Automatic Debonding and Critical Point
An automatic debonding (shielding) pattern is generated by clicking the Auto Debond button on the Debonding Pattern. Precast/Prestressed Girder will generate an automatic debonding (shielding) pattern according to the following algorithm.
Precast/Prestressed Girder shields strand groups in lengths that are multiples of the Debonding Length Increment (defined on the Materials tab) in an attempt to bring the following stresses within the allowable:
The maximum shielding length is determined by the following:
- To develop the ultimate capacity in the strand at midspan, a distance equal to the strand development length (or a multiple, as specified by user) must remain unshielded.
- Since all shielding must stop at a distance at least equal to the strand development length from midspan, stresses at release will not be affected by shielding in a region that extends from midspan to a point located at a distance equal to the transfer length, measured from the end of shielding. This point is called the critical point, since it is the point that is closest to the beam end, and therefore, where the self-weight is the smallest, which is not effected by shielding.
If the constraints are specified on the Materials screen, Precast/Prestressed Girder will use the constraints of maximum debonded percentage, per row, and per total, when performing automatic debonding.