Building Design and Construction

Deep Beams

The ACI 318 Building Code defines deep beams as flexural members with clear span-depth ratios less than 2.5 for continuous spans and 1.25 for simple spans.
Some types of building components behave as deep beams and require analysis for nonlinear stress distribution in flexure. Some common examples are long, precast panels used as spandrel beams; below-grade walls, with or without openings, distributing column loads to a continuous slab footing or to end walls; and storyheight  walls used as beams to eliminate lower columns in the first floor area.
Shear. When the clear span-depth ratio is less than 5, beams are classified as deep for shear reinforcement purposes. Separate special requirements for shear apply when span-depth ratio is less than 2 or between 2 and 5. The critical section for shear should be taken at a distance from face of support of 0.15Ln <= d for uniformly loaded deep beams, and of 0.50a <= d for deep beams with concentrated loads, where a is the shear span, or distance from concentrated load to face of support,  Ln the clear span, and d the distance from extreme compression surface to centroid of tension reinforcement. Shear reinforcement required at the critical section should be used throughout the span.

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