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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
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 2
Topics to be AddressedTypes of connectors
Tightening procedures
Behavior of Bolted & Riveted connections
Types of Bolted connections
Types of connection failures
Code Requirements
Design Examples
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 3
Components which make up the complete structure are fastened together by means of:
1. RIVETS (older version)
2. BOLTS (newer version)
3. WELDS
Types of Connectors
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 4
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.
Types of Connectors
Typical Round Head Rivet
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
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)
1. Rivets:
Types of Connectors
5
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
Countersunk RivetRound Head Rivet
1. Rivets:
Types of Connectors
6
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
1. Rivets:
Types of Connectors
7
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
Rivet Heating Oven Rivet Heater
Types of Connectors1. Rivets: Riveting processes
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
Earlier Riveting Gun Modern Riveting Gun
Types of Connectors1. Rivets: Riveting processes
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
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.
Types of Connectors1. Rivets: Characteristics of riveted connections
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CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
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 Connectors1. Rivets: Causes of rivet obsolescence
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CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
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 Connectors1. Rivets: Causes of rivet obsolescence
12
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 13
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.
Types of Connectors2. Bolts: Two common types of bolts are:
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 14
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.
Types of Connections2. Bolts: Two common types of bolts are:
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 15
Types of Connections2. Bolts:
Typical High Strength Bolt
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 16
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
Tightening procedures
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
Torque Wrench
Tightening procedures
17
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
Positive Tension Shear Bolt
Bolt Installation Procedure
Tightening procedures
18
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
Direct Tension Indicating Washers
Tightening procedures
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CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
T = Tensile Force on
Connection
∆ = Joint Displacement
TT
Behavior of Bolted & Riveted connections
20
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 21
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.
Behavior of Bolted & Riveted connections
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
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
Types of Bolted connection
22
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
The clamping force applied to the bolt brings the two members closeenough so that appreciable friction is produced between them whichis then responsible for resisting the load. The more the clampingforce the more is the friction and strong is the connection but the clamping force need not to be greater than tensile strength of thebolt.
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.
23
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
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.
Types of Bolted connection
24
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
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 without any friction between faying surfaces.
25
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 26
Type of connection Failures
1. Shearing Failure of Bolts.
2. Bearing Failure of plate.
3. Tearing failure at edge of plate.
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 27
1. Shearing failure of bolts
Type of connection Failures
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 28
1. Shearing failure of bolts
Type of connection Failures
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 29
2. Bearing Failure of Plate
Type of connection Failures
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 30
Shear & Bearing Area
Type of connection Failures
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 31
3. Tearing Failure at edge of Plate
Shearing Failure edge of plate Transverse Tension Failure
Type of connection Failures
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 32
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.
Type of connection Failures3. Tearing Failure at edge of Plate
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 33
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)
Type of connection Failures3. Tearing Failure at edge of Plate
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 34
------- (C)
Eqn (C) can be approximated as
So Eqn becomes
Type of connection Failures3. Tearing Failure at edge of Plate
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 35
LRFD ASD
= 0.75 With FOS= 2
Tearing length or Edge distance
Type of connection Failures3. Tearing Failure at edge of Plate
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 36
LRFD ASD
Type of connection Failures3. Tearing Failure at edge of Plate
Spacing between holes
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 37
Eccentricity of Applied Force
Plates of lap joint tends to bend.
Type of connection Failures
Bending produces non uniform bearing of the fastener on the plates
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
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 A502 Rivets
Table 2-12
Design Strength of Fasteners Table 2-13 Table J3.2
38
Code Requirements
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
AISC Minimum Edge Distance
39
Code Requirements
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 40
Minimum installation tension
Code Requirements
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 41
Allowable Stresses
Code Requirements
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 42
Properties of structural bolts
Code Requirements
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 43
Allowable load for Slip critical connection
Code Requirements
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 44
Design strength of fasteners
Code Requirements
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
Design Example No.1 (ASD Method)
45
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 46
Design Example No.1 (ASD Method)
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 47
Design Example No.1 (ASD Method)
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 48
Design Example No.1 (ASD Method)
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 49
Design Example No.1 (LRFD Method)
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 50
Design Example No.1 (LRFD Method)
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 51
Design Example No.1 (LRFD Method)
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 52
Design Example No.1 (LRFD Method)
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
W = 10 int = .25in
53
Design Example No.2 (LRFD Method)
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan 54
Design Example No.2 (LRFD Method)
CE-409: Lecture 04 Prof. Dr Akhtar Naeem Khan
Fub
55
Design Example No.2 (LRFD Method)
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan
2”
2”
2”
6”
3”
P = 77 Kips
56
Design Example No.2 (LRFD Method)
CE-409: Lecture 04 Prof. Dr. Akhtar Naeem Khan 57
Thanks