What Will You Gain From This Presentation?*Why steel structures?What is connections?Components of connectionsDesign philosophyClassification criteria of connectionsUnderstanding different types of connectionsSpecial connections

Why Steel?Steel allows for reduced frame construction time and the ability to construct in all seasonsSteel makes large spans and bay sizes possible, providing more flexibilitySteel is easier to modify and change to an extent facility over its lifeSteel is lightweight and can reduce foundation costsSteel is durable, long-lasting and recyclable

There is always a solution in steel -AISC

ConnectionsConnects different inter/intra-elements Load transmission medium top to foundationDecide behavior of structure Rigid / FlexibleBrittle failureCost 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 ConnectionsCutting, Drilling, Bolting, Welding of Plates, Cleats, Angle, Rolled sections

Design Philosophy

+ 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 rotationsDeformation 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 connections

1 Riveted2 Bolted3 Welded1 Axial2 Shear3 Moment1 Single plate-angle 2 Double web angle3 Seated angle4 Stiffened seat1 Beam to beam2 Column to column3 Beam to column4 Base1 Shop2 Field

Based on connecting mediumManufactured from mild steel, aluminium, copper, brass and special alloys. Length > GripHeating up to 980OCCold rolled used in aircraft industryIntermediate between friction and bearing typeSimilar to pileObsolete in structure

Based on connecting mediumBolts are classified as Black bolts, Turned/close tolerance and HFSGGrade = 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9. =12 to 68mm

Black bolts = Most commonly used, ductile, static condition, rough surfaceTurned bolts = Machined surface, more expensive, dynamic conditionsHSFG Bolts = Proof load is used (no yield point), slip critical connections, good where vibration & impact is induced, pretensioned

Based on connecting mediumfailure of bolted connections

Shearing of Bolts & platesBearing of Bolts & PlatesTension failure of Bolts & PlatesBearing of plate, t

Based on connecting mediumLoad transfer mechanism bolted connections

Based on connecting mediumTypes of welds

Based on connecting mediumIn the design procedure the internal force on the fillet weld is resolved into components parallel andtransverse to the critical plane of the weld throatA uniform stress distribution is assumed on the critical throat section of the weld, leading to the normal stresses and shear stresses

f1wwCritical plane

Type of force connection is expected transferAxial force is transferred by shear through weld or bolts using cover platesCover plates = 5/8 t

Axial Connections

Type of force connection is expected transferAxial Connections

Type of force connection is expected transferCurve 1: At a very low moment it safely yields (M1 ) and allows the connection to rotate ( ) , This is typical of top angle, web framing angles, connectionsCurve 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 restraintCurve 3 : Using a top connecting plate detailed to develop the full end moment

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

Type of force connection is expected transferStiffened & unstiffened seat angle connections

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

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

Type of force connection is expected transferEnd plate connectionsEnd plate

Type of force connection is expected transferEnd plate connections

Type of force connection is expected transferEnd plate connections

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

Type of force connection is expected transferSplit Beam/T- Stub connectionsShear is transferred by web angleF = M/DbFind thickness of web of stubFlange design Tension & Prying effect

Type of force connection is expected transferBracket connection

Type of members the connection are joining

Beam spliceDesigned for M and VFlange splice plate work as flangeWeb splice plate work as webFlanges transfer MWeb transfer V (Except slender web)Flush end plate as end plate moment connections

Type of members the connection are joining

Tension field Post buckling behaviour

Type of members the connection are joining

Column spliceAxial force are transferred in accordance with the area of flanges and web

Type of members the connection are joining

Column basesAxial force are transferred in accordance with the area of flanges and web

ReferencesOwens & Cheal Structural Steel Work ConnectionsEuro code -3AISC Connection ManualAkbar Tamboli Handbook of Connection DesignSubramanian Design of Steel StructuresINSDAG Teaching ResourcesESDEP Notes -European Steel Design Education Programme

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