Effectiveness of externally bonded CFRP strips for strengthening flanged beams under torsion: An experimental study

All over the world, fiber reinforced polymer (FRP) is currently being used for strengthening concrete elements, thus improving the building sustainability. The most recent report by the American Concrete Institute Committee 440 suggested that any proposed anchorage system should be heavily scrutinized before field implementation [4]. A comprehensive literature review was conducted, which showed that anchored U-jacket strips and un-anchored extended U-jacket strips were never examined for the case of RC flanged beams under significant torsion. The objective of this study is to investigate the behavior of FRP externally strengthened flanged beams subjected to torsion. Eleven beams were tested under significant torsion. Both the anchored U-jacket and the extended U-jacket strips were found to be more effective strengthening techniques compared to the un-anchored U-jacket strips and as effective as the fully wrapped strips. Using externally bonded FRP strips enhanced the torsional behavior of the flanged beams; however, the level of enhancement depended mainly on the effectiveness of the implemented strengthening technique.