Shrinkage and Temperature Reinforcement

LRFD

For 4-sided precast structures, use the greater of 5.10.8/5.10.6 or 0.002Ag, except that 5.10.8/5.10.6 does not apply to sections less than 16 feet in length.  For 3-sided structures, see 12.14.5.8, which requires a minimum of 0.002Ag.  Article 5.10.8/5.10.6 does not apply to 3-sided structures.  LRFD does not provide any guidance for fill depths greater than 2 feet, therefore the program applies the above logic, as other minimum steel requirements will probably  control in the design.

 For CIP structures at all depths, see Article 5.10.8/5.10.6.

Standard Specification

For 4-sided precast structures, use the greater of 0.125 in2/ft (8.20), or 0.002Ag (16.7.4.8), however note that 8.20 does not apply for structures with lengths under 16 feet.  For 3-sided precast structures, see 16.8.5.8 (0.002Ag), however, 8.20 does not apply for any length structure.  While there is no guidance for fill depths greater than 2 feet, the program applies the same logic as listed above, as it is likely that other minimum steel criteria will ultimately control.

 For CIP structures at any fill depth, see 8.20.

CHBDC

Per 7.8.11.2, the minimum area and maximum spacing of shrinkage and temperature reinforcement shall be in accordance with Table 7.18.  In Table 7.18, precast box culverts with a depth of cover equal to or greater than 0.6m shall have a minimum area of reinforcement of 300 mm²/m, at a maximum spacing of 250mm above the principal reinforcement on the inside face.