Behavior of partially strengthened reinforced concrete columns from two or three sides of the perimeter

Reinforced concrete jacketing has been widely used for strengthening RC columns. In some cases, such as corner and edge columns, using full jacket for the column's strengthening can't be executed. Fully strengthened reinforced concrete columns have been studied in many researches, while partially strengthened RC columns from two and three sides needs more research. This paper evaluates the effectiveness of strengthening the corner and edge columns and focuses on the behavior of RC columns strengthened by RC jackets from two, three, and four sides of the perimeter. Also, it investigates the effect of using the different interaction methods between original columns and strengthening jackets such as friction, dowels, and stirrups' welding. The experimental study consists of columns specimens which were divided into eight cases. The investigated parameters were the number of strengthening sides, surface connections, and the type of jacket to column stirrups connection. The columns were loaded with an axial load up to failure. Mode of failure and axial column capacity were demonstrated and discussed. To be more insight on the behavior, a finite element analysis was conducted for some of the tested columns. The results of both experimental and theoretical studies were compared together and showed good agreement. The partially jacketed columns showed an acceptable increase in column capacity. The results showed that the most effective stirrups’ configuration for partially jacketed columns is by welding stirrups of the jacket to those of the existing column.