Title:
Experimental Behavior of Concrete Columns Reinforced with Thermomechanically Treated and Cold-Twisted Ribbed Steel Bars
Author(s):
Muhammad Saad Khan, Muhammad Masood Rafi, and Humberto Varum
Publication:
Structural Journal
Volume:
122
Issue:
3
Appears on pages(s):
57-70
Keywords:
base rotation; displacement ductility; drift ratio; equivalent damping; hysteresis loops; lap splice; reinforced concrete (RC) column; secant stiffness
DOI:
10.14359/51744392
Date:
5/1/2025
Abstract:
This paper presents experimental testing results on full-scale reinforced concrete (RC) column specimens subjected to quasi-static
cyclic loading. Two types of lap-spliced steel reinforcing bars were
used: hot-rolled thermomechanically treated (TMT) and coldtwisted
ribbed bars. The specimens were tested under varying
axial load levels: CD-10 and CD-20 specimens, reinforced with
TMT bars, were loaded at 10% and 20% of the column’s axial
load capacity, respectively, while the CT-20 specimen, reinforced
with cold-twisted ribbed bars, was axially loaded at 20% capacity.
In contrast to the cold-twisted bars, the TMT bars’ yield strength
exceeded the specified strength by 38%, leading to an underestimation of the required reinforcing bar splice length and significantly impacting cracking patterns and curvature near the dowel end. The CD-20 and CT-20 specimens showed comparable lateral load capacity and initial stiffness, substantially higher than the CD-10 specimen. The CT-20 specimen exhibited symmetrical hysteretic behavior, indicating a consistent response to reversed cyclic loading, with (on average) 10% and 45% higher peak and ultimate displacement capacity than CD-10 and CD-20, respectively,
and 45% higher displacement ductility capacity. Notably, only the
CT-20 specimen met the acceptance criteria for structural testing
described by the code of practice, while the lower ductility and
ultimate rotation capacity of CD-10 and CD-20 resulted from the
unintended increase in reinforcing bar yield strength.