APPLIED ARCHITECTURAL STRUCTURES: …faculty.arch.tamu.edu/media/cms_page_media/4350/notes17...1 F2012abn APPLIED ARCHITECTURAL STRUCTURES: STRUCTURAL ANALYSIS AND SYSTEMS ARCH 631

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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

F2007abn

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


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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


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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


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• connected members in tension cause shear stress

• connected members in

compression cause bearing stress

Point Connectors

Connections 6

Lecture 17


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• seen when 2 members are connected

Single Shear

4

2dv

P

A

Pf

π==

Connections 7

Lecture 17


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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


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• compression & contact

• projected area

Bearing Stress

td

P

A

Pf

projected

p ==

F=

3

Connections 9

Lecture 17


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Beam Stresses

• shear – horizontal & vertical

Connections 10

Lecture 17


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Beam Stresses

• shear – horizontal & vertical

Connections 11

Lecture 17


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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


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Vertical Connectors

• isolate an area with vertical interfaces

pI

VQnF

areaconnected

connector ⋅≥

p p

p

4

Connections 13

Lecture 17


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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


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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


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Wood Connections

• mechanical

Connections 16Lecture 17


5

Connections 17

Lecture 17


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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


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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


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Lag Screws

• tension stress (pullout)

– avoid parallel to grain

• shear stress

Connections 20

Lecture 17


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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


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Plate Connections

• rigid

– bolts or nails

– plate

– continuous at top & bottom

• shear

– metal plate with teeth

Connections 22

Lecture 17


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Miscellaneous Connectors

• beam hangers

• frame anchors

• seats

• etc…

Connections 23

Lecture 17


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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


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Bolts

• bolted steel connections

http://courses.civil.ualberta.ca

(AISC - Steel Structures of the Everyday)

7

Connections 25

Lecture 17


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Welds

• welded steel connections

Connections 26

Lecture 17


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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

Su2011abn


• Unified steel

– shear:

• bolt strengths

– bolt types

• A325-SC, A490-SC

• A325-N, A490-N

• A325-X, A490-XConnections 28Lecture 17


Ω≤ n

a

RR

nvu RR φ≤

750.v =φ002.=Ω

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• 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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• single shear or tension

• double shear

• bolt area

– threads excluded

– threads included



bnn AFR = 750.=φ

bnn AFR 2=

nu RR φ≤

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• bearing at bolt holes

– deformation is concern

– deformation isn’t concern

– long slotted holes

Lc – clear length to edge or next hole



750.=φ

uucn dtF.tFL.R 4221 ≤=

nu RR φ≤



Su2011abn

Tension Members

• Ae = AnU

– An is actual net area

– U is shear lag factor by element type



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)



nu RR φ≤

gyn AFR. == 90φ

eun AFR. == 750φ



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Welded Connection Design

• considerations

– shear stress

– yielding

– rupture



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• weld terms

– butt weld

– fillet weld

– plug weld

– throat

• weld materials

– E60XX

– E70XX

FEXX = 70 ksi

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• 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)



10

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• minimum

– table

• maximum

– material thickness ( to ¼”)

– 1/16” less

• min. length

– 4 x size min.

– ≥ 1 ½”



163

165

83

167

85

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• shear

– table for φS



area

Ω≤ n

a

RR

nu RR φ≤750.=φ

SlTlF.R EXXn == 60

Connections 38

Lecture 18


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Framed Beam Connections

• angles

– bolted

– welded


Lecture 17


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• terms

– coping

(AISC - Steel Structures of the Everyday)

11

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• tables for standard

bolt holes & spacings

• n = # bolts

• bolt diameter, angle leg thickness

• bearing on

beam web




Lecture 17


ARCH 631

Other Beam Connections

• seated beam

– unstiffened

– stiffened

• continuous

– beam to column

– beam to beam


http://www.steel-connections.com


Lecture 17


ARCH 631

Other Connections

• rigid frame knees

• beam splice

• column splice


Connections 43

Lecture 17


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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

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Beam Connections

• LRFD design of connected elements

– shear yielding

– shear rupture

– block shear rupture



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



900.=φ gyn AFR =

750.=φ eun AFR =

900.b =φ )net(yn ZFM =

http://aisc.org



F2007abn

Beam Connections

• block shear rupture • tension rupture



F2007abn

Beam Bearing

• design considerations

– web crippling

– base plate

bending

– bearing on

concrete, etc.

• load distributed

13


Lecture 17


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://www.steel-connections.com

APPLIED ARCHITECTURAL STRUCTURES: …faculty.arch.tamu.edu/media/cms_page_media/4350/notes17...1 F2012abn APPLIED ARCHITECTURAL STRUCTURES: STRUCTURAL ANALYSIS AND SYSTEMS ARCH 631

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