Flexural Behavior of Unbonded Post Tensioned Concrete T Beams Externally Bonded With CFRP Sheets Under Static Loading

This paper presents a study on flexural behavior of unbonded post-tensioned concrete T-beams (UPC) externally strengthened by CFRP sheets under static loading with or without the presence of U-strip CFRP anchorage systems. A total of nine UPC T-beams in large size including one control unstrengthened beam and eight beams externally strengthened with varied number of CFRP sheets (2, 4, and 6 plies) were tested. Two types of transverse CFRP U-strip anchorage system were also retrofitted in the shear span. The results showed that CFRP sheets significantly increased the flexural capacity (up to 37%), decreased deflection in serviceability state, improved ductility, and reduced crack width (up to 48%) of the tested beams. The maximum strain in CFRP sheets in strengthened UPC T-beams ranged from 38.7 to 69.3% of the rupture strain of the CFRP sheets and tended to decrease with a large number of CFRP sheets. Strain in tendons of strengthened beams was significantly affected by the CFRP sheets and transverse U-strip anchorage system.