Deep beam identification: a continuous reinforced concrete beam is deemed a deep beam when the ratio of effective span to overall depth satisfies which criterion?

Introduction / Context:
Deep beams behave differently from slender beams because plane sections do not remain plane, and load paths resemble strut-and-tie or arching action. Codes distinguish deep beams by span-to-depth ratios, with separate detailing and shear provisions. The limit varies for simply supported versus continuous members.

Given Data / Assumptions:

• Member: continuous reinforced concrete beam.
• Parameters: effective span l and overall depth D.
• Objective: threshold on l/D to classify as a deep beam.

Concept / Approach:
For continuous members, a commonly used threshold is stricter than for simply supported members due to continuity-induced stiffness and different moment distributions. Educational references typically adopt l/D < 2.5 as the deep-beam threshold for continuous spans, while simply supported spans use l/D < 2.0.

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