Lecture -04 Bolted Connections
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Transcript of Lecture -04 Bolted Connections
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N-W.F.P. University of Engineering and
Technology Peshawar
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 1
By: Prof Dr. Akhtar Naeem [email protected]
Lecture 04: Bolted Connections
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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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Components which make up thecomplete structure are fastened togetherby means of:
1. RIVETS (older version)
2. BOLTS (newer version)
3. WELDS
Types of Connectors
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1. Rivets:
They are made from rivet bar stock in amachine which forms one head and shears therivet to desired length.
Steel rivets are always heated before driving Most rivets are driven by pressure-type riveters
which complete riveting in one stroke.
Types of Connectors
Typical Round Head Rivet
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Rivets are generally made from steelconforming to ASTM A502 and comes in 2grades:
i. Grade 1(carbon steel)
ii. Grade 2 (carbon-manganese steel)
1. Rivets:
Types of Connectors
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Countersunk RivetRound Head Rivet
1. Rivets:
Types of Connectors
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1. Rivets:
Types of Connectors
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Rivet Heating Oven Rivet Heater
Types of Connectors
1. Rivets: Riveting processes
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Earlier Riveting Gun Modern Riveting Gun
Types of Connectors
1. Rivets: Riveting processes
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In riveted connections magnitude of
clamping is function of length of rivet
and magnitude of shrinkage after thehead is formed.
Magnitude of slip depends on the extent
to which rivet fills the hole.
Types of Connectors
1. Rivets: Characteristics of riveted connections
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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
Types of Connectors
1. Rivets: Causes of rivet obsolescence
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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
Types of Connectors
1. Rivets: Causes of rivet obsolescence
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a) Unfinished (A307)
A307 is known by names unfinished, rough,common, ordinary and machine.
They are made of low carbon steel havingtensile strength of 60Ksi.
Types of Connectors
2. Bolts: Two common types of bolts are:
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b) High strength bolt (A325,A449,A490).
A325 is made of medium carbon steel whosetensile strength decreases with increase in dia.
High strength bolts can be tightened to largetensions.
Types of Connections
2. Bolts: Two common types of bolts are:
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Types of Connections
2. Bolts:
Typical High Strength Bolt
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Research Council on StructuralConnections (RCSC) prescribes four
tightening procedures.
1. Turn of the nut method2. Calibrated-wrench tightening
3. Installation of alternate design bolts
4. Direct-tension-indicator tightening
Tightening procedures
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Torque Wrench
Tightening procedures
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Positive Tension Shear Bolt
Bolt Installation Procedure
Tightening procedures
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Direct Tension Indicating Washers
Tightening procedures
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T = Tensile Force on
Connection
= Joint Displacement
TT
Behavior of Bolted & Riveted
connections
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In riveted connections magnitude of
clamping is function of length of rivet
and magnitude of shrinkage after thehead is formed.
Magnitude of slip depends on the extent
to which rivet fills the hole.
Behavior of Bolted & Riveted
connections
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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, vibrationor where slip is objectionable
Types of Bolted connection
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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 theclamping force need not to be greater than tensile strength of the
bolt.
Types of Bolted connection
1. Slip-Critical connections
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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2. Bearing type connections
Load is transferred by shearing and
bearing on the bolt.
Capacity in shear depends on whethershear plane intersects the body of bolt
or threaded portion.
Types of Bolted connection
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2. Bearing type connections
Types of Bolted connection
Bearing type connection is the most widely used general type
connection in which the load is resisted by the bolt body withoutany 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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1. Shearing failure of bolts
Type of connection Failures
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1. Shearing failure of bolts
Type of connection Failures
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2. Bearing Failure of Plate
Type of connection Failures
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Shear & Bearing Area
Type of connection Failures
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3. Tearing Failure at edge of Plate
Shearing Failure edge of plate Transverse Tension Failure
Type of connection Failures
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Tests showed, failure by tearing through free edge of materialwill not occur if Lemeasured parallel to line of applied force is
not less diameter of bolt multiplied by ratio of bearing stress
to tensile strength of connected part.
Type of connection Failures3. Tearing Failure at edge of Plate
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Force transmitted by the bolt
P = fpD t------------------------(A)
Force to cause failure along two shear planes
P = 2(LeD / 2 ) t u
u= 0.7 Fu
P = 1.4DtFu(Le/D1/2) -----(B)Equating (A) & (B)
Type of connection Failures
3. Tearing Failure at edge of Plate
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------- (C)
Eqn (C) can be approximated as
So Eqn becomes
Type of connection Failures
3. Tearing Failure at edge of Plate
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LRFD ASD
= 0.75 WithFOS= 2
Tearing length or Edge distance
Type of connection Failures
3. Tearing Failure at edge of Plate
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LRFD ASD
Type of connection Failures
3. Tearing Failure at edge of Plate
Spacing between holes
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Eccentricity of Applied Force
Plates of lap joint tends to bend.
Type of connection Failures
Bending produces non uniform bearing ofthe fastener on the plates
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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 Slip-
Critical Connections
Table 2-10 Table J3.6
Allowable Stresses A502Rivets
Table 2-12
Design Strength of Fasteners Table 2-13 Table J3.2
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Code Requirements
C
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AISC Minimum Edge Distance
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Code Requirements
C d R i t
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Minimum installation tension
Code Requirements
C d R i t
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Allowable Stresses
Code Requirements
C d R i t
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Properties of structural bolts
Code Requirements
C d R i t
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Allowable load for Slip critical connection
Code Requirements
C d R i t
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Design strength of fasteners
Code Requirements
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)
Design Example No 1 (ASD Method)
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Design Example No.1 (ASD Method)
Design Example No 1 (ASD Method)
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Design Example No.1 (ASD Method)
Design Example No 1 (LRFD Method)
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Design Example No.1 (LRFD Method)
Design Example No 1 (LRFD Method)
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Design Example No.1 (LRFD Method)
Design Example No 1 (LRFD Method)
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Design Example No.1 (LRFD Method)
Design Example No 1 (LRFD Method)
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Design Example No.1 (LRFD Method)
Design Example No 2 (LRFD Method)
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W = 10 int = .25in
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Design Example No.2 (LRFD Method)
Design Example No 2 (LRFD Method)
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Design Example No.2 (LRFD Method)
Design Example No 2 (LRFD Method)
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Fub
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Design Example No.2 (LRFD Method)
Design Example No 2 (LRFD Method)
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2
2
2
6
3
P = 77 Kips
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Design Example No.2 (LRFD Method)
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Thanks