general connection in steel.ppt

11/09/2020 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


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


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


Components of Connections

Connectors Connecting Part

Cutting, Drilling, Bolting, Welding of Plates, Cleats, Angle, Rolled sections


Design PhilosophyConnections

Art Science

Involves equilibrium, limit states andlower bound theorem

+Determination of most efficientload paths because all connectionsare 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


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


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



• 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



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



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



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



• 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


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



Axial Connections


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



Shear or Pin Connections

(a) (b)

(c) (d)



Stiffened & unstiffened seat angle connections

R

Seat angle

Stiffener

45O

Clip

Bearing

)/(/ moyw YftwRb)(1 bf rTbb

)//( moybr YfRA



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



Moment Connections

(a) (b)

(c) (d)



End plate connections

End plate



• Prying forces arises when a relatively thin plate deflects outward, thus pressing the unsupported edges against the supporting piece



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



Bracket connection

2/ diMdiR 2/ yiMyT n


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



Tension field – Post buckling behaviour



Column splice

• Axial force are transferred in accordance with the area of flanges and web



Column bases

• Axial force are transferred in accordance with the area of flanges and web


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

general connection in steel.ppt

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