If the tensile stress in the concrete does not exceed then there is no need for crack control reinforcement and none of the following applies.
Section (a) with the limit is ignored because it does not give any guidance on how much reinforcement is necessary. Section (b) is always used instead.
Reinforcement is added to try to keep bonded tendon and mild steel stress changes on the tension face within the values given in Table 8.6.2 as the moment changes from decompression to service level.
In extremely rare circumstances (where the service reinforcement stress in compression, even though the concrete stress exceeds ) this criterion is skipped as adding reinforcement will reduce the compression (increase the tension) making it impossible to satisfy the criterion by increasing the reinforcement.
The decompression reinforcement stress is calculated using gross section strains, while the service reinforcement stress is calculated using cracked section strains.
Reinforcement is also added if necessary to provide a centre-to-centre reinforcement spacing of 300 mm or less.
For this requirement, 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 effective tendon ducts are assumed to be optimally positioned to minimize the number of mild steel bars required – the plan layout of the ducts is ignored.
A fractional number of bars and number of spaces may be specified to meet the spacing requirement.
User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.
