Connections are critical components that join structural elements to transfer forces safely. Steel connections influence construction costs and failures often originate from connections. Common steel connections include bolted, welded, and riveted joints. Bolted connections can be bearing type or friction grip bolts. Welded joints include fillet and butt welds. Connections must be designed for the expected loads, with shear connections allowing rotation and moment connections resisting it. Proper connection design is important for structural integrity and economy.

1. Connections In Steel
Structures
By Hariyali Pujara

2. Introduction
• Connections are the devices which are used to join elements of a
structure together at a point such that forces can be transferred
between them safely.
• Historically, most major structural failures have been due to some
form of connection failure.
• Steel connections have a direct influence on the cost of the framing
system.
• While a connection may be efficient in the use of material, it may still
be very expensive to erect. Repetitive connection design may save
costs.

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• Components of connection
• Bolts
( Image is from Google)

4. Rivets
Continue….
( Image is from Google)

5. • Weld
Continue….
( Image is from Google)

6. • Connecting Plates • Connecting Angles
Continue….seat angle and clip plate, end plate, cleats
( Image is from Google)

7. Types Of Connections
Connections depend on: Type of loading, Strength and stiffness,
Economy, Difficulty or ease of erection
Based on means of connections
1. Bolted Connections
2. Welded Connections
3. Riveted Connections
Based on forces to be transferred
1. Shear Connections
2. Moment Connections
Beam and column Splices connections
Bracket connections etc….

8. 1.Bolted Connections
• Bolting is the preferred method of connecting members on the site.
• Several types of bolts are used in bolted connection.
1) Unfinished bolts or black bolts or C grade bolts (IS 1363 : 2002)
2) Turned bolts
i. Precision bolts or A grade bolts (IS 1364 : 2002)
ii. Semi-precision bolts or B grade bolts (IS 1364 : 2002)
3) Ribbed bolts
4) High strength friction grip bolts (IS 3757 : 1985 and IS 4000 : 1992)

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1. Black Bolts:
• It is the most common type of bearing bolts in clearance holes, often
referred to as ordinary bolts.
• They are popular since they are economical, both in terms of material
and installation costs.
• The force transfer mechanism under shear is as shown in Fig.

10. Bolt Shear Transfer Mechanism In Bearing
Connections
• The force is transferred by bearing
between the plate and bolts at the bolt
holes. The bolts experience single or
double shear depending upon the
plate configuration. The failure may
be either by shearing of the bolts or
bearing of the plate and the bolt.
Disadvantage: Bearing type of bolted connections is that the elements
undergo some slip even under a small shear, before being able to transfer
force by bearing
( Image is from Google)

11. 2. High strength friction grip (HSFG) bolts.
• In HSFG bolted joints, high strength bolts are pre-tensioned against the
plates to be bolted together, so that contact pressure is developed between
the plates being joined.
• When external shear force is applied, the frictional resistance to slip
between the plates prevents their relative slip. These bolted joints achieve
higher stiffness in shear because of frictional resistance between the contact
surfaces.
Continue..

12. Bolt Shear Transfer Mechanism In HSFB
Connections
• Only when the externally
applied force exceeds the
frictional resistance between
the plates, the plates slip and
the bolts bear against the bolt
holes. Thus even after slip,
there is a reserve strength due
to bearing.
Disadvantage: The HSFG bolts are expensive both from material and
installation points of view. They require skilled labour and effective
supervision.
( Image is from Google)

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• Bolted connection further can be classified in two:
1. Lap joint
2. Butt Joint
Lap Joint:
• When the two members to be
connected together by
overlapping then the joint is
called lap joint.
• A single bolted lap joint and a
double bolted lap joint are shown
in figure respectively.
( Image is from Google)

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Butt Joint:
• When the two members are to
be connected by placing the
members end to end and
additional plate/plates provided
on either one or both sides to
attach them properly, then this
joint is called butt joint and the
additional plate is called cover
plate.( Image is from Google)

15. Which joint is better and which joint is more desirable?
It is more desirable to provide a butt joint rather than a lap joint for main
two reasons:
• In the case of a double cover butt joint, the total shear force to be
transmitted by the members is split into two parts and the force acts on
each half. But in the case of lap joints, there is only one plate one
which the forces acts and therefore, the shear-carrying capacity of a
bolt in a double cover butt joint is double that of a bolt in a lap joint.
• In the case of a double cover butt joint, eccentricity of forces does not
exist and hence bending is eliminated, whereas it exists in the case of a
lap joint.

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( Image is from Google)

17. 2.Riveted Connections
• Riveted joints are very rare in
modern steel construction practice,
were predominantly used in
railway bridges (vibration) in India
and it is very similar to bearing
type of bolted connections.
• Structural rivets are driven hot, the
rivet shank expands to fill the hole
while being driven.
( Image is from Google)

18. Types of riveted joints
A riveted joint may be classified according to arrangement of rivets
and plates
Lap joint
i. Single riveted lap point
ii. Double riveted lap point
Butt joint
i. Single riveted single cover butt joint
ii. Single riveted double cover butt joint
iii. Double rivet double cover butt joint

19. 3.Welded Connections
• Welded connections are direct and efficient means of transferring
forces from one member to the adjacent member.
• Welded connections are generally made by melting base metal from
parts to be joined with weld metal, which upon cooling form the
connection.
• The welded connections in a majority of the cases may be categorised
as fillet weld and butt (or groove) welds.

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• Fillet welds, are made against two
surfaces of adjacent plates to join
them together.
• Butt welds, are made by butting
plate surfaces against one another
and filling the gap between
contact surfaces with weld metal,
in the process fusing the base
metal also together.
( Image is from Google)

21. Fillet Weld Butt Weld
simple, fast and economical to make more expensive than fillet welds because of the
edge preparation required
no prior edge preparation is necessary, easily designed and fabricated to be as strong as
the member
does not require very skilled labour. require more skilled manpower, than that required
for filled welds.
less attractive in appearance. better appearance, compared to fillet welds, and
poorer performance under fatigue loading, and better fatigue characteristics, compared to fillet
welds,
Throat thickness=0.707 x weld size Thickness=(5/8) x thickness of thinner plate
not appropriate to transfer forces large in
magnitude
easy to detail and the length of the connection is
considerably reduced.
Difference Between Fillet Weld And Butt Weld

22. Based on forces to be transferred
1. Shear Connection
• A shear connection (also called a
simple connection) transfers
shear forces and little or no
moment to the connecting
member, thus allowing end
rotation of the member.
• Shear connections may be
made to the web of the
supported member while the
flanges remain unconnected.
( Image is from Google)

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Colum web in shear
( Image is from Google)

24. 2. Moment Connections
• Moment connections are also called rigid
connections.
• Moment connections carry a portion or
the full moment capacity of the supported
member thus preventing any end-rotation
of the member and also carry the shear
component of the load.
• Relative rotation between the supporting
and supported members is negligible.
• In this type of connection both the webs
and flanges are connected. ( Image is from Google)

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Column flange in bending
( Image is from Google)

26. 3. Beam and column splices
• It is often required to join structural
members (Beam, column) along their
length due to the available length of
sections being limited and also due to
transportation and erection
constraints. Such joints are called
splices.
• Typical bolted column splices used
for rolled I section and hollow
section members are shown in the
figure on the right.
( Image is from Google)

27. Thank You….!!!!