_analysis of Moment Resisting Connections

analysis of moment resisting connections

basic principles of connection design •

Provide as direct a load path as possible

•

Avoid complex stress conditions

•

Weld in the shop, bolt on site

basic principles of connection design •

Provide as direct a load path as possible

•

Avoid complex stress conditions

•

Weld in the shop, bolt on site

Welded connections

moment connection of an I-Beam

•

•

Bending moment is carried mainly by the flanges Therefore connect flanges for moment transfer 

M

moment connection of an I-Beam

•

•

Welded connection "$T • Fillet elds • F!ll penetration elds "ompression transfer d can also be accomplished thro!gh direct bearing

#es!ltant tension force T $ M%d

M

shear connection of an I-Beam •

&hear is carried mainly by the eb

•

Therefore connect the eb for shear transfer 

'

shear connection of an I-Beam •

Fillet elds in shear are commonly !sed

•

"onnect entire eb and ad(!st eld si)e to s!it shear load

'

moment connection of a plate Stress in weld σ = M (d/2) / I = M (d/2) / (ad3/12) [kN/m2] q =σa = M (d/2) / (d3/12) = M (d/2) / I’ [kN/m] Where I’ = I/a

M d

hen !h""se a weld si#e a that will !arr$ q * $ +a

moment connection of a plate %an als" &se sim'liied a''r"a!h •

•

•

*reak m"ment int" a "r!e !"&'le

"$T

%h""se a s&ita+le weld si#e

M d

hen !al!&late the req&ired len,th " the weld t" !arr$ the tensi"n "r!e  #es!ltant tension force T $ M%d

* $ T%l

elded shear plate ' ' "entroid of eld gro!p

e

M $ 'e

simplified approach 'e0%d •

•

Brea eccentric load !p into a vertical force along the vertical eld and a pair .co!ple/ of hori)ontal forces along the hori)ontal elds Then choose lengths of elds to carry the calc!lated forces

' d

'

'e0%d e0

1&tress2 calc!lations

'

'

3 M $ 'e

M $ 'e

1&tress2 calc!lations for vertical force ' *'

'

4ivide shear e*!ally amongst all the eld lines * $ ' % .total length of eld/ "hoose a eld si)e that can carry the 1stress2 * 5ote * is act!ally a force per length 65%m7

1&tress2 calc!lations for Moment M $ 'e xB

xA

Treat the eld gro!p as a crosssection s!b(ected to a torsional moment

A *Ax *Ay *AM

yA

*Ax $ M yA % I0p *Ay $ M xA % I0p

M $ 'e *By *BM *Bx

I0p8 $ I0x8 3 I0y8 here I0 $ I%a

yB

B

*AM $ .*Ax8 3 *Ay8/9: &imilarly for point B Then select eld si)e for max *

1&tress2 calc!lations for combined ' and M A

*Ax

*Ay '

*A' *A M $ 'e

B

"ombine the eld 1stress2 components from the vertical force and the torsional moment

*A $ 6*Ax8 3 .*A' 3 *Ay/879: &imilarly for point B or any other point that might be critical Then select eld si)e for the maxim!m val!e of *

example of a complex connection

bolted connections

moment splice in a col!mn

moment splice of an I-Beam • •

Bolted connection "$T 4ivide tension and compression res!ltant e*!ally beteen bolts

M d

#es!ltant tension force T $ M%d

shear connection in bridge diaphragm girder  .Alex Fraser Bridge/

shear connection of an I-Beam •

Bolted connections to transfer shear are commonly !sed

•

"onnect entire eb to avoid stress concentrations and shear lag

'

=nd plate "oped flanges to fit in beteen col!mn flanges

shear connection via end plate

moment connection ith and end or base plate

moment connection ith f!lly elded end plate Tmax

Ti $ Tmax .hi % hmax/ Ti

M $ > Ti hi

hmax hi

"$>T

M

pre-tensioned moment connection

pre-tensioned Moment "onnection Apply both tension and compression forces to pretensioned bolts "ompression force can be seen as a release of the tension force

Ti

3 TM

M

$

M

bolted shear plate e

P

P "entroid of bolt gro!p

M $ Pe

vertical load 'P

P

4ivide the force by n, the n!mber of bolts 'P $ P % n

'P

moment Treat the bolt gro!p as a cross-section s!b(ected to a torsional moment

xi bolt i

FxM r i

FyM

FMi

M

yi

Ip $ >i A r i8 $ >i A .xi8 3 yi8/ and ith I0P $ IP %A FxM $ M yi % I0p FyM $ M xi % I0p

bolt area A

FMi $ .FxM8 3 FyM8/9: Then select a bolt si)e for the