A Study of Pretensioned High Strength Concrete Girders in Composite Highway Bridges- Laboratory Tests

Recent studies have shown that it is commercially feasible to produce prestressed concrete girders utilizing concrete strengths in the 12,000 psi range. However, current codes and specification provisions for flexural strength are based on tests using concrete strengths less than 6000 psi. This program was undertaken to evaluate the adequacy of current design provisions for flexural capacity when applied to high strength concrete girders.

Due to the lack of data in the literature on composite bridge construction with high strength concrete pretensioned girders, two test programs were developed to provide data that would allow evaluation of the use of high strength concrete in the design of pretensioned bridge girders. The first series was a limited comparison of transfer characteristics of 0.5-in.-diameter strand in normal and high strength concrete. These tests provided data to evaluate whether current transfer length provisions found in the codes could be applied to high strength concrete pretensioned girders with a normal strength composite deck, representative of actual long-span bridge designs. Tests of two one-third scale girder specimens provided data for the evaluation of current design provisions, for verification of analysis techniques, and permitted development of recommendations where revision of the codes was necessary as covered in a subsequent report.