Title:
Determination of Yield Strength for Nonprestressed Steel Reinforcement
Author(s):
Wiss, Janney, Elstner Associates, Inc.
Publication:
CRC
Volume:
Issue:
Appears on pages(s):
Keywords:
non-stressed reinforcement, ACI 318-71, steel bar, steel
DOI:
Date:
12/31/2013
Abstract:
The goal of this study is to determine if it would be appropriate to change the method specified by the ACI Code for measuring the yield strength of nonprestressed reinforcement without a well-defined yield point. The present method is the extension under load method at a strain of 0.35 percent, as first required
by the 1971 edition of the ACI Code (ACI 318-71). The change of yield measurement method is in part prompted at the request of the industry that manufactures steel bar reinforcement, who ask that the requirement be changed to the offset method at an offset strain of 0.2 percent. The 0.2 percent offset method is used for virtually all other forms of steel products in the U.S. and for most steel bar reinforcement around the world. The change will allow for a more consistent determination of yield
strength in reinforcement, and will encourage the use of modern measurement methods in testing laboratories and steel mills. The request is based in part on the roundhouse nature of the stress-strain curves of coiled bars and of some higher-grade reinforcing steels. The change would align the ACI Code
with common industry practice.