Connections of steel member by rivet and bolt

8/11/2019 Connections of steel member by rivet and bolt

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CONNECTIONS

RAJU SHARM A

ASSISTANT PROFESSOR

DEPARTMENT OF CIVIL ENGINEERING

CHANDIGARH UNIVERSITY

GHARUAN, M OHALI

DSS-I

Chapter-2


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Connections

Connections

Riveted

Bolted

Welded

Subjected to axial and eccentric load


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The design of connection is very important becausethe failure of joint is sudden and catastrophic.

Following three types of connections my be made bysteel structures:

Riveted

Bolted

Welded


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Riveted Connections

Riveted Connection

Riveting is a method of joining together pieces of metal by

inserting ductile metal pins called rivets into holes of pieces to beconnected and forming a head at the end of the rivet to prevent

each metal piece from coming out

Rivet hole are made in the structural member to be connected by

punching or by drilling.


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Disadvantages of Riveted connections

a) It is associated with high level of noise pollution

b) It needs beating the rivet to red hot

c) Inspection of connection is skilled work

d) Removing poorly installed rivets is costly

e) Labour cost is high


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Bolted

A bolt is a metal pin with a head formed at one end and

shank threaded at the other in order to receive a nut.

Bolts are used for joining together pieces of metal by

inserting them through hole in the metal and tighteningthe nut at the threaded ends..

Bolts are classified as:

Unfinished (Black ) Bolts

Finished (Turned) Bolts High Strength Friction Grip (HSFG) Bolts


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Unfinished/Black Bolts

These bolts are made from mild steel rods with square or hexagonal head.

The shank is Left unfinished i.e. Rough as rolled. Black hole of nominal

diameter of sizes 12,16,20,22,24,27,30 and 33 and 36 mm are available.

These bolts are designated as M16,M20,M20,M24 etc. IS 1364 part 1

gives specifications for such bolts. The shanks of black bolts are

unfinished, the bolt may not establish contact with structural member at

entire zone of contact surface. Joints remain quite loose resulting into

large deflections. The yield strength of commonly used black bolts is 240

N/mm and ultimate strength 400 N/mm.


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High Strength Friction Grip Bolts (HSFG)

The HSFG bolts are made from high strength steel rods. The

surface of the shank is kept unfinished as in the case of black

bolts. These bolts are tightened to a proof load using calibrated

wrenches. Hence they grip the members tightly. If the joint is

subjected to shearing load it is primarily resisted by frictional

force between the members and washers. The shank of the bolt is

not subjected to any shearing. The result into no- sllipage in the

joint. Hence such bolts can be used to connect members subjected

to dynamic loads also


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Classification of Bolts based on Type of Load

Transfer

a) Bearing Type

b) Friction Group Type

Unfinished (black) bolts and finished (turned) bolts belong to

bearing type since they transfer shear force from one member

to other member by bearing, whereas HSFG bolts belong to

friction grip type since they transfer shear by friction.


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Advantage of HSFG Bolts over bearing type Bolts

1. Joints are rigid i.e; no slip take place in the joint

2. As load transfer is mainly by friction, the bolts are not

subjected to shearing and bearing stresses.

3. High static strength due to high frictional resistance

4. High fatigue strength since nuts are prevented from loosening

and stress concentrations avoided due to friction grip

5. Smaller number of bolts result into smaller sizes of gusset

plates


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Disadvantages of HSFG Bolts

1. Material cost is high

2. The special attention is to be given to workmanship especially

to give them right amount of tension


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Advantages and Disadvantages of BoltedConnection

Making joint is noise less

Do not need skilled labour

Need less labour Connection can be made quickly

Structure can be put to use immediately

Accommodates minor discrepancies in dimensions

Alterations, if any ,can be done easily

Working area required in the field is less


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Disadvantages

1. Tensile strength is reduced considerably due to stress

concentrations and reduction of area at the root of the thread

2. Rigidity of joints is reduced due to loose fit, resulting into

excessive deflections.

3. Due to vibrations nuts are likely to loosen, endangering the

safety of the structures.

Documents

Connections of steel member by rivet and bolt