FOR U-BARS / CREATED BY
SURFACE REINFORCEMENT DISTRIBUTION-BARS OPTION
To avoid the fatal errors related to the modification of the ASD2010-REINFORCEMENT-(SURFACE REINFORCEMENT DISTRIBUTION-BARS), the Minimum bar length for surface distribution ( defined in Job preferences / Bars / Options ) should be > = [ (2 x Bar diameter which is shown in the required projection) + Bent diameter (according to the selected code) ].
This because the Minimum bar length for surface distribution does not mean the total length of the bar, but it means the projection length of the bar.
If the fatal errors still exist, chamfering the corner with an edge length > = [ (2 x Bar diameter which is shown in the required projection) + Bent diameter (according to the selected code) ] will prevent the errors to come.
Moreover, the fatal errors are very sensitive to illogical / unreasonable modifications in the following fields (fields of Reinforcement detailing tab in the Reinforcement: definition and detailing dialog box.) :
1- two edit fields allow determining a value of the distance between the extreme reinforcement and the zone border; there is a possibility to block the distance value for each zone – once the distance on one side is blocked, the distance value on the other side will be automatically adjusted to a specified number of bars and a spacing value; after blocking the distance on both sides, the spacing will be adjusted automatically to a given number of bars.
2-the button located between the edit fields enables centering the distribution.
Also, increasing the bar diameter or the cover values without taking care about the above notes, will create the fatal errors.
I hope that Autodesk to check / review this part of the program, and issue new hotfix or service pack.
Best of luck.