A stress-strain relationship for Grade 270 low-relaxation prestressing strands is presented. It is based on recent extensive testing by the authors requested by the PCI Industry Handbook Committee. The testing has resulted in refined constants of the previously developed power formula which has been shown in several studies to predict prestressing steel stress for a given strain to within 1 percent error of any prescribed experimental value. Tables and stress-strain graphs for other common types of prestressing steel are reproduced here, from an earlier study, for the convenience of readers.
