Implementation and field evaluation of pretensioned concrete girder end crack control.

WisDOT SPR# 0092-15-01Wisconsin bulb tee pretensioned concrete girders are currently used for bridge construction. Their efficiency in load resistance has made them particularly desirable. To provide that efficiency, these girders are heavily prestressed. Cracking is evident, however, at the girder ends during de-tensioning. These cracks may create durability and capacity problems as cracks can lead corrosive water to the steel strands, endangering the structure. Cracks in the bottom flange, close to the strands, are the main concerns of this study. The primary focus was on proving the effectiveness of strand debonding at girder ends as a solution to cracking. This was accomplished through construction of prototype girders, monitoring their behavior, and using analytical techniques to understand the cause of the cracking A second goal was to provide the Wisconsin Department of Transportation with design recommendations for effectively using debonded strand in girders.The construction of girders with debonded strand for two bridges proved that debonding was an effective solution for end crack control and elimination. Comparison of analytic predicted behavior and measured girder response data showed that the nonlinear analysis techniques used were accurate. Those techniques were then used to examine the behavior of Wisconsin 54W and 72W girders with various strand debonding patterns to provide the Department with recommendations for the best girder designs, in a range of strand contents, using debonded strand