Section 9.5.3.2 Minimum Shrinkage and Temperature Reinforcement in Primary Direction
This criterion is applied as part of the minimum reinforcement designer as it is independent of the magnitude of forces upon a cross section.
This criterion is applied to both beams and slabs, although its application to beams is not required by AS 3600.
The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the "Min. Reinforcement Pattern" selected in the design strip segment or design section.
Reinforcement may be applied to both faces if the cross section is subject to both positive and negative moments and the "tension face" reinforcement location is chosen.
- All bars on the appropriate face (including fractional components for bars at an angle to the cross section) are considered for spacing requirements. A fractional number of bars and spaces may be used.
- For sections declared as post-tensioned, each bonded tendon duct (that is in the tension zone based on gross section stresses) is considered to be equivalent to a single mild steel bar (even if it is far from the tension face). In the spacing calculation, all bonded tendon ducts are assumed to be optimally positioned to minimize the number of mild steel bars required.
User-defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.
- For "protected" environments, the amount of reinforcement provided is: As = (0.75)(1.75 – 2.5 σcp)(Ag)/1000
- For "normal" environments, the amount of reinforcement provided is: As = (0.75)(3.5 – 2.5 σcp )(Ag)/1000
- For "corrosive" or "very corrosive" environments, the amount of reinforcement provided is: As = (0.75)(6.0 – 2.5 σ cp )(Ag)/1000
For non-PT design strips and design sections, σcp is taken as zero.