Effect of confinement materials and damage degree on the seismic behavior of RRACFST columns

Abstract

In order to investigate the influence of seismic pre-damage and reinforcement materials on seismic behavior of seismic-damaged rectangular recycled aggregate concrete-filled steel tubular (RRACFST) columns, seven columns were designed and manufactured, which composed of three undamaged RRACFST columns, two moderately pre-damaged RRACFST columns and two severely pre-damaged RRACFST columns. The inter-story displacement angle of 1/100 and 1/50 were used to simulate the moderate pre-damage and severe pre-damage of the specimens, which were then strengthened with carbon fiber reinforced polymer sheets (CFRPs) or enveloped-steel jacket (ESJ). The quasi-static destructive experiment results indicate that, with the increase of seismic pre-damage, the fullness and area of hysteresis curves decreases gradually, and the stiffness, energy dissipation capacity and deformation performance of specimens decrease significantly, due to different reinforcement materials. The average ductility coefficient and the average peak load of CFRPs and ESJ strengthened specimens were increased by 30.3%, 22.3%, 14.3%, 22.0%, 20.2%, 8.3% and 22.0%, 17.0%, 2.9%, 31.7%, 26.8%, 8.9% respectively. After being strengthened, the severely pre-damaged specimen, due to the moderate improvement of its ductility and bearing capacity, can resist earthquakes again. The research result will provide basis for the seismic evaluation and reinforcement technical specifications of the RRACFST structure.