Riveted joint strength calculations: When calculating joint strength in tearing, shearing, and crushing, which diameter should be used?

Introduction / Context:
Accurate strength assessment of riveted joints requires correct geometric parameters. In practice, the plate is weakened by the hole, not by the rivet shank size alone. Hence, the diameter used in tearing, shearing, and bearing (crushing) checks must reflect the hole actually present in the plate.

Given Data / Assumptions:

• Hole is drilled or punched to a specified diameter slightly larger than the rivet shank to allow driving/expansion.
• Joint efficiency calculations consider plate net section, rivet shear area, and bearing area.

Concept / Approach:
For tearing of plate, the net section is based on hole diameter because material is removed at the hole. For shearing of rivet and crushing (bearing) between rivet and plate, areas are also dependent on the hole size since contact and shear planes are governed by the hole geometry after fabrication.

Step-by-Step Solution:

Verification / Alternative check:
Design codes specify hole diameter in joint efficiency calculations to incorporate clearance and fabrication tolerances. Using rivet shank diameter unconservatively overestimates capacity and ignores weakening due to hole enlargement or fitting clearances.

Why Other Options Are Wrong:

• Rivet diameter underestimates the removed area and overestimates strength.
• Mean or smaller of the two diameters lacks physical basis in the stress paths.
• Nominal (pre-driving) diameter does not reflect finished hole size.

Common Pitfalls:
Confusing nominal rivet size with finished hole size; neglecting allowance (typically hole ≈ rivet + 1 mm to 1.5 mm depending on size and practice).

Final Answer:
actual diameter of hole drilled for rivet