For deep beams, at what depth do the skin reinforcements is required if it is not written on the contract drawings?

1) ACI Codes (Amercan Concrete Institute)

If the depth, h, of non-prestressed or partially prestressed members exceeds 900mm, longitudinal skin reinforcement shall be provided on both side faces of the component. Such reinforcement shall be uniformly distributed along both side faces for a distance h/2 nearest the flexural tensile reinforcement. The spacing, s, in inches shall satisfy:

s  ≤  15(40/fs) – 2.5Cc ≤ (h/6) ≤   12                                                    (1)

where:

 Cc = is the clear cover to the side face of the member (in.)

 h = overall thickness or depth of the component (in.)

fs= tensile stress in steel reinforcement at theservice limit state (ksi).  fs maybe assumed to be (2/3)fy(ksi)

fy= yield strength of reinforcement (ksi)

The maximum spacing of the skin reinforcement shall not exceed either h/6 or 12.0 in. Such reinforcement may be included in strength computations if a strain compatibility analysis is made to determine stresses in the individual bars or wires. The skin reinforcement shall not be less than #4 at 12 in. in both side faces.

The total area of skin reinforcement Ask in both side faces need not exceed 10% of the flexural tensile reinforcement

BS (British Codes)

In(British Spefication) BS8110, secondary or Skin reinforcement should be provided for beams exceeding 750mm deep at a distance measured 2/3 depth from the tension face

As per Indian standard IS:456, if the depth exceeds more than 750mm, side reinforcement is to be provided on both side.