Transfer Length and Splitting Force Calculation for Pretensioned Concrete Girders with High-Capacity Strands

Abstract

Pretensioned members such as AASHTO I-girders and bulb tees (BTs) are widely used in the construction of bridges. In response to the challenges of longer bridge spans and more application of high-strength concrete in future girder design, high-capacity strands (HCSs) have recently been introduced in the construction of pretensioned concrete girders. These HCSs, such as 18-mm (0.7-in.) diameter Grade 270 (1,860 MPa) strands and 16-mm (0.62-in.) diameter Grade 330 (2,275 MPa) strands, can provide large prestressing forces and lead to increased bridge spans without switching from AASHTO I-girders and BTs to other girders. Currently, there is limited research concerning the application of these HCSs in AASHTO I-girders and BTs; therefore, this study focuses on the transfer length and strand spacing of the HCSs in these girder sections. The research results from this study indicate that the transfer length of these HCSs from experimental tests is considerably smaller than that predicted by several codes. On the basis of the concrete used in this study, the 50-mm (2.0-in.) strand spacing is applicable to the HCSs. Finally, this paper discusses the splitting effect within anchorage zones. Tractable equations are suggested to calculate the splitting forces in AASHTO I-girders and BTs prestressed by the HCSs.