Prevention of Splitting Failure at Ends of Prestressed Beams During Fabrication, Summary Report; Summary rept

摘要

The purpose of this research project was to determine the cause of vertical cracks that sometimes occur near the ends of the bottom flange of prestressed AASHTO, Florida Bulb-T, and Florida U beams. These vertical cracks were primarily observed on long-span beams and occurred during the transfer of the prestressing force to the concrete. The project initiated with mail surveys submitted to three FDOT prestressed beam manufacturers in Florida to determine the extent and types of end cracking each manufacturer was experiencing during the production process of their AASHTO, Florida Bulb-T, and Florida U beams. Site visits followed the surveys to observe the beam production process and to discuss when each type of crack forms with field personnel. The primary recommendation resulting from this research was that the coefficient of friction be reduced at the ends of the beams in order to reduce the tension stresses caused by friction as the beam displaces and cambers. A possible method for accomplishing this is to provide embedded steel base plates at the ends of the beams. Requirements for manufacturer's to install embedded steel plates were implemented by the FDOT> two years following this implementation, follow-up studies with the manufacturers indicated that the addition of the embedded plate has been effective in eliminating vertical end cracking.