Strut-and-tie method for externally bonded FRP shear-strengthened large-scale RC beams

The main objective of this study is to evaluate the effectiveness of the strut-and-tie method (STM) in predicting the capacity of shear-strengthened large-scale beams with externally bonded (EB) and carbon fibre reinforced polymers (CFRPs). The STM approach is validated with 14 specimens shear-strengthened with a U-wrap scheme. The test specimens are grouped into four series on the basis of the spacing between their steel stirrups: 140, 203, 406 and 610 mm. Each series of girders includes a control specimen, with no external CFRP for shear strengthening, and specimens strengthened with one, two, and for the second and fourth series, three layers of CFRP. A practical analysis and detailed design for the CFRP shear-strengthened girders using the STM is presented. In the method, externally bonded CFRP strips on a CFRP shear-strengthened RC member can act as additional tension ties. The tensile forces in the steel stirrups and the CFRP laminates are combined according to a proposed equation. The results obtained using the STM are compared with the experimental results as well as the Canadian Bridge Design code (CSA-S6-06). The STM analysis approach, without considering the safety factor proposed by the ACI, shows its capability to predict the loading capacities of FRP shear-strengthened large-scale beams with good accuracy.