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F2012abn
APPLIED ARCHITECTURAL STRUCTURES:
STRUCTURAL ANALYSIS AND SYSTEMS
ARCH 631
DR. ANNE NICHOLS
FALL 2015
seventeen
connections Connections 1Lecture 17
Applied Architectural StructuresARCH 631
lecture
Connections 2
Lecture 17
Architectural Structures III
ARCH 631
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Connection Design Considerations
• joints often critical in design– can influence choice of structural system
• types used influenced by:
– member behavior
– member geometry
• basic types join by:
– lapping
– deforming and interlocking
– butting
Connections 3
Lecture 17
Architectural Structures III
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Connectors
• “third-elements”
– bolts
– nails
– welds
– splice plates
• transfer load at a point, line or surface
– generally more than a point due to stresses
Connections 4
Lecture 17
Architectural Structures III
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Connector Rigidity
• pinned joints
– point type
• rigid joints
– line and surface types
– multiple “points”
separated by
distance resist
moment
CdTdM ==CT =
2
Connections 5
Lecture 17
Architectural Structures III
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• connected members in tension cause shear stress
• connected members in
compression cause bearing stress
Point Connectors
Connections 6
Lecture 17
Architectural Structures III
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• seen when 2 members are connected
Single Shear
4
2dv
P
A
Pf
π==
Connections 7
Lecture 17
Architectural Structures III
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• seen when 3 members are connected
Double Shear
4
2
22
2 dv
P
A
P
A
Pf
π===
)2
(20 PPF +−==Σ
Connections 8
Lecture 17
Architectural Structures III
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• compression & contact
• projected area
Bearing Stress
td
P
A
Pf
projected
p ==
F=
3
Connections 9
Lecture 17
Architectural Structures III
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Beam Stresses
• shear – horizontal & vertical
Connections 10
Lecture 17
Architectural Structures III
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Beam Stresses
• shear – horizontal & vertical
Connections 11
Lecture 17
Architectural Structures III
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• plates with
– nails
– rivets
– bolts
• splices
• V from beam loadrelated to Vlongitudinal
Connectors Resisting Beam Shear
x
y
ya
4”
2”
2”
12”
8” p
p p
4.43”
I
VQ
p
V allongitudin=
pI
VQnF
areaconnected
connector ⋅≥
Connections 12
Lecture 17
Architectural Structures III
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Vertical Connectors
• isolate an area with vertical interfaces
pI
VQnF
areaconnected
connector ⋅≥
p p
p
4
Connections 13
Lecture 17
Architectural Structures III
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Tension Members
• members with holes have reduced area
• increased tension stress
• Ae is effective net area
=
ee
tA
Tor
A
Pf
Connections 14
Lecture 17
Architectural Structures III
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Effective Net Area
• likely path to “rip” across
• bolts divide transferred force too
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Wood Connectors
• adhesives
– used in a controlled environment
– can be used with nails
• mechanical
– nails
– bolts
– lag bolts or lag screws
– split ring and
shear plate connectors
– timber rivetsConnections 15Lecture 17
Applied Architectural StructuresARCH 631
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Wood Connections
• mechanical
Connections 16Lecture 17
Applied Architectural StructuresARCH 631
5
Connections 17
Lecture 17
Architectural Structures III
ARCH 631
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Nails
• tension stress (pullout)
• shear stress
• nails presumed to share load by
distance from centroid of nail pattern
Connections 18
Lecture 17
Architectural Structures III
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Bolts
• bearing stress
– parallel to grain
– perpendicular to grain
• shear stress
• tension stress in member
• concerned with end shear rupture
Connections 19
Lecture 17
Architectural Structures III
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Lag Screws
• tension stress (pullout)
– avoid parallel to grain
• shear stress
Connections 20
Lecture 17
Architectural Structures III
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Split Ring Connectors
• bearing stress
– parallel to grain
– perpendicular to grain
• shear stress
• tension stress in member
• concerned with end shear rupture
• (like bolts)
6
Connections 21
Lecture 17
Architectural Structures III
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Plate Connections
• rigid
– bolts or nails
– plate
– continuous at top & bottom
• shear
– metal plate with teeth
Connections 22
Lecture 17
Architectural Structures III
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Miscellaneous Connectors
• beam hangers
• frame anchors
• seats
• etc…
Connections 23
Lecture 17
Architectural Structures III
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Steel Connections
• needed to:– support beams by columns
– connect truss members
– splice beams or columns
• transfer load
• subjected to
– tension or compression
– shear
– bending
F2008abnConnections 24
Lecture 18
Architectural Structures III
ARCH 631
Bolts
• bolted steel connections
http://courses.civil.ualberta.ca
(AISC - Steel Structures of the Everyday)
7
Connections 25
Lecture 17
Architectural Structures III
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Welds
• welded steel connections
Connections 26
Lecture 17
Architectural Structures III
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Bolted Connection Design
• considerations
– bearing stress
• yielding
– shear stress
• single & double
– member
• rupture
F2007abnConnections 27Lecture 17
Architectural Structures IIIARCH 631
Bolts
• types
– materials
• high strength
– location of threads
• included
• excluded
– friction or bearing
• always tightened
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Bolted Connection Design
• Unified steel
– shear:
• bolt strengths
– bolt types
• A325-SC, A490-SC
• A325-N, A490-N
• A325-X, A490-XConnections 28Lecture 17
Architectural Structures IIIARCH 631
Ω≤ n
a
RR
nvu RR φ≤
750.v =φ002.=Ω
8
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Bolted Connection Design
Connections 29Lecture 17
Applied Architectural StructuresARCH 631
• Unified steel
– bearing:
• bolts rarely
fail by bearing
• other part fails first
– slip critical
• tightened down
– holes are 1/16” larger
– effective hole widths
are 1/8” more
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Bolted Connection Design
• single shear or tension
• double shear
• bolt area
– threads excluded
– threads included
Connections 30Lecture 17
Architectural Structures IIIARCH 631
bnn AFR = 750.=φ
bnn AFR 2=
nu RR φ≤
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Bolted Connection Design
• bearing at bolt holes
– deformation is concern
– deformation isn’t concern
– long slotted holes
Lc – clear length to edge or next hole
Connections 31Lecture 17
Architectural Structures IIIARCH 631
750.=φ
uucn dtF.tFL.R 4221 ≤=
nu RR φ≤
uucn dtF.tFL.R 0351 ≤=
uucn dtF.tFL.R 0201 ≤=
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Tension Members
• Ae = AnU
– An is actual net area
– U is shear lag factor by element type
Connections 32Lecture 17
Architectural Structures IIIARCH 631
g
stAAA holesallofgn
4Σ+−=
9
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Tension Members
• limit states for failure
1. yielding
2. rupture*
Ag - gross area
Ae - effective net area
Fu = the tensile strength
of the steel (ultimate)
Connections 33Lecture 17
Architectural Structures IIIARCH 631
nu RR φ≤
gyn AFR. == 90φ
eun AFR. == 750φ
Connections 34Lecture 17
Architectural Structures IIIARCH 631
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Welded Connection Design
• considerations
– shear stress
– yielding
– rupture
Connections 35Lecture 17
Architectural Structures IIIARCH 631
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Welded Connection Design
• weld terms
– butt weld
– fillet weld
– plug weld
– throat
• weld materials
– E60XX
– E70XX
FEXX = 70 ksi
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Welded Connection Design
• shear failure assumed
• 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)
Connections 36Lecture 17
Architectural Structures IIIARCH 631
10
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Welded Connection Design
• minimum
– table
• maximum
– material thickness ( to ¼”)
– 1/16” less
• min. length
– 4 x size min.
– ≥ 1 ½”
Connections 37Lecture 17
Architectural Structures IIIARCH 631
163
165
83
167
85
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Welded Connection Design
• shear
– table for φS
Connections 38Lecture 17
Architectural Structures IIIARCH 631
area
Ω≤ n
a
RR
nu RR φ≤750.=φ
SlTlF.R EXXn == 60
Connections 38
Lecture 18
Architectural Structures III
ARCH 631
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Framed Beam Connections
• angles
– bolted
– welded
F2007abnConnections 39
Lecture 17
Architectural Structures III
ARCH 631
Framed Beam Connections
• terms
– coping
(AISC - Steel Structures of the Everyday)
11
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Framed Beam Connections
• tables for standard
bolt holes & spacings
• n = # bolts
• bolt diameter, angle leg thickness
• bearing on
beam web
Connections 41Lecture 17
Architectural Structures IIIARCH 631
F2007abnConnections 41
Lecture 17
Architectural Structures III
ARCH 631
Other Beam Connections
• seated beam
– unstiffened
– stiffened
• continuous
– beam to column
– beam to beam
http://courses.civil.ualberta.ca
http://www.steel-connections.com
F2007abnConnections 42
Lecture 17
Architectural Structures III
ARCH 631
Other Connections
• rigid frame knees
• beam splice
• column splice
http://courses.civil.ualberta.ca
Connections 43
Lecture 17
Architectural Structures III
ARCH 631
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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
12
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Beam Connections
• LRFD design of connected elements
– shear yielding
– shear rupture
– block shear rupture
Connections 45Lecture 17
Architectural Structures IIIARCH 631
001.=φ gyn AF.R 600=
750.=φ nvun AF.R 600=
750.=φ
ntubsgvyntubsnvun AFUAF.AFUAF.R +≤+= 6060
where Ubs is 1 for uniform tensile stress
Su2011abn
Beam Connections
– tension yielding
– tension rupture
– flexural yielding
– local web buckling
– lateral torsional buckling
Connections 46Lecture 17
Architectural Structures IIIARCH 631
900.=φ gyn AFR =
750.=φ eun AFR =
900.b =φ )net(yn ZFM =
http://aisc.org
Connections 46Lecture 17
Architectural Structures IIIARCH 631
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Beam Connections
• block shear rupture • tension rupture
Connections 47Lecture 17
Architectural Structures IIIARCH 631
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Beam Bearing
• design considerations
– web crippling
– base plate
bending
– bearing on
concrete, etc.
• load distributed
13
F2007abnConnections 48
Lecture 17
Architectural Structures III
ARCH 631
Column Base Plates
• attached by anchor bolts– usually 4
– 2 if no moment
• plate level– by shims & grout
– leveling nuts
• considers– bearing on steel
– bending of plate
http://courses.civil.ualberta.ca
http://www.steel-connections.com