What is the reinforced concrete deep beam and where it used?

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## aviratdhodare

## R/f’ed concrete deep beam

It is a special structure in beams. In the deep beam, the depth of the beam is greater than eff. span. The assumptions of the normal beam are not applicable in a deep beam. As the depth is more, the distribution of the stress is not uniform. So we found some in finding the values of the lever arm & the other related things.

Defn of Deep Beam as per IS 456: 2000The beam having greater depth in comparison to its eff. span is called as Deep Beam.

Uses of Deep BeamThe foundation beams transferring the conc column load to the supporting soil.Foundation beams:at an intermediate floor level of a bldg where some columns are read to be stopped for some particular reasons.Transfer girder or wall beamswhere the walls itself act as a deep beamBunker or tanksIS Codes provisions of a Deep Beamwhere, L = Eff span, D = Overall depth.

To calculate eff span = c/c dist betn supports or 1.15 x clear span. (Consider less value)

Lever Arm (Z):As the stress distn along the depth of the beam is non-linear. Due to this the lever arm bent the comp & tensile forces can’t be easily determined.The values of Lever Arm as per IS 456:2000

Z = 0.2 (L+2D) If 1 ≤ L/D ≤ 2

Z = 0.6 L If L/D < 1

Z = 0.2 (L+1.5D) If 1 ≤ L/D ≤ 2.5

Z = 0.5 L If L/D < 1

R/F provision as per IS 456-2000In the case of deep beam, tension is still to be extended over the whole length of the span & should be well anchored in the support.

+ve moment r/f:Embedded length = 0.8 x Development length

= 0.8 x (0.87 f

_{y}φ / 4 τ_{bd})Zone of depth = 0.25D – 0.05l

-ve moment r/f:Provided to resist the -ve B.M

Termination of r/f – Half of the r/f may be terminated at a dist of 0.5D from the face of the support & remaining should be extended over the whole span.

Distribution

When 1 ≤ L/D ≤ 2.5, wholly have to distribute the total tensile r/f in 2 zones

Zone – 1 = 0.2D having Ast

_{1}Ast_{1}= 0.5 (l/D – 0.5)AstZone – 2 = 0.3D (on either side of mid depth) having Ast

_{2}= Ast – Ast_{1}If l/D ≤ 1 = zone → 0.89 (evenly distributed)

Hanging action → Bars or suspension stirrups to be provided.Vertical r/f:Side face r/f:To resist the effect of shrinkage & temp

It also can be provided in vertical direction & horizontal direction.

% of total c/s’al area is to be provided given in IS 456:2000 cl: 29.3.4 → cl 32.4

Min req’ts of r/s in wall as per IS 456:2000 cl 32.4Vertical Horizontal

_{y}≥ 415 N/mm^{2}Spacing of side face r/f ≤ 3 x thkness or 450mm

## Komal Bhandakkar

This answer was edited.## Reinforced Concrete Deep Beam:

Thank You.

## Komal Bhandakkar

This answer was edited.## Use of reinforced concrete deep beam:

Definition of deep beam:A member who is loaded on one face and supported on the opposite face. Hence, compression strut can develop between the loads and the supports.

The clear span of the reinforced concrete deep beam is equal to or less than four times the overall member depth.

## nikeetasharma

Reinforced concrete deep beam is defined as that members with clear spans in equal or less than four times the overall member depth or regions of beams that are loaded on one face with concentrated loads within twice the member depth from the support and supported on the opposite face so that compression struts can be developed between the loads and supports.