Earthquake-Resistant T-shaped Concrete Walls with High-Strength Steel Bars

For many years, U.S. building codes for structural concrete have not permitted the use of high-strength reinforcing bars with a nominal yield strength greater than 80 ksi (550 MPa) for purposes other than as transverse reinforcement for confinement. Increased understanding and acceptance of high-strength steel bars would allow designers to reduce the amount of reinforcement used in structural members, resulting in less reinforcement congestion, simpler construction, and reduced cost. The main objective of this study is to determine the effect of the tensile-to-yield strength ratio of high-strength reinforcing bars on longitudinal reinforcement strain demands and on the overall behavior of slender T-shaped reinforced concrete walls. This investigation also aimed to determine the minimum uniform elongation required of high-strength reinforcement used in earthquake-resistant structures. Study of T-shaped walls is important because the shape of the cross-section results in larger longitudinal reinforcement tensile strain demands than in most other members. The effect of replacing conventional Grade 60 (420) reinforcement with a reduced amount of high-strength Grade 100 (690) reinforcement (with nominal yield strength of 100 ksi, or 690 MPa) is evaluated in this study using data from tests of large-scale reinforced concrete walls subjected to reversed cyclic displacements.