Purpose of shear reinforcement in R.C.C.: Shear reinforcement is primarily provided to resist which internal action produced by shear?

Introduction / Context:
Concrete is strong in compression and weak in tension. Under shear, inclined tensile stresses (diagonal tension) develop, causing potential cracking. Shear reinforcement (stirrups/bent-up bars) is used to intercept these cracks and carry tensile forces safely, enhancing ductility and preventing brittle web shear failure in beams.

Given Data / Assumptions:

• Reinforced concrete beam under typical gravity loading.
• Shear forces cause inclined principal stresses.
• Standard code provisions for shear design are assumed.

Concept / Approach:

Shear in beams leads to diagonal tension (tensile principal stress on planes approximately at 45 degrees). Concrete alone cannot resist this tension beyond a small limit (diagonal tension capacity). Shear reinforcement functions as tension ties across these potential crack planes, while concrete and aggregate interlock provide residual shear transfer.

Step-by-Step Solution:

Verification / Alternative check:

Design formulas decompose shear resistance into concrete contribution and steel contribution; the steel leg force is proportional to A_sv * f_y * (d / s) for vertical stirrups, directly addressing diagonal tension.

Why Other Options Are Wrong:

Horizontal shear relates to composite action along interfaces; diagonal compression is typically carried by concrete. “Vertical shear” wording misses the mechanism of crack control; torsion requires special closed stirrups and longitudinal reinforcement beyond ordinary shear design.

Common Pitfalls:

Underestimating shear near supports; exceeding maximum stirrup spacing; inadequate hooks/anchorage for stirrups.

Final Answer:

Diagonal tension