Riveted joints – efficiency: How is the efficiency of a riveted joint defined, relative to the original (unperforated) plate strength?

Introduction / Context:
Riveted joints reduce the net area of plates due to holes and introduce additional failure modes. To compare a riveted joint to the uncut (solid) plate, designers use the term efficiency, indicating how much of the original plate strength is retained after riveting.

Given Data / Assumptions:

• Riveted plate with one or more rows of rivets.
• Possible failure modes: plate tearing across holes, rivet shear, and bearing (crushing) of rivet/plate.
• Efficiency is a ratio, not a stress value.

Concept / Approach:

Compute joint strength for each failure mode and take the least of these as the critical joint strength. Divide this least joint strength by the strength of the solid plate (without holes) across the same width to obtain efficiency, typically expressed as a percentage. This provides a direct measure of capacity retained after introducing fastener holes.

Step-by-Step Solution:

Verification / Alternative check:

Across textbooks, this definition is uniform. The efficiency cannot exceed 100% because holes inevitably reduce the solid plate capacity in the joint region.

Why Other Options Are Wrong:

• Greatest joint strength over solid plate (option b) overestimates efficiency.
• Ratios that invert numerator/denominator (option c) are not meaningful measures of retained strength.
• “All of the above” is incorrect because only one definition is valid.

Common Pitfalls:

• Forgetting to use net width for plate tearing.
• Ignoring stagger effect on net area when rivets are zig-zag.

Final Answer:

Least strength of the riveted joint divided by the strength of the solid plate.