Post-Compressed Plates for Strengthening Preloaded Rectangular Reinforced Concrete Columns

Abstract

Steel jacketing has been extensively adopted for strengthening of reinforced concrete (RC) columns. A large number of experiments have been conducted to estimate the ductility and shear strength of steel jacketed columns. However, stress lagging problem between the old column and new jacket due to the pre-existing load, and non-uniform confinement of rectangular RC columns have not been resolved. In this paper, a simple and innovative post-compression approach is proposed to strengthen preloaded RC columns, in which slightly curved steel plates are bolted to the RC column. As the plates provided are longer than the clear height of the column, progressive tightening the anchor bolts can generate a thrust on the beam supports by means of arching actions. Therefore, the existing axial loads in the original column can be actively shared with the additional steel plates. The stress relief in the original column and post-stress developed in the steel plates could alleviate the stress lagging and displacement incompatibility problems. As similar strains are induced in the RC column and steel plates, a better utilization of both components in resisting external load and a higher axial load-carrying capacity can be achieved. A design example is given to illustrate the effectiveness of the post-compression approach.