Effect of Pre-release Cracks on Prestressed Bridge Girder Performance including Remaining Fatigue Life

Project summary:

Pre release cracks have been found to develop during construction of prestressed bridge girders. They develop at the top flange and penetrate vertically downward toward the bottom flange. The cracks generate as a result of shrinkage and cooling of the girders while they are still restrained in the precasting bed. Flexural cracking tests conducted in an earlier study indicate that these pre release cracks may cause local increases in strain in the bottom flange of the girders in the vicinity of the pre release cracks. As a result, the girders are observed to undergo flexural cracking at lower than expected loads which may have detrimental effects on long-term durability and fatigue life. Th project described herein is an analytical study to investigate the effect of pre release cracks on girder strains and to determine design situations in which the pre release cracks may have an effect on the girder fatigue life.