Analysis of Optimised Truss Model for FRP Shear Strengthened Beams

There is lack of agreement in terms of accuracy and prediction method in the current design guidelines on externally bonded Fiber Reinforced Polymer (FRP) shear strengthening for reinforced concrete (RC) structures. This paper is produced aiming to improve prediction of the effective FRP shear strain using an improved optimised strut tie model (STM). It is generally believed that the 45o truss analogy that is adopted in current design codes have not been able to present the actual failure behavior due to oversimplification. The FRP shear strength contribution to RC beam method that is to be calibrated based on the optimised STM, is derived from the minimum strain energy principle. This had reflected the internal stress field more closely, in the RC beam shear span region. The strain optimised STM has been reconsidered depending on shear span to depth ratio. Effective length contributing to the shear capacity has been evaluated to improve the U Wrap FRP scheme. The result is promising, showing better potential to be integrated into design code. The calibrated empirical equation will be beneficial to engineering society in obtaining the effective FRP shear strain and obtaining the FRP shear strength which can be adopted in design purposes.