Pp were computed using a tensile strength of 500 MPa,
which corresponds to the longitudinal tensile strength of 503 MPa listed in Table 2 for the
125 × 125 × 4 section.
It can be seen that in general satisfactory butt welds were obtained using either MMAW or
GMAW process. Note also that Specimen 29, which failed in the weld at a load significantly
below the predicted value, was reproduced as Specimen 37 using the same welding procedure
and joint preparation. The reproduced coupon failed in the brace.
It appears from the test results of Specimens 19 and 20 that the maximum MMAW
electrode size that can be used without a gap between the flat end of the 125 × 125 × 4 RHS
brace and the 125 × 125 × 6 RHS chord (g = 0 mm) is 4.0 mm. Note that Specimen 20 failed in
the weld (nominal tensile strength = 480 MPa) at about the same level of load as the other
specimens.
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Table 5. 125 × 125 × 4 brace to 125 × 125 × 6 chord, MMAW
g
G
(mm) (mm)
Special preparation
Electrode
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
19£
0
3.6
None
3.25
3
0.97
1.12
Brace
20
0
3.6
None
4.00
3
0.95
1.09
Weld
21
1.0
4.4
None
3.25
3
0.95
1.09
Brace
22
1.0
4.4
None
4.00
3
0.96
1.10
Brace
23
1.5
4.8
2.5-mm fill bar
3.25
7
0.95
1.10
Brace
24
1.5
4.8
2.5-mm fill bar
4.00
5
0.97
1.11
Brace
25
2.0
5.2
None
3.25
6
0.96
1.11
Brace
26
2.0
5.2
None
4.00
5
0.95
1.09
Brace
27
2.0
5.2
3-mm backing strip
3.25
4
0.97
1.11
Brace
28
2.0
5.2
3-mm backing strip
4.00
4
0.99
1.14
Brace
£ Macro shown in Appendix IV
Table 6. 125 × 125 × 4 brace to 125 × 125 × 6 chord, GMAW
g
G
(mm) (mm)
Special preparation
Wire
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
29*
0
3.6
None
0.9
4
0.86
0.99
Weld
30
0
3.6
Purged
0.9
4
0.99
1.19
Brace
31
1.0
4.4
None
0.9
4
0.99
1.19
Brace
32
1.0
4.4
Purged
0.9
4
1.00
1.20
Brace
33
1.5
4.8
5-mm fill bar
0.9
3
0.99
1.19
Brace
34
2.0
5.2
None
0.9
5
1.01
1.21
Brace
35
2.0
5.2
3-mm backing strip
0.9
4
1.01
1.22
Brace
36
2.0
5.2
Purged
0.9
5
0.98
1.17
Brace
37#
0
3.6
None
0.9
4
0.98
1.17
Brace
* redone as specimen 37
# macro shown in Appendix III
As with the 125 × 125 × 6P C450 RHS supplied by Palmer Tube Mills, the heat-affectedzone of the 125 × 125 × 4 C350 RHS supplied by OneSteel Market Mills is not significantly
weakened by welding heat input incurred in the present work. Appendix II shows the arc
energy used in the production of Specimens 19, 27, 30, 35 and 37.
Department of Civil Engineering
Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Tables 7 and 8 list the tensile test results of the butt welded coupons cut from the T-joints
between 150 × 150 × 9 RHS braces and 250 × 150 × 9 RHS chords supplied by OneSteel
Market Mills, fabricated using MMAW and GMAW processes, respectively. Appendix II
shows the welding procedure used in the production of Specimens 38, 42, 43 and 48. For
these coupons, the predicted failure loads Pp were computed using a tensile strength of 475
MPa, which corresponds to the longitudinal tensile strength of 476 MPa listed in Table 2 for
the 150 × 150 × 9 section.
Table 7. 150 × 150 × 9 brace to 250 × 150 × 9 chord, MMAW
g
G
(mm) (mm)
Special preparation
Electrode
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
38
0.
5.4
None
4.00
5
0.99
1.04
Brace
39
1.0
6.3
None
4.00
5
1.02
1.07
Brace
40#
1.5
6.7
4-mm fill bar
4.00
5
0.82
0.86
Weld
41
2.0
7.1
None
4.00
8
0.98
1.03
B/W
42
2.0
7.1
10-mm backing strip
4.00
4
1.00
1.05
Brace
# Macro shown in Appendix III
Table 8. 150 × 150 × 9 brace to 250 × 150 × 9 chord, GMAW
g
(mm)
G
(mm)
Special preparation
Wire
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
43
0.
5.4
None
1.2
4
1.03
1.08
Brace
44
0.
5.4
Purged
1.2
4
1.01
1.06
Brace
45
1.0
6.3
None
1.2
5
0.99
1.04
Brace
46
1.0
6.3
Purged
1.2
6
1.02
1.06
Brace
47
1.5
6.7
4-mm fill bar
1.2
4
1.03
1.08
Brace
48
2.0
7.1
None
1.2
6
1.01
1.06
Brace
49
2.0
7.1
10-mm backing strip
1.2
6
0.98
1.03
Brace
50
2.0
7.1
Purged
1.2
5
N/A
N/A
Brace
The reason for not using the lower transverse tensile strength of 435 MPa listed in Table 2
for the 250 × 150 × 9 section to compute the predicted failure loads Pp is that the coupons were
found to fail in the braces rather than in the chords, as shown in Fig. 14. These results were
apparently caused by the fact that the steel materials in and around a highly cold-worked RHS
corner are significantly stronger than those away from the corners. The virgin coupon and the
butt welded coupon test results indicate that the transverse tensile strength of the steel around
a corner of the 250 × 150 × 9 RHS is well above 435 MPa, and is higher than 475 MPa.
Department of Civil Engineering
Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. 14 Failure in the 150 × 150 × 9 RHS brace of Specimen 38
It can be seen that in general satisfactory butt welds between 150 × 150 × 9 RHS braces and
250 × 150 × 9 RHS chords were obtained using either MMAW or GMAW process. However,
it appears from the result of Specimen 40 that the use of a fill bar may sometimes interfere
with the production of a full penetration butt weld. It also appears from the test results of
other sections, such as Specimen 15, that the use of a fill bar is not helpful. In this regard, it is
worth noting that the fill bar were inserted from inside the tube, not from outside as illustrated
in Fig. 6. Apparently, the latter technique is likely to result in even less penetration of the butt
weld.
Tables 9 and 10 list the tensile test results of the butt welded coupons cut from the Tjoints between 150 × 150 × 5 RHS braces and 250 × 150 × 9 RHS chords supplied by OneSteel
Market Mills, fabricated using MMAW and GMAW processes, respectively. Appendix II
shows the welding procedure used in the production of Specimens 61, 62 and 70. For these
coupons, the predicted failure loads Pp were computed using a tensile strength of 495 MPa
listed in Table 2 for the 150 × 150 × 5 section loaded in the longitudinal direction.
Table 9. 150 × 150 × 5 brace to 150 × 150 × 9 chord, MMAW
g
G
(mm) (mm)
Special preparation
Electrodes
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
51
0.
7.8
None
3.25
8
0.99
1.09
Brace
52
0.
7.8
None
4.00
6
0.97
1.06
Brace
53
1.0
8.6
None
3.25
8
0.99
1.08
Weld
54
1.0
8.6
None
4.00
9
0.98
1.08
Brace
55
1.5
9.0
6.5-mm fill bar
3.25
5
0.98
1.08
Weld
56#
1.5
9.0
6.5-mm fill bar
4.00
7
0.67
0.74
Weld
57
2.0
9.4
None
3.25
10
0.98
1.08
Brace
58#
2.0
9.4
None
4.00
7
0.88
0.96
Weld
59#
2.0
9.4
8-mm backing strip
3.25
5
0.94
1.03
Weld
60
2.0
9.4
8-mm backing strip
4.00
6
0.95
1.04
Weld
61
2.0
9.4
8-mm fill bar
3.25
5
0.98
1.08
Brace
# Macro shown in Appendix III
Department of Civil Engineering
Research Report No R817
17
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Table 10. 150 × 150 × 5 brace to 150 × 150 × 9 chord, GMAW
g
G
Special preparation
(mm) (mm)
Wire
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
62£
0.
7.8
None
0.9
7
1.03
1.13
Brace
63
0.
7.8
Purged
0.9
7
1.02
1.12
Brace
64
1.0
8.6
None
0.9
7
1.03
1.12
Brace
65
1.0
8.6
Purged
0.9
7
1.00
1.10
Brace
66
1.5
9.0
6.5-mm fill bar
0.9
5
1.02
1.12
Brace
67
2.0
9.4
None
0.9
7
1.03
1.13
Brace
68
2.0
9.4
8-mm backing strip
0.9
5
1.04
1.14
Brace
69
2.0
9.4
Purged
0.9
7
1.03
1.13
Brace
70
2.0
9.4
8-mm fill bar
0.9
5
1.00
1.10
Brace
£ Macro shown in Appendix IV
Among all specimens fabricated and tested in the present work, the T-joints between
150 × 150 × 5 RHS braces and 250 × 150 × 9 RHS chords have the largest root gaps of up to
almost 10 mm, as listed in Table 1. It can be seen from Tables 9 and 10 that the GMAW
process is also superior to the MMAW process in the case where a large gap has to be
overcome. As discussed previously for the Palmer Tube Mills specimens, the smaller size of
the GMAW wire resulted in better deposition of the butt welds in narrow gaps. More than half
the present MMAW coupons failed in the weld.
Tables 11 and 12 list the tensile test results of the butt welded coupons cut from the Tjoints between 125 × 125 × 6 RHS supplied by OneSteel Market Mills, fabricated using
MMAW and GMAW processes, respectively. Appendix II shows the welding procedures
used in the production of all the specimens. For these coupons, the predicted failure loads Pp
were computed using a tensile strength of 475 MPa, which corresponds to the transverse
tensile strength of 477 MPa (assuming failure in the chord) listed in Table 2.
Table 11. 125 × 125 × 6 brace to 125 × 125 × 6 chord (OneSteel), MMAW
g
(mm)
G
(mm)
Special preparation
Electrode
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
71
2.0
4.2
None
3.25
3
0.70
0.77
Weld
72
2.0
4.2
3-mm backing strip (1F)
3.25
4
1.03
1.14
Weld
73
2.0
4.2
6-mm fill bar
3.25
4
1.05
1.17
Brace
74
2.0
4.2
2-mm backing strip (2F)
3.25
4
1.02
1.13
Brace
Department of Civil Engineering
Research Report No R817
18
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Table 12. 125 × 125 × 6 brace to 125 × 125 × 6 chord (OneSteel), GMAW
g
(mm)
G
(mm)
Special preparation
Wire
(mm)
Passes
Pt/Pp
Pt/Pn
Failure
75
2.0
4.2
None (1F)
0.9
4
0.86
0.95
Weld
76
2.0
4.2
3-mm backing strip
0.9
4
1.02
1.13
Chord
77
2.0
4.2
Purged
0.9
4
0.89
0.99
Weld
78
2.0
4.2
None (2F)
0.9
4
1.01
1.12
Brace
Although Specimens 75 and 77 were found to fail in the weld at loads significantly below
the predicted failure loads, the corresponding T-joint stub specimens failed in the chords (Teh
& Rasmussen 2002). It is believed that as with Specimen 29, which was reproduced as
Specimen 37, full penetration can be achieved for this T-joint configuration without special
preparations. The present configuration should not be more problematic than the previous
ones. It is also noteworthy that Specimen 78, which was welded in the horizontal (2F)
position, as shown in Fig. 15, but otherwise had the same joint configuration and preparation
(none) as Specimen 75, failed in the brace.
Nevertheless, the test results do indicate the possibility of significant variation in weld
quality for a given joint configuration with a given welding procedure.
Fig. 15 Horizontal welding position (2F)
As stated previously, all the butt welded coupons reported above were produced in the flat
(1F) position unless stated otherwise. In practice, butt or fillet welds between RHS members
of a pre-fabricated truss are welded in either the flat (1F) or the horizontal (2F) position. In
order to investigate the implications of using the 2F position, a number of specimens were
welded in this position (see Appendix II for the welding procedures) and tested in the same
manner as the 1F specimens. Table 13 lists the results. The variable Pt2 denotes the ultimate
test load of a 2F specimen, and the ratio of the ultimate test load of a 2F specimen to that of
Department of Civil Engineering
Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
the corresponding 1F specimen is denoted Pt2/Pt1. The last column shows the ratios of the
number of weld runs (passes).
Table 13. Comparison of 2F and 1F specimens
2F
1F
Pt2/Pp
Failure
Pt2/Pt1
R2/R1
79
35
0.98
Brace
1.01
¾
80
37
0.99
Brace
0.98
¾
81
38
0.73
Weld
0.74
5
/5
82
43
1.00
Brace
1.03
4
/4
83
49
0.93
Brace
0.95
4
/5
84
57
1.05
Brace
1.07
6
85
62
0.99
Brace
1.03
4
/7
86
70
0.99
Brace
1.00
5
/5
/10
It appears from Table 13 that the horizontal (2F) position does not pose a difficulty in
achieving good butt weld penetration between equal-width rectangular hollow sections.
Furthermore, the required number of weld runs in the horizontal position is often less than
that in the flat position for a given joint configuration and preparation. One reason is that the
welding speed used by the welder tended to be slower in the horizontal position. Another,
which is not welder-dependent, is that in the flat position the molten weld tends to seep away
due to gravity when no backing is provided. This is evident in Fig. 16, which shows the
excess weld in Specimen 57.
Fig. 16 Weld “seeping” in Specimen 57 due to gravity
6
Macro inspection
It should be kept in mind that a pre-qualified SP joint must pass through the macro test, as
specified in Table 4.7.1 of AS/NZS 1554.1:2000 (SA/SNZ 2000). For the specimens which
were found to fail at an ultimate test loads Pt significantly below the predicted failure loads
Pp, the macro inspection indeed reveals that full butt weld penetration was not achieved. The
macros of such specimens are shown in Figs. III.1 through III.8 of Appendix III. The test
specimens are 3, 5, 10, 29, 40, 56, 58 and 59, as also marked in Tables 2-13.
Department of Civil Engineering
Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
In addition, the macros which indicate complete penetration of the butt welds are shown in
Figs IV.1 through IV.5. It can be seen from Figs IV.2, IV.4 and IV.5 that the butt welds
produced using the GMAW process tend to be oversize. This is due to the very convex shape
of the GMAW weld beads. The butt welds produced using MMAW are fairly flush with the
sidewalls, as shown in Fig. IV.1, although in some cases undercut, as shown in Fig. IV.3, and
in some case oversize.
7
Recommendations
The results shown in Tables 3-13 demonstrate that the use of fill bar is associated with
large variability in strength and often inferior strength because of either lack of penetration or
reduced thickness of weld. It is recommended that fill bar should not be used for fabricating
equal width RHS joints. The use of MMAW in combination with narrow root gaps less than
about 2.5 mm is also seen to produce lack of penetration and inferior strength, as shown in
Table 3. To incorporate the allowable tolerance for root gaps given in Table 5.2.2 of
AS/NZS1554.1, it is recommended that a minimum root gap of 4 mm be ensured when using
MMAW. The results do not suggest that a similar requirement is necessary for GMAW.
However, following good welding practice and allowing for a tolerance of ±1.5 mm, a
minimum gap of 3 mm is recommended for GMAW.
Precluding joints fabricated using fill bar and using root gaps less than 2.5 mm in the case
of MMAW, it appears from Tables 3-13 that the strength is generally close to that of the tube
material (Pt/Pp ≅ 1) and that fracture generally occurred in the tube, (in 84% and 65% of cases
for GMAW and MMAW processes, respectively). On this basis and acknowledging the
tolerance of ±1.5 mm allowed for the root gap in Table 5.2.2 of AS/NZS1554.1, it is
recommended that the investigated welding positions (flat and horizontal) and weld
preparations (no specific, purging gas and backing strip) be prequalified for the MMAW and
GMAW processes, subject to the requirement of a minimum root gap of 4 mm and 3 mm for
MMAW and GMAW respectively. Appendix V contains a specific proposal as to how these
recommendations may be implemented in AS/NZS1554.1 (SA/SNZ 2000).
Section 8 following contains a reliability analysis which shows that the strengths obtained
for those joints prequalified according to these recommendations in combination with a target
reliability factor of β = 2.5 produce capacity factors of φ = 0.8 and φ = 0.85 for MMAW and
GMAW, respectively. These values are in line with the value of φ = 0.9 specified for SP
category butt welds in AS4100 (SA 1998), albeit slightly lower. It should be noticed that the
slightly low values of capacity factor do not imply that the lower capacity factor should be
specified for equal width RHS joints, since in the past, the strength and capacity factor for
welded joints in RHS have been based on tests of complete joints rather than individual
welds.
8
Reliability analysis
The First Order Second Moment (FOSM) reliability analysis (Ravinda and Galambos
1978, SA/SNZ 1998) is used to calculate a capacity factor for the butt welds investigated in
the present report. The analysis is briefly outlined in this section. The calculation is made for
the combination of dead and live loads.
Department of Civil Engineering
Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Excluding joints fabricated using fill bar and using root gaps less than 3 mm in the case of
MMAW from the statistical analysis, values of the mean and coefficient of variation of the
ratio of test strength to predicted strength (P = Pt/Pp) have been obtained as shown in
Table 14.
Table 14. Mean and coefficient of variation of Pt/Pp
MMAW
GMAW
Mean (Pm)
0.96
1.01
COV (VP)
0.08
0.05
27
32
No. of samples
The resistance (R) is assumed to be a product of the variable P as well as material (M) and
a fabrication (F) variables defined as the ratios of measured to nominal values. Table 15
summarises generally accepted statistical data for the material (ultimate tensile strength) and
fabrication variables.
Table 15. Mean and coefficient of variation of M = Mt/Mn and F = Ft/Fn
M
F
Mean
Mm = 1.1
Fm = 1.0
COV
VM = 0.1
VF = 0.05
The mean resistance can be calculated as,
Rm = M m Fm Pm Rn
(2)
where Rn is the nominal value of strength. The coefficient of variation of the resistance can be
calculated as,
VR = VM2 + VF2 + V P2
(3)
Considering the combination of dead (G) and live (Q) load, the load effect (S) can be
expressed as,
S = γ
G
G + γ
Q
Q
(4)
where γG and γQ are the load factors for dead and live load respectively, specified in AS1170.1
(SA 1989) as,
γ G = 1.25
(5)
γ Q = 1.5
(6)
The mean load effect is simply,
S m = G m + Qm
Department of Civil Engineering
Research Report No R817
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(7)
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
where Gm and Qm are mean values of dead and live load respectively. Assuming the load
effects G and Q are uncorrelated, the coefficient of variation of the load effect (S) is,
VS =
(GmVG ) 2 + (QmVQ ) 2
G m + Qm
 Gm

 Gn
=
2
2
 2  G n   Qm
 VG 
 + 
Q

 n   Qn
G m G n Qm
+
G n Qn Qn
2
 2
 VQ

(8)
Table 16 summarises generally accepted statistical data for dead and live load.
Table 16. Mean and coefficient of variation of G and Q
Mean to nominal
G
Q
Gm/Gn = 1.05
Qm/Qn = 1.0
VG = 0.1
VQ = 0.25
COV
The ultimate limit state is defined as,
φRn = γ G Gn + γ Q Qn
(9)
Equations (8, 9) can be combined to obtain the ratio of the mean resistance to the mean load
effect,
Gn
+γQ
Rm
Qn
Rm 1
=
S m G m G n Qm R n φ
+
G n Qn Qn
γG
(10)
According to the FOSM reliability analysis, the reliability index (β) may be approximated by,
ln(
β=
Rm
)
Sm
(11)
V R2 + VS2
Equations (10, 11) can be combined to derive an expression for the capacity factor,
Gn
+γQ
Qn
G m G n Qm
+
G n Qn Qn
γG
φ=
Rm
exp( β VR2 + VS2 ) Rn
(12)
The capacity factor can be calculated for given value of β by combining eqns (2, 3, 5, 6, 8, 10,
12) and using the statistical values given in Tables 14-16. The capacity factor is plotted in
Figs 17 and 18 for MMAW and GMAW respectively for a reliability index of 2.5, which is
Department of Civil Engineering
Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
consistent with that used for structural members in the calibration underpinning AS/NZS4600.
The capacity factor is shown against the ratio of nominal dead to nominal live load (Gn/Qn).
The capacity factor varies between 0.78 and 0.88 for MMAW, and 0.83 and 0.95 for GMAW.
It is common practice to select the capacity factor for a value of Gn/Qn equal to 0.2, which
leads to capacity factors of 0.83 and 0.88 for MMAW and GMAW respectively.
0.90
φ
0.85
0.83
0.80
0.75
0
0.2
0.4
0.6
0.8
1.0
Gn / Q n
Fig. 17 Capacity factor versus Gn/Qn for MMAW
0.95
φ
0.90
0.88
0.85
0.8
0
0.2
0.4
0.6
0.8
1.0
Gn / Q n
Fig. 18 Capacity factor versus Gn/Qn for GMAW
Department of Civil Engineering
Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
9
April 2002
Conclusions
A total of 86 butt welded T-joint connections between equal-width rectangular hollow
sections were fabricated using MMAW and GMAW processes for this report. Five
combinations of brace and chord sizes, with root gaps ranging from 0.8 mm to 9.4 mm, were
selected for investigation. Backing strips and fill bar were used for some of the specimens
fabricated using either welding process, and purging gas was also used for some GMAW
specimens. The welding position was mostly flat, with some specimens welded in the
horizontal position. Tensile coupons were cut from the sides of the T-joints which contained
the butt welds, and their test results were compared with those of the unwelded tensile
coupons.
It was found that while large root gaps resulting from the rounded corners of the coldformed RHS chord members have been a concern, more attention should be paid to butt
welding between equal-width rectangular hollow sections with sharp corners. If insufficient
root gap is provided, then the use of oversized MMAW electrodes may result in lack of weld
penetration across the narrow gap.
In general, the GMAW process was found to produce higher strength and higher rate of
fracture in the tube compared to the weld than the MMAW process for butt welding between
equal-width rectangular hollow sections. In a narrow gap due to the sharp corner of the chord,
the much smaller size of the GMAW wire resulted in better penetration of the butt weld. In a
large root gap due to the rounded corner of the chord, the small size of the GMAW wire does
not create a difficulty as buttering can be used to bridge the gap. Almost all the GMAW
specimens had complete butt weld penetration. For MMAW, incomplete weld penetration and
low strength were experienced when the root gap was less than about 2.5 mm. Furthermore,
the joints fabricated using fill bar were found to have highly variable and often low strength,
particularly when using the MMAW process.
The recommendations of this report are that welds of equal width RHS can be prequalified
for the MMAW and GMAW processes for the flat and horizontal welding positions for the
following weld preparations: no specific preparation, purging gas and backing strip. Welds
prepared using fill bar are not prequalified. Furthermore, minimum root gaps of 4 mm and
3 mm are required for a prequalified weld using the MMAW and GMAW processes
respectively. Appendix V of this report contains a specific proposal as to how these
recommendations may be implemented in AS/NZS1554.1. It is noticed that a pre-qualified SP
joint needs to undergo the macro test.
The welding procedures and joint preparations for pre-qualified T-joints between equalwidth RHS should not be restricted to those described in this report. Satisfactory welding
procedures are dependent on the section thicknesses and the corner radius of the chord, among
other factors, and are not unique for a given joint configuration and a given welding process
(eg. GMAW). It is possible that satisfactory GMAW butt welds are produced using
procedures different from those described in Appendix II for the respective joint
configurations. However, the use of a fill bar does not appear to be helpful in achieving full
butt weld penetration.
Department of Civil Engineering
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
10
April 2002
Acknowledgements
This research project was carried out under the Corporative Research Centre for Welded
Structures. The report presents some of the results of the CRC project 2000-91 entitled
“Welding of Rectangular Hollow Section Members of Equal Width”. The financial support
provided by the CRC Welded Structures is greatly acknowledged as is the financial and inkind support provided by BHP, OneSteel Market Mills and Palmer Tubemills.
Department of Civil Engineering
Research Report No R817
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Appendix I. Chemical composition requirements of RHS specimens
Table is quoted from the structural hollow sections standard AS 1163-1991 (SA 1991a).
Department of Civil Engineering
Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Appendix II. Welding procedures
Specimen Number:
Specimen configuration:
11
125 × 125 × 6 brace to 125 × 125 × 6 chord (Palmer Tube)
Preparation:
None
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
220
610
0.63
Pass 2
225
720
0.54
Pass 3
225
755
0.52
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
Specimen configuration:
17
125 × 125 × 6 brace to 125 × 125 × 6 chord (Palmer Tube)
Preparation:
2-mm gap, 2-mm backing strip
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
225
605
0.65
Pass 2
205
755
0.47
Pass 3
215
690
0.54
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
19
Specimen configuration:
125 × 125 × 4 brace to 125 × 125 × 6 chord
Preparation:
None
Welding Position:
Flat (1F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
3.25
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
20
140
145
1.16
Pass 2
20
141
155
1.09
Pass 3
20
141
150
1.13
Department of Civil Engineering
Research Report No R817
AS 1553.1.E4113
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
27
Specimen configuration:
125 × 125 × 4 brace to 125 × 125 × 6 chord
Preparation:
2-mm gap, 3-mm backing strip
Welding Position:
Flat (1F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
3.25
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
22
140
165
1.12
Pass 2
22
140
170
1.09
Pass 3
18
143
185
0.83
Pass 4
22
140
170
1.09
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
30
125 × 125 × 4 brace to 125 × 125 × 6 chord
Specimen configuration:
Preparation:
No gap, purged
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
235
N/A
N/A
Pass 2
240
470
0.61
Pass 3
240
525
0.55
Pass 4
245
540
0.54
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
35
125 × 125 × 4 brace to 125 × 125 × 6 chord
Specimen configuration:
Preparation:
2-mm gap, 3-mm backing strip
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
230
370
0.75
Pass 2
245
505
0.58
Pass 3
245
505
0.58
Pass 4
245
540
0.54
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
37
125 × 125 × 4 brace to 125 × 125 × 6 chord
Specimen configuration:
Preparation:
None
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
220
410
0.64
Pass 2
225
475
0.57
Pass 3
230
475
0.58
Pass 4
235
605
0.47
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
38
Specimen configuration:
150 × 150 × 9 brace to 250 × 150 × 9 chord
Preparation:
None
Welding Position:
Flat (1F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
4.0
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
23
188
150
1.73
Pass 2
21
189
150
1.59
Pass 3
20
190
150
1.52
Pass 4
24
185
130
2.05
Pass 5
19
192
190
1.15
Department of Civil Engineering
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AS 1553.1.E4113
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
42
Specimen configuration:
150 × 150 × 9 brace to 250 × 150 × 9 chord
Preparation:
2-mm gap, 10-mm backing strip
Welding Position:
Flat (1F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
4.0
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
21
189
140
1.70
Pass 2
20
193
180
1.29
Pass 3
20
194
190
1.22
Pass 4
20
194
165
1.41
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
43
150 × 150 × 9 brace to 250 × 150 × 9 chord
Specimen configuration:
Preparation:
None
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
260
465
0.79
Pass 2
270
610
0.62
Pass 3
280
605
0.65
Pass 4
290
650
0.63
mm/min
Pass 1
1.2 mm ES4-GC/M-W503AH
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23.5
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
48
150 × 150 × 9 brace to 250 × 150 × 9 chord
Specimen configuration:
Preparation:
2-mm gap
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
mm/min
Pass 1
1.2 mm ES4-GC/M-W503AH
Arc
Energy
mm/min
kJ/mm
23.5
280
455
0.87
Pass 2
24
270
605
0.63
Pass 3
24
250
700
0.51
Pass 4
24
250
605
0.59
Pass 5
24
250
645
0.56
Pass 6
24
250
670
0.54
Department of Civil Engineering
Research Report No R817
9500
Welding
Speed
38
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
61
Specimen configuration:
150 × 150 × 5 brace to 250 × 150 × 9 chord
Preparation:
2-mm gap, 8-mm fill bar
Welding Position:
Flat (1F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
4.0
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
20
141
120
1.41
Pass 2
20
141
130
1.30
Pass 3
20
141
115
1.47
Pass 4
20
140
145
1.16
Pass 5
20
140
160
1.05
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
62
150 × 150 × 5 brace to 150 × 150 × 9 chord
Specimen configuration:
Preparation:
None
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min)
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
220
370
0.71
Pass 2
220
405
0.65
Pass 3
235
420
0.67
Pass 4
220
480
0.55
Pass 5
235
505
0.56
Pass 6
225
480
0.56
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
70
150 × 150 × 5 brace to 150 × 150 × 9 chord
Specimen configuration:
Preparation:
2-mm gap, 8-mm fill bar
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min)
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
N/A
N/A
N/A
Pass 2
220
N/A
N/A
Pass 3
220
755
0.35
Pass 4
220
865
0.30
Pass 5
215
1010
0.25
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
71
Specimen configuration:
125 × 125 × 6 brace to 125 × 125 × 6 chord (OS)
Preparation:
2-mm gap
Welding Position:
Flat (1F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
3.25
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
21
140
140
1.26
Pass 2
21
141
145
1.22
Pass 3
21
140
130
1.36
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
72
Specimen configuration:
125 × 125 × 6 brace to 125 × 125 × 6 chord (OS)
Preparation:
2-mm gap, 3-mm backing strip
Welding Position:
Flat (1F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
3.25
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
21
141
160
1.11
Pass 2
21
140
150
1.18
Pass 3
20
142
165
1.03
Pass 4
21
141
150
1.18
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
73
Specimen configuration:
125 × 125 × 6 brace to 125 × 125 × 6 chord (OS)
Preparation:
2-mm gap, 6-mm fill bar
Welding Position:
Flat (1F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
3.25
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
22
140
140
1.32
Pass 2
18
143
180
0.86
Pass 3
21
141
150
1.18
Pass 4
20
142
130
1.31
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
74
Specimen configuration:
125 × 125 × 6 brace to 125 × 125 × 6 chord
Preparation:
2-mm gap, 2-mm backing strip
Welding Position:
Horizontal (2F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
3.25
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
22
139
165
1.11
Pass 2
21
140
145
1.22
Pass 3
20
140
180
0.93
Pass 4
19
140
230
0.69
Department of Civil Engineering
Research Report No R817
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45
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
Specimen configuration:
75
125 × 125 × 6 brace to 125 × 125 × 6 chord (OneSteel)
Preparation:
2-mm gap
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
235
400
1.02
Pass 2
240
475
0.88
Pass 3
235
585
0.70
Pass 4
245
580
0.73
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
Specimen configuration:
76
125 × 125 × 6 brace to 125 × 125 × 6 chord (OneSteel)
Preparation:
2-mm gap, 3-mm backing strip
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
190
755
0.30
Pass 2
190
755
0.30
Pass 3
195
1015
0.23
Pass 4
195
690
0.34
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number
Specimen configuration:
77
125 × 125 × 6 brace to 125 × 125 × 6 chord (OneSteel)
Preparation:
2-mm gap, purged
Welding Position:
Flat (1F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
185
605
0.37
Pass 2
190
1170
0.19
Pass 3
185
730
0.30
Pass 4
195
950
0.25
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
Department of Civil Engineering
Research Report No R817
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20
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Specimen Number:
Specimen configuration:
78
125 × 125 × 6 brace to 125 × 125 × 6 chord (OneSteel)
Preparation:
2-mm gap
Welding Position:
Horizontal (2F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
225
275
0.98
Pass 2
220
310
0.85
Pass 3
225
430
0.63
Pass 4
230
410
0.67
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
Department of Civil Engineering
Research Report No R817
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20
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
79
125 × 125 × 4 brace to 125 × 125 × 6 chord
Specimen configuration:
Preparation:
2-mm gap, 3-mm backing strip
Welding Position:
Horizontal (2F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
235
350
0.81
Pass 2
235
380
0.74
Pass 3
235
380
0.74
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
Department of Civil Engineering
Research Report No R817
12500
50
20
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
80
125 × 125 × 4 brace to 125 × 125 × 6 chord
Specimen configuration:
Preparation:
None
Welding Position:
Horizontal (2F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
230
420
0.66
Pass 2
215
370
0.70
Pass 3
225
350
0.77
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
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20
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
81
Specimen configuration:
150 × 150 × 9 brace to 250 × 150 × 9 chord
Preparation:
None
Welding Position:
Horizontal (2F)
Welding Process:
MMAW
Welding Machine:
Transarc 500
Polarity:
AC
Electrode Trade Name:
CIGWeld Weldcraft
Electrode Diameter (mm) :
Weld
4.0
Electrode Classification
Pass 1
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
23
190
150
1.75
Pass 2
21
191
170
1.42
Pass 3
23
189
160
1.63
Pass 4
18
194
215
0.97
Pass 5
20
192
205
1.12
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AS 1553.1.E4113
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
82
150 × 150 × 9 brace to 250 × 150 × 9 chord
Specimen configuration:
Preparation:
None
Welding Position:
Horizontal (2F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
275
365
0.85
Pass 2
275
445
0.70
Pass 3
250
N/A
N/A
Pass 4
250
410
0.69
Pass 5
270
455
0.68
Pass 6
250
455
0.63
mm/min
Pass 1
1.2 mm ES4-GC/M-W503AH
Department of Civil Engineering
Research Report No R817
9500
53
19
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
83
150 × 150 × 9 brace to 250 × 150 × 9 chord
Specimen configuration:
Preparation:
2 mm gap, 10-mm backing strip
Welding Position:
Horizontal (2F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min):
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
260
465
0.79
Pass 2
270
610
0.62
Pass 3
280
605
0.65
Pass 4
290
650
0.63
mm/min
Pass 1
1.2 mm ES4-GC/M-W503AH
Department of Civil Engineering
Research Report No R817
9500
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23.5
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
85
150 × 150 × 5 brace to 150 × 150 × 9 chord
Specimen configuration:
Preparation:
None
Welding Position:
Horizontal (2F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min)
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
215
250
1.03
Pass 2
225
300
0.90
Pass 3
230
330
0.84
Pass 4
230
260
1.06
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
Department of Civil Engineering
Research Report No R817
12500
55
20
The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
Specimen Number:
April 2002
86
150 × 150 × 5 brace to 150 × 150 × 9 chord
Specimen configuration:
Preparation:
2-mm gap, 8-mm fill bar
Welding Position:
Horizontal (2F)
Welding Process:
GMAW, short-arc transfer
Welding Machine:
CIG Transmig 330 transformer; Transmig 2Rse feeder
Polarity:
DCEP
Stick-out:
15 mm
Electrode Trade Name:
CIGWeld Autocraft
Gas Trade Name:
Argoshield 51
Gas Composition:
16% CO2, 81.5% Ar, 2.5% O2
Gas Flow Rate (L/min)
Weld
Electrode Classification
25
Wire Speed
V
A
Welding
Speed
Arc
Energy
mm/min
kJ/mm
225
270
1.00
Pass 2
225
305
0.88
Pass 3
235
290
0.97
Pass 4
230
360
0.77
Pass 5
230
330
0.84
mm/min
Pass 1
0.9 mm ES4-GC/M-W503AH
Department of Civil Engineering
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Appendix III. Macros of welds with incomplete penetration
Fig. III.1: Specimen 3, MMAW
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. III.2: Specimen 5, MMAW
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. III.3: Specimen 10, MMAW
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. III.4 Specimen 29, GMAW
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. III.5: Specimen 40, MMAW
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. III.6: Specimen 56, MMAW
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. III.7: Specimen 58, MMAW
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. III.8 Specimen 59, MMAW
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Appendix IV. Macros of welds with complete penetration
Fig. IV.1: Specimen 7, MMAW
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. IV.2: Specimen 11, GMAW
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. IV.3 Specimen 19, MMAW
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. IV.4 Specimen 43, GMAW
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. IV.5a: Specimen 62, GMAW
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Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Fig. IV.5b: Specimen 62, GMAW
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Research Report No R817
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Appendix V. Proposed changes to AS/NZS1554.1
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
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Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
References
CIDECT (1984) Construction with Hollow Steel Sections, Corby, England.
CIDECT (1986) “The strength and behaviour of statically loaded welded connections in
structural hollow sections”, Monograph No. 6, Comite International pour le
Developpement et l’Etude de la Construction Tubulaire, (International Committee for the
Development and Study of Tubular Structures), British Steel Corporation.
Davies, G., and Panjeshahi, E. (1984) “Tee joints in rectangular hollow sections (RHS) under
combined axial loading and bending,” Proc., 7th Int. Symp. on Steel Structures, Gdansk,
Poland.
Davies, G., Wardenier, J., and Stolle, P. (1981) “The effective width of branch crosswalls for
RR cross joints in tension,” Stevin Report No. 6-81-7, Delft University of Technology,
The Netherlands.
De Koning, C. H. M., and Wardenier, J. (1985) “The static strength of welded joints between
structural hollow sections or between structural hollow sections and H-sections. Part 2:
Joints between rectangular hollow sections,” Stevin Report No. 6-84-19, Delft University
of Technology, The Netherlands.
Key, P. W., and Hancock, G. J. (1985) “An experimental investigation of the column
behaviour of cold-formed square hollow sections,” Research Report No. R493, School of
Civil and Mining Engineering, University of Sydney, Australia.
Lu L. H., de Winkel, G. D., Yu Y., and Wardenier J. (1994) “Deformation limit for the
ultimate strength of hollow section joints,” Proc., 6th Int. Symp. on Tubular Structures,
Melbourne, P. Grundy, A. Holgate, and B. Wong, eds., Balkema, Rotterdam, 341–7.
Mang, F., Steidl, G., and Bucak, O. (1979) “Investigations of weld imperfections in butt welds
of structural hollow sections (HSS),” Document No. XV-444-79, International Institute
of Welding, Karlsruhe University, Germany.
Packer, J. A. (1983) “Developments in the design of welded HSS truss joints with RHS
chord,” Can. J. Civ. Engrg., 10 (1), 92-103.
Packer, J. A., and Henderson, J. E. (1997) Hollow Structural Section Connections and
Trusses: A Design Guide, Canadian Institute of Steel Construction, Willowdale, Ontario.
Packer, J. A., Wardenier, J., Kurobane, Y., Dutta, D., and Yeomans, N. (1992) Design Guide
for Rectangular Hollow Section (RHS) Joints under Predominantly Static Loading,
Verlag TUV Rheinland, Koln.
Rasmussen, K. J. R., and Young, B. (2001) “Tests of X- and K-joints in SHS stainless steel
tubes,” ASCE J. Struct. Engrg., 127 (10), 1173-1182.
Department of Civil Engineering
Research Report No R817
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The University of Sydney
Strength of Butt Welded Connections between Equal-Width Rectangular Hollow Sections
April 2002
Ravindra, M.K., and Galambos, T.V. (1978), “Load and resistance factor design for steel”, J.
Struct. Div., ASCE, Vol. 104, No. ST9, 1337-1353.
SA (1989) SAA loading code, Part 1: Dead and live loads and load combinations, AS 1140.11989, Standards Australia, Sydney.
SA (1991a) Structural Steel Hollow Sections, AS 1163-1991, Standards Australia, Sydney.
SA (1991b) Methods for tensile testing of metals, AS 1391-1991, Standards Australia,
Sydney.
SA (1998) Steel Structures, AS 4100-1998, Standards Australia, Sydney.
SA/SNZ
(1996a)
Cold-Formed
Steel
Structures,
AS/NZS
4600:1996,
Standards
Australia/Standards New Zealand, Sydney.
SA/SNZ (1996b). Welding – Electrodes - Gas Metal Arc - Ferritic Steel Electrodes, AS/NZS
2717.1:1996, Standards Australia/Standards New Zealand, Sydney.
SA/SNZ (1998) Cold-formed steel structures – Commentary, AS/NZS4600 Supplement 1,
Standards Australia/Standards New Zealand, Sydney.
SA/SNZ (2000) Structural Steel Welding – Part 1: Welding of Steel Structures, AS/NZS
1554.1:2000, Standards Australia/Standards New Zealand, Sydney.
Syam, A., and Chapman, B. (1996) Design of Structural Steel Hollow Section Connections,
Vol. 1: Design Models, Australian Institute of Steel Construction, North Sydney,
Australia.
Teh, L. H., and Rasmussen, K. J. R. (2002) “Strength of arc welded T-joints between equalwidth cold-formed rectangular hollow sections,” Research Report, Department of Civil
Engineering, University of Sydney.
Wardenier, J., and De Koning, C. H. M. (1974) “Static tensile tests on T-joints in structural
hollow sections,” Stevin Report No. 6-74-7, Delft University of Technology, The
Netherlands.
Wardenier, J. (1982) Hollow Section Joints, Delft University Press, Delft.
Wilkinson, T. (1999) The Plastic Behaviour of Cold-Formed Rectangular Hollow Sections,
PhD thesis, Department of Civil Engineering, University of Sydney, Australia.
Zhao, X. L. (2000) “Deformation limit and ultimate strength of welded T-joints in coldformed RHS sections,” J. Constr. Steel Res., 53 (2), 149-165.
Zhao, X. L., and Hancock, G. J. (1991) “T-joints in rectangular hollow sections subject to
combined actions.” ASCE J. Struct. Engrg., 117 (8), 2258-2277.
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