Release methodology of strands to reduce end cracking in pretensioned concrete girders

Results of numerical and experimental investigations concerning the causes of prestressed concrete girder end cracks are reported in this paper. The cracks, which developed during the flame-cutting release process, resulted from the restraining effect of unreleased strands as the girders shortened from the partially transferred prestress and from shear stresses generated by the cutting order of the strands. Several methods were examined to eliminate the cracks, including 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. The first two of these methods were implemented in the field and found to be successful.