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07/04/23 General Connections In Steel Structures 1
07/04/23 General Connections In Steel Structures 2
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
07/04/23 General Connections In Steel Structures 3
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
07/04/23 General Connections In Steel Structures 4
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
07/04/23 General Connections In Steel Structures 5
Components of Connections
Connectors Connecting Part
Cutting, Drilling, Bolting, Welding of Plates, Cleats, Angle, Rolled sections
07/04/23 General Connections In Steel Structures 6
Design PhilosophyConnections
Art Science
Involves equilibrium, limit states and lower bound theorem
+ Determination of most efficient load paths because all connections are indeterminateStrength : Forces are calculated applying equilibrium > AnalysisStiffness : 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
07/04/23 General Connections In Steel Structures 7
Classification of connectionsConnections
Type of connecting medium
Type of force connection is
expected transfer
Structural element that made up the
connection
Type of members the connection are
joiningBased on location
1 Riveted2 Bolted3 Welded
1 Axial2 Shear3 Moment
1 Single plate-angle 2 Double web angle3 Seated angle4 Stiffened seat
1 Beam to beam2 Column to column3 Beam to column4 Base
1 Shop2 Field
07/04/23 General Connections In Steel Structures 8
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
07/04/23 General Connections In Steel Structures 9
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
07/04/23 General Connections In Steel Structures 10
Based on connecting medium
failure of bolted connections
Shearing of Bolts & plates
Bearing of Bolts & Plates
Tension failure of Bolts & Plates
mbsbsnbn YAnAnfuVnsb ))(3/(( )
mbnub YAfTnb /)90.0(
mbub YdtfkVnpb /)5.2(Bearing of plate, t<0.5bolt dia
07/04/23 General Connections In Steel Structures 11
Based on connecting medium
Load transfer mechanism bolted connections
(a) Bearing Connection
(b) Friction Connection
T
Frictional Force TClamping Force, PO
Bearing stresses
Tension in bolt
T
T
T
Clamping Force, PO
07/04/23 General Connections In Steel Structures 12
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
AA
Section A-A
(d) Plug weld
07/04/23 General Connections In Steel Structures 13
Based on connecting medium
• In the design procedure the internal force on the fillet weld is resolved into components parallel andtransverse 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 22 3 wfwfu
)*3/(*707.0* Ymfysizefd
07/04/23 General Connections In Steel Structures 14
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
07/04/23 General Connections In Steel Structures 15
Type of force connection is expected transfer
Axial Connections
07/04/23 General Connections In Steel Structures 16
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
07/04/23 General Connections In Steel Structures 17
Type of force connection is expected transfer
Shear or Pin Connections
(a) (b)
(c) (d)
07/04/23 General Connections In Steel Structures 18
Type of force connection is expected transfer
Stiffened & unstiffened seat angle connections
R
Seat angle
Stiffener
45O
Clip
Bearing
)/(/ moyw YftwRb
)(1 bf rTbb
)//( moybr YfRA
07/04/23 General Connections In Steel Structures 19
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
07/04/23 General Connections In Steel Structures 20
Type of force connection is expected transfer
Moment Connections
(a) (b)
(c) (d)
07/04/23 General Connections In Steel Structures 21
Type of force connection is expected transfer
End plate connections
End plate
07/04/23 General Connections In Steel Structures 22
Type of force connection is expected transfer
End plate connections
07/04/23 General Connections In Steel Structures 23
Type of force connection is expected transfer
End plate connections
07/04/23 General Connections In Steel Structures 24
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
07/04/23 General Connections In Steel Structures 25
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
07/04/23 General Connections In Steel Structures 26
Type of force connection is expected transfer
Bracket connection
2/ diMdiR 2/ yiMyT n
07/04/23 General Connections In Steel Structures 27
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
07/04/23 General Connections In Steel Structures 28
Type of members the connection are joining
Tension field – Post buckling behaviour
07/04/23 General Connections In Steel Structures 29
Type of members the connection are joining
Column splice
• Axial force are transferred in accordance with the area of flanges and web
07/04/23 General Connections In Steel Structures 30
Type of members the connection are joining
Column bases
• Axial force are transferred in accordance with the area of flanges and web
07/04/23 General Connections In Steel Structures 31
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
07/04/23 General Connections In Steel Structures 32
07/04/23 General Connections In Steel Structures 33