Bolted-Welded Connection Design

8/13/2019 Bolted-Welded Connection Design

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CONNECTION DESIGN

Connections must be designed at the strength limit state

Average of the factored force effect at the connection and the force effectin the member at the same oint

At least !"# of the force effect in the member

End connections for diahragms$ cross%frames$ lateral bracing forstraight fle&ural members % designed for factored member loads

Connections should be s'mmetrical about member a&is At least t(o bolts or e)uivalent (eld er connection *embers connected so that their gravit' a&es intersect at a oint

Eccentric connections should be avoided

End connections for floorbeams and girders T(o angles (ith thic+ness , -./!" in.

*ade (ith high strength bolts If (elded account for bendin moment in desi n


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0O1TED CONNECTIONS

Sli%critical and bearing t'e bolted connections.

Connections should be designed to be sli%critical (here2 stress reversal$ heav' imact loads$ severe vibration

3oint sliage (ould be detrimental to the serviceabilit' of the structure

4oints that must be designed to be sli%critical include 4oints sub3ect to fatigue loading or significant load reversal.

4oints (ith oversi5ed holes or slotted holes

4oints (here (elds and bolts sharing in transmitting load

4oints in a&ial tension or combined a&ial tension and shear

0earing%t'e bolted connections can be designed for 3ointssub3ected to comression or 3oints for bracing members


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S1I6%C7ITICA1 0O1TED CONNECTION

Sli%critical bolted connections can fail in t(o (a's2 8a9 sli at theconnection: 8b9 bearing failure of the connection

Sli%critical connection must be designed to2 8a9 resist sli at load

Service II; and 8b9 resist bearing ; shear at strength limit states


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Sli%critical bolted connections can be installed (ith such a degree

of tightness large tensile forces in the bolt clam the

connected lates together

Alied Shear force resisted b' friction

Tightened

P

P

TightenedTightened

P

P

P

P

Tb

N =Tb

N =Tb

N =Tb

P

F=N

Tb

N = Tb

F=N

N = Tb

N =Tb

P

Tb

N =Tb

Tb

N =Tb

N =Tb

N =Tb

P

F=N

N =Tb

N =Tb

P

F=N

Tb

N = Tb

Tb

N = Tb

F=N

N = Tb

N =Tb

P

F=N

N = Tb

N =Tb

N = Tb

N =Tb

P


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Slip-critical connectionscan resist the shear force using friction. If the alied shear force is less than the friction that develos bet(een

the t(o surfaces$ then no sli (ill occur bet(een them

Nominal sli resistance of a bolt in a sli%critical connection

7n< =h=sNs6t

>here$ 6t< minimum re)uired bolt tension secified in Table ?=h< hole factor secified in Table ?

=s< surface condition factor secified in Table /


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@a'ing surfaces nainted clean mill scale$ and blast%cleaned surfaces (ith Class Acoating

nainted blast%cleaned surfaces (ith Class Bcoating

Bolt diameter(in.)

Required Tension(kips)

A3! A"#$

!%& '# "3%" & 3!

%& 3# "#' !' "

'*'%& ! &$'*'%" ' '$'*3%& &! '''*'% '$3 '"&

For standard holes '.$

For o+ersi,e and short*slotted holes $.&!

For long slotted holes -ith the slotPerpendiular to the /ore diretion

$.$

For long*slotted holes -ith the slot

Parallel to the /ore diretion

$.$

Values of Kh

Values of Pt

For 0lass A sur/ae onditions $.33

For 0lass B sur/ae onditions $.!$

For 0lass 0 sur/ae onditions $.33

Values of Ks


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S1I6%C7ITICA1 CONNECTION

Connection sub3ected to tensile force 8Tu9$ (hich reduces claming

Nominal sli resistance should be reduced b' 8?% Tu;6t9

Sli is not a catastrohic failure limit%state because sli%criticalbolted connections behave as bearing t'e connections after sli.

Sli%critical bolted connections are further designed as bearing%t'ebolted connection for the alicable factored strength limit state.


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0EA7ING CONNECTION

In a bearing%t'e connection$ bolts are subjected to shearand theconnecting ; connected lates are sub3ected to bearing stresses 2

Bolt in shear

Bearing stresses in plate


TT

T

T

Bolt in shear



Bolt in shear



TT

T

T


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0EA7ING CONNECTION

0earing t'e connection can fail in several failure modesa9Shear failure of the bolts

b9E&cessive bearing deformation at the bolt holes in the connected artsc9 Edge tearing or fracture of the connected late

d9Tearing or fracture of the connected late bet(een t(o bolt holese9@ailure of member being connected due to fracture or bloc+ shear or ...


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0EA7ING CONNECTION

Nominal shear resistance of a bolt

Threads e&cluded2 7n< -. Ab@ubNs

Threads included2 7n< -./ Ab@ubNs>here$ Ab< area of the bolt corresonding to the nominal diameter

@ub< ?- +si for A/" bolts (ith diameters -." through ?.- in.

@ub< ?-" +si for A/" bolts (ith diameters ?.?" through ?." in.

@ub< ?"- +si for AF- bolts.

Ns< number of shear lanes

7esistance factor for bolts in shear < s< -.-

E)uations above % valid for 3oints (ith length less than "-.- in. If the length is greater than "- in.$ then the values from the e)uations

have to be multilied b' -.


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0EA7ING CONNECTION

Effective bearing area of a bolt < the bolt diameter multilied b' the thic+ness

of the connected material on (hich it bears 0earing resistance for standard$ oversi5e$ or short%slotted holes in an'

direction$ and long%slotted holes arallel to the bearing force2

@or bolts saced (ith clear distance bet(een holes greater than or e)ual to /.- dand for bolts (ith a clear end distance greater than or e)ual to .- d

Rn= 2.4 d t Fu

@or bolts saced (ith clear distance bet(een holes less than /.- dand for bolts (ith clear end distances less than .- d

Rn= 1.2 Lct Fu

>here$ d < nominal bolt diameter

1c< clear distance bet(een holes or bet(een the hole and the end of the member in

the direction of alied bearing force

@u< tensile strength of the connected material


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0EA7ING CONNECTION

S6ACING 7EHI7E*ENTS *inimum sacing bet(een centers of bolts in standard holes shall not

be less than three times the diameter of the bolt

@or sealing against enetration of moisture in 3oints$ the sacing on asingle line ad3acent to the free edge shall satisf' s 8.- J .- t9 !.-

*inimum edge distances

Bolt diameter(in.)

1hearededge

Rolled or2as 0ut edge

!%& '*'%& %&

3%" '*'%" '

%& '*'% '*'%&' '*3%" '*'%"

'*'%& '*'%'*'%" *'%" '*!%&'*3%& *3%& '*3%"


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0O1TED CONNECTION

Example 1 Design a sli%critical slice for a tension member. @orthe Service II load combination$ the member is sub3ected to a

tension load of -- +is. @or the strength limit state$ the member is

sub3ected to a ma&imum tension load of /-- +is.

The tension member is a W8 x 28section made from *!-%Gr. "-steel. se A/" bolts to design the sli%critical slice.

Step I.Service and factored loads Service 1oad < -- +is.

@actored design load < /-- +is

Tension member is W8 x 28section made from *!- Gr."-. Thetension slice must be sli critical 8i.e.$ it must not sli9 at service loads.


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0O1TED CONNECTION

Step II.Sli%critical slice connection

Sli resistance of one full'%tensioned sli%critical bolt < 7n< =h=sNs6t

< ?.- for sli%critical resistance evaluation

Assume bolt diameter < d < K in. Therefore 6t< +is from Table ? Assume standard holes. Therefore =h< ?.-

Assume Class A surface condition. Therefore =s< -.//

Therefore$ 7n< ?.- & -.// & ? & < F. +is

Therefore$ number of K in. diameter bolts re)uired for slice to besli%critical at service loads < -- ; F. < ?.L.

Therefore$ number of bolts re)uired M


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0O1TED CONNECTION

Step III:1a'out of flange%late slice connection

To be s'mmetric about centerline$ need the number of bolts < multile of . Therefore$ choose full' tensioned /; in. A/" bolts (ith la'out above.

Sli%critical strength of the connection < & F. +is < ?.! +is

*inimum edge distance 81e9 < ? in. from Table . Design edge distance 1e< ?." in.

*inimum sacing < s < / & bolt diameter < / & K < ." in. Design sacing < ." in.


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0O1TED CONNECTION

Step IV:Connection strength at factored loads The connection should be designed as a normal shear;bearing

connection be'ond this oint for the factored load of /-- +is

Shear strength of high strength bolt E1DED CONNECTIONS

The shear strength of the base metal must be considered2

7n< v& -." Ag@'

(here$ v< ?.-

@'is the 'ield strength of the base metal and Agis the gross area in shear

Strength of (eld in shear Strength of base metal

< -.- & -.L- & @e&&& -.!-! & a & 1( < ?.- & -." & @'& t & 1(

T

6le+ation Plan

T

6le+ation Plan


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@I11ET >E1DED CONNECTIONS

Lmtatons on !eld dmensons

*inimum si5e 8amin9 >eld si5e need not e&ceed the thic+ness of the thinner art 3oined.

amin deends on the thic+ness of the thic+er art 3oined

If the thic+ness of the thic+er art 3oined 8T9 is less than or e)ual to K in.a

min

< in.

If T is greater than K in. amin< ";?L in.

*a&imum si5e 8ama&9 *a&imum si5e of fillet (eld along edges of connected arts

for material (ith thic+ness -." in.$ ama&%< thic+ness of the material

for lates (ith thic+ness -." in.$ ama&< thic+ness of material % ?;?L in.

*inimum length 81(9

*inimum effective length of fillet (eld < & si5e of fillet (eld Effective len th of fillet (eld , ?." in.


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@I11ET >E1DED CONNECTIONS

>eld terminations and end returns End returns must not be rovided around transverse stiffeners

@illet (elds that resist tensile forces not arallel to the (eld a&is orroortioned to (ithstand reeated stress shall not terminate at corners

of arts or members

>here end returns can be made in the same lane$ the' shall bereturned continuousl'$ full si5e around the corner$ for a length e)ual to

t(ice the (eld si5e 8a9


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@I11ET >E1D DESIGN

Example 1 Design the fillet (elded connection s'stem for a double

angle tension member !" & /P & ?; made from A/L steel to carr'

a factored ultimate load of "- +is.

Step I. Design the (elded connection

Considering onl' the thic+ness of the angles: amin< ?; in. Considering onl' the thic+ness of the angles: ama&< ?; % ?;?L in. < !;?L in.

"esi#n$ a < /; in. < -./!" in.

Shear strength of (eld metal < 7n < -.- & -.L- & @E& -.!-! & a & 1(

< .F & 1(+is

Strength of the base metal in shear < 7n< ?.- & -." & @'& t & 1(

< ?-. 1(+is

Shear strength of (eld metal governs$ 7n< .F 1(+is


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@I11ET >E1D DESIGN

Design strength 7n, "- +is Therefore$ .F 1(, "- +is

Therefore$ 1(, .? in.

Design length of /; in. E!- fillet (eld < /-.- in. Shear stren#th o$ $illet %eld & 2'7 (ips

Connection la'out Connection must be designed to minimi5e eccentricit' of loading.

Therefore$ the center or gravit' of the (elded connection must coincide

(ith the center of gravit' of the member.

Tu

/ 5

/ 5'

5'

5

3." in.Tu

/ 5

/ 5'

5'

5

3." in.


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@I11ET >E1D DESIGN

The tension force Tuacts along the c.g. of the member$ (hich is?.L" in. from the to and /./" in. from the bottom 8AISC manual9.

1et$ $be the strength of the fillet (eld er unit length.

Therefore$ fL1" fL2= #u

And fL2x $.$% & fL1x 1.'% = ( % ta+ing moments about the member c.g.

Therefore$ 1?< .- 10ut$ 1?J 1< ?".- in.

Therefore$ 1?< ?- in. and 1< " in.

Design2 1?< ?-.- in. and 1< ".- in.


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@I11ET >E1D DESIGN

Consider another la'out

Tu

/ 5

5'

5

/ 5'

!/ 3." iTu

/ 5

5'

5

/ 5'

!/ 3." i

f1?J f1

J "f < T

u

f1& /." J "f & -." % f1

?& ?.L" < - % *oment about member c.g.

Additionall'$ 1

?J 1

J " < ?".- in.

Therefore$ 1?< !.L in. and 1

< . in.

Design2 1?< .- in. and 1< /.- in.


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Groove >elded Connections

Connects structural members that are aligned in the same lane

0asic T'es2 Comlete 3oint enetration groove (eld2 transmits full load of the member the' 3oin

and have the same strength as the base metal.

6artial enetration groove (eld2 >elds do not e&tend comletel' through thethic+ness of the ieces being 3oined.

ld


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Groove >elds

Comlete enetration groove (elded connections

Tension and comression loaded

@actored resistance < factored resistance of base metal

Shear loaded on effective area lesser of

@actored resistance of (eld < -.L & e)& @e&&< -.L & -." & @e&& L-# of factored resistance of base metal in tension

6artial enetration groove%(elded connections

Tension or comression arallel to the (eld a&is and comression normal toeffective area factored resistance of the base metal

Tension normal to the effective area lesser of

@actored resistance of the (eld < -.L e2@e&&< -.L- & -.- & @e&& @actored resistance of the base metal

Shear loaded lesser of

@actored resistance of the (eld < -.L e2@e&&< -.L- & -.- & @e&&

@actored resistance of base metal < -." @'

Groove >elds


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Groove >elds

Bolted-Welded Connection Design

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