CE591MomentConn_F13

8/13/2019 CE591MomentConn_F13

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Welded Moment Connections

Develop moment(typically M pbeam )at joint

Prefer compactsectionsSpecify CompleteJoint Penetration

Weld (CJP) withmatching weld CJP Weld

Shear Tab

Beam

Column


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Basic Design Assumptions

Bending Moment tension andcompression in flangesShear webconnection

Eccentricity may beignored [AISC 12-3]

Column may require horizontal stiffenersContinuity Plates


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Moment Connections (Seismic)

Adequate strength and stiffness for FRconnection+ Considerations / detailing for ductile

behavior (moment frame)

Rotation ( q )

M o m e n t

( M )

FR

PR

Simple


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DS S I V W R

Special Moment Frame 8

Ordinary Moment Frame 3.5V Elastic

Inelastic

D y D u

q

q

Note: R=3Not specificallydetailed forseismicresistance


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Special Moment Frame 8

Ordinary Moment Frame 3.5

Note: R=3Not specificallydetailed forseismicresistance

R = 3Design according to AISC Specifications(no special detailing required)

R>3Must follow detailing requirements in AISC SeismicProvisions

DS S I V W R


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Strong Column Weak Beam Concept

0.1**

pb

pc

M M M pb

M pc

Includes reduction for axial force in column

Includes factors toincrease based onexpected yieldstress, etc.

AISC Seismic Provisions 2010, Section E3


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Expected Strength Factor, R y

Hot-rolledShapes

Ry

A36 1.5

A992 1.1nominal y

expected y

F F

AISC Seismic Provisions 2010, Table A3.1


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Special Moment

Frames (SMF)Expected to withstandsignificant inelasticdeformations

Must have story driftrotation capacity of0.04 radiansFlexural strength must

be at least 0.8 M pbeam at0.04 radiansMust have qualifyingcyclic test results or bePrequalified

Expected to withstandlimited inelasticdeformations

Must develop momentin connection of1.1R yMpbeam or max M uDetailing requirements

FR or PR allowed

Ordinary Moment

Frames (OMF)

(Intermediate Moment Frames(IMF) are in between)

AISC Seismic Provisions 2010, Chapter E


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Recommended b/t ratios

y f

f

F E

t

b3.0

2

yw F E

t h

45.2

Flanges in I-shaped Beams

Webs in FlexuralCompression in SMF(zero axial load)

AISC Seismic Provisions Table D1.1

For Highly Ductile

For Highly Ductile


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Required Shear Strength, V u

1.2D + 0.5L + 0.2 S (for example)+ V p resulting from 1.1R y F y Z

M pV p

M p

V p L

Distance betweenplastic hingesFor directly-welded flange moment connection,

hinge location typ. ~ d b/2 from column face


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Northridge Earthquake

January 17, 1994Brittle fractures ofwelded momentconnections

Included sites with onlymoderate shaking SAC Joint Venture (SAC Steel Project)

SAC = SEAOC, ATC, CUREE

Studies of connection performance, metallurgy, steelframing systems, etc.Prequalified connections and other recommendations(FEMA-350 series)


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Pre-Northridge Connection

Backing Bar

Weld Access Hole

CJP Weld

Shear Tab

Beam

Column

Continuity Plate

Panel Zone


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Pre-Northridge Detail to Prequalified WUF-B

WUF-B Welded Unreinforced Flange,Bolted Web

Detailing requirements, specified originally byFEMA-350More stringent inspection requirementsInitially prequalified for Ordinary MomentFrames only; now, some WUF-B details arerequired for welded OMF (AISC SeismicProvisions 2010)


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Weld Access Holes

Pre-NorthridgeStrain concentrations attoes of weld access holes

WUF-BRecommended geometriesfor weld access holes(+ shall be ground smooth)


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Improved Weld Access Hole

Notes:1. Bevel as required for selected

groove weld.2. Larger of t b f or in. (13 mm) (plus

t b f , or minus t b f )

3. t b f to t b f , in. (19 mm) minimum ( in.) ( 6 mm)

4. 3/8 in. (10 mm) minimum radius (plusnot limited, minus 0)

5. 3 t b f ( in.) ( 13 mm)Tolerances shall not accumulate to the

extent that the angle of the accesshole cut to the flange surfaceexceeds 25 .

Examples of requirements


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Backing Bar

Pre-NorthridgeTypically left in placeCrack initiator

WUF-B

Bar removed, weldback-gouged,reinforcing fillet weldadded


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Typical: 3/8 root

30-degree bevel on beamflange

Bottom flangeback-up bar tack

welded into place .


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Typical Pre-NorthridgeBottom Flange Weld


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Improved POST-Northridge Bottom Flange Weld

Weld tabs andrunoff regionsremoved; groundsmooth

Back-up bar removed; root visually

inspected, defects removed; smallreinforcing fillet weld placed atbottom of groove weld


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BeamPre-Northridge

A572 Gr. 50 typically

WUF-B (originalrequirements fromFEMA350)

A992 recommendedVery DEEPsections

W36 and shallowerbeams only+ minimum span to depthratio, L/d = 7

THICK flanges1 thick flange, maximum


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Tri-Axial Stress State

Distortion Energy(Timoshenko Goodier p. 248)

In a pure tri-axial stress state, we do not have strain due

to distortion (slip/shear), but we have volumetric strainSo, theoretically, we can never be on the yield envelope,but we can get enough strain to FRACTURE

222222

2

1

6

1 yz xz xy x z z y y x

G E


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Panel Zone & Continuity Plates

Pre-NorthridgeMay have weakpanel zones

WUF-BRecommendshear yield in panelzone at same timeas yield in beam,Or all yield in beam

Some connectionsw/o continuity plates failed

New recommendationsfor continuity plates

local kinking


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Very weak panelzone; localizedkinks causestrainconcentrations,ultimately leadingto fracture invicinity of beam

flange groovewelds.


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Same specimen

as previous slide.Connection failedat moment wellbelow M n


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FEMA 350

Moment connectiondetails -- prequalified

connections Recommended design

procedures, limits ofusage (e.g., OMF only,W36 beams andshallower, flangethickness limits, webconnection, etc.)

Not a standard; butstill a valuablereference


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WUF-B


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ANSI/AISC 358-10


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Reduced BeamSection (RBS)

Also called Dogbone connection; less costly, simpler

than reinforced connections

Forces hinge formation to

occur within reduced section

Now one of the mostcommonly used connections


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Connection at q 0.04 radian......


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-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

-0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.04 0.05

Drift Angle (radian)

B e n

d i n g M

o m e n

t ( k N - m

)

RBS Connection

Mp

Mp


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Bolted Unstiffened and Stiffened Extended End-PlateMoment Connections

End Plate Connections


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Sumner, et al., 2000

End-Plate Connections

End Plate Connections


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Sumner, et al., 2000

End-Plate Connections


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End plate and column flange bending strengths aredetermined using yield line analysis.


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Bolted Flange Plate (BFP)

BFP 3


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BFP-3

Sato, A., Newell, J.D., Uang, C.-M.Cyclic Behavior and Seismic Design ofBolted Flange Plate Steel MomentConnections, AISC Engineering

Journal, Fourth Quarter, 2008.


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Section 8 6


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Section 8.6Beam Web-to-

ColumnConnectionLimitations

Shear tab thicknessequal at least to that

of beam web;

overlap with weldaccess holes asspecified

Kaiser Bolted Bracket (KBB)


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Kaiser Bolted Bracket (KBB)


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Experimental Evaluation of KaiserBolted Bracket Steel Moment-Resisting Connections

Scott M. Adan and William Gibb

AISC Engineering Journal 2009

http://www.steelcastconnections.com/

ConXtech ConXL moment connection


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ConXtech ConXL moment connection


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http://dcm-designs.com/steel-prefabricated-moment-frame/

This innovativeconnection system

enables beams to besimply lowered and locked

onto square columns inthe field, resulting in a

dimensionally accuratestructural chassis. Thesystem is often referred toas a full- scale erector set.

http://www.conxtech.com/conx-system/


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Double Tee


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Double Tee

http://www.aisc.org/uploadedcontent/2012NASCCSessions/N11/

Simpson Strong Frame (Yield Link)


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Simpson Strong Frame (Yield Link)



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SidePlate


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SidePlate


SOM Pin Fuse Joint


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SOM Pin Fuse Joint

Steel Connections: Proprietary or Public Domain? by P. Cordova & R.Hamburger, Modern Steel Construction, October 2011


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Documents

CE591MomentConn_F13