RETROFITTING AND STRENGTHENING OF REINFORCED CONCRETE COLUMNS USING STEEL JACKETS; MECHANICAL PERFORMANCE AND APPLICATIONS

Abstract

Concrete jacketing is a commonly used method to retrofit or strengthen existing columns for axial loads. This can be made by longitudinal steel bars and additional concrete around an existing column or placing a jacket around the column. Each one of these methods has its difficulties regarding the new construction forms needed and the modification in column’s dimensions or the difficult welding works and corrosion problems. Recently, the topic of interest in the infrastructure community is to enhance the confinement of columns by using GFR or FRP composite sheets. Techniques of applying steel jackets around reinforced concrete columns are almost un–covered in the literature. The main objective of this research is to characterize the mechanical performance of reinforced concrete columns retrofitted or strengthened by using steel jackets made of hot rolled sections. Three types of columns having rectangular, square and circular cross-sections were investigated and tested under static axial compression loading. Cracking and ultimate loads, deformation properties as well as strains in both the concrete column and steel jacket were recorded and analyzed. Pattern of cracks and mode of failure were identified. The mechanical performance of retrofitted and strengthened columns was significantly improved. The ultimate loads obtained from testing retrofitted columns were found to be higher than the original ones by a value of 15-18%. The proposed steel jacketing technique, adopted in this research, has been successfully applied to some buildings, in our region, in order to retrofit or strengthen the existing columns. An excellent beneficial serviceability has been achieved. Photographs showing the steps of executing the steel jackets to existed deteriorated columns are attached.