N-W.F.P. University of Engineering and
Technology Peshawar
Lecture 04: Bolted Connections
By: Prof Dr. Akhtar Naeem Khan
chairciv@nwfpuet.edu.pk
CE-409: Lecture 04
Prof. Dr. Akhtar Naeem Khan
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Topics to be Addressed
 Types of connectors
 Tightening procedures
 Behavior of Bolted & Riveted connections
 Types of Bolted connections
 Types of connection failures
 Code Requirements
 Design Examples
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Prof. Dr Akhtar Naeem Khan
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Types of Connectors
 Components which make up the
complete structure are fastened together
by means of:
1. RIVETS (older version)
2. BOLTS (newer version)
3. WELDS
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Types of Connectors
1. Rivets:
 They are made from rivet bar stock in a
machine which forms one head and shears the
rivet to desired length.
 Steel rivets are always heated before driving
 Most rivets are driven by pressure-type riveters
which complete riveting in one stroke.
Typical Round Head Rivet
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Types of Connectors
1. Rivets:
 Rivets are generally made from steel
conforming to ASTM A502 and comes in 2
grades:
i.
Grade 1(carbon steel)
ii.
Grade 2 (carbon-manganese steel)
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Types of Connectors
1. Rivets:
Round Head Rivet
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Countersunk Rivet
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Types of Connectors
1. Rivets:
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Types of Connectors
1. Rivets: Riveting processes
Rivet Heating Oven
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Rivet Heater
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Types of Connectors
1. Rivets: Riveting processes
Modern Riveting Gun
Earlier Riveting Gun
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Prof. Dr. Akhtar Naeem Khan
Types of Connectors
1. Rivets: Characteristics of riveted connections
 In riveted connections magnitude of
clamping is function of length of rivet
and magnitude of shrinkage after the
head is formed.
 Magnitude of slip depends on the extent
to which rivet fills the hole.
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Types of Connectors
1. Rivets: Causes of rivet obsolescence

Riveting required a crew of 4 to 5
experienced riveters

Bolt installation is less labor intensive

Riveting is time consuming operation
requiring preheating, driving and finishing
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Types of Connectors
1. Rivets: Causes of rivet obsolescence

Rivet strength is low compared to high
strength bolts

High strength bolts are now economical

Riveting is still used in some industries and
applications such as aircraft industry
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Types of Connectors
2. Bolts: Two common types of bolts are:
a) Unfinished (A307)
 A307 is known by names unfinished, rough,
common, ordinary and machine.
 They are made of low carbon steel having
tensile strength of 60Ksi.
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Types of Connections
2. Bolts: Two common types of bolts are:
b) High strength bolt (A325,A449,A490).
 A325 is made of medium carbon steel whose
tensile strength decreases with increase in dia.
 High strength bolts can be tightened to large
tensions.
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Types of Connections
2. Bolts:
Typical High Strength Bolt
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Tightening procedures
 Research Council on Structural
Connections (RCSC) prescribes four
tightening procedures.
1. Turn of the nut method
2. Calibrated-wrench tightening
3. Installation of alternate design bolts
4. Direct-tension-indicator tightening
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Tightening procedures
Torque Wrench
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Tightening procedures
Positive Tension Shear Bolt
Bolt Installation Procedure
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Tightening procedures
Direct Tension Indicating Washers
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Behavior of Bolted & Riveted
connections
T
T
T = Tensile Force on
Connection
∆ = Joint Displacement
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Behavior of Bolted & Riveted
connections
 In riveted connections magnitude of
clamping is function of length of rivet
and magnitude of shrinkage after the
head is formed.
 Magnitude of slip depends on the extent
to which rivet fills the hole.
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Types of Bolted connection
1. Slip-Critical connections

Connection transmits the force by friction
produced between the faying surfaces by
the clamping action of the bolts.

Slip-critical connections are recommended
for joints subjected to stress reversal,
severe stress fluctuation, impact, vibration
or where slip is objectionable
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Types of Bolted connection
1. Slip-Critical connections
The clamping force applied to the bolt brings the two members close
enough so that appreciable friction is produced between them which
is then responsible for resisting the load. The more the clamping
force the more is the friction and strong is the connection but the
clamping force need not to be greater than tensile strength of the
bolt.
Slip critical connection becomes bearing type connection after the
slip occurs so every slip critical connection is essentially a bearing
type connection also.
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Types of Bolted connection
2. Bearing type connections
 Load is transferred by shearing and
bearing on the bolt.
 Capacity in shear depends on whether
shear plane intersects the body of bolt
or threaded portion.
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Types of Bolted connection
2. Bearing type connections
Bearing type connection is the most widely used general type
connection in which the load is resisted by the bolt body without
any friction between faying surfaces.
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Type of connection Failures
1. Shearing Failure of Bolts.
2. Bearing Failure of plate.
3. Tearing failure at edge of plate.
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Type of connection Failures
1. Shearing failure of bolts
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Type of connection Failures
1. Shearing failure of bolts
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Type of connection Failures
2. Bearing Failure of Plate
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Type of connection Failures
Shear & Bearing Area
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Type of connection Failures
3. Tearing Failure at edge of Plate
Shearing Failure edge of plate
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Transverse Tension Failure
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Type of connection Failures
3. Tearing Failure at edge of Plate
 Tests showed, failure by tearing through free edge of material
will not occur if Le measured parallel to line of applied force is
not less diameter of bolt multiplied by ratio of bearing stress
to tensile strength of connected part.
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Type of connection Failures
3. Tearing Failure at edge of Plate
Force transmitted by the bolt
P = fp D t ------------------------(A)
Force to cause failure along two shear planes
P = 2(Le – D / 2 ) t u
u = 0.7 Fu
P = 1.4DtFu(Le/D –1/2) -----(B)
Equating (A) & (B)
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Type of connection Failures
3. Tearing Failure at edge of Plate
------- (C)
Eqn (C) can be approximated as
So Eqn becomes
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Type of connection Failures
3. Tearing Failure at edge of Plate
ASD
LRFD
 Tearing length or
Edge distance
 = 0.75
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With FOS= 2
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Type of connection Failures
3. Tearing Failure at edge of Plate
ASD
LRFD
 Spacing between holes
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Type of connection Failures
Eccentricity of Applied Force
 Plates of lap joint tends to bend.
 Bending produces non uniform bearing of
the fastener on the plates
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Code Requirements
Topic
Ref. Text Book
Ref. LRFD Code
Minimum edge Distance
Table 2-8
Table J3.4
Allowable Working Stress on
Fasteners or Connected
Material
Table 2-9
Allowable Load for SlipCritical Connections
Table 2-10
Allowable Stresses A502
Rivets
Table 2-12
Design Strength of Fasteners Table 2-13
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Table J3.6
Table J3.2
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Code Requirements
AISC Minimum Edge Distance
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Code Requirements
Minimum installation tension
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Code Requirements
Allowable Stresses
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Code Requirements
Properties of structural bolts
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Code Requirements
Allowable load for Slip critical connection
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Code Requirements
Design strength of fasteners
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Design Example No.1 (ASD Method)
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Design Example No.1 (ASD Method)
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Design Example No.1 (ASD Method)
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Design Example No.1 (ASD Method)
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Design Example No.1 (LRFD Method)
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Design Example No.1 (LRFD Method)
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Design Example No.1 (LRFD Method)
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Design Example No.1 (LRFD Method)
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Design Example No.2 (LRFD Method)
W = 10 in
t = .25in
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Design Example No.2 (LRFD Method)
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Design Example No.2 (LRFD Method)
Fub
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Design Example No.2 (LRFD Method)
2”
6”
P = 77 Kips
2”
2”
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3”
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Thanks
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