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

    http://cache.viewimages.com/xc/3258752.jpg?v=1&c=ViewImages&k=2&d=12F00EB112845DECFD45A4C43873E1C2A55A1E4F32AD3138
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    Earlier Riveting Gun Modern Riveting Gun

    Types of Connectors

    1. Rivets: Riveting processes

    http://www.ustool.com/images/Huge%20images/US4RH.jpg
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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