Anchorage value of a standard hook in tension reinforcement: If the bar diameter is d, what is the anchorage value contributed by a standard hook?

Introduction / Context:
Anchorage length provides the necessary bond to develop the bar's tensile force. Standard bends and hooks add equivalent straight length, reducing the straight embedment otherwise required at bar terminations.

Given Data / Assumptions:

• Plain or deformed bar with a standard 180° hook (common detailing at ends).
• Bar diameter = d.

Concept / Approach:
Design standards assign equivalent anchorage values to bends and hooks. A standard hook typically contributes an anchorage value of about 16d for a 180° hook in tension, which can be added to the straight development length to meet the required L_d.

Step-by-Step Reasoning:
Determine required development length from bond considerations.Account for end hook: add 16d as anchorage contribution of the hook.

Verification / Alternative check:
Many codes tabulate equivalent lengths: 90° bends ≈ 8d, 135° hooks ≈ 12d, and 180° hooks ≈ 16d (exact values may vary slightly by code and bar type).

Why Other Options Are Wrong:
4d / 8d / 12d: Correspond to smaller bend angles; insufficient for a standard full hook.20d: More than typical requirement, not standard.

Common Pitfalls:

• Confusing added anchorage value with the total development length needed.
• Not checking cover and bend radii that affect practicality of detailing.

Final Answer:
16d