Riveted lap joint strength and efficiency

Types of riveted joints

• Lap joint: plates overlap and are riveted (single, double or triple riveted; chain or zigzag arrangement).
• Butt joint: plates are placed edge to edge and covered by one or two cover plates (single or double strap).

Modes of failure

1. Tearing of the plate across the rivet hole line.
2. Shearing of the rivet (single shear in lap joint).
3. Crushing of the rivet or plate where they bear on one another.
4. Tearing of the plate at the edge (avoided by margin of 1.5d).
5. Shearing of the plate in front of the rivet (avoided by margin).

Calculation (per pitch length)

Given: t = 10 mm, d = 18 mm, p = 50 mm, $\sigma_t$ = 100 MPa, $\tau$ = 60 MPa, $\sigma_c$ = 150 MPa; one rivet per pitch.

Tearing of plate:

$$P_t = (p - d)\,t\,\sigma_t = (50-18)\times 10\times 100 = 32{,}000\ \text{N}$$

Shearing of rivet (single shear):

$$P_s = \frac{\pi}{4}d^2\tau = \frac{\pi}{4}(18)^2\times 60 = 15{,}268\ \text{N}$$

Crushing:

$$P_c = d\,t\,\sigma_c = 18\times 10\times 150 = 27{,}000\ \text{N}$$

Strength of the joint is the least of the three: $P = 15{,}268$ N (shear failure).

Strength of the solid plate:

$$P_{solid} = p\,t\,\sigma_t = 50\times 10\times 100 = 50{,}000\ \text{N}$$ $$\eta = \frac{P}{P_{solid}} = \frac{15{,}268}{50{,}000} = 0.305$$

Answer: joint strength = 15.27 kN per pitch (rivet shearing governs); efficiency = 30.5%.