Structures Design Guidelines | Jan 2008
3 - Substructure and Retaining Walls |

## 3.10 Crack Control (07/07) July 2007 - Revised "A" per TDB C07-04, added construction loading and Service III loading. Added commentary.
Jan 2007 - Modified A. to apply to pier columns, pier caps and bent caps
Jan 2006 Added paragraph limited longitudinal stresses in mildly reinforced piers and pier caps to 24 ksi (Grade 60 Steel.)

A. Limit service tension stresses in longitudinal reinforcing steel for all mildly reinforced pier columns, pier caps and bent caps under construction loading and Service III Loading to 24 ksi for Grade 60 reinforcing.

Commentary: The tensile limit 24 ksi for mild reinforcing, combined with proper distribution of reinforcement, is intended to ensure the durability of pier columns, pier caps and bent caps by limiting crack widths.

B. Long Walls and other similar construction:

1.) Limit the length of a section to a maximum of 30 feet between vertical construction joints. See the limits of concrete pours in tall piers
elsewhere in this Chapter.

2.) Clearly detail required construction joints on the plans.

3.) Specify construction or expansion joints fitted with a water barrier when necessary to prevent water leakage.

C. Footings: Specify that footings be cast monolithically. Attach struts and other large attachments as secondary castings.

D. Keyways: Do not place keyways in horizontal construction joints except that a keyway will be used at the junction of a cast-in-place concrete wall and footing. Provide keyways at formed surfaces of vertical construction joints and elsewhere as necessary to transfer applied loads from one cast section to an adjacent, second pour. Specify or detail trapezoidal keyways for ease of forming and stripping. For example, a typical joint must have a keyway about 2-inches deep and about 6-inches wide (or one third the thickness of the member for members less than 18-inches in thickness) running the full length.