Flanged (T-beam) action in reinforced concrete: Under what conditions may a portion of a slab be considered to act as the flange of a T-beam integral with the web (beam)?

Introduction / Context:
Monolithic slab-beam systems often develop T-beam action where the slab contributes compression as a flange while the beam web carries shear and houses tension reinforcement. Recognizing when such action is valid ensures economical and safe flexural design.

Given Data / Assumptions:

• Beam and slab cast together (typical floor system).
• Load induces compression at the slab top over the beam.
• Proper reinforcement and bond between slab and web.

Concept / Approach:
T-beam behavior requires: monolithic casting (or equivalent shear connection), adequate transverse reinforcement to control cracking and distribute compression, and effective bond so that strain compatibility is maintained. With these, a code-defined effective flange width participates in compression block calculations.

Step-by-Step Solution:
Check casting sequence or connectors to ensure composite action.Provide transverse slab steel for crack control and load distribution.Ensure interface preparation and shear transfer (bond) meet code provisions.

Verification / Alternative check:
Compute effective flange width per code limits (functions of beam span, slab thickness, and spacing between webs) and verify compression block remains within flange thickness or includes web if needed.

Why Other Options Are Wrong:
Each individual condition is necessary but not sufficient alone; together they justify T-beam behavior. Hence “All the above” best captures the requirement.

Common Pitfalls:
Overestimating effective flange width, ignoring cracking and bond, or assuming composite action without adequate transverse reinforcement and interface shear capacity.

Final Answer:
All the above.