External steel ties and CFRP jacketing effects on seismic performance and failure mechanisms of substandard rectangular RC columns

Abstract One of the feasible retrofitting techniques for existing reinforced concrete (RC) structures is to use Fiber Reinforced Polymers (FRPs). On the other hand, the efficiency of the FRP jacketing strategy in rectangular RC columns is less than square and circular cross-section. For this purpose, the seismic retrofit of five full-scale substandard rectangular RC columns is evaluated both numerically and experimentally in terms of load–displacement performance, failure mechanism and autopsy after the test. Besides, the study introduces an enhanced strategy employing carbon fiber reinforced polymers (CFRPs) as well as external steel ties to retrofit the full-scale RC columns with rectangular cross-section loaded through the weak direction. The findings demonstrate that the CFRP jackets and external steel ties considerably usefulness in comparison to the used retrofitting strategy specifically concerning ductility and energy dissipation capacity. Regarding the analytical work, the non-elastic performance of the retrofitted and reference specimens was established by using realistic material models employing Seismostruct as a finite element platform. Lastly, the analytical forecasting carried out employing the FRP retrofitting design methods presented by the Turkish Seismic Design Code (TSDC), ACI 440.2R and Eurocode 8 Part 3 are compared with experimental results.