The load resisting capacity of reinforced-concrete (RC) structures reduces due to various sources such as earthquakes, corrosion and aging effects. Even under neutral circumstances, the performance of buildings can be reduced over time due to the strength and deformation degradation of concrete and steel. Reconstruction of such structures may be an option, but it may cause significant costs, labor and time. Therefore, depending on the priority of the structure, strengthening becomes one of the alternatives and may be a sustainable solution to increase the capacity in terms of both strength and ductility.
There have been many studies on the strengthening of buildings and the different methods that have been improved and applied. Among these strengthening methods, RC jacketing is considered one of the most common methods in over the world. The advantage of this method is that it needs little labor and equipment, with low costs, and method itself can improve the strength, stiffness and, to some degree,ductility of structural elements by increasing the cross-section andlateral confinement, thus increasing the performance and service life.
Based on the above, this study examines the behavior of different cross-sections' strength with RC jacketing. Using the improved jacketing behavior models in the experimental studies, the mechanical behavior of RC jacketing was investigated using three different reinforced-concrete square sections with varying jacketing thicknesses. The axial load ratio of a column before strengthening was taken as 30%, and the longitudinal reinforcement ratio of the jacketed and as-built sections was assumed to be 1%. The compressive strength of the existing column and RC jacket was 15MPa and 40MPa, respectively. The changes in the strength and ductility of the sections were evaluated using parameters such as ratio of jacket thickness to cross-section depth (Δ/h) and ratio of cross-sectional area to area of jacketed RC section (A1/A2). The evaluations revealed a strong relationship between these parameters and the section responses.