One of the major strengthening applications of fiber-reinforced polymer (FRP) composites is as additional web reinforcement (of various forms) for enhancing the shear resistance of reinforced concrete (RC) beams. Because linear FRP differs from nonlinear steel reinforcement, the design theory of FRP-strengthened RC members exhibits unique characteristics, particularly for shear capacity design. Research on FRP shear strengthening has been limited compared to that on FRP flexural strengthening of RC beams. Nonetheless, the substantial available research has established a general understanding of structural behavior and has inspired several strength models, which are based on experimental observations and the corresponding theoretical assumptions. In this chapter, a comprehensive review of existing shear and torsional strength models is presented.

In addition, different failure mechanisms and factors influencing strengthening performance are presented briefly using finite element modeling. A prediction model of shear capacity developed based on numerical analyses is also proposed.