Seismic Performance of Circular Concrete Columns Reinforced with High-Strength Steel

In modern seismic design of reinforced concrete structures, areas designed to form plastic hinges are reinforced with ASTM A706 steel because of its ability to sustain large elongations, as well as its tightly controlled specifications on yield and ultimate strength. The A706 standard now includes reinforcing steel with a nominal yield strength of 550 MPa (80 ksi), but its use in seismic applications is limited given the lack of experimental data on its behavior in members forming plastic hinges. In this paper, the results of four circular Grade 80 (550) reinforced columns tested under reverse cyclic loading are discussed and compared with companion Grade 60 (420) reinforced columns. The results showed that columns reinforced with Grade 80 (550) steel exhibited rebar fracture at lower levels of column deformation, although the onset of bar buckling, plastic hinge lengths, and energy dissipation were similar to columns reinforced with Grade 60 (420) steel. (C) 2019 American Society of Civil Engineers.