Axial strengthening of preloaded rectangular concrete columns by precambered steel plates

Steel jacketing has been widely used for strengthening reinforced concrete (RC) columns. Previous experimental studies have evaluated the ductility and shear performance of steel jacketed columns. However, in practice, the RC columns to be strengthened are usually subjected to pre-compressed axial loads. The stress-lagging effect between the original column and the new jacket due to the pre-existing load has not been addressed previously. In this paper, a simple and innovative decompression approach, using precambered steel plates, is proposed to upgrade the axial capacity of preloaded RC columns. An experimental study was conducted to validate the effectiveness of this approach for increasing the axial load capacity of RC columns. A theoretical model was also developed to predict the axial load capacity of the plate-strengthened columns. Comparison of theoretical and experimental results showed that the theoretical model accurately predicted the axial load-carrying capacities of the plate-strengthened columns.