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1/20Spr ing 2012 |PCI Journal2

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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2/20 14PCI Journal|Spr ing 2012

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-76 Stainless steel 304 71.4 100.0 5.1 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-92 Stainless steel 304 -2.2 95.5 5.5 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.

7/28/2019 JL-12-SPRING-14


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.

7/28/2019 JL-12-SPRING-14


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.

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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.

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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

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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.

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