Presents the results of an investigation on the transfer and development lengths required for Grade 270, 0.6 in. (15.2 mm) diameter prestressing strand spaced at 2 in. (51 mm) on center in high performance concrete prestressed box girders. Three 411 in. (10400 mm) long box girders with composite topping slabs were tested. The specified compressive strength of the girder concrete is 10,000 psi (69 MPa). The average transfer length required for these girders was determined to be 23.4 in. (593 mm). The required development length was measured using an iterative testing process involving six flexural tests. The development length for these girders was determined to be 60 in. (1500 mm). The AASHTO/ACI formulas overestimate the transfer length of the girders by 18 percent and the development length by 53 percent. The average pullout strength attained in strand pullout tests is 48 kips (215 kN). The average strand slip measured right after stress transfer is 0.06 in. (1.52 mm).
