This presentation discusses steel connections, including why steel structures are used, the components and types of connections, and the design philosophy. It covers the classification of connections based on the connecting medium (riveted, bolted, welded), type of force transferred (axial, shear, moment), and members joined (beams, columns, bases). Connection types discussed include axial, shear/pin, moment, end plate, split beam, bracket, beam splice, column splice, and column bases. The objectives are to understand the role of connections in load transfer and structural behavior, as well as the design of different connection configurations.

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What Will You Gain From This Presentation?
2
• Why steel structures?
• What is connections?
• Components of connections
• Design philosophy
• Classification criteria of connections
• Understanding different types of connections
• Special connections

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Why Steel?
• Steel allows for reduced frame construction time and the
ability to construct in all seasons
• Steel makes large spans and bay sizes possible, providing
more flexibility
• Steel is easier to modify and change to an extent facility over
its life
• Steel is lightweight and can reduce foundation costs
• Steel is durable, long-lasting and recyclable
‘There is always a solution in steel’ -AISC

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Connections
• Connects different inter/intra-elements
• Load transmission medium – top to foundation
• Decide behavior of structure – Rigid / Flexible
• Brittle failure
• Cost of connections > steel work (60 – 40)
• All chores – Analysis & Design - Appropriate
- Drawings – Sufficient
- Execution - Practical
‘A structure is only strong as its weakest link’ –N Subramanian

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Components of Connections
Connectors Connecting
Part
Cutting, Drilling, Bolting, Welding of Plates, Cleats, Angle, Rolled sections

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Design Philosophy
Connections
Art Science
Involves equilibrium, limit states
and
lower bound theorem
+
Determination of most efficient
load paths because all connections
are indeterminate
Strength : Forces are calculated applying equilibrium > Analysis
Stiffness : The stiffness of the connection affects the level of loading for which it should
be designed.
Rigid – No influence of their deformations (High rotational stiffness)
Pinned connections - Flexible enough to accommodate rotations
Deformation Capacity : Qualitative & difficult to check
Ductile connections that have a great deformation capacity contribute to the
overall safety of the structure in the event that the connection becomes
overloaded. plastic design is employed with plastic hinges forming in the
connections

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Classification of connections
Connections
Type of connecting
medium
Type of force
connection is
expected transfer
Structural element
that made up the
connection
Type of members
the connection are
joining
Based on location
1 Riveted
2 Bolted
3 Welded
1 Axial
2 Shear
3 Moment
1 Single plate-angle
2 Double web angle
3 Seated angle
4 Stiffened seat
1 Beam to beam
2 Column to column
3 Beam to column
4 Base
1 Shop
2 Field

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Based on connecting medium
• Manufactured from mild
steel, aluminium,
copper, brass and special
alloys.
• Length > Grip
• Heating up to 980OC
• Cold rolled used in
aircraft industry
• Intermediate between
friction and bearing type
• Similar to pile
• Obsolete in structure

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Based on connecting medium
• Bolts are classified as Black bolts, Turned/close tolerance and HFSG
• Grade = 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9. Ø=12 to 68mm
• Black bolts = Most commonly used, ductile, static condition, rough surface
• Turned bolts = Machined surface, more expensive, dynamic conditions
• HSFG Bolts = Proof load is used (no yield point), slip critical connections,
good where vibration & impact is induced, pretensioned

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Based on connecting medium
failure of bolted connections
Shearing of Bolts & plates
Bearing of Bolts & Plates
Tension failure of Bolts & Plates
mb
sb
s
nb
n Y
A
n
A
n
fu
Vnsb )
)(
3
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(( )

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mb
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ub Y
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(
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mb
u
b Y
dtf
k
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)
5
.
2
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Bearing of plate, t<0.5bolt dia

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Based on connecting medium
Load transfer mechanism bolted connections
(a) Bearing Connection
(b) Friction Connection
T
Frictional Force T
Clamping Force, PO
Bearing stresses
Tension
in bolt
T
T
T
Clamping Force, PO

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Based on connecting medium
Types of welds
A
Ends shall be semi
circular
A
Section A-A
(c) Slot weld
(a) Groove welds
(b) Fillet welds
A
A
Section A-A
(d) Plug weld

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Based on connecting medium
• In the design procedure the internal force on the fillet weld is
resolved into components parallel and
transverse to the critical plane of the weld throat
• A uniform stress distribution is assumed on the critical throat
section of the weld, leading to the normal stresses and shear
stresses
f1
w
w
Critical
plane    2
2
3 w
fw
fu 


)
*
3
/(
*
707
.
0
* Ym
fy
size
fd 

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Type of force connection is expected transfer
• Axial force is transferred by shear through weld or bolts using cover plates
• Cover plates = 5/8 t
Axial Connections

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Type of force connection is expected transfer
Axial Connections

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Type of force connection is expected transfer
• Curve 1: At a very low
moment it safely yields (M1 )
and allows the connection to
rotate (θ ) , This is typical of
top angle, web framing
angles, connections
• Curve 2 : Under working load
it elastically yields sufficiently
to provide the necessary
rotation of the connection,
and yet has sufficient
resistance to develop the
proper end moment.
Although thick top angles
have been suggested for
service as semi-rigid
connections, they are
impractical to design and
fabricate with the desired
built-in restraint
• Curve 3 : Using a top
connecting plate detailed to
develop the full end moment

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Type of force connection is expected transfer
Shear or Pin Connections
(a) (b)
(c) (d)

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Type of force connection is expected transfer
Stiffened & unstiffened seat angle connections
R
Seat angle
Stiffener
45O
Clip
Bearing
)
/
(
/ mo
yw Y
f
tw
R
b
)
(
1 b
f r
T
b
b 


)
/
/( mo
y
br Y
f
R
A 

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Type of force connection is expected transfer
Single or double web angle connections
Web Angle
• Depth of cleat = (0.6 to 0.7 Db)
• Minimum thickness of web
angle is 8mm, Db= 450
• Thicker the angle = Stiffer the
angle

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Type of force connection is expected transfer
Moment Connections
(a) (b)
(c) (d)

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Type of force connection is expected transfer
End plate connections
End plate

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Type of force connection is expected transfer
End plate connections

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Type of force connection is expected transfer
End plate connections

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Type of force connection is expected transfer
• Prying forces arises when a relatively thin plate deflects outward, thus pressing the
unsupported edges against the supporting piece

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Type of force connection is expected transfer
Split Beam/T- Stub connections
Bolts in single
shear
Bolts in
tension (Prying
effect)
• Shear is transferred by web
angle
• F = M/Db
• Find thickness of web of stub
• Flange design – Tension &
Prying effect

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Type of force connection is expected transfer
Bracket connection

 2
/ di
Mdi
R 
 2
/ yi
My
T n

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Type of members the connection are joining
Beam splice
• Designed for M and V
• Flange splice plate work as flange
• Web splice plate work as web
• Flanges transfer M
• Web transfer V (Except slender web)
• Flush end plate as end plate
moment connections

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Type of members the connection are joining
Tension field – Post buckling behaviour

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Type of members the connection are joining
Column splice
• Axial force are transferred in
accordance with the area of
flanges and web

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Type of members the connection are joining
Column bases
• Axial force are transferred in accordance with the area of flanges and web

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References
• Owens & Cheal – Structural Steel Work Connections
• Euro code -3
• AISC Connection Manual
• Akbar Tamboli – Handbook of Connection Design
• Subramanian – Design of Steel Structures
• INSDAG – Teaching Resources
• ESDEP Notes -European Steel Design Education Programme

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