Seismic behavior of preloaded rectangular RC columns strengthened with precambered steel plates under high axial load ratios

In the past 20 years, numerous tests have been conducted to demonstrate the effectiveness of additional fiber reinforced polymers (FRPs) or steel jacketing in the seismic retrofit of circular reinforced concrete (RC) columns. However, very few studies have explored the seismic retrofit of rectangular RC columns, in particular under high axial load ratios (ALRs). To address this issue, a simple and innovative approach is used in this study, in which rectangular RC columns subjected to high ALRs are retrofitted with post-compressed steel plates under severe lateral reversed cyclic loads. An experimental study is conducted to validate the effectiveness of this approach for improving the seismic performance of RC columns under high ALRs. Specimens with identical geometric and reinforcement layouts are fabricated and tested. One of the columns, which is not strengthened, is used as the control whereas the others are strengthened by using bolted steel plates. The effects of plate thickness, initial precamber and ALR on the failure mode, as well as ductility, strength degradation and energy dissipation, are investigated. The results demonstrate that this approach is effective in increasing the lateral displacement ductility capacity while maintaining the high axial load-carrying capacity of the columns.