Question

The anchorage value for a bar of 20 mm diameter bent into an angle of 90º is

• A. 40 mm
• B. 80 mm
• C. 160 mm
• D. 320 mm

Hint:

Memorize the anchorage values of bends from IS 456:
- For every 45-degree bend, the anchorage value is 4$\phi$.
- Therefore, for a 90-degree bend, it is $2 \times 4\phi = \textbf{8$$}$.
- For a U-hook (180-degree bend), it is $4 \times 4\phi = \textbf{16$$}$.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the anchorage value of a standard 90-degree bend for a 20 mm diameter rebar, as per IS 456.

Step 2: Detailed Explanation:
Anchorage is required to transfer the force from a reinforcing bar into the surrounding concrete. This can be achieved by providing a sufficient straight length of bar (development length) or by using hooks and bends.
According to IS 456:2000 (Clause 26.2.2.1), the anchorage value of a hook or a bend is specified to account for the additional grip provided by the bent shape.
For a standard 90-degree bend (U-type hook), the code specifies that the anchorage value is equivalent to a straight length of

8 times the diameter of the bar ($8\phi$).
For every 45-degree bend, the anchorage value is $4\phi$. A standard hook (180-degree bend) has an anchorage value of $16\phi$.
The question specifies a 90-degree bend.

Step 3: Detailed Explanation:
We are given:
- Bar diameter ($\phi$) = 20 mm
The anchorage value for a 90-degree bend is $8\phi$.
\[ \text{Anchorage Value} = 8 \times \phi = 8 \times 20 \text{ mm} \] \[ \text{Anchorage Value} = 160 \text{ mm} \]

Step 4: Final Answer:
The anchorage value for a 20 mm diameter bar bent into a 90-degree angle is 160 mm.