Is there a good test method for shrinkage deformation of prestressed steel strand clips?

The Code for Clip Anchorage stipulates that the allowable retraction cannot exceed 4 mm.

Retraction in actual operation can be measured on site.

The specific method is as follows:

1. Make a mark on the tensioned steel strand with talcum powder to measure the distance from a reference object, which can be a fixed beam, beam end and other fixed objects.

2. Measure again after tensioning and anchoring, and the difference between the two measurements is the retraction.