Reinforcement Anchorage – Standard U-hook anchorage value for a bar of diameter d in tension.

Introduction:
Anchorage length ensures that a reinforcing bar develops its design stress without pullout. Hooks provide additional anchorage where straight embedment is limited.

Given Data / Assumptions:

• Standard U-type (180-degree) hook in tension zone.
• Bar diameter = d.
• Normal concrete, adequate cover, and spacing.

Concept / Approach:

A standard U or 180-degree hook contributes an equivalent anchorage value commonly taken as 16 d for tension bars, supplementing the straight development length as permitted by code.

Step-by-Step Solution:

Verification / Alternative check:

Detailing guides map 180-degree hook to ≈ 16 d anchorage contribution; site practice confirms improved pullout resistance.

Why Other Options Are Wrong:

4 d and 8 d underestimate anchorage; 12 d is still low; 20 d is conservative but not the standard value used for U-hooks.

Common Pitfalls:

Counting hook value without ensuring adequate concrete cover or confining reinforcement; ignoring bar bend radii.

Final Answer:

16 d