Structural performance of flexibly formed concrete T beams with wound FRP reinforcement

Flexible formwork has been used in the casting of structural concrete since the 1980s. Research has shown that it is potentially unconservative to design fabric formed concrete beams in shear using existing codes and standards. In addition, with traditional steel reinforcement, it is time and labour consuming to fabricate the cage of beam with variable depth and the difficulty of bending steel leads to inaccurate locating of the cages. Moreover, corrosion of steel will increase the life-cycle cost of concrete structures. In this work, Wound Fibre Reinforced Polymer (W-FRP) was introduced to flexibly formed concrete. Eight T-beams with W-FRP reinforcement were designed and tested. Different codes and a revised Modified Compression Field Theory (MCFT) model were compared with the test results. The flexural and shear performances of the specimens were analysed. Key conclusions are that 1) W-FRP reinforcement is capable of supplying sufficient shear capacity; 2) arranging W-FRP in an optimal pattern can increase the shear capacity of the specimens and avoid shear failure; 3) debonding failures demonstrate the importance of longitudinal bars in carrying shear and the anchorage strength in design; and 4) the MCFT model gave better predictions than the two codified predictions.