Prestress losses and flexural behavior of reinforced concrete beams strengthened with posttensioned CFRP sheets

An experimental study was conducted to investigate the flexural behavior and long-term prestress losses of reinforced concrete (RC) beams strengthened with posttensioned carbon fiber-reinforced polymer (CFRP) sheets. The experimental program consisted of tensile tests of flat CFRP coupons under sustained loads and flexural tests of a total of eight RC beams: six strengthened with posttensioned CFRP sheets, one strengthened with nonprestressed CFRP sheets, and one control beam. The main objective of the tests was to gain a better understanding of the long-term prestress losses of CFRP sheets in the posttensioned system under different prestress levels and strengthening ratios. It is shown that the prestress losses of CFRP sheets in the posttension system are mainly attributable to anchorage set (approximately 12.6 to 18.2% of the initial prestress), whereas the time-dependent losses caused by creep and shrinkage of concrete and relaxation of CFRP sheets are relatively small (approximately 2.3 to 3.9% of the initial prestress).