Seismic Behavior of Circular Concrete Columns Reinforced by Low Bond Ultrahigh Strength Rebars

Abstract

To develop a resilient reinforced concrete frame structure, the seismic performance of circular concrete columns reinforced by low bond ultrahigh strength (LBUS) rebars is investigated experimentally in this paper. Eight 1/3-scale circular columns with LBUS rebars confined by spirals or steel plates were tested. Compared with the columns with high strength reinforcements with a normal bond, the columns with LBUS rebars exhibited better seismic performance and higher self-centering regardless of their lateral confinement methods. This is explained by the strong restoring force provided by the ultrahigh steel rebars and the small physical damage of concrete surrounding LBUS rebars’ surface during large deformations. All the features reduce the degradation of the load-carrying capacity of the columns induced by the P-Δ effect and serious spalling of concrete cover. Several models for predicting the hysteretic response and the energy dissipation capacity of the columns were proposed and their accuracy and reliability was presented by comparing them with their experimental results. The results prove that it is possible to achieve a resilient reinforced concrete (RC) column with a high self-centering capability up to the drift ratio of 3.0% using the LBUS rebars, after which the column’s load-carrying remains almost the same or continues to increase until a drift ratio of 5.0% is reached.