To describe main reinforcement, two possible static schemes of deep beams are considered.
One-span deep beam
The total cross-section of the lower main reinforcement equals
where:
z = 0,2(l + 2h), if 0,5 <= h <= l
z = 0,6*l, if h > l.
Reinforcement is distributed in the lower zone of the deep beam at the height = min(0,15*h; 0,15*l). It ends with flat 180 o hooks. If there is no near-support stiffening, apply additional reinforcement (shackles) in the zone where hooks are located (figure 2 page 435 - Charon).
Multi-span deep beam
Symbols:
Mt - Span moment.
Ma - Support moment.
Both quantities are calculated by means of the simplified method.
The main reinforcement cross-section equals
Lower span reinforcement
where:
z = 0,2(l + 0.15h), if 0,5 <= h <= l
z = 0,5*l, if h > l.
This reinforcement is distributed in the lower zone of a deep beam at the height = min(0,15*h; 0,15*l), along the entire length of the span. If it is not extended over to the next span, then, it should be appropriately anchored. The anchoring length is calculated from the intermediate axis of the support. For extreme supports, the anchoring should be realized as in the case of one-span deep beams (it should end with flat 180 o hooks and secured with a shackle) when there is no near-support stiffening (figure 2 page 435 - Charon).
Upper support reinforcement
where:
z = 0,2(l + 1.5h), if 0,5 <= h <= l
z = 0,5*l, if h > l.
This reinforcement (As) is mainly distributed over the following.
- The upper part of the deep beam at the height of 0.10h if h <= l.
- In the deep beam zone = 0.1h. The zone should begin at the deep beam height = 0.9*l. In this case, one should apply additional reinforcement in the zone between l and 1.5*l. The (horizontal) reinforcement should have the cross-section equal = As/4.