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The use o precast concrete enables year-round, high-
quality construction o buildings and bridges. The
individual components are typically manuactured
in an environmentally controlled acility. This allows or
consistency o concrete production, steel installation, andconcrete placement. Connections between precast concrete
elements are oten made by welding steel plates embedded
in the precast concrete components. Figure1 illustrates
a standard double teetoinverted tee connection. When
designed in accordance with PCI recommendations, these
connections (PCI Connections Manual or Precast and
Prestressed Concrete Construction)1 provide stability
during erection and strength or service and ultimate-load
cases.
In most cases, certain connections are welded initially dur-
ing erection o the precast concrete component to providestability. The remaining embedded connections are com-
pleted later to provide the ull service and strength load
capacity. Welding o the connections needed or erection
stability is perormed in the eld under a variety o wind,
humidity, and temperature conditions. Current American
Welding Society (AWS) specications2,3 are either restric-
tive or unclear about the conditions under which eld
welds can be made. A research program sponsored by PCI
was conducted to investigate the eects o environmental
conditions on the quality o eld-welded precast concrete
connections.
A research study was conducted to investigate the quality ofwelded connections between precast concrete components
made under environmental conditions typically encountered in
precast concrete construction.
The effects of wind, humidity, temperature, and surface mois-
ture on the quality of shielded metal arc welds (SMAWs) on
ASTM A36 Type 304 stainless steel and ASTM A36 galvanized
steel plates were examined.
The results showed that good-quality SMAW welds can be
made in wind up to 35 mph (56 kph), in temperatures as low
as -10 F (-23.3 C), and under wet conditions.
Effect of environmentalconditions on field welding of
precast concrete connections
Clay Naito, Jason Zimpfer, Richard Sause, and Eric Kaufmann
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Welding requirementsfor precast concrete systems
Field welds o steel connection plates embedded in pre-
cast concrete components are commonly made using the
shielded metal arc welding (SMAW) method. This method,
also called stick welding, uses a fux-coated electrode
rod. During welding, the wire transmits current, creating
an electric arc to the base metal. The rod melts and then
solidies, becoming the weld metal (ller), while the fux
shields the molten weld metal rom the atmosphere. Flux
core arc welding (FCAW) is also used in precast concrete
construction; however, this method uses a continuous-eed
electrode wire. The size o the equipment used to eed the
wire oten makes it dicult to use in multistory precastconcrete construction. Due to the limited use o the FCAW
method in precast concrete construction, the research study
ocused on the welds made using SMAW.
Limits on environmentalconditions for welding
The standards oten used or welding in the United States
are produced by AWS. Two specications apply or con-
nections used in precast concrete construction: Structural
Welding CodeSteel (AWS D1.1)2 and Structural Welding
CodeStainless Steel (AWS D1.6).3AWS D1.1 providesa summary o unacceptable environmental conditions or
welding in section 5.12.2: Welding shall not be done (1)
when the ambient temperature (temperature in immedi-
ate vicinity o weld) is below 0 F (-18 C), or (2) when
suraces are wet or exposed to rain, snow, or (3) high wind
velocities, or (4) when welding personnel are exposed to
inclement conditions.
In accordance with AWS D1.1, preheat is required or
ASTM A364 base metals with a thickness between 1/8 in.
and 3/4 in. (3 mm and 19 mm) welded with low-hydrogen
electrodes using the SMAW process. The minimum preheat
temperature is 32 F (0 C). I the base metal temperature
is below 32 F, the base metal must be preheated to at least
70 F (21 C).
For high wind velocities, a suitable shelter must be used to
protect the weld.2 High wind velocity is dened as 5 mph
(8 kph) or weld processes that use a gas shield to protect
the molten weld metal rom the environment. These gas-
shielded processes require a low wind condition to main-
tain the shield. Because the SMAW process does not use a
gas shield, a wind velocity limit is not directly prescribed
by AWS.
AWS D1.6 similarly states that welding should not be
perormed on suraces that are wet or in wind that wouldadversely aect shielding o the molten weld metal in the
welding process. The AWS D1.6 code does not quantiy
the wind velocity that would aect the shielding process.
The American Petroleum Institute (API) has similar envi-
ronmental restrictions within its document Welded Steel
Tanks or Oil Storage.5 With respect to wind, eld weld-
ing is not allowed during periods o high wind unless the
welder and weld are sheltered adequately. With respect to
moisture, welding is not allowed when suraces are wet
rom any orm o precipitation or when precipitation is
alling. Finally, API requires preheat i the ambient tem-perature is between 0 F and 32 F (-18 C and 0 C), and
welding is orbidden i the temperature is below 0 F.
To summarize, current welding codes prohibit welding
at ambient temperatures under 0 F (-18 C) and permit
welding, with associated preheat, at ambient temperatures
between 0 F and 32 F (-18 C and 0 C). Limitations
on welding using the SMAW process under high wind
conditions are ambiguous. Last, there are no limitations on
ambient moisture, but welding is prohibited when suraces
to be welded are wet.
Figure 1. Field welding o precast concrete connections.
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Electrode exposure to environment
Exposure o standard carbon steel electrodes is limited by
AWS D1.1 to our hours outside a hermetically sealed con-
tainer or holding oven at 250 F (121 C), and electrodes
that have been wet are prohibited rom use. AWS D1.1 also
states that electrodes with the supplemental designation R
(such as the E7018-H4R electrodes used in this study) areapproved or nine hours o exposure to the environment.
AWS D1.6 states that electrodes or the SMAW o stainless
steel can be kept in a hermetically sealed container pro-
vided it is reclosed immediately ater opening. Otherwise,
electrodes must be stored in a holding oven. A maximum
exposure time is not dened.
Research overview
A research program was initiated to evaluate the quality
o welded connections made under various environmental
conditions. Welds were made under a variety o tem-
perature, humidity, and wind conditions simulating those
encountered in precast concrete construction. Three steel
types used in precast concrete construction, ASTM A36,
ASTM A36 galvanized, and Type 304 stainless steel,
were examined. The study ocused on the most com-
monly used llet weld sizes o1/4 in. and3/16 in. (6 mm and
5 mm) produced with the SMAW process. The welds were
examined visually and microscopically and by destructive
testing to evaluate their adequacy with respect to the AWS
standards. The destructive testing was designed to evaluate
the strength o welds made under base conditions (71 F
[22 C], 35% relative humidity [RH], 0 mph wind) and lessavorable environmental conditions.
The environmental conditions used in the study represented
extreme conditions encountered in U.S. construction. Three
temperatures were chosen. Standard room temperature o
71 F (22 C) was used as a base condition, 32 F (0 C) was
used as the temperature below which preheat is required by
AWS, and 0 F (-18 C) was selected as a lower bound or
practical construction conditions. Due to practical limita-
tions, the ambient temperature varied marginally rom the
target value during welding. The humidity levels o 35%,
50%, and 95% RH were chosen to represent low-, average-,and near-saturation humidity. In addition, a surace wet
condition was included to examine the eect o liquid or
rozen water on the base metal plate suraces. The surace
wet condition was achieved by misting with a spray bottle,
with the exception o one o the stainless specimens (SS-88),
which achieved the surace wet condition by liquid droplets.
Surace moisture was provided beore welding only. No ad-
ditional moisture was added during or ater welding.
Finally, the wind speeds were chosen as 0 mph, 5 mph,
10 mph, 20 mph, and 35 mph, (8 kph, 16 kph, 32 kph, and
36 kph) with 5 mph being the maximum allowable wind
speed or many welding processes according to AWS D1.1.
The greatest wind speed, 35 mph, was chosen as an upper
bound under which welders would be willing to oper-
ate. The 10 mph and 20 mph conditions were chosen to
provide adequate data to quantiy the eects o wind on
the welds. Table1 summarizes the combinations o steel
types and actual environmental conditions under which test
welds were made.
Three series o specimens were abricated. The
ASTM A36 (36 series) specimen and the stainless steel
(SS series) specimen were orensically examined through
sectioning and surace observations. The T series specimen
was evaluated or strength. Zimper et al.6 provides urther
details on each specimen.
Forensic evaluation of welds
Fillet welds are susceptible to a variety o discontinuities
that can aect their strength. These include weld prole
irregularities, slag inclusions, porosity, and discontinuities
that are cracklike in nature. A brie description o each
type o discontinuity ollows.
Weld prole irregularities include undercut, concavity or
convexity, and overlap. Figure2 illustrates samples o
these irregularities. Undercut occurs parallel to the junction
o weld metal and base metal at the top o the prole, and
the associated stress concentration can reduce the strength
o the weld. Convexity and concavity are specic orms o
oversized or undersized welds, respectively. Concavity is
detrimental rom the reduction o the weld cross-section
area, but weld passes can be added to increase the weldarea. Oversized welds are not inherently harmul to weld
quality or strength but might interere with the assembly
geometry and might produce excessive distortion o the
base metal plates. Overlap (not shown) is usually caused
by improper procedure or improper preparation o the base
metal due to intererence o surace oxides with the usion
process.
Weld surace irregularities or ripples can be caused by im-
proper technique or by excessive wind acting on the mol-
ten weld pool. However, variations in weld dimensions, de-
pressions, nonuniormity o weld ripples, and other suraceirregularities are not classied as weld discontinuities.7
Incomplete usion is a lack o usion between the weld
metal and the base metal along one or more o the weld
boundaries. It can result rom improper preparation o the
base metal beore welding (insucient cleaning) or insu-
cient welding current. It can result in crack ormation (Fig.3).
Slag inclusions are nonmetallic solid materials trapped in
the weld metal or at the interace o the weld metal and
base metal. With proper welding procedures and technique,
slag should rise to the surace o the molten weld metal.
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Table 1. Test matrix
Specimen
identifcation
Base material Temperature,
F
Relative
humidity, %
Wind
velocity, mph
Electrode
condition
Plate surace
condition*
36-1 ASTM A36 72.0 41.0 0 AWS D1.1 Dry
36-3 ASTM A36 72.5 98.2 0 AWS D1.1 Dry
36-6 ASTM A36 76.6 94.3 20.0 AWS D1.1 Dry
36-7 ASTM A36 73.6 97.8 34.7 AWS D1.1 Dry
36-8 ASTM A36 78.3 92.4 0 AWS D1.1 Wet
36-14 ASTM A36 39.0 75.5 20.0 AWS D1.1 Dry
36-15 ASTM A36 31.0 100.0 32.4 AWS D1.1 Dry
36-22 ASTM A36 -5.0 99.9 21.3 AWS D1.1 Dry
36-23 ASTM A36 -13.0 100.0 27.0 AWS D1.1 Dry
36-17(95)(1) ASTM A36 72.9 92.0 0 ~4% Dry
36-17(95)(2) ASTM A36 77.1 88.6 0 ~4% Dry
36-C1 ASTM A36 Hi-C(1) -6.0 100.0 0 AWS D1.1 Dry
36-C2 ASTM A36 Hi-C(1) -4.0 66.7 0 AWS D1.1 Dry
36-PC1 ASTM A36 88.9 43.4 0 AWS D1.1 1 wet, 1 dry
36-PC2 ASTM A36 91.1 50.0 0 AWS D1.1 1 wet, 1 dry
36-PC3 ASTM A36 91.9 28.8 0 AWS D1.1 Dry
36-PC4 ASTM A36 84.5 50.0 0 AWS D1.1 Wet
36-PC5 ASTM A36 15.0 85.3 0 AWS D1.1 Wet (ice)
36-PC6 ASTM A36 Hi-C(2) 74.2 17.6 0 AWS D1.1 Wet
36G-25 ASTM A36 galvanized 73.0 43.0 4.3 AWS D1.1 Dry
36G-33(1) ASTM A36 galvanized 36.0 28.5 3.0 AWS D1.1 Dry
36G-33(2) ASTM A36 galvanized 20.0 33.6 3.0 AWS D1.1 Dry
36G-17(95) ASTM A36 galvanized 77.3 84.6 3.0 4% Dry
SS-73 Stainless steel 304 73.0 35.7 0 AWS D1.6 Dry
SS-74 Stainless steel 304 73.7 47.7 0 AWS D1.6 Dry
SS-75 Stainless steel 304 77.0 100.0 0 AWS D1.6 Dry
SS-76 Stainless steel 304 71.4 100.0 5.1 AWS D1.6 Dry
SS-77 Stainless steel 304 74.8 95.7 10.1 AWS D1.6 Dry
SS-78 Stainless steel 304 75.5 94.8 20.1 AWS D1.6 Dry
SS-79 Stainless steel 304 75.8 90.9 33.2 AWS D1.6 Dry
SS-82 Stainless steel 304 45.5 48.8 0 AWS D1.6 Dry
SS-83 Stainless steel 304 35.6 99.2 0 AWS D1.6 Dry
SS-84 Stainless steel 304 43.4 100.0 5.1 AWS D1.6 Dry
SS-85 Stainless steel 304 39.8 100.0 10.0 AWS D1.6 Dry
SS-86 Stainless steel 304 37.2 100.0 19.3 AWS D1.6 Dry
SS-87 Stainless steel 304 33.8 100.0 33.1 AWS D1.6 Dry
SS-88 Stainless steel 304 35.7 99.9 ~15.0 AWS D1.6 Wet
(continued on the next page)
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stress concentrations at the tip o the crack. AWS D1.1 does not al-
low cracking. The required ield inspection or the presence o cracks
in illet welds, however, is limited to a visual observation o the weld
surace. In most cases, no microscopic or nondestructive examina-
tion o the weld is required; thereore, cracks o concern include
those visible to the naked eye. For visual identiication, a minimum
crack length o approximately 1/32 in. (0.8 mm) is needed. For this
investigation, the term microcrackreers to cracks less than approxi-
mately 1/32 in. long, while the term crackreers to those longer thanapproximately 1/32 in. Microcracks are oten present ater welding but
in most cases are stable and do not propagate. Figure 2 shows two
microcracks visible in a magniied view o a weld.
Welds made under the various environmental conditions were
examined to assess compliance with AWS requirements. The
examination and evaluation criteria were as ollows:
Prole: The concavity and convexity o the weld
prole were measured. Convexity must be less than1/8 in. (3 mm) or
1/4 in. (6 mm) llet welds, and1
/16 in. (2 mm) or3
/16 in. (5 mm) llet welds.
Slag inclusions reduce weld strength by reducing the weld
cross section and by creating stress concentrations.
Porosity is the presence o voids in the weld metal. These voids have
a variety o appearances. The main types are uniormly scattered,
clustered, linear, and wormhole (elongated). Porosity is caused by
the presence o gases in concentrations above their solubility limits as
the weld metal solidiies. Hydrogen, oxygen, and nitrogen gases are
soluble in the weld metal. Hydrogen is the primary cause o porosityin welds. Hydrogen can enter the molten weld pool rom moisture in
the cellulose constituents o the electrode coating or through dissocia-
tion o water. Water can be present on the electrode, the base metal
plates, or in the air surrounding the weld.8 Porosity reduces the weld
cross section and creates stress concentrations, both o which reduce
the weld strength. Results rom slow bend tests show that scattered,
unaligned, unclustered porosity has little eect on the static yield
strength, the ultimate strength, and the ductility o welds when com-
posing less than 5% o the cross section and in some cases up to 7%.9
Cracks in the weld or heat-aected zone o the base metal (adjacent
to the weld) increase the propensity or abrupt weld racture due to
Table 1. Test matrix
Specimen
identifcation
Base material Temperature,
F
Relative
humidity, %
Wind
velocity, mph
Electrode
condition
Plate surace
condition*
SS-89 Stainless steel 304 -4.6 24.7 0 AWS D1.6 Dry
SS-90 Stainless steel 304 -5.0 49.5 0 AWS D1.6 Dry
SS-91 Stainless steel 304 -5.4 100.0 0 AWS D1.6 Dry
SS-92 Stainless steel 304 -2.2 95.5 5.5 AWS D1.6 Dry
SS-93 Stainless steel 304 -2.4 93.0 10.0 AWS D1.6 Dry
SS-94 Stainless steel 304 -3.0 100.0 20.6 AWS D1.6 Dry
SS-95 Stainless steel 304 -1.2 100.0 26 to 27 AWS D1.6 Dry
SS-96 Stainless steel 304 -2.0 99.9 0 AWS D1.6 Wet
SS-4(100) Stainless steel 304 73.0 96.7 0 4 HR** Dry
SS(1/4)-35 Stainless steel 304 73.0 94.6 32.0 AWS D1.6 Dry
SS(1/4)-0 Stainless steel 304 78.0 45.4 0 AWS D1.6 Dry
T-1 ASTM A36 84.0 15.4 0 AWS D1.1 Dry
T-2 ASTM A36 Hi-C(2) 77.9 26.4 0 AWS D1.1 Dry
T-3 ASTM A36 Hi-C(2) -15.4 73.0 0 AWS D1.1 Dry
T-4 ASTM A36 Hi-C(1) 72.0 32.3 0 AWS D1.1 Wet
T-5 ASTM A36 Hi-C(2) 72.7 19.3 0 AWS D1.1 Wet
* Wet indicates that the surface was intentionally wet before welding. Electrodes were stored and used in accordance with provisions outlined in AWS D1.1 and D1.6.Approximate percentage of moisture in electrode by weight (17-hour exposure to > 80% relative humidity). Specimens were not sectioned according to standard procedure but were welded for the purpose of examination for porosity and cracking behavior
and inspected as needed for these purposes.** Refers to exposure of 308-16 electrodes for four hours to moist environment (within AWS D1.6 limits).
Note: C = (5/9)(F 32); 1 mph = 1.6 kph.
(cont.)
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Undercut: Undercut was identied and measured on
polished weld cross sections. The undercut must be
less than 1/32 in. (0.8 mm).
Cracks: Visible cracks (longer than 1/32 in. [0.8 mm])
were identied on polished weld cross sections andweld suraces. Such cracks were considered unaccept-
able. Microcracks (shorter than 1/32 in.) were noted when
observed under the microscope but were acceptable.
Porosity: Porosity was identied and measured on
polished weld cross sections and weld suraces. For
statically loaded welds, the sum o the visible pip-ing porosity 1/32 in. (0.8 mm) or greater in diameter
Figure 2. Welding discontinuities. Note: " = inch. 1 in. = 25.4 mm.
Figure 3. Crack ormation due to incomplete usion on specimen 36-22. Note: 1 mm = 0.0394 in.
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was not to exceed 3/8 in. (10 mm) in any linear inch o
weld or 1/4 in. (6 mm) in each 4 in. (100 mm) o weld
length. For cyclically loaded welds, the requency o
piping porosity was not to exceed one in each 4 in.
o weld length and the maximum diameter was not to
exceed 3/32 in. (2 mm).
Slag inclusion: Slag inclusions were identied and
measured on polished weld cross sections. The sum o
greatest dimensions o the slag inclusions on a cross
section must be less than 1/4 in. (6 mm).
Experimental program
The specimen conguration was similar to a double-
teetoinverted-tee connection (Fig. 1). The specimen
consisted o two base plates and one cover plate orientedin a horizontal position (Fig. 4). The base plates were
recessed in a 4-in.-thick (100 mm) concrete block to rep-
licate plate embedment and heat sink conditions typical
o precast concrete construction. The plates were clamped
at all our corners to simulate a ully restrained condition.
This restraint allowed residual stresses in the welded joint
to develop on cooling o the weld metal. The cover plate
was held stationary as shown by a single, unobtrusive
hold-down point in the center o the plate. This congu-
ration was used or all 36 series and SS series orensic
specimens.
The welding was perormed in an environmentally con-
trolled chamber. Within the chamber, ambient temperature
and relative humidity were controlled, with the ability to
create temperatures as low as -18 F (-28 C) and relative
humidity rom approximately 35% to 100%. Wind was
simulated with a variable powered centriugal blower with
air fow transverse to the llet weld (normal to weld axis).
The an was congured to achieve wind speeds ranging
rom 0 mph to 35 mph (56 kph) at the weld, with the wind
being applied at a nominal distance o 6 in. (150 mm) rom
the llet weld.
For each test specimen, measurements were taken and
recorded inside the chamber to veriy the wind speed, hu-
midity, and temperature. Relative humidity was measured
in the center o the chamber using a handheld meter with
an accuracy o 3%. The temperature was measured in
the air in the vicinity o the weld, as well as on the surace
o the steel plates near the weld joint and on the concrete
surace about an inch away rom the plate recess. The wind
speed was measured approximately 6 in. (150 mm) rom
the opening o the blower with a device with an accuracy
o 3%.
Strength evaluation setup
The abrication setup used or the T series strength speci-
mens was modied rom the orensic specimen setup to
acilitate testing. The top plate was oset to accommodatethe necessary grip length in the tensile testing machine and
to ensure ailure o the specimens through the weld metal
rather than a base metal racture. The specimen involved
lapping one 4 in. 6 in. (100 mm 150 mm) cover plate
over one 4 in. 6 in. base plate, with both plates oriented
in the same direction such that the weld metal was depos-
ited along the 6 in. plate length. Restraint was maintained
using the edge clamps as previously discussed. The start
and stop portions o the weld were not included in the
tested specimen because these portions typically contain a
disproportionately high level o discontinuities and are not
representative o the majority o the weld. Finally, a boltwas placed through holes drilled in the cover plate o these
two halves, as well as through a central 3/4 in. (19 mm)
plate, which served as a grip or the testing machine
through which tension could be applied concentrically and
distributed equally to the welds on either side. Figure5
illustrates the specimen and testing conguration. The
tests were conducted at a quasi-static rate o 9.2 kip/min
(41 kN/min). The specimens were loaded until a complete
loss in load-carrying capacity occurred.
Figure 4. Forensic weld specimen setup. Note: 1 in. = 25.4 mm.
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H4R electrodes were used in accordance with AWS D1.1
Table 3.1. Electrodes were stored and used in accordance
with the restrictions ound in AWS D1.1 section 5.3.2,
except in cases where the electrodes were exposed to the
environment to evaluate the eects o this exposure on
weld quality. Namely, the E7018-H4R electrodes were pur-
chased in hermetically sealed containers, stored in a hold-
ing oven held at a nominal temperature o 250 F (120 C),
and not exposed to the environment or at least nine hours.
For the A36 and A36 galvanized welds, 5/32-in.-diameter(3.9 mm), E7018-H4R electrodes were used to make 1/4 in.
(6 mm) llet welds in a single pass. The E70 designation
indicates a nominal tensile strength o 70 ksi (480 MPa)
or the weld metal. The H4 designation indicates that the
electrodes met the requirement o having less than 4 mL
(0.135 oz) average diusible hydrogen in 100 g (0.22 lb)
o deposited weld metal when tested in the as-received
condition. The R identies electrodes that pass the ab-
sorbed moisture test ater exposure to an environment o
80 F (26.7 C) and 80% relative humidity or a period o
at least nine hours.
One-eighth inch (3.2 mm) 308-16 electrodes were chosen
at the beginning o the study or the purpose o producing1/4 in. (6 mm) llet welds in a single pass on stainless steel
specimens. The weld size was measured ater the speci-
mens were sectioned, and the stainless steel welds were
ound to have a nominal size o3/16 in. (5 mm). This was
not the specied weld size but is acceptable or the 3/8 in.
(10 mm) plate thickness used according to AWS D1.1
Table 5.8. Rather than remake the specimens and welds,
all remaining stainless steel welds were made using 1/8 in.
(3 mm) electrodes, and data were analyzed with respect to
a3
/16 in. weld instead o a1
/4 in. (6 mm) weld.
Base metal and electrodes
The steel types in the experimental program include
ASTM A36 (nongalvanized), ASTM A36 galvanized, and
stainless steel Type 304. Fillet welds on three types o
A36 were examined, one with a moderate carbon content
(A36-1) and two with relatively high carbon content (HC1
and HC2). This variation allowed or an assessment o the
eect o carbon content on the potential or cracking. The
material originated rom three dierent manuacturers.
Mill certicates were obtained or each steel type and asample o each steel type was sent or independent chemi-
cal analysis. A spectrographic analysis was perormed on
each o the samples, and the results o the independent
analyses were compared with mill certicate values.
The sensitivity o the potential or cracking in the heat-
aected zone o the base metal to the steel carbon content
can be summarized using the Graville diagram (Fig.6).
Steel materials in zone I are unlikely to crack except when
high concentrations o hydrogen are introduced during
welding and the weld joint is highly restrained against
local deormation. Steel materials in zones II and III havea greater potential or cracking in the heat-aected zone,
which can be mitigated by using proper energy input
or preheat. The classication o steels presented in the
Graville diagram depends on both the carbon content and
the carbon equivalent (Fig. 6). All A36 steel materials used
in the project are in zone II, meaning that there is some
potential or cracking i proper energy input and/or preheat
is not used.
Standard welding electrodes typical o precast concrete
building erection were used in the experimental program.
For the A36 and A36 galvanized steel base plates, E7018-
Figure 5. Weld strength evaluation.
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Ater the welds were sectioned and polished, inspec-
tion was perormed on the cross sections with the naked
eye and a magniying glass, by measurements made on
photographs taken o the cross section, and by microscope.
Quantiable weld discontinuities were measured using a
magniying glass and digital caliper. The largest dimen-
sions o pores and inclusions were measured, and undercut
was quantied as the distance rom a line passing through
the original plate edge to the deepest point o the undercut
in the cross section. Discontinuities were urther investi-
gated under the microscope, measured when appropriate,
and recorded. The acceptability o the weld proles wasdetermined rom the cross-section photographs.
Experimental results
Effect of wind speed on weld profile
Examination o welds made under dierent wind speeds
(Fig.8) indicates that wind acting on the molten weld
pool results in ripples in the welds made under high wind
speeds. The eect is most noticeable or winds o 35 mph
(56 kph). Figure 8 shows that the eect was greater or
A36 steel than or stainless steel. In addition, the high
The welding setup involved the use o a constant current
welding power source. Grounding was provided directly to
the restraint clamp, which was in contact with the plates.
The energy input or the 1/4 in. (6 mm) welds on the plain
A36 steel plates ranged rom 33 kJ/in. to 48 kJ/in.
(13 kJ/cm to 19 kJ/cm). The energy input or welds on the
A36 galvanized plates ranged rom 41 kJ/in. to
48 kJ/in. (16 kJ/cm to 19 kJ/cm), and the energy input
or the smaller 3/16 in. (5 mm) welds on the stainless steel
plates ranged rom 30 kJ/in. to 33 kJ/in. (12 kJ/cm to
13 kJ/cm). The lower energy input or the stainless welds
refects the smaller electrode size and smaller weld sizesbecause less energy is required or smaller welds.
Evaluation procedure
Table 1 gives the environmental conditions under which the
welds were made. The welds were sectioned ater at least
24 hours to allow cracks to develop. The outer aces o the
center cut sections were polished with a 1200-grit grinding
surace, bued with a 0.3 m (0.0001 in.) particle solution,
and etched using an appropriate acid etching agent. The
nal product was a clean surace with a clear view o the
weld in cross section (Fig.7).
Figure 6. Graville diagram heat aected zone (HAZ) crack susceptibility. Note: C= carbon; Cr= chromium; Cu= copper; Mn= manganese; Mo= molybdenum;
Ni= nickel; Si= silicon; V= vanadium.
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wind caused the arc to behave erratically. Lowenburg et
al.10 reported in the context o pipeline abrication that
weld ailure can be initiated rom ripples on the weld sur-
ace, which underscores the importance o maintaining the
weld prole.
In all cases, the wind direction was perpendicular to the
longitudinal axis o the weld. High wind speed did not
cause any signicant prole skew in the sections exam-
ined. The sensitivity o wind direction on the weld was not
examined; however, it is hypothesized that head wind or
tail wind in the direction o the welding axis may have a
greater eect on the ormation o ripples and a lesser eect
on concavity. This hypothesis should be veried throughadditional experimentation.
Effect of wind speed
on slag inclusions
Figure9 plots the sum o the greatest dimensions o slag
inclusions on a cross section versus the wind speed under
which the weld was made. The temperature and humidity
are held constant or each data set. Linear trends o the
three data series conducted at 95% RH and three dierent
temperatures (-10 F, 32 F, and 71 F [-23 C, 0 C, and
22 C]) are presented. The 32 F condition (8 sections ex-
amined) has the highest correlation, ollowed by the 71 F
condition (12 sections examined). The -10 F condition (8
sections examined) shows no correlation; however, this is
attributed to the limited number o samples examined. In
all cases the linear t is poor.
Slag inclusions were observed regularly in the sections
taken rom the stainless steel specimens. In act, 62 o the
100 sections examined exhibited at least one inclusion.The presence and size o inclusions tended to increase
with wind speed, as was the case or the A36 specimens
(Fig. 9).
The majority o the slag was observed at the root o the
weld (Fig. 9). Three possible reasons or this are hypoth-
esized:
Figure 7. Specimen section procedure. Note: 1 mm = 0.0394 in.
Figure 8. Weld quality under various wind speeds. Note: 1 mph = 1.6 kph.
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Negative pressure caused by wind blowing over and
around plate suraces provides suction at the root o
the joint, trapping slag.
At higher speeds, the wind may push the slag ahead
o the molten weld metal pool, trapping the slag underthe advancing weld bead.
Higher wind speeds decrease the welding arc stability,
which infuences the uniormity o the molten weld
metal pool and results in slag inclusions.
Regardless o the cause, the sizes o the inclusions are well
below a level (about 5% cross-sectional area) that has an
eect on weld strength and are within the acceptability
limits rom AWS D1.1.
Effect of moisture on porosity
Porosity was observed and quantied in two ways. Surace
(piping) porosity was measured as the sum o the diameters o
surace pores or a 4-in.-long (100 mm) weld. Section porosity
was measured as the sum o the diameters o pores in a polished
cross section. Because the second method examines only two
discrete sections o the 4-in.-long welds made on each specimen,
the likelihood o sectioning through a pore is low. Consequently,
surace porosity is used to represent the porosity conditions.
It was expected that moisture would have the greatest e-
ect on porosity, as discussed earlier. Because welds are
oten made in the eld under wet conditions (or example,
rom alling rain), it was decided that attention should be
given to the cases o surace wetness. Six additional speci-
mens (specimens 36-PC1 through 36-PC6) were made with
wet surace conditions. For specimen 36-8, surace wetness
was created by misting the clamped plate assembly at theweld joint beore welding. Specimens 36-PC1 to 36-PC6,
were wetted beore laying the cover plate on top o the base
plates. Ater the cover plate was in place, the assembly was
urther moistened using a misting bottle, and in some cases,
pouring water over the plates until a pool o water was vis-
ible on plate suraces.
Figure10 plots the total surace porosity o welds made on
A36 steel and stainless steel against the conditions o the
plates and electrode. The plot includes 24 welds conducted
with dry electrodes on a dry A36 steel surace, 9 welds con-
ducted with dry electrodes on a wet A36 steel surace, 4 weldsconducted with moist electrodes on a dry A36 steel surace,
and 49 welds conducted with dry electrodes on a dry stainless
steel surace.
The moist electrodes generated the greatest surace poros-
ity, ollowed by the surace wet and dry conditions. The
surace wet conditions did not generate appreciable surace
porosity. For the wet conditions, initiation o the weld
was sometimes dicult, but once it was started, moisture
was driven o ahead o the welding arc. The dry welding
conditions or the A36 and stainless steel material did not
generate signicant porosity.
Figure 9. Inuence o wind on slag inclusions at 95% relative humidity. Note: 1 in. = 25.4 mm; 1 mph = 1.6 kph; C = (5/9)(F 32).
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in the cross sections. Furthermore, crack ormation in the
heat-aected zone (HAZ), though not observed, is related
to the presence o hydrogen; thereore, moisture should
be avoided. It is recommended that electrodes be used
according to manuacturer guidelines and AWS require-
ments and surace wetness, whenever practical, should be
eliminated using preheat. This preheat might not need to
match AWS D1.1 requirements. The goal is to drive o themoisture on plate suraces beore welding. In cases where
preheat is not practical, moisture should be wiped o with
a cloth.
Effect of environmental conditionson crack formation
Visual inspection o the suraces o welds made under
various conditions did not reveal any cracks longer than1/32 in. (0.8 mm). Following visual inspection, the welds
were sectioned and examined using an optical micro-
scope. For A36 steel specimens, cracks on the order o
All welds made under the various environmental condi-
tions met the surace porosity limits o AWS or statical-
ly loaded nontubular connections. The porosity observed
was less than the static connection limits but exceeded
the requirements or cyclically loaded welds. For this
case, the requency o surace porosity exceeded the
AWS limit o one in each 4 in. (100 mm) o weld length.
In precast concrete building system applications, lletwelds o the type investigated in this study are not typi-
cally subjected to high cycle atigue loading. However,
precast concrete members in bridge applications may be
subjected to high cycle atigue loading. In cases where
atigue is a concern, care should be taken to ensure that
the electrodes are dry.
The results indicate that surace wetness does not generate
unacceptably high surace porosity, while moist electrodes
generate greater but acceptable (or static loading) poros-
ity. Radiographic examination might, however, reveal
subsurace pores. Some subsurace pores were observed
Figure 10. Total surace porosity versus plate and electrode condition. Note: The area o the light-shaded circles in the plot represents the number o occurrences o a
given level o measured surace porosity. The dark-shaded circles and black bars represent the average level o surace porosity measured or the indicated plate and
electrode conditions. 1 in. = 25.4 mm.
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ing occurs rarely when the Vickers hardness is less than
265 HV (Vickers pyramid number) but is common when
the Vickers hardness approaches 470 HV i precautionsto prevent cracking are not taken.7 Preheat treatment is a
precaution against a high cooling rate that might promote
martensite ormation in the HAZ. The thermal mass o
the specimens used in the present study is relatively low;
thus, welding tends to heat the entire specimen, resulting
in a relatively slow cooling rate. Preheat treatment was
not used in this study.
Microhardness tests were perormed on ve specimens
(Fig.11). The approximate crack-susceptibility threshold
o 265 HV is indicated in the gure, as are the approximate
zones (weld metal, HAZ, and base metal) where readingswere taken or the tested specimens.
Figure 11 shows that the Vickers hardness o the speci-
mens is not sensitive to the ambient temperature but might
be sensitive to the carbon content. The variation in hard-
ness in the weld metal and HAZ region o the base metal
was similar or all specimens examined. The hardness was
highest in the HAZ at the interace with the weld metal.
At this location the hardness was closest to, but below, the
cracking-susceptibility threshold o 265 HV or all cases.
Elevated carbon content resulted in two o the three highest
hardness levels at the HAZ boundary. The weld made on
1/64 in. to1/16 in. (0.4 mm to 1.6 mm) long were observed
where the weld metal meets the HAZ and near the root
or toe o the welds, at discontinuities where the stressconcentration is high.
Crack ormation in welded joints is related to the hard-
ness o the HAZ. Cracking tends to occur in areas o
greater hardness where ductility is low and residual
stresses are high. Hardness measurements were made on
several specimens. The Vickers microhardness test was
used, which has the capacity to measure the hardness
across regions o the HAZ.7 The test is perormed using a
pyramid-shaped diamond indenter that is pressed into the
specimen with a given load or 10 seconds. The indenta-
tion is measured using a microscope, and the dimensionso the indentation are used to calculate the hardness on
the Vickers scale.
The hardness across the weld cross section is controlled
by the steel microstructure created during welding and
subsequent cooling. Depending on chemical composi-
tion and the thermal history o the weld metal and base
metal, including the carbon content and cooling rate o
the base metal, martensite can orm in the HAZ, increas-
ing hardness and susceptibility to cracking. The hard-
ness o the HAZ is a good indicator o the amount o
martensite present and susceptibility to cracking. Crack-
Figure 11. Plot o Vickers hardness rom microhardness tests. Note: 1 in. = 25.4 mm; C = (5/9)(F 32).
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Effect of environmental conditions
on weld strength
Five conditions were examined to determine the infuence
o environment on the weld strength. Each weld was per-
ormed on an ASTM A36 plate with no wind and with dry
electrodes. Temperature, humidity, and surace conditions
were varied. Table2 presents the details o the ve test
specimens abricated.
The maximum loads at ailure were recorded, and the
sections were examined orensically to assess whether any
unexpected ailure mode occurred. All ailures occurred in
the weld metal. The ailure was characterized by yielding
and signicant plastic deormation in the weld region ol-
lowed by racture on a plane approximately 45 rom theroot. Figure13 illustrates examples o ailure modes. Frac-
ture suraces were examined under an optical microscope
to determine whether any discontinuities were present that
may have infuenced their ultimate strength.
The nominal capacity was predicted in accordance with the
American Institute o Steel Constructions (AISCs) Steel
Construction Manual11 ormulation or strength o a llet
weld in transverse tension (Eq. [1]). The nominal capac-
ity was computed with the nominal electrode strength
and with measured electrode strength. For both cases,
the measured throat and weld length were used. Becausemeasured values were used, no strength reduction actors
are included.
P = FT(2l)(1.5) (1)
P = nominal tensile strength
F = tensile strength o the weld metal
T = minimum throat thickness
l = weld length
moderate carbon content base metal at room temperature
produced the second highest hardness level.
The welds made on higher carbon steel, namely speci-
mens 36-C1 and 36-C2, while having slightly higher peak
values (10% on average compared with moderate carbon
samples), did not approach hardness levels that indicate
that the HAZ is crack susceptible. The study used ratherthin plates (3/8 in. [10 mm]). A thicker plate would produce
an increased cooling rate due to its greater thermal mass.
Contact with a thick concrete slab would also promote
more rapid cooling, but the eect o the concrete mass on
the cooling rate would be less than that o a thicker steel
plate.
The occurrence o root microcracks was not aected by en-
vironmental conditions. Root microcracking was observed
in 15 sections (three sections rom 36-C2; two sections
rom 36-8, 36-23, 36-C1, and 36-PC6; and one section
rom 36-1, 36-14, 36-22, and 36-17HR[1]). These speci-
mens were welded in temperatures ranging rom 74.2 F
to -13 F (23.4 C to -25 C), 41% RH to 100% RH, wind
speeds rom 0 mph to 27 mph (0 kph to 43.5 kph), with dry
and wet electrodes, and with dry and wet surace condi-
tions. The root microcracking observed was widespread
among specimens with no apparent correlation to any
specic environmental conditions.
The eect o surace wetness on crack ormation was
examined in specimen PC-6. This specimen was abricated
with surace water present at a temperature o 74.2 F
(23.4 C), 17.6% RH, and under a 0 mph (0 kph) wind
condition. The specimen was restrained or 24 hours inthe concrete test block beore removal. Four sections were
taken rom the specimen, and two o them were observed
to have microcracks. One o the sections had microcracks
through a slag inclusion near the root. Another section had
root microcracks, as well as toe microcracks. Although
only these our sections rom a single specimen were stud-
ied, it appears that surace wetness may aect the poten-
tial or cracking. Thus, welding over surace wetness is a
concern because the moisture might increase the presence
o dissolved hydrogen in the microstructure and increase
the potential or cracking.
Microcracks were more numerous when discontinuities
such as slag inclusions were present. These local discon-
tinuities can generate a high stress concentration resulting
in cracking through the inclusion (Fig. 12). This cause
o cracking is important because those actors contribut-
ing to slag inclusions, even i the inclusions are small and
acceptable, can contribute to microcracking. Other discon-
tinuities, such as porosity or undercut, can also serve as
initiation points or microcracks.
Figure 12. Root o specimen T-3.
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results, the tensile strength was not aected by any o the
environmental conditions examined. Furthermore, the AISC
ormulations or strength conservatively estimate strength
when the nominal strength o the ller metal is used.
One ailure surace was urther examined under a scanning
electron microscope, and an image taken with this mi-
croscope revealed the ductile nature o the shear racture.
Figure14 shows a high-magnication secondary electron
image o the ductile shear racture surace. The surace is
composed o regions shaped like elongated ovals, each o
which surrounds a small inclusion, appearing as a whitedot in the image. These microvoids elongate and coalesce
under shear loading as the weld metal deorms plastically
to orm a ductile shear ailure surace. The small slag
inclusions are well below a size that would have any eect
on weld strength and are only detectable at a level o mag-
nication such as that in the secondary electron image.
Two values are used or F: the nominal weld metal strength
FEXX, 70 ksi (480 kN), and the ultimate tensile strength as
determined rom Rockwell B hardness measurements FUTS.
A minimum o our hardness measurements were taken
and averaged to determine the tensile strength o the weld
metal. The minimum throat thickness Tand weld length
l were measured or each weld. Because the weld length
is or only one side, a multiplier o 2 is included in the
ormulation. Table 2 presents the hardness measurements,
ultimate tensile strength, and length and throat dimensions
or all o the test specimens.
The limited study indicated that the weld strength is not a-
ected by variations in temperature or humidity. The measured
strength exceeded the predicted strength, computed using the
nominal weld metal strength, by an average o 30%. When the
measured weld tensile strength was used, the AISC ormula-
tion predicted the tensile strength within 10%. Based on these
Table 2. Strength performance of welds
Sp
ecimen
Ba
semetal
Platesurfacecondition
Temperature,
F
Re
lativehumidity,
%
Th
roatsize,
in.
Av
eragehardness,
Ro
ckwellB
Estimatedtensile
str
engthF
UTS,
ksi
PredictedF
EXX
capacity,kip
PredictedF
UTS
capacity,kip
Me
asuredstrength,
kip
FactorofsafetyforF
EXX
FactorofsafetyforF
UTS
T-1 A36-1 Dry 84.0 15.4 0.186 92.0 92.0 23.4 30.8 33.1 1.41 1.07
T-2 HC2 Dry 77.9 26.4 0.215 89.7 88.7 26.9 34.1 33.8 1.26 0.99
T-3 HC2 Dry -15.4 73.0 0.244 87.1 84.2 32.4 38.9 42.8 1.32 1.10
T-4 HC1 Wet 72.0 32.3 0.195 90.4 89.4 24.8 31.7 30.2 1.22 0.95
T-5 HC2 Wet 72.7 19.3 0.215 87.9 85.8 26.3 32.3 35.1 1.33 1.09
Note: FEXX = nominal weld metal strength; FUTS = ultimate tensile strength as determined from Rockwell B hardness measurements.
1 in. = 25.4 mm; 1 kip = 4.448 kN; 1 ksi = 6.895 MPa; C = (5/9)(F 32).
Figure 13. Failure modes or tension tests o specimen T-1 and specimen T-5.
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generally be used or galvanized steel or the SMAW pro-
cess. The document notes that slower travel speeds and a
whipping action o the electrode should be used to volatil-
ize as much o the zinc coating as possible and avoid its in-
troduction into the molten weld pool. The issue o welding
through zinc galvanization, however, does not appear to
be settled when considering research, current practice, and
codication surrounding the issue. Problems with arc sta-
bility may be encountered by welding through the irregular
zinc coating and generating vapors. The zinc coating, when
vaporizing, can create porosity i gases become trapped in
the weld joint between two coated suraces. In addition, i
zinc is present in solution in the molten weld pool, it could
create a cracking hazard as metal cools around the lower
melting point zinc compounds and restrains their cooling
contraction, orming tears in the weld metal.
The proles o the welds made through the galvanized
coatings tended to have a higher rate o unacceptability
than those welded on nongalvanized carbon steel in the
study. Fourteen out o the sixteen sections examined, or87.5%, ailed to meet the prole acceptability criteria. This
may be a unction o poor arc stability or low visibility
when the galvanization is vaporized. Microcracking was
observed at a higher percentage in galvanized specimens
compared with nongalvanized specimens. In addition, a
solidication crack was detected by visual observation
unaided by microscopy on one specimen. The crack was
located at the root o a section taken rom specimen 36G-
17HR (77.3 F [25.2 C], wet electrode, 4 mph [6.4 kph]
wind).
The welds made through galvanization were ree romporosity both on the weld suraces and in cross sections.
Only one o the 16 sections exhibited a small (0.008 in.
[0.2 mm]) slag inclusion. Two sections exhibited undercut,
and one example o undercut exceeded the 1/32 in. (0.8 mm)
limit set orth in AWS D1.1. The relative lack o discon-
tinuities in the sections examined indicates that welding
through the galvanizing might not have a great eect on
porosity or slag inclusions. Due to the small sample size,
urther study o welding through zinc coatings and more
thorough nondestructive evaluation o such welds is neces-
sary beore drawing a conclusion.
Effect of weldingthrough galvanized steel
Two welds were conducted under the ambient outdoor en-
vironmental conditions typical o winter in Pennsylvania.
The conditions at the time o welding were 37 F (2.8 C),
30% RH, 0 mph (0 kph) wind. Two specimens were
welded to compare results between welds and because the
conditions outdoors were suciently cold to replicate a set
o conditions rom the test matrix. To assess the eect o
moist electrodes on the galvanized steel, a specimen was
welded using E7018-H4R electrodes that had been exposed
to a moist environment or approximately 17 hours, result-
ing in electrode moisture content near 4.0% by weight.
Welding through a galvanized plate is prohibited by current
codes, including AWS D1.1 and the PCI Design Hand-
book: Precast and Prestressed Concrete.12 Removal o
galvanizing in the area o the weld joint is recommended.
Removal is oten accomplished by grinding or burning.
Because welding through galvanizing is prohibited andgenerates a health hazard by creating zinc oxide umes,
only a small sample was examined in this study. Additional
tests are required to generate denitive conclusions. A PCI
survey13 reports that 70% o reporting PCI Producer Mem-
bers remove galvanizing on plates beore welding, and
73% remove galvanizing on reinorcement beore weld-
ing. In addition, 63% o the respondents have developed
an associated welding procedure specication or welding
galvanized components.
Welding through a hot-dip galvanized zinc coating requires
the volatilization o the zinc coating as the electrode passesalong the weld joint. The melting point o zinc, the primary
component o hot-dip galvanized coatings, is approxi-
mately 788 F (420 C), and the temperature at which zinc
vaporizes is approximately 1665 F (907 C). The melting
point o steel is approximately 2500 F (510 C), and the
temperature o an arc in the SMAW process can be as high
as 10,500 F (5800 C). As a result, it is possible that some
o the zinc coating is vaporized as the arc approaches.
Sperko14 reported that it is possible to weld through a
galvanized coating without aecting weld strength. The
AWS D19.0 document Welding Zinc-Coated Steel15 also
reports that the same practices used or uncoated steel can
Figure 14. Weld ailure surace magnifcation. Note: 1 mm = 0.0394 in.
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Research findings
Wind tends to produce rippling o the molten weld
pool and poor proles. Increases in wind speeds tend
to increase the presence and severity o slag inclu-
sions, but not beyond AWS acceptability up to 35 mph
(56 kph).
Undercut was observed in several specimens but
does not appear to correlate strongly with a specic
environmental parameter. All observed undercut was
within the AWS limit o1/32 in. (0.8 mm).
Porosity increases when the electrodes used are ex-
posed to a moist environment beyond AWS D1.1 code
recommendations (nine-hour exposure limit to moist
environment).
Surace porosity is not signicantly aected by weld-
ing through surace wetness. Welding through suracewetness has the potential to increase microdiscontinu-
ities and create visible cracking and should be urther
investigated. Cracking as a result o welding through
surace wetness merits urther investigation. In addi-
tion, subsurace porosity was generated in the case o
the surace wet specimen T-5 but did not reduce the
strength o the specimen.
Microcracking was widely observed and was more
prevalent in specimens welded using higher carbon
plate material. The presence o these microcracks was
not correlated with environmental conditions.
Poor t-up o plates as a result o the rough galvaniza-
tion coating can contribute to root cracks where large
plate gaps exist. Microcracking was observed at a
higher percentage in galvanized specimens compared
with nongalvanized specimens. Few discontinuities
were observed in the sections made on galvanized
welds, indicating that the galvanized coating does not
signicantly increase porosity or slag inclusions.
Surace porosity was more widely observed in welds
made on stainless steel plate than on carbon steel plate
A problem that arises rom welding galvanized plates
is that the gap between the base plates and cover plate
appears susceptible to cracking at the root o the weld. Be-
cause hot-dip galvanized coating is inherently irregular and
creates a plate surace that is not smooth, large gaps result.
The poor t between plates produces inclusions or voids at
the root, which can lead to microcracks (Fig.15).
Based on the limited results obtained in the study, urther
research is recommended beore conclusions can be drawn
on the susceptibility to cracking and discontinuities in
welds made through galvanized coatings on A36 plates.
I weld quality is a concern, the procedures o the Ameri-
can Galvanizers Association can be ollowed, namely,
the removal o galvanic coatings 1 in. to 4 in. (25 mm to
100 mm) away rom the weld joint beore welding.
Conclusions andrecommendations
The research examined the infuence o wind, temperature,
humidity, and moisture on the integrity o welded connec-
tions used in precast concrete construction. The conclu-
sions and recommendations are limited in application to
the scope o the research study and may not be applicable
to variables beyond those examined. The bounds o the
study include:
single-pass llet welds made with the SMAW process
low-hydrogen electrodes (E7018-H4R) or ASTM A36
steel
308-16 electrodes or Type 304 stainless steel
plate thicknesses o3/8 in. (10 mm)
plate sizes typical o precast concrete connections on
the order o 4 in. 6 in. (100 mm 150 mm)
static loading
Figure 15. Root gap and microcracks in galvanized specimens. Note: 1 mm = 0.0394 in.
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Wind High wind speed had a negative eect on the prole
and surace geometry o the welds and increased the pres-
ence o slag inclusions. The amount o slag included, how-
ever, was below AWS limits. In addition, successul SMAW
welds were made in wind up to 35 mph (56 kph). I the cor-
rect weld prole and good weld surace conditions can be
achieved by a welder in a high-wind condition, then weld-
ing should be permitted. The resulting prole must be veri-ed in accordance with the details set orth in AWS D1.1.
Strength The welds that were evaluated or strength
perormed adequately and predictably. There was no
appreciable reduction in strength or welds exhibiting dis-
continuities o the type and severity seen in the orensic
examination. Design codes are conservative with regard to
the prediction o strength or 1/4 in. (6 mm) llet eld welds
made with the SMAW process.
Recommendationsfor precast concrete construction
Based on the results presented in this report, 1/4 in.
(6.3 mm) llet welds made on 3/8-in.-thick (9.5 mm)
A36 base plates using E7018-H4R electrodes and 3/16 in.
(4.8 mm) llet welds made on 3/8-in.-thick Type 304
stainless steel base plates using E308-16 electrodes can
be perormed under any o the ollowing environmental
conditions as long as the welder is able to create a weld
meeting the AWS acceptability criteria:
wind up to 35 mph (56 kph)
ambient temperature o 0 F (-18 C) and above with-out preheat treatment
relative humidity up to 100%
SMAW electrodes should be stored, handled, and used in
accordance with manuacturer guidelines and AWS D1.1
and D1.6 requirements. Failure to ollow these require-
ments might result in excess porosity and crack orma-
tion in the weld. Due to limitations o the study, welding
through surace wetness or in alling rain is not recom-
mended. Excess moisture should be removed rom the base
metal beore welding.
All o the ambient environmental conditions will have a
direct eect on the welder and might decrease his or her
ability to successully deposit a weld. Furthermore, skill
level varies among welders; thereore, it is imperative that
welders operate within their abilities. This may require the
abrication o a wind shield or covered structure in certain
environmental conditions.
but was acceptably low in all cases. Few microcracks
were observed in stainless steel specimens. Micro-
cracking was not correlated with any environmental
parameter.
The transverse shear strength o llet welds made with
the SMAW process on A36 plates was not sensitive
to the environmental conditions studied and was ac-curately approximated using the AISC ormulations.
Microcracking o the size and shape observed in the
specimens did not have a signicant eect on weld
strength.
Research conclusions
The ollowing conclusions are derived rom the results o
the research and relate to the eect o environmental condi-
tions on the quality o welds simulating the welds used in
precast concrete construction.
HumidityAmbient humidity is not correlated with the
presence o weld discontinuities. High humidity increases
the presence o hydrogen in the vicinity o the weld; how-
ever, it was not ound to aect the quality o the welds. The
exposure o electrodes to humid conditions, however, did
aect weld quality, increasing the potential or porosity
and cracking. The guidelines and restrictions in AWS D1.1
regarding exposure o electrodes should be closely ol-
lowed.
Surface wetness Welds made on wet plates did not
exhibit greater surace porosity. The moisture was driven
away rom the weld joint as the weld metal was deposited.Welding through surace wetness also has the potential to
increase microcracking and create visible cracking and
should be urther investigated. The eect o moisture in the
orm o alling rain entering the weld pool was not studied,
and this condition should be examined urther. Until such
research is perormed, it is recommended that welding not
be perormed when the weld pool is subject to alling pre-
cipitation and, whenever possible, that surace moisture be
eliminated rom the plate suraces beore welding.
Temperature Temperatures as low as -13 F (-25 C)
were examined and ound to have no eect on porosityor slag inclusions. Low temperatures have a tendency to
increase cooling rates, increasing the propensity or high
hardness and crack ormation. The hardness levels mea-
sured in the specimens, however, were below a level that
would increase the propensity or cracking. Microcracks
were observed in welds made over a variety o temperatures
and are more sensitive to base metal composition, restraint,
and hydrogen present than the ambient temperature during
welding.
7/28/2019 JL-12-SPRING-14
19/20Spr ing 2012 |PCI Journal0
13. PCI. 2006. Survey Results on the Use o Galvanizing
or Precast Concrete Structures. PCI Journal, V. 51,
No. 4 (JulyAugust): pp. 106110.
14. Sperko Engineering Services Inc. 1999. Welding Gal-
vanized SteelSaely. www.sperkoengineering.com/
html/articles/WeldingGalvanized.pd (accessed July 7,
2011).
15. Bland, Jay, and AWS Technical Department. 1972.
Welding Zinc-Coated Steel. AWS WZC/D19.0-72.
Miami, FL: AWS.
Notation
F = ultimate tensile strength o the weld metal
FEXX = nominal weld metal strength
FUTS = ultimate tensile strength as determined rom Rock-
well B hardness measurements
l = weld length
P = nominal strength o connection
T = minimum throat thickness
References
1. PCI Details Committee. 2008. PCI Connections
Manual or Precast and Prestressed Concrete Con-
struction. MNL 138-08. 1st ed. Chicago, IL: PCI.
2. American Welding Society (AWS) Committee on
Structural Welding. 2008.Structural Welding Code
Steel. AWS D1.1/D1.1M:2008. Miami, FL: AWS.
3. AWS Committee on Structural Welding. 2007.
Structural Welding CodeStainless Steel. AWS D1.6/
D1.6M:2007. Miami, FL: AWS.
4. ASTM Subcommittee A01.02. 2005.ASTM A36/
A36M-08 Standard Specifcation or Carbon Struc-
tural Steel. doi:10.1520/A0036_A0036M-08, www
.astm.org/Standards/A36.htm. West Conshohocken,
PA: ASTM International.
5. American Petroleum Institute (API). 1980. Welded
Steel Tanks or Oil Storage. 7th ed. Washington, DC:
API.
6. Zimper, J., C. Naito, R. Sause, and E. Kaumann.
2008.Investigation o the Impact o Environmental
Conditions on Field Welding o Precast Concrete
Connections. ATLSS report no. 07-03. Bethlehem, PA:
Lehigh University.
7. Conner, L. P. 1987. Welding Handbook: Welding Tech-
nology. 8th ed. V. 1. Miami, FL: AWS.
8. Lundin, C. D. 1984. Fundamentals o Weld Discon-
tinuities and Their Signifcance. Welding Research
Council (WRC) bulletin 295. New York, NY: WRC.
9. Lundin, C. D. 1976. The Signifcance o Weld Dis-
continuitiesA Review o Current Literature. WRC
bulletin 222. New York, NY: WRC.
10. Lowenburg, A. L., E. B. Norris, and A. R. Whit-
ing. 1968.Evaluation o Discontinuities in Pipeline
Weld JointsSummary Report No. 1. Pressure Vessel
Research Committee o WRC, Southwest ResearchInstitute, San Antonio, TX.
11. American Institute o Steel Construction (AISC)
Committee on Manuals and Textbooks. 2005. Steel
Construction Manual. 13th ed. Chicago, IL: AISC Inc.
12. PCI Industry Handbook Committee. 2004. PCI Design
Handbook: Precast and Prestressed Concrete. MNL-
120. 6th ed. Chicago, IL: PCI.
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About the authors
Clay Naito is an associateproessor or the Department o
Civil and Environmental Engi-
neering at Lehigh University in
Bethlehem, Pa.
Jason Zimper, MSCE, is a ormer
graduate research assistant or
Lehigh University. He is currently
a structural engineer at AECOM
in Horsham, Pa.
Richard Sause is the ATLSS direc-
tor and Joseph T. Stuart Proessor
o Structural Engineering or
Lehigh University.
Eric Kaumann is a senior
research scientist or the ATLSS
Research Center at Lehigh
University.
Abstract
A research study was conducted to investigate the
quality o welded connections between precast
concrete components made under environmental
conditions typically encountered in precast concrete
construction. The eects o wind, humidity, tempera-
ture, and surace moisture on the quality o shielded
metal arc welds (SMAWs) were examined. The study
ocused on ASTM A36 Type 304 stainless steel and
ASTM A36 galvanized steel plates. Weld suraces andcross sections were examined visually and with optical
microscopy. The results o the examinations were com-
pared with limits or various weld discontinuities in
accordance with American Welding Society specica-
tions D1.1 and D1.6. In addition, tests were perormed
to assess the impact o environmental conditions on
strength. The results showed that good quality SMAW
welds can be made in wind up to 35 mph (56 kph), in
temperatures as low as -10 F (-23.3 C), and under
wet conditions. In general, acceptable welds were
abricated under the variety o environmental condi-
tions examined. Various types o discontinuities were
observed but were not ound to cause a signicant
reduction in the transverse shear strength o the welds.
Keywords
Connection, humidity, temperature, welding, wind.
Review policy
This paper was reviewed in accordance with the
Precast/Prestressed Concrete Institutes peer-review
process.
Reader comments
Please address any reader comments to journal@pci.
org or Precast/Prestressed Concrete Institute, c/o PCI
Journal 200 W. Adams St., Suite 2100, Chicago, IL
60606. J
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