Connections 1Lecture 26

Architectural Structures IENDS 231

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ARCHITECTURAL STRUCTURES I:STATICS AND STRENGTH OF MATERIALS ENDS 231

DR. ANNE NICHOLS

FALL 2007

lecturetwenty sixsteel connections:

bolts, welds &tension members

Connections 2Lecture 26

Architectural Structures IENDS 231

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Connections• needed to:

– support beams by columns– connect truss members– splice beams or columns

• transfer load• subjected to

– tension or compression– shear– bending

Connections 3Lecture 26

Architectural Structures IENDS 231

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Bolts• bolted steel connections

Connections 4Lecture 26

Architectural Structures IENDS 231

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Welds• welded steel connections

Connections 5Lecture 26

Architectural Structures IENDS 231

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Fasteners• wood connections

Connections 6Lecture 26

Architectural Structures IENDS 231

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Bolted Connection Design• considerations

– bearing stress• yielding

– shear stress• single & double

– member• rupture

Connections 7Lecture 26

Architectural Structures IENDS 231

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Bolted Connection Design• ASD steel

– shear:

• bolt strengths• single & double

– bolt types• A325-SC, A490-SC• A325-N, A490-N• A325-X, A490-X

vv Ff ≤

Connections 8Lecture 26

Architectural Structures IENDS 231

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Bolted Connection Design• ASD steel

– bearing:• bolts rarely

fail by bearing• other part fails first

Connections 9Lecture 26

Architectural Structures IENDS 231

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Tension Members• steel members can have holes• reduced area• increased stress

Connections 10Lecture 26

Architectural Structures IENDS 231

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Effective Net Area• likely path to “rip” across• bolts divide transferred force too

Connections 11Lecture 26

Architectural Structures IENDS 231

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ASD – Tension Members• non-pin connected members:

– Ft = 0.60Fy on gross area– Ft = 0.50Fu on net area

• pin connected members: – Ft = 0.45Fy on net area

• threaded rods of approved steel: – Ft = 0.33Fu on major diameter – (for static loading only)

Connections 12Lecture 26

Architectural Structures IENDS 231

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LRFD - Tension Members• limit states for failure1. yielding

2. rupture*

Ag - gross area Ae - effective net area Fu - tensile strengthof the steel (ultimate)

ntu PP φ≤

gynt AFP == 9.0φ

eunt AFP == 75.0φ

Connections 13Lecture 26

Architectural Structures IENDS 231

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Welded Connection Design• considerations

– shear stress– yielding– rupture

Connections 14Lecture 26

Architectural Structures IENDS 231

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Welded Connection Design• weld terms

– butt weld– fillet weld– plug weld– throat

• weld materials– E60XX– E70XX

FEXX = 70 ksi

Connections 15Lecture 26

Architectural Structures IENDS 231

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Welded Connection Design• ASD

– shear• Fv = 0.30Fweld

– throat• T =0.707 x weld size

– area• A = T x length of weld

– weld metal generally stronger than base metal (ex. Fy = 50 ksi)

vv Ff ≤

Connections 16Lecture 26

Architectural Structures IENDS 231

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Framed Beam Connections• angles

– bolted– welded

Connections 17Lecture 26

Architectural Structures IENDS 231

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Framed Beam Connections• terms

– coping

Connections 18Lecture 26

Architectural Structures IENDS 231

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Framed Beam Connections• tables for

standard bolt holes & spacings

• n = # bolts• angle leg

thickness• length needed

Connections 19Lecture 26

Architectural Structures IENDS 231

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Beam Connections• LRFD provisions

– shear yielding– shear rupture– block shear rupture– tension yielding– tension rupture– local web buckling– lateral torsional buckling

Connections 20Lecture 26

Architectural Structures IENDS 231

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Beam Connections• block shear rupture • tension rupture