Steel Pipe Retrofitting Method to Enhance the Seismic Performance of RC Column Under Combined Load

A reinforced concrete column is subjected to a combination of axial load, lateral load, and torsion during earthquake excitations. Torsion induced under combined load can result in brittle failure in these columns. This study introduces a retrofitting technique using steel pipes designed to resist combined loads. To evaluate the seismic performance of the steel pipe, four specimens were fabricated, varying the presence of axial force eccentricity and retrofitting. The experimental results demonstrated that the steel pipe retrofitting technique enhanced strength, ductility, energy dissipation, and torsional resistance compared with conventional columns. The maximum torsional moment of the retrofitted specimens increased by up to 2.36 times, the maximum load capacity increased by 2.2 times, and the energy dissipation capacity increased by 2.8 times compared with the unretrofitted specimen.