Definition threshold for deep beams (continuous members): A continuous reinforced concrete beam shall be deemed a ‘‘deep beam’’ if the ratio of effective span (L_eff) to overall depth (D) is which of the following?

Introduction / Context:

Deep beams are members in which plane sections do not remain plane; arching and strut-and-tie action dominate over classical beam theory. Codes therefore define deep beams by geometric limits that flag when special analysis and detailing rules are required.

Given Data / Assumptions:

• Continuous beam (not a simple one-way slab strip).
• Effective span L_eff and overall depth D are known.

Concept / Approach:

For continuous beams, a typical code-style threshold is L_eff / D < 2 to classify a member as a deep beam. Such members need refined design approaches (e.g., strut-and-tie modeling), web reinforcement provisions, and special detailing at supports/openings due to nonlinear stress fields.

Step-by-Step Solution:

Verification / Alternative check:

Design guides align with the same order-of-magnitude limit (with slightly different wording for simply supported vs. continuous members). The intent is to capture members where shear span is short and arching prevails.

Why Other Options Are Wrong:

• 2.0 or 2.5 without the inequality does not state the classification boundary.
• less than 2.5: Too lenient; would misclassify many ordinary beams as deep.
• greater than 3: Opposite of deep-beam behavior; that is relatively slender.

Common Pitfalls:

• Using span/effective depth (L/d) rather than span/overall depth (L/D) without checking the specific code clause and member category (simply supported vs. continuous).

Final Answer:

less than 2