Types of Connectors

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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
  4. 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.

  • Round Head Rivet

  • Countersunk Rivet

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Rivets:

    1. Rivets: Riveting processes

Rivet Heating Oven

  • Rivet Heater
    1. Rivets: Riveting processes

US4RL rivet gun

Modern Riveting Gun

Earlier Riveting Gun

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.

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

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.

b) High strength bolt (A325, A449, and 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.
  1. Bolts:
  • HSFG

Typical High Strength Bolt

 

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

Torque Wrench

 

Tightening procedures

Positive Tension Shear Bolt

Bolt Installation Procedure

 

Direct Tension Indicating Washers

 

30Behavior of Bolted & Riveted connections

T = Tensile Force on Connection

∆ = Joint Displacement

  • 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 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.
    • 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.

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.
    • 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.

Type of connection Failures

  1. Shearing Failure of Bolts.
  2. Bearing Failure of plate.
  3. Tearing failure at edge of plate.

1: Shearing failure of bolts

  1. Bearing Failure of Plate

Shear & Bearing Area

  1. Tearing Failure at edge of Plate

  • Shearing Failure edge of plate

Transverse Tension Failure

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  • Shearing Failure 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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