Release Methodology of Prestressed Strands

Summary

This report presents the results of numerical and experimental investigations to determine the causes of prestressed concrete girder end cracks. The cracks, which develop during the flame-cutting release process, result from the restraining effect of unreleased strands as the girder shortens from the partially transferred prestress and from shear stresses generated by the cutting order of the strands. Researchers examined several methods to elimate the cracks, such as making changes to the strand cutting pattern, debonding some of the strands in the end regions, and increasing the slope of the top surface of the bottom flange. Implementation of the first two of these methods in the field proved successful.