Epoxy-Coated and Uncoated Strand Transfer Lengths for PC Panels

Abstract

An experimental and analytical study was conducted to determine the feasibility of using grit-impregnated, epoxy-coated, prestressing strands (coated strands) and smooth surfaced, epoxy-coated, deformed, welded-wire-fabric in thin prestressed concrete (PC) subdeck panels and to determine the transfer lengths for 9.53-mm (3/8 in.) diameter, seven-wire, 1,860-MPa (270 ksi), low-relaxation, coated and bare (uncoated) strands. When coated strands are located at the middepth of a PC panel, the experimental testing revealed that a 76-mm (3 in.) minimum thickness was required to prevent concrete cracking when the strands were cut, that the amount of concrete side cover affected the uncoated-strand transfer lengths, and that a 152-mm (6 in.) strand spacing did not appear to affect the transfer lengths for either the coated or uncoated strands. The experimental and analytical investigations showed that the measured coated-strand transfer lengths were about one-half of those measured lengths for uncoated strands and that the American Concrete Institute (ACI) Building Code expression for strand transfer length overestimates the coated-strand transfer lengths and underestimates the uncoated-strand transfer lengths.