Seismic Performance of Defective Reinforced Concrete Columns With Replacement Strengthening Using Cementitious Grouting Material

This study investigates the seismic performance of deficient‐strength reinforced concrete (DSRC) columns strengthened by replacement with cementitious grouting material (CGM). Nine specimens were tested under cyclic loading, including standard, DSRC, and corresponding CGM replacement columns. Additionally, a fiber model built in OpenSees was used to study the effects of defect locations and replacement thicknesses on the seismic performance of strengthened DSRC columns. Parameters such as failure mode, hysteresis, skeleton curves, ductility, energy dissipation, and stiffness degradation were analyzed. All specimens exhibited flexural failure. Middle‐defect columns developed cracks more rapidly and extensively than bottom‐defect columns. With increasing replacement thickness, both initial cracking and final failure were delayed, and energy dissipation was significantly enhanced. The cumulative energy dissipation of the middle‐ and bottom‐defect columns increased by up to 63% and 106%, respectively. The strengthening effect of middle‐defect columns was slightly lower than that of bottom‐defect columns. A method was proposed to predict the flexural capacity of the cementitious grouting material–concrete core (CGM–CC) section, which showed good agreement with experimental results. An optimal sectional replacement ratio of 60%–80% for middle‐defect columns and 50%–70% for bottom‐defect columns is recommended.