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Questions and Answers
Define pitch in the context of riveted joints.
Pitch is the distance between two centers of consecutive rivets in a single row.
What is back pitch or transverse pitch in riveted joints?
Back pitch or transverse pitch is the shortest distance between two successive rows in a multiple riveted joint.
Explain what diagonal pitch is in the context of riveted joints.
Diagonal pitch is the distance between the centers of rivets in adjacent rows of a zigzag riveted joint.
How is the strength of a rivet joint measured?
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What is the significance of the margin pitch in riveted joints?
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Study Notes
Riveted Joints Terminology
- Margin or marginal pitch is the distance between the centre of the rivet hole to the nearest edge of the plate, denoted by symbol 'm' and is usually 1.5 times the diameter of the rivet (m = 1.5d).
Lap Joint
- A lap joint is subjected to bending moment Mb due to the eccentric force P.
- The bending moment Mb is given by Mb = P × t, where t is the thickness of the plate.
- The bending moment causes distortion of the plates, which is a drawback of lap joints.
Failure Modes in Riveted Joints
- Failure of a riveted joint may occur in one or more of the following ways:
- Shear failure of the rivet.
- Tensile failure of the plate between two consecutive rivets.
- Crushing failure of the plate.
- Shear failure of the plate in the margin area.
- Tearing of the plate in the margin area.
Strength Equations of Riveted Joints
- Strength of a riveted joint is defined as the force that the joint can withstand without causing failure.
- Strength equations can be written for each type of failure.
- In analysis of riveted joints, mainly three types of failure are considered: shear failure of the rivet, tensile failure of the plate between rivets, and crushing failure of the plate.
Shear Strength of Rivet
- A rivet is in single shear.
- Margin (m) is 1.5 times the diameter of the rivet (m = 1.5d).
- Transverse pitch (pt) is equal to p.
Design of a Riveted Joint
- Consider a double-strap butt joint with a tensile force P of 250 kN and plate width w of 200 mm.
- The rivets and plates are made of the same steel with permissible stresses in tension, compression, and shear of 70, 100, and 60 N/mm², respectively.
- The diameter of the rivets, thickness of the plates, dimensions of the seam (p, pt, and m), and efficiency of the joint can be calculated.
Eccentrically Loaded Riveted Joint
- A group of rivets is employed in structural joints, and when the line of action of the external force does not pass through the center of gravity of these rivets, the joint is called an eccentrically loaded joint.
- The analysis of an eccentrically loaded riveted joint is identical to an eccentrically loaded bolted joint in shear.
- Primary and secondary shear forces are vectorially added to get the resultant shear force.
- The maximum loaded rivet becomes the criterion of design.
- Rivets are subjected to direct shear stress.
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Description
Learn about the margin or marginal pitch in riveted joints, which is the distance between the rivet hole center to the nearest plate edge. Explore how bending moments affect lap joints due to eccentric forces, with calculations for bending moment Mb = P * t.
