Connections 1Lecture 26

Architectural Structures IENDS 231

S2007abn

ARCHITECTURAL STRUCTURES I:STATICS AND STRENGTH OF MATERIALS ENDS 231

DR. ANNE NICHOLS

SPRING 2007

lecturetwenty sixsteel connections:

bolts, welds &tension members

Connections 2Lecture 26

Architectural Structures IENDS 231

S2007abn

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

S2007abn

Bolts• bolted steel connections

Connections 4Lecture 26

Architectural Structures IENDS 231

S2007abn

Welds• welded steel connections

Connections 5Lecture 26

Architectural Structures IENDS 231

S2007abn

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

S2007abn

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

S2007abn

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

S2007abn

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

S2007abn

Welded Connection Design• considerations

– shear stress– yielding– rupture

Connections 14Lecture 26

Architectural Structures IENDS 231

S2007abn

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

S2007abn

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

S2007abn

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

S2007abn

Beam Connections• block shear rupture • tension rupture