Riveted joints: identify the incorrect statement among the following descriptions of joint types and efficiencies.

Introduction / Context:
Riveted joints are classic permanent fastenings used in boilers, bridges, and structural fabrications. Understanding lap vs. butt joints and the definition of efficiency helps in evaluating joint capability and terminology.

Given Data / Assumptions:

• Lap joint: plates overlap and are riveted directly.
• Butt joint: plates meet edge-to-edge and are connected with cover straps.
• Efficiency compares the riveted joint to an unpunched plate of equal width and material.

Concept / Approach:
Terminology distinguishes joint geometry. A “double riveted lap joint” uses two rows on overlapping plates. A “double riveted butt joint” uses two rows on cover straps over abutting plate edges—not overlap.

Step-by-Step Solution:
Check each statement against definitions.Riveting is permanent: correct.Overlap with two rows called double riveted butt joint: incorrect—this is a double riveted lap joint.Shank smaller than hole: correct to allow insertion and setting.Efficiency definition: correct.

Verification / Alternative check:
Standard machine design texts show lap joints as overlapping plates; butt joints employ single or double cover straps with plates meeting edge to edge.

Why Other Options Are Wrong:
A, C, D, E are aligned with standard definitions; B mislabels a lap joint as a butt joint.

Common Pitfalls:
Confusing “rows of rivets” with “butt vs. lap” geometry.Ignoring the role of cover plates/straps in butt joints.

Final Answer:
A joint made by overlapping plates and two rows of rivets is called a double riveted butt joint.