Bond Stress-Slip Model for 0.6 in. (15.2 mm) Diameter Strand

Abstract

In pretensioned concrete members, strand bond is necessary for transferring prestress force from the prestressing strands to the adjacent concrete. This paper proposes a new bond stress-slip model for 0.6 in. (15.2 mm), Grade 270 prestressing strands. The proposed model is incorporated into a nonlinear second-order differential equation of strand slip along the transfer zone to investigate strand behavior The transfer length at release estimated by the analytical method is verified using experimental data from 19 pretensioned concrete beams collected from the literature and 45 beams cast at the University of Arkansas. Three parametric studies were conducted. The results indicated that: 1) the transfer length is shortened as concrete compressive strength increases; 2) pullout force is an important factor affecting the transfer length; and 3) the transfer length predicted by ACI 318 is conservative for concrete having compressive strength of 4 ksi (26.7 MPa) or greater at release.