Effective length of a double-angle strut (back-to-back) connected on both sides of a gusset For a double-angle strut with angles placed back-to-back and connected to both sides of a gusset plate by at least two rivets at each end, the effective length is taken as:

Introduction / Context:
Effective length reflects end restraint and the ability of the connection to reduce buckling length. For short, gusseted angle struts with adequate end fasteners, classical guides recommend an effective length factor below 1.0.

Given Data / Assumptions:

• Double angles back-to-back.
• Connected to both sides of a gusset plate.
• At least two rivets at each end provide fixity against rotation and translation.

Concept / Approach:
Gusseted struts gain partial end restraint, typically modeled by an effective length about 0.85 L for design checks, reflecting improved stability relative to pin–pin length L.

Step-by-Step Solution:
Recognize improved end restraint due to both-side connection.Adopt recommended factor → Le ≈ 0.85 L.

Verification / Alternative check:
Coefficient tables for gusseted compression members list 0.85 L for well-connected ends, matching empirical performance.

Why Other Options Are Wrong:

• L (1.0 L) ignores added restraint.
• 0.50 L or 0.67 L are too low unless full fixity/strut framing warrants it.
• 2 L is non-physical here.

Common Pitfalls:
Applying 0.85 L without verifying end connection quality (minimum fasteners, detailing) can be unsafe.

Final Answer:
0.85 L