Length over which shear stirrups are required near supports: An RCC beam with effective span L develops maximum shear near the supports (q_max at the ends). Over what distance from each support should designed shear reinforcement (stirrups based on shear) be provided before transitioning to nominal shear reinforcement?

Introduction / Context:
Shear forces in simply supported beams are highest near supports and reduce towards midspan under typical gravity loading. Code-based detailing requires designed shear reinforcement where design shear exceeds the concrete’s nominal shear capacity; beyond a certain region, only nominal shear reinforcement is needed.

Given Data / Assumptions:

• Effective span = L.
• Maximum design shear q_max occurs at the ends.
• Typical UDL or comparable loading scenario producing decreasing shear towards midspan.

Concept / Approach:
For common loading patterns, the region significantly affected by shear typically extends up to midspan. A conservative and widely taught rule for exam problems is to provide designed shear stirrups up to about half the span from each support, after which the required shear usually falls, permitting nominal stirrups.

Step-by-Step Solution:
Identify the region of high shear demand: from support towards midspan.Adopt the conservative academic guideline: provide designed shear reinforcement up to L/2 from each end.Beyond that region, nominal shear reinforcement suffices, subject to check of actual shear diagram.

Verification / Alternative check:
Plot the shear force diagram for a simply supported beam under UDL: shear reduces linearly to zero at midspan. Designed stirrup spacing is often reduced near supports and can be relaxed towards midspan as demands reduce.

Why Other Options Are Wrong:

• L/4 or L/3: May be unconservative for longer spans or higher shears.
• 2d only: Too short; ignores the continued shear demand well beyond two effective depths.

Common Pitfalls:
Applying a single spacing throughout; not checking actual shear distribution; confusing the region for maximum stirrup spacing with the region requiring designed stirrups.

Final Answer:
L/2 from each end