Strengthening of Reinforced Concrete Columns with Post-Compressed Plates

Abstract

Reinforced concrete (RC) columns in buildings often need strengthening after fire or earthquake attack. Steel jacketing, concrete jacketing and composite jacketing, are commonly adopted for upgrading the axial load capacity of RC columns. However, no matter which jacket is used to strengthen RC columns, stress-lagging effect between the preloaded concrete core and the new jacket exist; which can lead to significant reduction in the ultimate load capacity of the strengthened column. In this presentation, post-compressed plates will be introduced to strengthen rectangular RC columns. In this approach, curved steel plates with a total length slightly longer than the clear height of the column are attached to the column. By pressing the curved steel plates to a flat shape through tightening the bolts, the column is stretched due to arching actions, and the existing axial load in the original column is simultaneously shared with the steel plates. As similar strains are induced in the RC column and external steel plates, the stress-lag problem is alleviated. A higher axial load capacity for the strengthened columns can be achieved. Experimental results will be shown to illustrate the effectiveness of this new strengthening method. A practical application of using the proposed method for strengthening RC columns in an old building in Shanghai will also be briefly presented.