Experimental investigation on different strengthening techniques of high‐strength concrete columns subjected to concentric and eccentric loading

This study investigates the effectiveness of various strengthening techniques on high‐strength concrete columns subjected to both concentric and eccentric loading. The experimental program involved testing a series of high‐strength concrete columns, which were retrofitted using different methods with different combinations, including carbon fiber reinforced polymers (CFRP) sheets and an engineered cementitious composite (ECC) jacket. Two major variables were considered: load eccentricity and strengthening procedure. The experimental research involves testing 12 defective columns with dimensions of 150 × 150 × 800 mm. The specimens were examined under both concentric and eccentric loadings. The ultimate capacity, axial ductility, absorbed energy capacity, initial stiffness, and failure mechanism were all determined. The results of this study indicate that both strengthening techniques significantly improved the load‐carrying capacity by up to 29.8% in the case of concentric loading and up to 42.7% in the case of eccentric loading, and significantly improved the ductility of the columns. However, the performance varied depending on the type of loading and the retrofitting method used. Various strategies considerably increased ductility, maximum deflection, and absorbed energy capacity in both loading scenarios. The results provide valuable insights into the selection of appropriate strengthening techniques for high‐strength concrete columns in different loading conditions and assistance for the structural engineer in identifying the most efficient repair strategy for such columns.