Title: Residual Properties of Heat-Treated Thermomechanically Treated Steel Reinforcing Bars

Author(s): Muhammad Masood Rafi, Abdul Basit Dahar, Tariq Aziz, and Sarosh Hashmat Lodi

Publication: Materials Journal

Volume: 118

Issue: 4

Appears on pages(s): 15-26

Keywords: elastic modulus; post-fire exposure; residual strain; residual strength; strain hardening; stress-strain curve; thermomechanically treated (TMT) bar

DOI: 10.14359/51732596

Date: 7/1/2021

Abstract:
This paper presents the details of experimental testing of thermomechanically treated (TMT) steel bars subjected to high temperatures. Bars with a diameter of 10, 12, 16, 20, and 25 mm (0.39, 0.47, 0.63, 0.79, and 1 in.) were included in the testing program. These bars were heat-treated at temperatures varying from 100 to 900°C (212 to 1652°F) in increments of 100°C (180°F) and cooled down to room temperature. Similar bars were tested without heat treatment to serve as control specimens. The heating of the bar caused metallographic changes, which reduced the hardness of the entire cross section of the bar to become the same at 900°C (1652°F). The yield strengths of all the barsʼ control specimens were significantly higher than that recommended by the relevant bar manufacturing standard. The residual tensile properties of different diameter bars were similar, which permits using an average value representative of these properties. A polynomial expression was suggested to predict the post-yielding strain-hardening region of the tested bars. The results from the suggested expression correlated well with the observed data of reinforcing bar strain hardening.