Question

In a reinforced concrete beam, the maximum spacing of vertical shear reinforcement measured along the axis shall not exceed

• A. 0.5d or 300 mm
• B. 0.5d or 250 mm
• C. 0.75d or 300 mm
• D. 0.75d or 250 mm

Hint:

Memorize the IS 456 rules for maximum stirrup spacing:
- Vertical Stirrups: Lesser of $0.75d$ or $300$ mm.
- Inclined Stirrups: Lesser of $d$ or $300$ mm.
The $0.75d$ limit is the most common one to remember.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the maximum permissible spacing for vertical stirrups (shear reinforcement) in a reinforced concrete beam, as per IS 456.

Step 2: Key Formula or Approach:
According to IS 456:2000 (Clause 26.5.1.5), the maximum spacing of shear reinforcement (stirrups) measured along the axis of the member shall not exceed the lesser of the following values:
1. 0.75 times the effective depth ($0.75d$) for vertical stirrups.
2. 1.0 times the effective depth ($d$) for inclined stirrups.
3. An absolute maximum of 300 mm.

Step 3: Detailed Explanation:
The question specifically asks for

vertical shear reinforcement. Therefore, the applicable limits are:
- $0.75d$
- $300$ mm
The spacing must not exceed the smaller of these two values. The option that correctly states these two limits is (C).
There is also a condition for minimum shear reinforcement. If the nominal shear stress is very low, the maximum spacing can be increased, but the question asks for the general rule which applies when shear reinforcement is required.

Step 4: Final Answer:
The maximum spacing of vertical shear reinforcement shall not exceed 0.75d or 300 mm, whichever is less.