AISC Bolting and Welding

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IntroductionThis presentation was developed as a teaching aid with the support of theAmerican Institute of Steel Construction. Its objective is to provide technicalbackground and information for bolting and welding. The information

id d i b d d i d t ti ti fprovided is based on common design and construction practices forstructures of twelve stories or less.

The AISC Digital Library case study presentations document the constructionThe AISC Digital Library case study presentations document the constructionof a steel frame for an office building. The case study includes photographsthat were taken throughout the construction of the structural steel frameincluding detailing fabrication and erection Project data including plansincluding detailing, fabrication, and erection. Project data including plans,schedules, specifications and other details are also included. The case studypresentations are available in the Learning Opportunities section atwww aisc orgwww.aisc.org.

This presentation provides technical information on bolting and welding, aswell as the impacts of details and design choices on schedule, cost,well as the impacts of details and design choices on schedule, cost,sequence and overall project management.

The information is presented with concerns of a construction manager or

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p ggeneral contractor in mind.

What Will You Gain From This P t ti ?Presentation?

• General knowledge of structural steel

A d t di f th diff t th t t t l t l i t d• An understanding of the different ways that structural steel is connected

• Insight into types of bolts and their installation

• An awareness of types of bolted joints used for structural steel

• Knowledge of welding terminology, weld types, and welding processes

• Familiarity with common weld inspection methods and considerationsassociated with field welding

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Benefits of Structural Steel

Some benefits associated with use of structural steel for owners are:

• Steel allows for reduced frame construction time and the ability to constructin all seasons

• Steel makes large spans and bay sizes possible, providing more flexibility forownersowners

• Steel is easier to modify and reinforce if architectural changes are made to afacility over its life

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• Steel is lightweight and can reduce foundation costs

• Steel is durable, long-lasting and recyclable (AISC 1999)

Unique Aspects of Steel Construction

Procurement and management of structural steel is similar to other materials,but there are some unique aspects to steel construction:• Steel is fabricated off-site (above left)

• On-site erection is a rapid process (above right)

• This gives use of structural steel some scheduling advantages

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• Coordination of all parties is essential for achieving potential advantages

(AISC 1999)

Connecting Structural Steel

• The primary connection methods for structural steel are bolting and welding

• A structure’s strength depends on proper use of these connection methods

• Connections made in a fabrication shop are called shop connections

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• Connections made in the field by the steel erector are called field connections

• Bolting and welding may be used for shop connections and field connections

Connecting Structural Steel

• A fabrication shop will have a desired fastening method suited to its equipmentand fabrication methods

• Field connections are typically bolted

• Welding may be used for field connections where bolting is either impractical orndesirable

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undesirable

• Welding is better suited to the controlled environment of a fabrication shop

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Structural Bolting

• The Research Council on Structural Connections (RCSC) preparesThe Research Council on Structural Connections (RCSC) preparesspecifications and documents related to structural connections

• RCSC’s Specification for Structural Joints Using ASTM A325 or A490 Bolts(2000) is a widely used specification which discusses joints fasteners limit

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(2000) is a widely used specification which discusses joints, fasteners, limitstates, installation, and inspections

Structural Bolting

• During hoisting, connectors will install a minimum of two bolts per connection

• The rest of the bolts are installed and tightened after the structure is plumbed

• A systematic pattern must be followed when tightening bolts so that a joint is

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drawn together and all fasteners are properly installed

(SSTC 2001)

Structural Bolting

Per the Occupational Safety & Health Administration Standard 1926.754(b)(2), “Atno time shall there be more than four floors or 48 feet (14.6 m), whichever is less,

f fi i h d b lti ldi b th f d ti t tl

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of unfinished bolting or welding above the foundation or uppermost permanentlysecured floor, except where the structural integrity is maintained as a result of thedesign.”

Structural Bolting

(AISC & NISD 2000)

• There are many bolt types, installation methods, and joint types used instructural steel construction

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• When left exposed, bolts may be used to make an architectural expression

(Green, Sputo, and Veltri)

ASTM Bolt Types

(AISC & NISD 2000)

• A307 – Low carbon steel

Not commonly used Not commonly used

Only used for secondary members

• A325 – High-strength medium carbon steel (above left)A325 High strength medium carbon steel (above left)

Most common bolts used in building construction

• A490 – High-strength heat treated steel (above right)

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Cost more than A325’s, but are stronger so fewer bolts may be necessary

• Note that the ASTM designation is indicated on the head of the bolts above

Common Bolt Sizes

• A325 and A490 bolts are available in diameters ranging from 1/2” to 1-1/2”

• The most common sizes are 3/4”, 7/8”, and 1”

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• High-strength bolts are commonly available in incremental lengths up to 8”

(AISC)

Washers

• Hardened steel washers are used in many structural connections to spreadpressure from the bolt tightening process over a larger area

• Washers may also be used to cover an oversized or slotted hole (RCSC 2000)

• Flat washers are most commonly used

• Tapered washers (above left) are used when the surface being bolted has asloped surface, such as the flange of a channel or an S shape

• A325 bolts require a washer under the element (head or nut) being turned to

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A325 bolts require a washer under the element (head or nut) being turned totighten the bolt (shown under the nut, above right)

• A490 bolts require a washer under both the head and nut (AISC & NISD 2000)

Parts of the Bolt AssemblyGrip Washer

NutWasher Face

Grip

Shank ThreadHead

Thread

Length

• Grip is the distance from behind the bolt head to the back of the nut or washer

It is the sum of the thicknesses of all the parts being joined exclusive of It is the sum of the thicknesses of all the parts being joined exclusive ofwashers

• Thread length is the threaded portion of the bolt

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• Bolt length is the distance from behind the bolt head to the end of the bolt

(AISC & NISD 2000)

Bolted Joint Types

• There two basic bolted joint types:

Bearing

o The load is transferred between members by bearing on the bolts

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Slip-critical

o The load is transferred between members by friction in the joint

Bolted Joint Failure Modes

BearingB i Bearing Bearing Fracture

Bearing Yield

Bearing Fracture

Bearing Yield

• Bolts in bearing joints are designed to meet two limit states:

Yield

1. Yielding, which is an inelastic deformation (above left)

2. Fracture, which is a failure of the joint (above left)

Th t i l th b lt b i t i l bj t t i ldi f t if it i• The material the bolt bears against is also subject to yielding or fracture if it isundersized for the load (above right)

• Tension connections act similarly to bearing connections

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y g

Many times, connections in direct tension are reconfigured so that the boltsact in shear (AISC)

Bearing Joints

• In a bearing joint the connected elements are assumed to slip into bearingagainst the body of the bolt

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against the body of the bolt

• If the joint is designed as a bearing joint the load is transferred through bearingwhether the bolt is installed snug-tight or pretensioned (AISC)

Th h l i th l

Threads in the Shear Plane• The shear plane is the plane

between two or more piecesunder load where the piecestend to move parallel fromtend to move parallel fromeach other, but in oppositedirections

• The threads of a bolt mayeither be included in theshear plane or excluded

Threads Included In The Shear Planefrom the shear plane

• The capacity of a bolt isgreater with the threads

Threads Included In The Shear Plane

g eate t t e t eadsexcluded from the shearplane

• The most commonly used• The most commonly usedbolt is an ASTM A325 3/4”bolt with the threadsincluded in the shear plane

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included in the shear plane

(AISC & NISD 2000)Threads Excluded From The Shear Plane

Slip-Critical Joints

• In a slip-critical joint the bolts must be fully pretensioned to cause a clampingforce between the connected elements

• This force develops frictional resistance between the connected elements

• The frictional resistance allows the joint to withstand loading without slippinginto bearing against the body of the bolt, although the bolts must still be

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into bearing against the body of the bolt, although the bolts must still bedesigned for bearing

• The faying surfaces in slip-critical joints require special preparation (AISC)

When to Use Slip-Critical Joints

Per the RCSC Specification (2000), Slip-critical joints are only required in thefollowing applications involving shear or combined shear and tension:1. Joints that are subject to fatigue load with reversal of the loading direction

(not applicable to wind bracing)

2 J i t th t tili i d h l2. Joints that utilize oversized holes

3. Joints that utilize slotted holes, except those with applied load approximatelyperpendicular to the direction of the long dimension of the slot

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p p g

4. Joints in which slip at the faying surfaces would be detrimental to theperformance of the structure

Snug-tight Installation

Snug-tight is the tightness attained with a few hits of an impact wrench or the fulleffort of an ironworker using an ordinary spud wrench to bring the connected plies

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g y p g pinto firm contact

(RCSC 2000)

Turn-of-Nut Installation

• Installation beyond snug-tight is called pretensioning

• Turn-of-nut pretensioning involves several steps:p g p

1. The bolt is snug-tightened

2. Matchmarks are placed on each nut, bolt, and steel surface in a straight linep g

3. The part not turned by the wrench is prevented from turning

4. The bolt is tightened with a prescribed rotation past the snug-tight condition

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• The specified rotation varies by diameter and length (between 1/3 and 1 turn)

(RCSC 2000, AISC)

Calibrated Wrench Installation

• Calibrated Wrench pretensioning uses an impact wrench (above left) to tightenth b lt t ifi d t ithe bolt to a specified tension

• A Skidmore-Wilhelm calibration device (above right) is used to calibrate theimpact wrench to the torque level which will achieve the specified tension

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p q p

• A sample of bolts representative of those to be used in the connections aretested to verify that the correct tension will be achieved (RCSC 2000, AISC)

ASTM F1852 Installation(AISC)

• F1852 bolts are twist-off-type tension-control bolts

• These bolts must be pretensioned with atwist-off-type tension-control bolt installationwrench that has two coaxial chucks

• The inner chuck engages the splined end ofthe bolt

The o ter ch ck engages the n t• The outer chuck engages the nut

• The two chucks turn opposite to oneanother to tighten the bolt

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• The splined end of the F1852 bolt shearsoff at a specified tension (AISC 2003)

ASTM F959 Direct Tension IndicatorsDTI’sDTI s

• Another way to try to ensure proper pretensioning of a bolt is through the use ofdi t t i i di t (DTI )

Feeler Gages

direct tension indicators (DTIs)

• These washers have protrusions that must bear against the unturned element

• As the bolt is tightened the clamping force flattens the protrusions and reduces• As the bolt is tightened the clamping force flattens the protrusions and reducesthe gap

• The gap is measured with a feeler gage

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• When the gap reaches the specified size the bolt is properly pretensioned

(AISC & NISD 2000)

Installation of DTIs

(Adapted from Figure C 8 1 RCSC 2000)

It is essential that direct tension indicators be properly oriented in the assembly

a) The bolt head is stationary while the nut is turned DTI under bolt head

(Adapted from Figure C-8.1 RCSC 2000)

a) The bolt head is stationary while the nut is turned – DTI under bolt head

b) The bolt head is stationary while the nut is turned – DTI under nut (washer required)

c) The nut is stationary while the bolt head is turned – DTI under bolt head (washer required)

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d) The nut is stationary while the bolt head is turned – DTI under nut

(RCSC 2000)

Nominal Bolt Hole Dimensions

• Bolts are installed in one of four types of holes (see table above)(Table 3.1 RCSC 2000)

• Standard holes can be used anywhere

• Oversized holes may only be used in slip-critical connections

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• Short-slotted holes are used with the slot perpendicular to the direction of stress

• Long-slotted holes are primarily used when connecting to existing structures

Equipment Requirements

• Common tools used by Ironworkers include spud wrenches, pins, andcorrections bars of various sizes (above left)corrections bars of various sizes (above left)

• Impact wrenches will be needed for certain installations (above center)

• Electricity or compressed air is required depending on the impact wrench being

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Electricity or compressed air is required depending on the impact wrench beingused

A generator as well as an air compressor may be needed (above right)

Storage of Components

Per the RCSC Specification:

• Fastener components must be protected from dirt and moisture in closedcontainers on the jobsite

O l f t ti i t d t b i t ll d d i th k hift t b t k• Only fasteners anticipated to be installed during the work shift are to be takenfrom protected storage

• Protected storage is defined as the continuous protection of fastener

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g pcomponents in closed containers in a protected shelter

• Any unused fasteners must be promptly returned to protected storage

Storage of Components

Th l b i ti f t i it l t th i i t ll ti• The lubrication on fasteners is vital to their proper installation

• A water-soluble oil is used on most black bolts

This oil is easily washed off when exposed to moisture• This oil is easily washed off when exposed to moisture

• Fasteners that accumulate rust or dirt must be cleaned and relubricated beforethey may be installed

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• F1852 bolts (shown above) shall not be relubricated, except by themanufacturer (RCSC 2000, SSTC 2001)

Storage of Galvanized Fasteners

• Galvanized bolts and nuts (above) are provided by the supplier in a set andGa a ed bo ts a d uts (abo e) a e p o ded by t e supp e a set a dspecial storage requirements

• Each bolt/nut set is pretested by the supplier and shipped together and must bekept together as an assemblykept together as an assembly

• Poor thread fit may result if the bolt and nut are mismatched

• The lubrication on galvanized fasteners is generally more durable than that on

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• The lubrication on galvanized fasteners is generally more durable than that onblack bolts, but protected storage is still recommended

• A490 bolts are not allowed to be galvanized (SSTC 2001)

Production Lots

• Production lot traceability is required by many standards

• Even if not required, it is good practice to record the lot numbers and keep allfasteners separated by lotfasteners separated by lot

• It is necessary to keep lots separate for proper pre-installation verificationtesting which is required for pretensioned and slip-critical joints

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• Mixing bolts and nuts from different production lots is not permitted

(SSTC 2001)

Inspections

• In addition to the erector’s quality control program, tests and inspection arespecified by the Engineer of Record and/or the local building authority

• A local building inspector may request that tests in addition to those specifiedA local building inspector may request that tests in addition to those specifiedby the Engineer of Record be performed

• Snug-tightened joints require visual inspection for firm contact and proper usef hof washers

• Pretensioned joints require pre-installation verification and routine observationof proper application

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p p pp

• Slip-critical joints require inspection of the faying surfaces in addition to theabove inspections

Inspections for the Construction Manager

There are several bolted connection inspections a construction manager canp gperform:• Look at the bolt stick-out (above)

Sti k t i th t th b lt t d b d th t id f f th Stick-out is the amount the bolt extends beyond the outside surface of thenut

Positive or zero stick-out is acceptable

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p

Negative stick-out, where the end of the bolt is inside the nut, is notacceptable

Inspections for the Construction Manager

• Inspect the turn-of-nut matchmarks to ensure the bolts have been pretensioned

• If F1852 bolts are used, make sure the ends have been snapped off all bolts(above)

In some cases due to insufficient clearance for the installation wrench

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In some cases, due to insufficient clearance for the installation wrench,F1852 bolts will be tightened by alternative methods so the ends will not besnapped off

Bolting Cost Considerations

The types of joints used in a structure are somewhat dependent on the overalldesign of the structure, but these are some points to consider:• The erector may prefer certain bolt and joint types over others due to

equipment requirements, experience, and installation times

S ti ht d j i t ll th t i l b lt d j i t (R b

design of the structure, but these are some points to consider:

• Snug-tightened joints are normally the most economical bolted joints (Ruby2003)

• For pretensioned joints, F1852’s and DTI’s are popular and can be economical

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p j , p p

• Slip-critical joints are the most costly joints, and should only be specified whennecessary (Ruby 2003)

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Structural Welding

• Another common method for connecting structural steel is welding

• Welding can be performed in the shop or in the field• Welding can be performed in the shop or in the field

• Many fabrication shops prefer to weld rather than bolt

• Welding in the field is avoided if possible due to welding condition requirements

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Welding in the field is avoided if possible due to welding condition requirements

• There are several welding processes, types, and positions to be considered inbuilding construction

Structural Welding

• The American Welding Society (AWS) is a nonprofit organization with a goal toadvance the science, technology and application of welding and related joiningdi i lidisciplines

• AWS develops codes, recommended practices, and guides under strictAmerican National Standards Institute (ANSI) procedures

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( ) p

• D1.1 Structural Welding Code – Steel, one of the most consulted codes in theworld, is produced by AWS (AWS 2004a)

Structural Welding

• Welding is the process of fusing multiple pieces of metal together by heating

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Welding is the process of fusing multiple pieces of metal together by heatingthe filler metal to a liquid state

• A properly welded joint is stronger than the base metal

Strength of Structural Welds

(Part of Table J2.5 AISC 2005)

• Welds may be loaded in shear, tension, compression, or a combination of these

• Capacities for welds are given in the AISC Specification Section J2 (2005)

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• The strength of a weld is dependent on multiple factors, including: base metal,filler metal, type of weld, throat and weld size

Welding Terminology

• Tack Weld (above left)

A temporary weld used to hold parts in place while more extensive, finalwelds are made

• Continuous WeldContinuous Weld

A weld which extends continuously from one end of a joint to the other

• Stitch Weld (above right)

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Stitch Weld (above right)

A series of welds of a specified length that are spaced a specified distancefrom each other

Welding Terminology

ButtLap Corner

TeeEdge

• Shown above are types of structural joints which are established by positions ofthe connected material relative to one another

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the connected material relative to one another

• Lap, tee, and butt joints are most common (AISC)

Welding Terminology

Fillet Full penetration single bevel groove weld

Partial penetration single bevel groove weldgroove weld groove weld

Full penetration Partial penetrationPlug

Full penetration double vee groove weld

Partial penetration single J groove

weld

W ld t d fi th fi ti f th ld d it d l i d i• Weld types define the configuration of the weld and its underlying designapproach

• Fillet welds and groove welds are most commong

• Groove welds fall into two categories

Full penetration – the entire member cross-section is welded

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Partial penetration – just part of the member cross-section is welded

(AISC)

Fillet Welds

Symbolic ProfilesSymbolic Profiles

Actual Profiles

• The most commonly used weld is the fillet weld

• Fillet welds are theoretically triangular in cross-section

• Fillet welds join two surfaces at approximately right angles to each other in lap, tee and corner joints

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tee, and corner joints

(AISC & NISD 2000)

Groove Welds

• Groove welds are specified when a fillet weld is not appropriate for the job

The configuration of the pieces may not permit fillet welding

A strength greater than that provided by a fillet weld is required

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• Groove welds are made in the space or groove between the two pieces beingwelded (AISC & NISD 2000)

Full Penetration Groove Welds

• The bevel or “J” preparation extends over most of or the entire face of thep pmaterial being joined

• Complete fusion takes place

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• In some types of full penetration groove welds the material will be beveled fromone side of the plate with a separate plate on the opposite side – called backingor a backing bar (AISC & NISD 2000)

Partial Penetration Groove Welds

Partial joint penetration welds are used when it is not necessary for the strength of

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Partial joint penetration welds are used when it is not necessary for the strength ofthe joint to develop the full cross section of the members being joined

(AISC & NISD 2000)

Welding Positions

• There are four recognized welding positions:

Fl t Th f f th ld i i t l h i t l d ldi i Flat – The face of the weld is approximately horizontal and welding isperformed from above the joint

Horizontal – The axis of the weld is horizontal

Vertical – The axis is approximately vertical or in the upright position

Overhead – Welding is performed from below the joint

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• The flat position is preferred because it is easier and more efficient to weld inthis position (AISC & NISD 2000)

• Weld symbols are used

Weld SymbolsWeld symbols are usedto communicate thespecific details andrequirements of eachequ e e ts o eacweld to the welder

• Weld symbols areincluded on fabricationincluded on fabricationand erection drawings

Horizontal Weld LineHorizontal Weld Line

Tail Note (Indicating this is

Field Weld Symbol

Leader Line

(Indicating this is a typical weld)

Length and Spacing of weld(In Inches)Size of weld

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Basic Weld Symbol (Fillet weld symbol shown)

Size of weld(In Inches)

Weld Size

• The size of a weld must match the size specified on the drawings

• Some welds may meet the required size after a single pass of the welder

• Larger weld sizes may require multiple passes to meet the size requirement

• Common single pass welds include fillet welds up to and including 5/16 inchand thin plate butt welds with no preparation

• Common multiple pass welds include single bevel full penetration groove welds

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• Common multiple pass welds include single bevel full penetration groove welds,single bevel partial penetration groove welds, and fillet welds over 5/16 inch

• The weld in the above picture is a multiple pass fillet weld

Weld Accessibility• Access holes are required forAccess holes are required for

some welds, such as the weldedflange connection shown to theright

Extension Barright The top access hole allows

for a continuous backingbar to be placed under thebar to be placed under thetop flange

The bottom access holell f l t

Colum

n Weld Access H l

Backing Bar

allows for complete accessto weld the entire width ofthe bottom flange

n

Holes

• A detail of a weld access holefor a welded flange connectionis shown below

Seat Angle

54(Adapted from AISC 2001)(Adapted from AISC 2002a)

SMAW Welding

• Shielded Metal Arc Welding (SMAW) is also known as manual, stick, or handwelding

• An electric arc is produced between the end of a coated metal electrode andthe steel components to be welded

• The electrode is a filler metal covered with a coatingThe electrode is a filler metal covered with a coating

• The electrode’s coating has two purposes:

• It forms a gas shield to prevent impurities in the atmosphere from getting

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g p p p g ginto the weld

• It contains a flux that purifies the molten metal (AISC & NISD 2000)

GMAW Welding

G M t l A W ldi (GMAW) i l k MIG ldi• Gas Metal Arc Welding (GMAW) is also known as MIG welding

• It is fast and economical

• A continuous wire is fed into the welding gunA continuous wire is fed into the welding gun

• The wire melts and combines with the base metal to form the weld

• The molten metal is protected from the atmosphere by a gas shield which is fed

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through a conduit to the tip of the welding gun

• This process may be automated (AISC & NISD 2000)

FCAW Welding

• Flux Cored Arc Welding (FCAW) is similar to the GMAW process

• The difference is that the filler wire has a center core which contains flux

• With this process it is possible to weld with or without a shielding gas

This makes it useful for exposed conditions where a shielding gas may be

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affected by the wind

(AISC & NISD 2000)

SAW Welding

S b d A W ldi (SAW) i l f d b t ti• Submerged Arc Welding (SAW) is only performed by automatic orsemiautomatic methods

• Uses a continuously fed filler metal electrodey

• The weld pool is protected from the surrounding atmosphere by a blanket ofgranular flux fed at the welding gun

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• Results in a deeper weld penetration than the other process

• Only flat or horizontal positions may be used (AISC & NISD 2000)

Welding Equipment

• Equipment used for welding will vary depending on the welding process andwhether the welding is being done in the shop or in the field

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• A Flux Cored Arc Welding machine for shop welding is pictured above left

• A Shielded Metal Arc Welding machine for field welding is pictured above right

Weather Impacts on Welding

• Welding in the field is avoided if possible due to welding condition requirements

• Field welding is not to be performed while it is raining, snowing, or below 0° Fg p g, g,

• In certain ambient temperatures preheating of the material to be welded isrequired

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• AWS Code D1.1 (2004b) specifies minimum preheat and interpasstemperatures, which are designed to prevent cracking

Welding Safety

• It is important for both the welder and those working in the area around awelding process to be safety conscious

• The welding arc should never be looked at with the naked eye

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The welding arc should never be looked at with the naked eye

• AWS publishes many safety and health fact sheets which are available fordownload at their web site: www.aws.org

Welding Safety

A welder should wear the proper protective gear including:• Helmet

• Face shield or goggles

• Heavy fabric or leather shirt

• Cuffless pants

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• Gloves

• Boots

• Leather leggings

Welding in Existing Structures

Welding to existing structures during retrofit projects requires careful considerationWelding to existing structures during retrofit projects requires careful considerationof numerous factors:• Determine weldability – Identify the steel grade to establish a welding

procedurep• Select and design the weld – Fillet welds are preferred and avoid over welding• Surface preparation – Remove contaminants such as paint, oil, and grease• Loads during retrofit – An engineer should determine the extent to which a

member will be permitted to carry loads while heating, welding, or cutting• Fire hazards – Follow all governing fire codes regulations and safety rules to

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Fire hazards Follow all governing fire codes, regulations, and safety rules toavoid fires

• For complete details see the AISC Rehabilitation and Retrofit Guide (2002b)

Weld Inspections

• In addition to the erector’s quality control program, tests and inspections arespecified by the Engineer of Record and/or the local building authorityspecified by the Engineer of Record and/or the local building authority

• A local building inspector may request that tests in addition to those specifiedby the Engineer of Record be performed

• Some problems that can be found in welds include:

Lack of fusion Cracks Wrong size

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Porosity Insufficient penetration • There are several weld tests and inspections that are commonly used

Poor workmanship

Visual Inspection

• Visual inspection is the most frequently used inspection and is the onlysua spect o s t e ost eque t y used spect o a d s t e o yinspection required unless the specification calls for a more stringent inspectionmethod

• Inspection is done by the welder before during and after welding• Inspection is done by the welder before, during, and after welding

• When outside inspection is required it should also be done before, during, andafter welding

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• Minor problems can be identified and corrected before the weld is complete

(AISC & NISD 2000)

Dye Penetrant Test

• Dye penetrant testing locates minute surface cracks and porosity

• Dye types that may be used include:y yp y

Color contrast dye - which shows up under ordinary light

Fluorescent dye – which shows up under black light

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• The dye is normally applied by spraying it directly on the weld

(AISC & NISD 2000)

Magnetic Particle Inspection

• Magnetic particle inspection uses powdered magnetic particles to indicate• Magnetic particle inspection uses powdered magnetic particles to indicatedefects in magnetic materials

• A magnetic field is induced in the part

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• The magnetic powder is attracted to and outlines cracks within the material

(AISC & NISD 2000)

Ultrasonic Inspection

• Ultrasonic inspection can be used to detect flaws inside welds

• High frequency sound waves are directed into the metal with a probe held at aspecific anglespecific angle

• The flaws reflect some energy back to the probe

• Flaws show up as indications on a screen (above) and are subject to

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• Flaws show up as indications on a screen (above) and are subject tointerpretation by an inspector

(AISC & NISD 2000)

Radiographic Inspection

• Radiographic inspection or X ray can also be used to detect flaws inside welds• Radiographic inspection, or X-ray, can also be used to detect flaws inside welds

• Invisible rays penetrate the metal and reveal flaws on an x-ray film orfluorescent screen (above)

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• This is the most costly of the inspection methods

(AISC & NISD 2000)

Welding Cost Considerations

• Fillet weld is less expensive than groove weldFillet weld is less expensive than groove weld

No special preparation

No backing requiredNo backing required

Less volume of weld

• Partial penetration groove weld is less expensive than full

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p g ppenetration groove weld

• Labor represents the majority of the cost associated with welding

Bolting and Welding Scheduling ConsiderationsScheduling Considerations

• Bolting is generally a faster operation than weldingg g y p g

• Bolting does not have the temperature and weather condition requirements thatare associated with welding

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• Unexpected weather changes may delay welding operations

Structural Steel: The Material of Choice

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ReferencesAISC. (n.d.). Steel Connections: Behavior and Practice [35mm Slide Show with Script].

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