Tacking rivets for compression plates (not exposed to weather): what is the maximum permitted pitch relative to the outer plate thickness?

Introduction / Context:
Tacking rivets or bolts are used to keep built-up compression elements acting as a unit (preventing buckling out of their own plane between primary connectors). Codes specify maximum spacing limits that depend on exposure conditions and plate thickness.

Given Data / Assumptions:

• Compression plates are not exposed to weather.
• We are checking the limit for tacking rivet pitch relative to the thickness of the outside plate.

Concept / Approach:
Typical practice (as reflected in many exam standards and legacy code guidance) limits the pitch of tacking rivets in compression members to the lesser of an absolute dimension (e.g., 300 mm) or a multiple of the outer plate thickness. For non-exposed plates, the multiple is 32 t; for weather-exposed, a tighter spacing such as 16 t is adopted.

Step-by-Step Solution:

Verification / Alternative check:
Compare with the stricter weather-exposed case (often 16 t or a smaller absolute value). Non-exposed allows a larger spacing.

Why Other Options Are Wrong:
16 t and 24 t are too restrictive for non-exposed; 36 t and 40 t exceed typical permitted limits and may allow plate separation or local buckling.

Common Pitfalls:
Forgetting that the absolute cap (like 300 mm) may govern even if 32 t is larger; applying the wrong exposure category.

Final Answer:
32 times the thickness of the outside plate