The behavior of strengthened and repaired RC columns with (CFRP) rope under different preloading levels

This study investigates impact of spacing between carbon fiber reinforced polymers (CFRP) ropes and the area of CFRP ropes on behavior of strengthened and repaired reinforced concrete (RC) circular columns that preloaded to different levels. RC columns were divided into three groups. First group (three specimens) were strengthened with NSM-CFRP rope using one layer and two layers at 100 and 200 mm spacing, whereas the second and third groups each had two columns preloaded to 50 and 75% of the control specimen's ultimate load. According to the findings, strengthening columns with one rope spaced 100 mm and two ropes spaced 200 mm enhanced ultimate load capacity by 79.7 and 14.9%, respectively, as the control column. With one rope at a spacing of 100 mm and two ropes in one groove at a spacing of 200 mm, the repaired column after 50% damage and 75% damage, respectively, achieved (114.12 and 107%) and (111.38 and 93.44%) of the ultimate load capacity. Load capacity increased as the distance between CFRP ropes decreased, resulting in a higher effective lateral confining pressure and enhanced CFRP efficacy. Finally, a good level of similarity was shown between the finite element analysis results and the test results.