Abstract
This study aimed to investigate the bond properties of prestressing strands embedded in ultra-high-performance fiber-reinforced concrete (UHPFRC). Toward this end, two types of prestressing strands with diameters of 12.7 and 15.2 mm were considered, along with various concrete cover depths and initial prestressing force magnitudes. The average bond strength of the strands in UHPFRC was estimated by using pullout tests, and the transfer length was evaluated based on a 95% average maximum strain method. Test results indicated that the average bond strength of the pretensioned strand reduced as the diameter of the strand increased, and was between the bond strengths of round and deformed steel rebars. Higher bond strength was also obtained with a lower embedment length. Based on a comparison of p value, the bar diameter and embedment length most significantly influenced the bond strength of strands in UHPFRC, compared to a ratio of cover depth to diameter and initial prestressing force. Pretensioned strands in UHPFRC exhibited much higher bond strength and shorter transfer length compared with strands embedded in ordinary high-strength concrete. Lastly, ACI 318 and AASHTO LRFD codes significantly overestimated the transfer length of the strands embedded in UHPFRC.
Highlights
Superior tensile performance and durability of ultra-high-performance fiber-reinforced concrete (UHPFRC) compared with ordinary concrete make it ideal for applications in bridge girders and decks (Richard and Cheyrezy 1995; Yoo et al 2014a, 2016a)
The pull-out tests were carried out to investigate the factors that affect bond behavior of prestressing strands embedded in UHPFRC, including strand diameter, concrete cover depth, embedment length, and initial prestressing force
2.2 Test Specimen, Setup and Procedure 2.2.1 Bond Strength The pull-out test was carried out according to the RILEM (1994) recommendation for steel reinforcement (Yuan and Graybeal 2015) to evaluate the bond behavior of prestressing strands embedded in UHPFRC
Summary
Superior tensile performance (over 8 MPa) and durability of ultra-high-performance fiber-reinforced concrete (UHPFRC) compared with ordinary concrete make it ideal for applications in bridge girders and decks (Richard and Cheyrezy 1995; Yoo et al 2014a, 2016a) For these applications, the load transfer mechanism between UHPFRC and the steel reinforcement, which is characterized by bonding action, is a crucial factor determining efficiency of the composite behavior of the members. The bond mechanism of a strand is a unique interaction that is characterized by adhesion, Hoyer’s effect, and mechanical interlock (Abrishami and Mitchell 1993; Dang et al 2014), and an understanding of the bond behavior of a strand embedded in UHPFRC should be fully investigated For this purpose, the research reported in this paper is aimed at providing new test data and demonstrating the effects of the several parameters that affect the bond behavior of prestressing strands in UHPFRC. The bond behavior of strands in UHPFRC was compared to that of strands in ordinary high-strength concrete, and the equations for predicting the transfer lengths of strands according to the current code approaches were evaluated with respect to the experimental results
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
