Bond Performance of High-Capacity Strands in High Strength Concrete

18-mm-diameter (0.7-in.) strand has the ability to introduce almost twice the prestressing force of 13-mm-diameter (0.5-in.) strand and 135% of the prestressing force of 15-mm-diameter (0.6-in.) strand, which could result in a significant increase in the span capacity of the current AASHTO bulb tee girders without having to modify the sections or acquire new forms. To date, the information regarding the bond performance of 18-mm-diameter (0.7-in.) prestressing strand is very limited, preventing its application despite its attractive high-strength. Also, our understanding of the bond mechanism is incomplete and non-quantitative; a rational understanding of the bond mechanism would help predict the bond behavior and develop design guidelines. Therefore, this study concentrated on these two topics. The finite element method was applied to simulate the bond between the prestressing strand and concrete. A parametric analysis was conducted to analyze the factors affecting transfer length. With the comparison of the non-pretensioned and pretensioned pull-out tests, the contribution of each bond mechanism was quantitatively analyzed. The tests indicated that the bond performance was dependent on the specimen length and the pretension level, and the pretension force significantly affected the transfer length.