BACKGROUND

There have been many studies dealing with prestressed concrete girders. Marshall and Mattock (J) were among the first investigators whose primary goal was to measure stresses in the end-block region and to study horizontal cracks usually observed in the end regions. From the results of their field survey and experiments, they concluded that end blocks are not necessary and that their presence in pretensioned, prestressed girders does not ensure absence of horizontal cracks. They pointed out that vertical reinforcement close to the end face of such girders will ensure satisfactory performance of the end zones. Furthermore, they suggested that fine, short horizontal cracks will not affect the service performance of the girders.

Gergely et al.(2) developed a direct method of designing transverse reinforcement by assuming the initiation of a crack in the end zones. They determined that for an eccentric load, the spalling stresses were larger for a rectangular end block than for an I-shaped one. They also proposed design specifications that could be applied to the anchorage zone of pretensioned members.