Title:
Experimental Behavior of Concrete Columns Reinforced with TMT and Cold-Twisted Ribbed Steel Bars (Prepublished)
Author(s):
Muhammad Saad Khan, Muhammad Masood Rafi, Humberto Varum
Publication:
Structural Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
base rotation; displacement ductility; drift ratio; equivalent damping; hysteresis loops; lap splice; reinforced concrete column; secant stiffness
DOI:
10.14359/51744392
Date:
12/6/2024
Abstract:
This paper presents experimental testing results on full-scale RC column specimens subjected to quasi-static cyclic loading. Two types of lap-spliced steel rebars were used: hot-rolled thermo-mechanically treated (TMT) and cold-twisted 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 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 rebar 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 rebar yield strength.